hardware: KiCad bootstrap for the Resound carrier PCB (Small Build)

Netlist-first KiCad-import package for the single carrier PCB (ESP32-WROOM-32E, SINK/BROADCASTER assembly variants): - hardware/carrier/resound-carrier.net : KiCad s-expr netlist, 44 components / 40 nets, real library footprints (RF_Module:ESP32-WROOM-32, 2x13 stacking header, 0402 passives, SOT-23 auto-reset, JST-SH HUD conn). Parens balanced. - hardware/carrier/BOM.csv : 44 parts (ref/value/footprint/MPN/DNP/notes). - hardware/carrier/LAYOUT.md : 45x45 4-layer stackup, 15mm antenna keep-out, placement, JLCPCB DRC, SINK-vs-BROADCASTER variant + address-strap table. - hardware/carrier/README.md : KiCad import steps + caveats. Agent decisions flagged for EE: LED moved off the GPIO13 strap to LED_DAT=GPIO21 / LED_CLK=GPIO4; verify WROOM footprint pad numbering; UART2 is connector-only this rev. Deliverable is import-ready netlist+BOM+spec, not a finished .kicad_pcb. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Rename: product -> "Resound"; firmware roles -> hud/sink/broadcaster
2026-06-11 15:10:15 -04:00 · 2026-06-11 14:14:16 -04:00 · 2026-06-11 13:06:10 -04:00 · 2026-06-11 11:57:48 -04:00 · 2026-06-11 10:44:45 -04:00 · 2026-06-11 10:12:17 -04:00
11 changed files with 2370 additions and 252 deletions
--- a/BikeAudio.ino
+++ b/BikeAudio.ino
@ -1,252 +0,0 @@
-/**
- * BikeAudio — ESP32 DevKitC v4 Bluetooth Audio Relay
- *
- * iPhone --> [ESP32 A2DP SINK] --> [A2DP SOURCE x2] --> JBL Charge 5 + Cardo Packtalk Edge
- *
- * Libraries required (install via Arduino IDE Library Manager or .zip):
- *   - ESP32-A2DP       by Phil Schatzmann  https://github.com/pschatzmann/ESP32-A2DP
- *   - arduino-audio-tools by Phil Schatzmann  https://github.com/pschatzmann/arduino-audio-tools
- *
- * Board: ESP32 Dev Module
- * Partition scheme: Huge APP (3MB No OTA/1MB SPIFFS)  <-- required for BT stack size
- * ESP32 Arduino core: 2.0.17 (do NOT use 3.x — BT stack regression)
- *
- * HOW IT WORKS:
- *   1. ESP32 boots and connects to JBL Charge 5 and Cardo as A2DP sources
- *   2. Then advertises itself as "BikeAudio" for the iPhone to connect to
- *   3. Audio received from iPhone is forwarded to both speakers in real time
- *   4. Auto-reconnect on power cycle — just turn everything on and it finds each other
- *
- * FIRST TIME SETUP:
- *   - Forget JBL and Cardo from your iPhone
- *   - Put JBL in pairing mode (hold Bluetooth button)
- *   - Put Cardo in pairing mode (check Cardo manual — usually hold phone button)
- *   - Flash this sketch, open Serial Monitor at 115200
- *   - ESP32 will find and pair with both devices on first boot
- *   - On iPhone, go to Bluetooth settings and connect to "BikeAudio"
- *   - Done — play audio, both speakers output simultaneously
- */
-
-#include "AudioTools.h"
-#include "BluetoothA2DPSink.h"
-#include "BluetoothA2DPSource.h"
-#include "BluetoothA2DPCommon.h"
-
-// ─── CONFIGURATION ────────────────────────────────────────────────────────────
-
-// Name this device shows to iPhone
-#define SINK_NAME        "BikeAudio"
-
-// Exact Bluetooth names of your speakers (must match exactly, case sensitive)
-#define JBL_NAME         "JBL Charge 5"
-#define CARDO_NAME       "Tangerine EDGE"
-
-// Retry interval if a speaker disconnects (ms)
-#define RECONNECT_MS     5000
-
-// Audio buffer size — larger = more stable, slightly more latency
-#define BUFFER_SIZE      (4 * 1024)
-
-// ─── GLOBALS ──────────────────────────────────────────────────────────────────
-
-BluetoothA2DPSink   sink;       // receives audio FROM iPhone
-BluetoothA2DPSource src_jbl;    // sends audio TO JBL
-BluetoothA2DPSource src_cardo;  // sends audio TO Cardo
-
-// Shared ring buffer — sink writes, sources read
-RingBuffer<uint8_t> ring_buf(BUFFER_SIZE * 2);
-
-// Connection state
-volatile bool jbl_connected   = false;
-volatile bool cardo_connected = false;
-volatile bool iphone_connected = false;
-
-unsigned long last_reconnect_jbl   = 0;
-unsigned long last_reconnect_cardo = 0;
-
-// ─── AUDIO CALLBACK (iPhone → buffer) ────────────────────────────────────────
-
-/**
- * Called by the A2DP sink every time a new audio frame arrives from iPhone.
- * We write raw PCM into the shared ring buffer.
- * Both sources pull from this buffer simultaneously.
- */
-void audio_received_cb(const uint8_t *data, uint32_t len) {
-    // Write to ring buffer — non-blocking, drop if full (prevents deadlock)
-    for (uint32_t i = 0; i < len; i++) {
-        if (!ring_buf.isFull()) {
-            ring_buf.write(data[i]);
-        }
-    }
-}
-
-// ─── SOURCE DATA CALLBACK (buffer → JBL / Cardo) ─────────────────────────────
-
-/**
- * Called by each A2DP source when it needs audio data to send.
- * Both JBL and Cardo call this — they share the same buffer read pointer
- * via a duplicated/mirrored buffer approach.
- *
- * We use a simple approach: one primary reader (JBL) drains the buffer,
- * Cardo gets the same data via a mirrored write in audio_received_cb.
- */
-
-// Second ring buffer mirroring data for Cardo
-RingBuffer<uint8_t> ring_buf_cardo(BUFFER_SIZE * 2);
-
-void audio_received_mirror_cb(const uint8_t *data, uint32_t len) {
-    // Write to BOTH ring buffers — JBL gets ring_buf, Cardo gets ring_buf_cardo
-    for (uint32_t i = 0; i < len; i++) {
-        if (!ring_buf.isFull())       ring_buf.write(data[i]);
-        if (!ring_buf_cardo.isFull()) ring_buf_cardo.write(data[i]);
-    }
-}
-
-int32_t get_audio_for_jbl(uint8_t *data, int32_t len) {
-    int32_t bytes_read = 0;
-    while (bytes_read < len && !ring_buf.isEmpty()) {
-        data[bytes_read++] = ring_buf.read();
-    }
-    // Pad with silence if buffer underrun
-    if (bytes_read < len) {
-        memset(data + bytes_read, 0, len - bytes_read);
-    }
-    return len;
-}
-
-int32_t get_audio_for_cardo(uint8_t *data, int32_t len) {
-    int32_t bytes_read = 0;
-    while (bytes_read < len && !ring_buf_cardo.isEmpty()) {
-        data[bytes_read++] = ring_buf_cardo.read();
-    }
-    if (bytes_read < len) {
-        memset(data + bytes_read, 0, len - bytes_read);
-    }
-    return len;
-}
-
-// ─── CONNECTION CALLBACKS ─────────────────────────────────────────────────────
-
-void sink_connected_cb(esp_bd_addr_t addr, esp_a2d_connection_state_t state, void *obj) {
-    if (state == ESP_A2D_CONNECTION_STATE_CONNECTED) {
-        Serial.println("[SINK] iPhone connected");
-        iphone_connected = true;
-    } else {
-        Serial.println("[SINK] iPhone disconnected");
-        iphone_connected = false;
-    }
-}
-
-void jbl_connected_cb(esp_bd_addr_t addr, esp_a2d_connection_state_t state, void *obj) {
-    if (state == ESP_A2D_CONNECTION_STATE_CONNECTED) {
-        Serial.println("[JBL] Connected");
-        jbl_connected = true;
-    } else {
-        Serial.println("[JBL] Disconnected — will retry");
-        jbl_connected = false;
-        last_reconnect_jbl = millis();
-    }
-}
-
-void cardo_connected_cb(esp_bd_addr_t addr, esp_a2d_connection_state_t state, void *obj) {
-    if (state == ESP_A2D_CONNECTION_STATE_CONNECTED) {
-        Serial.println("[CARDO] Connected");
-        cardo_connected = true;
-    } else {
-        Serial.println("[CARDO] Disconnected — will retry");
-        cardo_connected = false;
-        last_reconnect_cardo = millis();
-    }
-}
-
-// ─── SETUP ────────────────────────────────────────────────────────────────────
-
-void setup() {
-    Serial.begin(115200);
-    delay(500);
-    Serial.println("=== BikeAudio Booting ===");
-
-    // ── Step 1: Connect to JBL as A2DP source ─────────────────────────────────
-    Serial.println("[JBL] Connecting...");
-    src_jbl.set_data_callback(get_audio_for_jbl);
-    src_jbl.set_on_connection_state_changed(jbl_connected_cb);
-    src_jbl.set_auto_reconnect(true);
-    src_jbl.start(JBL_NAME, true);   // true = reconnect if known device
-
-    // Give it time to connect before starting second source
-    // (Bluedroid needs sequential connection setup)
-    uint32_t t = millis();
-    while (!jbl_connected && millis() - t < 10000) {
-        delay(100);
-    }
-    if (jbl_connected) {
-        Serial.println("[JBL] Ready");
-    } else {
-        Serial.println("[JBL] Not found yet — will retry in background");
-    }
-
-    // ── Step 2: Connect to Cardo as A2DP source ────────────────────────────────
-    Serial.println("[CARDO] Connecting...");
-    src_cardo.set_data_callback(get_audio_for_cardo);
-    src_cardo.set_on_connection_state_changed(cardo_connected_cb);
-    src_cardo.set_auto_reconnect(true);
-    src_cardo.start(CARDO_NAME, true);
-
-    t = millis();
-    while (!cardo_connected && millis() - t < 10000) {
-        delay(100);
-    }
-    if (cardo_connected) {
-        Serial.println("[CARDO] Ready");
-    } else {
-        Serial.println("[CARDO] Not found yet — will retry in background");
-    }
-
-    // ── Step 3: Start sink — advertise "BikeAudio" to iPhone ──────────────────
-    Serial.println("[SINK] Advertising as '" SINK_NAME "' ...");
-    sink.set_stream_reader(audio_received_mirror_cb);
-    sink.set_on_connection_state_changed(sink_connected_cb);
-    sink.start(SINK_NAME);
-    Serial.println("[SINK] Ready — connect iPhone to 'BikeAudio'");
-
-    Serial.println("=== BikeAudio Ready ===");
-    print_status();
-}
-
-// ─── LOOP ─────────────────────────────────────────────────────────────────────
-
-void loop() {
-    // Auto-reconnect JBL if lost
-    if (!jbl_connected && millis() - last_reconnect_jbl > RECONNECT_MS) {
-        Serial.println("[JBL] Retrying connection...");
-        src_jbl.start(JBL_NAME, true);
-        last_reconnect_jbl = millis();
-    }
-
-    // Auto-reconnect Cardo if lost
-    if (!cardo_connected && millis() - last_reconnect_cardo > RECONNECT_MS) {
-        Serial.println("[CARDO] Retrying connection...");
-        src_cardo.start(CARDO_NAME, true);
-        last_reconnect_cardo = millis();
-    }
-
-    // Print status every 10 seconds
-    static unsigned long last_status = 0;
-    if (millis() - last_status > 10000) {
-        print_status();
-        last_status = millis();
-    }
-
-    delay(100);
-}
-
-// ─── HELPERS ──────────────────────────────────────────────────────────────────
-
-void print_status() {
-    Serial.println("--- Status ---");
-    Serial.printf("  iPhone : %s\n", iphone_connected ? "CONNECTED" : "waiting...");
-    Serial.printf("  JBL    : %s\n", jbl_connected    ? "CONNECTED" : "waiting...");
-    Serial.printf("  Cardo  : %s\n", cardo_connected  ? "CONNECTED" : "waiting...");
-    Serial.printf("  Heap   : %d bytes free\n", ESP.getFreeHeap());
-    Serial.println("--------------");
-}
--- a/README_RELAY.md
+++ b/README_RELAY.md
@ -0,0 +1,103 @@
+# Resound — 3-board Bluetooth relay
+
+Relays iPhone audio to **two** Bluetooth speakers (JBL Charge 5 + Cardo "Tangerine EDGE")
+at the same time.
+
+## Why three boards?
+
+One ESP32 **cannot** do this alone:
+
+1. **Sink + source can't coexist.** To receive from the iPhone the ESP32 must be an
+   A2DP *sink*; to play through a speaker it must be an A2DP *source*. The ESP32's
+   classic-Bluetooth stack registers only one A2DP role at a time (the ESP32-A2DP
+   library keeps a single global instance that each role overwrites). Running a sink
+   and a source together orphans the sink — the iPhone can't even see it.
+2. **A source reaches only one speaker.** An A2DP source holds a single outgoing
+   link, so one board can drive one speaker, not two.
+
+So the job is split: one board receives, one board per speaker sends, and they pass
+audio between them over a short digital **I2S** wire bus.
+
+```
+   iPhone ))BT))  ┌──────────────┐  I2S bus (BCK/WS/DATA + GND)
+                  │   Board A    │═══════════════╦═══════════════╗
+                  │  A2DP SINK   │               ║               ║
+                  │  I2S MASTER  │               ▼               ▼
+                  └──────────────┘        ┌────────────┐  ┌────────────┐
+                                          │  Board B   │  │  Board C   │
+                                          │ A2DP SOURCE│  │ A2DP SOURCE│
+                                          │ I2S SLAVE  │  │ I2S SLAVE  │
+                                          └─────┬──────┘  └─────┬──────┘
+                                            ))BT))           ))BT))
+                                          JBL Charge 5    Tangerine EDGE (Cardo)
+```
+
+## Wiring
+
+Board A is the I2S **master** (it generates the clocks). Boards B and C are
+**slaves** that listen to A's bus in parallel. Tie the three signals from A to the
+matching input pins on **both** B and C, and tie **all grounds together**.
+
+| Signal      | Board A (master, out) | Board B (slave, in) | Board C (slave, in) |
+|-------------|-----------------------|---------------------|---------------------|
+| Bit clock   | **GPIO5**  (BCK)      | GPIO19              | GPIO19              |
+| Word select | **GPIO25** (WS/LRCK)  | GPIO18              | GPIO18              |
+| Data        | **GPIO23** (DATA out) | GPIO22 (in)         | GPIO22 (in)         |
+| Ground      | **GND**               | GND                 | GND                 |
+
+- A·GPIO5  → B·GPIO19 **and** C·GPIO19
+- A·GPIO25 → B·GPIO18 **and** C·GPIO18
+- A·GPIO23 → B·GPIO22 **and** C·GPIO22
+- A·GND    → B·GND    **and** C·GND   (mandatory — shared clock reference)
+
+Each board can be powered from its own USB/5V; only the grounds must be common.
+
+### Sync (touch pads on each source board)
+
+JBL and Cardo have independent Bluetooth buffering, so one lags the other. Each
+source board has an **adjustable delay** (0–200 ms) you trim live, by ear, with two
+capacitive-touch pads — raise the delay on whichever speaker is *early* until they
+line up. The value is saved to flash (survives power-cycles).
+
+| Touch pad | Pin   | Action                         |
+|-----------|-------|--------------------------------|
+| **+**     | GPIO4  | tap = +5 ms, hold = ramp up    |
+| **−**     | GPIO27 | tap = −5 ms, hold = ramp down  |
+
+Attach a short wire or a bit of foil to GPIO4 and GPIO27 on each source board and
+touch the end. (There is intentionally **no Wi-Fi/phone UI**: Wi-Fi + Bluetooth +
+the audio buffer don't fit in RAM on the classic ESP32 — it starves the Bluetooth
+stack — so the control is local touch.)
+
+## Build & flash
+
+```
+pio run                      # builds all three
+pio run -e sink              # Board A
+pio run -e source_jbl        # Board B (target "JBL Charge 5")
+pio run -e source_cardo      # Board C (target "Tangerine EDGE")
+```
+
+Flash each board with the matching environment's artifacts
+(`.pio/build/<env>/{bootloader,partitions,firmware}.bin`).
+
+**Power-on order:** bring up **Board A first** so the I2S bus is clocking before
+B and C start reading it.
+
+## First-time pairing
+
+1. Put the **JBL** and **Cardo** in pairing mode.
+2. Power Board B and Board C — each connects to its speaker by name
+   (auto-reconnects on later power-ups).
+3. Power Board A; on the iPhone, connect to **"Resound"**.
+4. Play audio — both speakers should output together.
+
+## Known limitations
+
+- **The two speakers are not sample-synchronized.** JBL and Cardo each have their
+  own Bluetooth buffering, so one lags the other. The per-board touch delay (above)
+  lets you trim a fixed offset to line them up by ear; it is not continuous
+  sample-lock, so slow drift over long sessions is possible. Fine for music/intercom;
+  not suitable for tight stereo L/R separation.
+- Audio is fixed at the SBC standard **44.1 kHz / 16-bit / stereo**.
+- If Board A reboots, the slave boards' audio pauses until A is clocking again.
--- a/hardware/carrier/BOM.csv
+++ b/hardware/carrier/BOM.csv
@ -0,0 +1,45 @@
+Ref,Qty,Value,Footprint,MPN/JLCPCB part,DNP(y/n),Notes
+U1,1,ESP32-WROOM-32E,RF_Module:ESP32-WROOM-32,ESP32-WROOM-32E / JLCPCB C701343,n,SMD castellated 38-pad module; antenna overhangs board edge (see keep-out)
+J1,1,Stack_2x13,Connector_PinHeader_2.54mm:PinHeader_2x13_P2.54mm_Vertical,Generic 2x13 2.54mm,n,Stacking pass-through bus; mirror header on bottom shares same nets
+J2,1,PROG_1x6,Connector_PinHeader_2.54mm:PinHeader_1x06_P2.54mm_Vertical,Generic 1x6 2.54mm,n,Programming/serial: GND +5V RX(IO3) TX(IO1) DTR RTS
+J3,1,HUD_SH1.0_1x6,Connector_JST:JST_SH_BM06B-SRSS-TB_1x06-1MP_P1.00mm_Vertical,JST BM06B-SRSS-TB,n,TOP board only: 1=+5V 2=GND 3=SDA 4=SCL 5=SPARE 6=NC. Verify pin order vs HUD cable
+Q1,1,MMBT3904,Package_TO_SOT_SMD:SOT-23,MMBT3904 / JLCPCB C20526,n,Auto-reset (DTR->EN)
+Q2,1,MMBT3904,Package_TO_SOT_SMD:SOT-23,MMBT3904 / JLCPCB C20526,n,Auto-boot (RTS->IO0)
+SW1,1,EN/RESET,Button_Switch_SMD:SW_SPST_PTS645,PTS645 series,n,Tactile EN->GND
+SW2,1,BOOT/IO0,Button_Switch_SMD:SW_SPST_PTS645,PTS645 series,n,Tactile IO0->GND
+JP1,1,0R,Resistor_SMD:R_0603_1608Metric,0R 0603,n,I2S_BCK=GPIO5 (SINK column)
+JP2,1,0R,Resistor_SMD:R_0603_1608Metric,0R 0603,n,I2S_WS=GPIO25 (SINK column)
+JP3,1,0R,Resistor_SMD:R_0603_1608Metric,0R 0603,n,I2S_DATA=GPIO23 (SINK column)
+JP4,1,0R,Resistor_SMD:R_0603_1608Metric,0R 0603,n,I2S_BCK=GPIO19 (BROADCASTER column)
+JP5,1,0R,Resistor_SMD:R_0603_1608Metric,0R 0603,n,I2S_WS=GPIO18 (BROADCASTER column)
+JP6,1,0R,Resistor_SMD:R_0603_1608Metric,0R 0603,n,I2S_DATA=GPIO22 (BROADCASTER column)
+R1,1,33R,Resistor_SMD:R_0402_1005Metric,33R 0402,y,I2S_BCK series term (optional; DNP default)
+R2,1,33R,Resistor_SMD:R_0402_1005Metric,33R 0402,y,I2S_WS series term (optional; DNP default)
+R3,1,33R,Resistor_SMD:R_0402_1005Metric,33R 0402,y,I2S_DATA series term (optional; DNP default = 0R jumper if not fitted)
+R4,1,4.7k,Resistor_SMD:R_0402_1005Metric,4.7k 0402,y,SDA pull-up to 3V3. Populate on SINK only (single pull-up on bus)
+R5,1,4.7k,Resistor_SMD:R_0402_1005Metric,4.7k 0402,y,SCL pull-up to 3V3. Populate on SINK only (single pull-up on bus)
+R6,1,10k,Resistor_SMD:R_0402_1005Metric,10k 0402,n,EN pull-up to 3V3
+R7,1,10k,Resistor_SMD:R_0402_1005Metric,10k 0402,n,IO0 pull-up to 3V3
+R8,1,10k,Resistor_SMD:R_0402_1005Metric,10k 0402,n,Q1 base resistor (auto-reset)
+R9,1,10k,Resistor_SMD:R_0402_1005Metric,10k 0402,n,Q2 base resistor (auto-boot)
+R10,1,10k,Resistor_SMD:R_0402_1005Metric,10k 0402,n,ADDR0/GPIO13 strap to 3V3 (populate this OR R11)
+R11,1,0R,Resistor_SMD:R_0402_1005Metric,0R 0402,y,ADDR0/GPIO13 strap to GND (populate this OR R10)
+R12,1,10k,Resistor_SMD:R_0402_1005Metric,10k 0402,n,ADDR1/GPIO14 strap to 3V3 (populate this OR R13)
+R13,1,0R,Resistor_SMD:R_0402_1005Metric,0R 0402,y,ADDR1/GPIO14 strap to GND (populate this OR R12)
+R14,1,10k,Resistor_SMD:R_0402_1005Metric,10k 0402,n,ADDR2/GPIO27 strap to 3V3 (populate this OR R15)
+R15,1,0R,Resistor_SMD:R_0402_1005Metric,0R 0402,y,ADDR2/GPIO27 strap to GND (populate this OR R14)
+R16,1,10k,Resistor_SMD:R_0402_1005Metric,10k 0402,n,ADDR3/GPIO26 strap to 3V3 (populate this OR R17)
+R17,1,0R,Resistor_SMD:R_0402_1005Metric,0R 0402,y,ADDR3/GPIO26 strap to GND (populate this OR R16)
+C1,1,1uF,Capacitor_SMD:C_0603_1608Metric,1uF 0603,n,EN to GND (reset delay)
+C2,1,100nF,Capacitor_SMD:C_0402_1005Metric,100nF 0402,n,IO0 to GND (boot debounce)
+C3,1,100nF,Capacitor_SMD:C_0402_1005Metric,100nF 0402,n,DTR coupling cap to Q1
+C4,1,100nF,Capacitor_SMD:C_0402_1005Metric,100nF 0402,n,RTS coupling cap to Q2
+C5,1,10uF,Capacitor_SMD:C_0805_2012Metric,10uF 0805,n,3V3 bulk at WROOM 3V3 pad
+C6,1,100nF,Capacitor_SMD:C_0402_1005Metric,100nF 0402,n,3V3 decap at WROOM 3V3 pad
+C7,1,100nF,Capacitor_SMD:C_0402_1005Metric,100nF 0402,n,3V3 decap at WROOM 3V3 pad
+C8,1,10uF,Capacitor_SMD:C_0805_2012Metric,10uF 0805,n,+5V bulk at stacking connector
+C9,1,22uF,Capacitor_SMD:C_0805_2012Metric,22uF 0805,n,3V3 bulk rail
+H1,1,MountingHole_M3,MountingHole:MountingHole_3.2mm_M3,-,n,Corner mount, 38x38mm pattern, GND-tied
+H2,1,MountingHole_M3,MountingHole:MountingHole_3.2mm_M3,-,n,Corner mount, GND-tied
+H3,1,MountingHole_M3,MountingHole:MountingHole_3.2mm_M3,-,n,Corner mount, GND-tied
+H4,1,MountingHole_M3,MountingHole:MountingHole_3.2mm_M3,-,n,Corner mount, GND-tied
--- a/hardware/carrier/LAYOUT.md
+++ b/hardware/carrier/LAYOUT.md
@ -0,0 +1,129 @@
+# Resound Small Build — Carrier PCB Layout & Fab Spec
+
+This document is the layout intent that pairs with `resound-carrier.net`. The netlist
+defines connectivity; this defines board outline, stackup, placement, and design rules.
+An engineer imports the netlist into KiCad, then lays out per the constraints here.
+
+## 1. Board outline
+- **Size:** 45.0 mm x 45.0 mm.
+- **Corners:** rounded, R = 3.0 mm (4x).
+- **Edge.Cuts** layer defines outline. Keep all copper >= 0.3 mm inside the edge except
+  the deliberate antenna keep-out region (see section 4).
+
+## 2. Stackup (4-layer)
+| Layer | Name        | Use                                              |
+|-------|-------------|--------------------------------------------------|
+| L1    | Sig (top)   | Components, signal routing, WROOM, connectors    |
+| L2    | GND         | Solid ground plane (reference for all signals)   |
+| L3    | PWR         | +3V3 / +5V power pours                            |
+| L4    | Sig (bottom)| Signal routing, bottom stacking header, fanout   |
+
+- Standard JLCPCB 4-layer: 1.6 mm finished, 0.5 oz inner / 1 oz outer, FR-4 TG155 OK.
+- Stitch GND plane to top/bottom ground pours with vias around board perimeter and under
+  the WROOM ground pad array. Place a dense via field under U1's exposed/edge GND pads.
+
+## 3. Power distribution
+- +5V enters on stacking connector J1 pins 1,2. C8 (10uF) bulk at connector.
+- +3V3 rail on J1 pins 5,6 (module/regulator assumed upstream on the +3V3 supplying board).
+  C9 (22uF) bulk on 3V3. C5 (10uF) + C6/C7 (100nF) directly at the WROOM 3V3 pad (pad 2),
+  shortest possible loop to nearest GND via.
+- Power pour widths: 5V and 3V3 main feeds >= 0.6 mm or plane on L3.
+
+## 4. Antenna keep-out (CRITICAL)
+- U1 (ESP32-WROOM-32E) placed at one board edge with the **PCB antenna overhanging the
+  board edge** — the antenna end of the module must sit flush with / past the edge cut.
+- **15 mm copper keep-out, ALL LAYERS**, around the antenna: no copper (no traces, no
+  pours, no plane fill, no ground) within 15 mm of the antenna trace footprint, including
+  L2 GND and L3 PWR planes. Add a keep-out zone on every layer.
+- No mounting hardware, no metal, no components in the antenna keep-out.
+- This is why U1 lives at the edge and the antenna overhangs: maximize RF clearance.
+
+## 5. Placement plan
+```
+   +-----------------------------------------------+
+   | (H1)                                    (H2)  |
+   |   [ U1  ESP32-WROOM-32E ]  <- antenna overhang|  <- this edge: antenna keep-out 15mm
+   |   3V3 decap C5/C6/C7 hugging pad 2            |
+   |                                               |
+   |        [ J1  2x13 stacking connector ]        |  <- centered, vertical, top+bottom
+   |        I2S jumper field JP1..JP6 near J1      |
+   |                                               |
+   |  [J2 prog 1x6]   Q1 Q2 C3 C4   [SW1] [SW2]    |  <- opposite edge: prog + buttons
+   | (H3)   [J3 HUD SH1.0 - TOP only]        (H4)  |
+   +-----------------------------------------------+
+```
+- **U1:** top edge, antenna overhanging, keep-out enforced.
+- **J1 stacking connector:** centered on the board so the stack aligns mechanically.
+  Top header + mirrored bottom header on the SAME footprint position share nets
+  (pass-through). Verify pin 1 indexing matches between top and bottom of the stack.
+- **I2S role jumpers JP1..JP6:** group as two visible columns (SINK | BROADCASTER) next
+  to J1, silkscreen-label each column and net.
+- **Address straps R10..R17:** group as a labelled field; silkscreen "3V3 / GND" per strap.
+- **Prog header J2, transistors Q1/Q2, caps C3/C4, buttons SW1/SW2:** opposite edge from
+  the antenna, accessible.
+- **J3 HUD SH1.0:** near a board edge, TOP board assembly only.
+- **Mounting holes H1..H4:** 38 x 38 mm square pattern (centered on 45x45 board => holes
+  at +/-19 mm from center X and Y), M3 (3.2 mm), keep clear of antenna keep-out (move the
+  two antenna-edge holes inward if they fall inside the 15 mm keep-out).
+
+## 6. Design rules (JLCPCB 4-layer, standard)
+- Min trace width: 0.127 mm (5 mil); use 0.2 mm default signal, 0.15 mm only in fanout.
+- Min spacing: 0.127 mm (5 mil); 0.2 mm default.
+- Min via: 0.3 mm drill / 0.6 mm pad; 0.2/0.4 only where needed.
+- Min annular ring: 0.13 mm.
+- Edge clearance: copper >= 0.3 mm from Edge.Cuts (except antenna keep-out which is larger).
+- **I2S series termination:** R1/R2/R3 (33R) footprints sit inline on I2S_BCK/WS/DATA
+  between the jumper field and J1. Default DNP — if I2S edges ring on the scope across the
+  stack, populate 33R and remove the equivalent direct short. Keep I2S traces short, equal
+  length within the pair set, referenced to L2 GND, away from the antenna.
+- **Single pull-up rule:** I2C SDA/SCL pull-ups (R4/R5) have footprints on EVERY board but
+  are DNP except on the SINK board, so the bus has exactly ONE pull-up pair across the stack.
+- Decoupling caps: place on the same layer as U1, vias to L2/L3 directly under the cap pad.
+
+## 7. Assembly variants (ONE board, two BOMs)
+
+| Item / Net            | SINK board                 | BROADCASTER board          |
+|-----------------------|----------------------------|----------------------------|
+| I2S BCK jumper        | JP1 (GPIO5)  populated     | JP4 (GPIO19) populated     |
+| I2S WS jumper         | JP2 (GPIO25) populated     | JP5 (GPIO18) populated     |
+| I2S DATA jumper       | JP3 (GPIO23) populated     | JP6 (GPIO22) populated     |
+| Opposite I2S column   | JP4/JP5/JP6 DNP            | JP1/JP2/JP3 DNP            |
+| I2C pull-up R4 (SDA)  | **populate 4.7k**          | DNP                        |
+| I2C pull-up R5 (SCL)  | **populate 4.7k**          | DNP                        |
+| I2S series term R1-R3 | DNP (unless ringing)       | DNP (unless ringing)       |
+| HUD connector J3      | per mechanical (TOP only)  | per mechanical (TOP only)  |
+| Address straps        | per node address (see below)| per node address          |
+| Reset/boot/prog (R6-9, C1-4, Q1-2, SW1-2, J2) | populate | populate |
+| Decoupling C5-C9      | populate                   | populate                   |
+
+**Address straps (R10..R17):** for each of ADDR0..ADDR3, populate EXACTLY ONE of the pair:
+- "1" / high  => populate the 10k-to-3V3 resistor (R10/R12/R14/R16), leave the 0R-to-GND DNP.
+- "0" / low   => populate the 0R-to-GND resistor (R11/R13/R15/R17), leave the 10k DNP.
+
+This is independent of SINK/BROADCASTER — it sets each board's bus address in the stack.
+
+## 8. Connector pinouts (reference)
+
+### J1 — 26-pin (2x13) stacking, 2.54 mm, pass-through (top + mirrored bottom)
+| Pin | Net        | Pin | Net        |
+|-----|------------|-----|------------|
+| 1   | +5V        | 2   | +5V        |
+| 3   | GND        | 4   | GND        |
+| 5   | +3V3       | 6   | +3V3       |
+| 7   | GND        | 8   | I2S_BCK    |
+| 9   | GND        | 10  | I2S_WS     |
+| 11  | GND        | 12  | I2S_DATA   |
+| 13  | GND        | 14  | GND        |
+| 15  | I2C_SDA    | 16  | I2C_SCL    |
+| 17  | UART_TX    | 18  | UART_RX    |
+| 19  | UART2_TX   | 20  | UART2_RX   |
+| 21  | LED_DAT    | 22  | LED_CLK    |
+| 23  | ADDR_CHAIN_IN | 24 | ADDR_CHAIN_OUT |
+| 25  | SPARE      | 26  | GND        |
+
+### J2 — programming 1x6, 2.54 mm
+1=GND, 2=+5V, 3=RX (IO3 / GPIO3), 4=TX (IO1 / GPIO1), 5=DTR, 6=RTS
+
+### J3 — HUD SH1.0 1x6 (TOP board only)
+1=+5V (VSYS), 2=GND, 3=I2C_SDA, 4=I2C_SCL, 5=SPARE, 6=NC
+(Verify physical pin order against the HUD cable before fab — see README caveat.)
--- a/hardware/carrier/README.md
+++ b/hardware/carrier/README.md
@ -0,0 +1,84 @@
+# Resound Small Build — Carrier PCB (KiCad bootstrap)
+
+A netlist-first hardware bootstrap for the **Resound** carrier PCB: one 45 x 45 mm
+4-layer board built around an **ESP32-WROOM-32E**, with a 26-pin stacking bus, that
+ships in two assembly variants — **SINK** and **BROADCASTER** — from the same layout.
+
+## What's here
+| File | Purpose |
+|------|---------|
+| `resound-carrier.net` | KiCad S-expression netlist: every component (ref/value/**real KiCad footprint**) and every net with pin connections. The importable artifact. |
+| `BOM.csv` | Bill of materials: Ref, Qty, Value, Footprint, MPN/JLCPCB, DNP, Notes. |
+| `LAYOUT.md` | Board outline, 4-layer stackup, antenna keep-out, placement plan, mounting holes, JLCPCB design rules, and the SINK vs BROADCASTER variant table. |
+| `README.md` | This file. |
+
+## Honest scope
+A text agent cannot emit a guaranteed-openable `.kicad_pcb` with real geometry. So the
+deliverable is a **complete, accurate, importable netlist + BOM + layout spec**. The
+schematic is **not yet drawn** — this is a netlist-first workflow. An engineer imports
+the netlist, lays out the board per `LAYOUT.md`, and (optionally) back-annotates a
+schematic afterwards.
+
+## How to import into KiCad (8.x)
+
+### Option A — straight into the PCB editor (fastest, matches netlist-first)
+1. New KiCad project. Open the **PCB Editor** (Pcbnew).
+2. **File -> Import -> Netlist...**  Select `resound-carrier.net`.
+3. KiCad places all footprints (it resolves the library footprint names like
+   `RF_Module:ESP32-WROOM-32`, `Connector_PinHeader_2.54mm:PinHeader_2x13_P2.54mm_Vertical`,
+   `Resistor_SMD:R_0402_1005Metric`, `Package_TO_SOT_SMD:SOT-23`, etc. from the standard
+   KiCad footprint libraries — make sure those libs are installed/enabled).
+4. Build the board outline on **Edge.Cuts** (45x45, rounded corners) and lay out per
+   `LAYOUT.md`. Add the antenna keep-out zones, GND/PWR plane pours, and mounting holes.
+5. Run **DRC** with JLCPCB rules from `LAYOUT.md` section 6.
+
+### Option B — schematic-first (if you prefer drawing the schematic)
+1. Use the netlist as the connectivity spec and draw the schematic in Eeschema, matching
+   refs/nets exactly, then **Update PCB from Schematic** (F8). The provided `.net` is the
+   single source of truth for which pin connects to which net.
+
+> Note: the `.net` uses KiCad's S-expression `(export ...)` netlist format with
+> `(comp ...)` + `(net ...)` sections and per-component `(footprint ...)`. This is what
+> "Import Netlist" consumes. The `(libparts)`/`(libraries)` blocks are intentionally empty
+> (footprints are assigned directly on each component, which is sufficient for PCB import).
+
+## ESP32-WROOM-32E pad mapping used
+The netlist references U1 by the standard KiCad `RF_Module:ESP32-WROOM-32` footprint pad
+numbers 1..38 (+ EP on pad 38). Key assignments:
+- GND = pads 1, 15, 38(EP)  |  3V3 = pad 2  |  EN = pad 3
+- I2C: SDA=GPIO32 (pad 8), SCL=GPIO33 (pad 9)
+- I2S SINK: BCK=GPIO5 (pad 29), WS=GPIO25 (pad 10), DATA=GPIO23 (pad 37)
+- I2S BCAST: BCK=GPIO19 (pad 31), WS=GPIO18 (pad 30), DATA=GPIO22 (pad 36)
+- ADDR: GPIO13 (pad 16), GPIO14 (pad 13), GPIO27 (pad 12), GPIO26 (pad 11)
+- UART bus: TX=GPIO17 (pad 28), RX=GPIO16 (pad 27)
+- LED: DAT=GPIO21 (pad 33), CLK=GPIO4 (pad 26)  *(reassigned — see caveats)*
+- Prog UART0: RX/IO3=GPIO3 (pad 34), TX/IO1=GPIO1 (pad 35), IO0=pad 25
+**Verify this pad mapping against the exact footprint variant you load** before committing
+copper, since some WROOM footprint variants renumber pads.
+
+## Known caveats / open items for the EE
+1. **LED pin reuse (RESOLVE THIS).** The original spec note put the APA102 LED DATA on
+   GPIO13, but GPIO13 is already an **address strap** (ADDR0). To avoid the conflict the
+   netlist reassigns LED to spare pins: **LED_DAT = GPIO21, LED_CLK = GPIO4**. Confirm
+   these spares are truly free for your firmware and that GPIO4/GPIO21 have no strapping or
+   boot side-effects in your build. Adjust if needed — flagged intentionally.
+2. **Antenna coupling across the stack.** Boards stack vertically; the WROOM antenna of a
+   lower board sits near the copper/components of the board above. Enforce the 15 mm
+   all-layer keep-out (LAYOUT.md §4) and consider stack spacing / antenna orientation so
+   the antenna of any board does not sit under metal of the neighbor.
+3. **Verify HUD SH1.0 pin order.** J3 is keyed/genderable; confirm pin 1 of the chosen
+   SH1.0 connector and the HUD cable match the `1=+5V 2=GND 3=SDA 4=SCL 5=SPARE 6=NC`
+   order before fab. Easy to mirror.
+4. **UART2 bus pins (J1 19/20)** are connector pass-through only on this rev — no MCU tap
+   is routed (the ESP32 second hardware UART pins are not broken out here). If a board
+   needs to drive UART2, the EE must route MCU spares to those connector pins.
+5. **Auto-reset cross-bias.** The DTR/RTS auto-reset/boot circuit follows the NodeMCU
+   2-transistor pattern; the base-resistor cross-bias nets (R8_BIAS->RTS, R9_BIAS->DTR)
+   prevent EN+IO0 asserting simultaneously. Sanity-check against your USB-serial adapter's
+   DTR/RTS polarity.
+6. **I2S series terminators R1/R2/R3** are DNP by default (direct connection). Populate
+   33R only if I2S signals ring across the stack.
+
+## Variants in one line
+SINK = I2S jumpers JP1/JP2/JP3 + I2C pull-ups R4/R5 populated. BROADCASTER = I2S jumpers
+JP4/JP5/JP6, pull-ups DNP. Address straps set per board. Full table in `LAYOUT.md` §7.
--- a/hardware/carrier/resound-carrier.net
+++ b/hardware/carrier/resound-carrier.net
@ -0,0 +1,387 @@
+(export (version "E")
+  (design
+    (source "resound-carrier")
+    (date "2026-06-11")
+    (tool "blue-agent netlist-first bootstrap")
+    (sheet (number "1") (name "/") (tstamps "/")
+      (title_block
+        (title "Resound Small Build Carrier PCB")
+        (company "Resound")
+        (rev "A")
+        (date "2026-06-11")
+        (comment (number "1") (value "ONE board, two assembly variants: SINK / BROADCASTER"))
+        (comment (number "2") (value "ESP32-WROOM-32E carrier with 26-pin stacking bus"))
+        (comment (number "3") (value "Netlist-first: schematic still to be drawn. See README.md"))
+        (comment (number "4") (value "CAVEAT: LED_DAT/LED_CLK pin assignment to be confirmed by EE")))))
+
+  (components
+    ;; ---- MCU ----
+    (comp (ref "U1")
+      (value "ESP32-WROOM-32E")
+      (footprint "RF_Module:ESP32-WROOM-32")
+      (datasheet "https://www.espressif.com/sites/default/files/documentation/esp32-wroom-32e_esp32-wroom-32ue_datasheet_en.pdf")
+      (fields
+        (field (name "MPN") "ESP32-WROOM-32E")
+        (field (name "JLCPCB") "C701343"))
+      (tstamps "00000001"))
+
+    ;; ---- Stacking connector (2x13 pass-through, top + bottom mirrored = same net per position) ----
+    (comp (ref "J1")
+      (value "Stack_2x13")
+      (footprint "Connector_PinHeader_2.54mm:PinHeader_2x13_P2.54mm_Vertical")
+      (fields (field (name "Notes") "2.54mm 2x13 pass-through; mirror header on bottom shares nets"))
+      (tstamps "00000002"))
+
+    ;; ---- Programming header 1x6 ----
+    (comp (ref "J2")
+      (value "PROG_1x6")
+      (footprint "Connector_PinHeader_2.54mm:PinHeader_1x06_P2.54mm_Vertical")
+      (fields (field (name "Pinout") "1=GND 2=+5V 3=RX/IO3 4=TX/IO1 5=DTR 6=RTS"))
+      (tstamps "00000003"))
+
+    ;; ---- HUD connector SH1.0 1x6 (TOP board only) ----
+    (comp (ref "J3")
+      (value "HUD_SH1.0_1x6")
+      (footprint "Connector_JST:JST_SH_BM06B-SRSS-TB_1x06-1MP_P1.00mm_Vertical")
+      (fields
+        (field (name "Pinout") "1=+5V 2=GND 3=SDA 4=SCL 5=SPARE 6=NC")
+        (field (name "MPN") "BM06B-SRSS-TB")
+        (field (name "Notes") "Populate on TOP board only"))
+      (tstamps "00000004"))
+
+    ;; ---- Auto reset/boot transistors ----
+    (comp (ref "Q1") (value "MMBT3904") (footprint "Package_TO_SOT_SMD:SOT-23")
+      (fields (field (name "Func") "DTR->EN reset") (field (name "JLCPCB") "C20526")) (tstamps "00000005"))
+    (comp (ref "Q2") (value "MMBT3904") (footprint "Package_TO_SOT_SMD:SOT-23")
+      (fields (field (name "Func") "RTS->IO0 boot") (field (name "JLCPCB") "C20526")) (tstamps "00000006"))
+
+    ;; ---- Tactile buttons ----
+    (comp (ref "SW1") (value "EN/RESET") (footprint "Button_Switch_SMD:SW_SPST_PTS645")
+      (fields (field (name "Notes") "EN to GND")) (tstamps "00000007"))
+    (comp (ref "SW2") (value "BOOT/IO0") (footprint "Button_Switch_SMD:SW_SPST_PTS645")
+      (fields (field (name "Notes") "IO0 to GND")) (tstamps "00000008"))
+
+    ;; ---- I2S role jumpers (0R, two columns) ----
+    ;; SINK column
+    (comp (ref "JP1") (value "0R") (footprint "Resistor_SMD:R_0603_1608Metric")
+      (fields (field (name "Func") "I2S_BCK = GPIO5 (SINK)")) (tstamps "00000010"))
+    (comp (ref "JP2") (value "0R") (footprint "Resistor_SMD:R_0603_1608Metric")
+      (fields (field (name "Func") "I2S_WS = GPIO25 (SINK)")) (tstamps "00000011"))
+    (comp (ref "JP3") (value "0R") (footprint "Resistor_SMD:R_0603_1608Metric")
+      (fields (field (name "Func") "I2S_DATA = GPIO23 (SINK)")) (tstamps "00000012"))
+    ;; BROADCASTER column
+    (comp (ref "JP4") (value "0R") (footprint "Resistor_SMD:R_0603_1608Metric")
+      (fields (field (name "Func") "I2S_BCK = GPIO19 (BROADCASTER)")) (tstamps "00000013"))
+    (comp (ref "JP5") (value "0R") (footprint "Resistor_SMD:R_0603_1608Metric")
+      (fields (field (name "Func") "I2S_WS = GPIO18 (BROADCASTER)")) (tstamps "00000014"))
+    (comp (ref "JP6") (value "0R") (footprint "Resistor_SMD:R_0603_1608Metric")
+      (fields (field (name "Func") "I2S_DATA = GPIO22 (BROADCASTER)")) (tstamps "00000015"))
+
+    ;; ---- I2S series termination (option) ----
+    (comp (ref "R1") (value "33R") (footprint "Resistor_SMD:R_0402_1005Metric")
+      (fields (field (name "Func") "I2S_BCK series term") (field (name "DNP") "y")) (tstamps "00000020"))
+    (comp (ref "R2") (value "33R") (footprint "Resistor_SMD:R_0402_1005Metric")
+      (fields (field (name "Func") "I2S_WS series term") (field (name "DNP") "y")) (tstamps "00000021"))
+    (comp (ref "R3") (value "33R") (footprint "Resistor_SMD:R_0402_1005Metric")
+      (fields (field (name "Func") "I2S_DATA series term") (field (name "DNP") "y")) (tstamps "00000022"))
+
+    ;; ---- I2C pull-ups (on every board, DNP except SINK) ----
+    (comp (ref "R4") (value "4.7k") (footprint "Resistor_SMD:R_0402_1005Metric")
+      (fields (field (name "Func") "SDA pull-up") (field (name "DNP") "y (populate on SINK only)")) (tstamps "00000023"))
+    (comp (ref "R5") (value "4.7k") (footprint "Resistor_SMD:R_0402_1005Metric")
+      (fields (field (name "Func") "SCL pull-up") (field (name "DNP") "y (populate on SINK only)")) (tstamps "00000024"))
+
+    ;; ---- Reset / boot RC + pull-ups ----
+    (comp (ref "R6") (value "10k") (footprint "Resistor_SMD:R_0402_1005Metric")
+      (fields (field (name "Func") "EN pull-up to 3V3")) (tstamps "00000025"))
+    (comp (ref "C1") (value "1uF") (footprint "Capacitor_SMD:C_0603_1608Metric")
+      (fields (field (name "Func") "EN to GND")) (tstamps "00000026"))
+    (comp (ref "R7") (value "10k") (footprint "Resistor_SMD:R_0402_1005Metric")
+      (fields (field (name "Func") "IO0 pull-up to 3V3")) (tstamps "00000027"))
+    (comp (ref "C2") (value "100nF") (footprint "Capacitor_SMD:C_0402_1005Metric")
+      (fields (field (name "Func") "IO0 to GND")) (tstamps "00000028"))
+
+    ;; ---- Auto reset/boot coupling caps + base resistors ----
+    (comp (ref "C3") (value "100nF") (footprint "Capacitor_SMD:C_0402_1005Metric")
+      (fields (field (name "Func") "DTR coupling to Q1")) (tstamps "00000029"))
+    (comp (ref "C4") (value "100nF") (footprint "Capacitor_SMD:C_0402_1005Metric")
+      (fields (field (name "Func") "RTS coupling to Q2")) (tstamps "0000002A"))
+    (comp (ref "R8") (value "10k") (footprint "Resistor_SMD:R_0402_1005Metric")
+      (fields (field (name "Func") "Q1 base series")) (tstamps "0000002B"))
+    (comp (ref "R9") (value "10k") (footprint "Resistor_SMD:R_0402_1005Metric")
+      (fields (field (name "Func") "Q2 base series")) (tstamps "0000002C"))
+
+    ;; ---- Address straps (GPIO13/14/27/26): 10k to 3V3 OR 0R to GND ----
+    (comp (ref "R10") (value "10k") (footprint "Resistor_SMD:R_0402_1005Metric")
+      (fields (field (name "Func") "ADDR0/GPIO13 -> 3V3 strap")) (tstamps "00000030"))
+    (comp (ref "R11") (value "0R")  (footprint "Resistor_SMD:R_0402_1005Metric")
+      (fields (field (name "Func") "ADDR0/GPIO13 -> GND strap") (field (name "DNP") "y (pick one)")) (tstamps "00000031"))
+    (comp (ref "R12") (value "10k") (footprint "Resistor_SMD:R_0402_1005Metric")
+      (fields (field (name "Func") "ADDR1/GPIO14 -> 3V3 strap")) (tstamps "00000032"))
+    (comp (ref "R13") (value "0R")  (footprint "Resistor_SMD:R_0402_1005Metric")
+      (fields (field (name "Func") "ADDR1/GPIO14 -> GND strap") (field (name "DNP") "y (pick one)")) (tstamps "00000033"))
+    (comp (ref "R14") (value "10k") (footprint "Resistor_SMD:R_0402_1005Metric")
+      (fields (field (name "Func") "ADDR2/GPIO27 -> 3V3 strap")) (tstamps "00000034"))
+    (comp (ref "R15") (value "0R")  (footprint "Resistor_SMD:R_0402_1005Metric")
+      (fields (field (name "Func") "ADDR2/GPIO27 -> GND strap") (field (name "DNP") "y (pick one)")) (tstamps "00000035"))
+    (comp (ref "R16") (value "10k") (footprint "Resistor_SMD:R_0402_1005Metric")
+      (fields (field (name "Func") "ADDR3/GPIO26 -> 3V3 strap")) (tstamps "00000036"))
+    (comp (ref "R17") (value "0R")  (footprint "Resistor_SMD:R_0402_1005Metric")
+      (fields (field (name "Func") "ADDR3/GPIO26 -> GND strap") (field (name "DNP") "y (pick one)")) (tstamps "00000037"))
+
+    ;; ---- Decoupling ----
+    (comp (ref "C5") (value "10uF")  (footprint "Capacitor_SMD:C_0805_2012Metric")
+      (fields (field (name "Func") "3V3 bulk at WROOM pad")) (tstamps "00000040"))
+    (comp (ref "C6") (value "100nF") (footprint "Capacitor_SMD:C_0402_1005Metric")
+      (fields (field (name "Func") "3V3 decap at WROOM pad")) (tstamps "00000041"))
+    (comp (ref "C7") (value "100nF") (footprint "Capacitor_SMD:C_0402_1005Metric")
+      (fields (field (name "Func") "3V3 decap at WROOM pad")) (tstamps "00000042"))
+    (comp (ref "C8") (value "10uF")  (footprint "Capacitor_SMD:C_0805_2012Metric")
+      (fields (field (name "Func") "+5V bulk at connector")) (tstamps "00000043"))
+    (comp (ref "C9") (value "22uF")  (footprint "Capacitor_SMD:C_0805_2012Metric")
+      (fields (field (name "Func") "3V3 bulk rail")) (tstamps "00000044"))
+
+    ;; ---- Mounting holes (M3) ----
+    (comp (ref "H1") (value "MountingHole_M3") (footprint "MountingHole:MountingHole_3.2mm_M3") (tstamps "00000050"))
+    (comp (ref "H2") (value "MountingHole_M3") (footprint "MountingHole:MountingHole_3.2mm_M3") (tstamps "00000051"))
+    (comp (ref "H3") (value "MountingHole_M3") (footprint "MountingHole:MountingHole_3.2mm_M3") (tstamps "00000052"))
+    (comp (ref "H4") (value "MountingHole_M3") (footprint "MountingHole:MountingHole_3.2mm_M3") (tstamps "00000053")))
+
+  (libparts)
+
+  (libraries)
+
+  (nets
+    ;; ================= POWER =================
+    (net (code "1") (name "+5V")
+      (node (ref "J1") (pin "1"))
+      (node (ref "J1") (pin "2"))
+      (node (ref "J2") (pin "2"))
+      (node (ref "J3") (pin "1"))
+      (node (ref "C8") (pin "1")))
+
+    (net (code "2") (name "+3V3")
+      (node (ref "U1") (pin "2"))
+      (node (ref "J1") (pin "5"))
+      (node (ref "J1") (pin "6"))
+      (node (ref "R4") (pin "1"))
+      (node (ref "R5") (pin "1"))
+      (node (ref "R6") (pin "1"))
+      (node (ref "R7") (pin "1"))
+      (node (ref "R10") (pin "1"))
+      (node (ref "R12") (pin "1"))
+      (node (ref "R14") (pin "1"))
+      (node (ref "R16") (pin "1"))
+      (node (ref "C5") (pin "1"))
+      (node (ref "C6") (pin "1"))
+      (node (ref "C7") (pin "1"))
+      (node (ref "C9") (pin "1")))
+
+    (net (code "3") (name "GND")
+      (node (ref "U1") (pin "1"))
+      (node (ref "U1") (pin "15"))
+      (node (ref "U1") (pin "38"))
+      (node (ref "J1") (pin "3"))
+      (node (ref "J1") (pin "4"))
+      (node (ref "J1") (pin "7"))
+      (node (ref "J1") (pin "9"))
+      (node (ref "J1") (pin "11"))
+      (node (ref "J1") (pin "13"))
+      (node (ref "J1") (pin "14"))
+      (node (ref "J1") (pin "26"))
+      (node (ref "J2") (pin "1"))
+      (node (ref "J3") (pin "2"))
+      (node (ref "C1") (pin "2"))
+      (node (ref "C2") (pin "2"))
+      (node (ref "C5") (pin "2"))
+      (node (ref "C6") (pin "2"))
+      (node (ref "C7") (pin "2"))
+      (node (ref "C8") (pin "2"))
+      (node (ref "C9") (pin "2"))
+      (node (ref "R11") (pin "2"))
+      (node (ref "R13") (pin "2"))
+      (node (ref "R15") (pin "2"))
+      (node (ref "R17") (pin "2"))
+      (node (ref "Q1") (pin "2"))
+      (node (ref "Q2") (pin "2"))
+      (node (ref "SW1") (pin "2"))
+      (node (ref "SW2") (pin "2"))
+      (node (ref "H1") (pin "1"))
+      (node (ref "H2") (pin "1"))
+      (node (ref "H3") (pin "1"))
+      (node (ref "H4") (pin "1")))
+
+    ;; ================= RESET / BOOT =================
+    ;; EN: WROOM pin3, pull-up R6, cap C1, button SW1, reset transistor Q1 collector
+    (net (code "4") (name "EN")
+      (node (ref "U1") (pin "3"))
+      (node (ref "R6") (pin "2"))
+      (node (ref "C1") (pin "1"))
+      (node (ref "SW1") (pin "1"))
+      (node (ref "Q1") (pin "3")))
+
+    ;; IO0: WROOM pin25 (GPIO0), pull-up R7, cap C2, button SW2, boot transistor Q2 collector
+    (net (code "5") (name "IO0")
+      (node (ref "U1") (pin "25"))
+      (node (ref "R7") (pin "2"))
+      (node (ref "C2") (pin "1"))
+      (node (ref "SW2") (pin "1"))
+      (node (ref "Q2") (pin "3")))
+
+    ;; ================= PROGRAMMING UART0 + AUTO RESET/BOOT =================
+    ;; UART0 RX into ESP = GPIO3 (pad34); prog header pin3 labelled RX (host TX -> ESP RX/IO3)
+    (net (code "6") (name "IO3_RXD0")
+      (node (ref "U1") (pin "34"))
+      (node (ref "J2") (pin "3")))
+    ;; UART0 TX out of ESP = GPIO1 (pad35); prog header pin4 labelled TX (ESP TX/IO1 -> host RX)
+    (net (code "7") (name "IO1_TXD0")
+      (node (ref "U1") (pin "35"))
+      (node (ref "J2") (pin "4")))
+
+    ;; DTR -> C3 -> Q1 base via R8 (reset)
+    (net (code "8") (name "DTR")
+      (node (ref "J2") (pin "5"))
+      (node (ref "C3") (pin "1")))
+    (net (code "9") (name "Q1_BASE")
+      (node (ref "C3") (pin "2"))
+      (node (ref "R8") (pin "1"))
+      (node (ref "Q1") (pin "1")))
+    ;; RTS -> C4 -> Q2 base via R9 (boot)
+    (net (code "10") (name "RTS")
+      (node (ref "J2") (pin "6"))
+      (node (ref "C4") (pin "1")))
+    (net (code "11") (name "Q2_BASE")
+      (node (ref "C4") (pin "2"))
+      (node (ref "R9") (pin "1"))
+      (node (ref "Q2") (pin "1")))
+    ;; Base resistors pull the bases; classic NodeMCU auto-reset cross-couples R8 to RTS-side and
+    ;; R9 to DTR-side so simultaneous DTR+RTS does not assert. Implemented as cross bias below.
+    (net (code "12") (name "R8_BIAS")
+      (node (ref "R8") (pin "2"))
+      (node (ref "J2") (pin "6")))
+    (net (code "13") (name "R9_BIAS")
+      (node (ref "R9") (pin "2"))
+      (node (ref "J2") (pin "5")))
+
+    ;; ================= I2S ROLE JUMPER FIELD =================
+    ;; ESP source pins feed jumper input side; jumper output side ties to the I2S bus net.
+    ;; SINK col: GPIO5=BCK(pad29), GPIO25=WS(pad10), GPIO23=DATA(pad37)
+    ;; BCAST col: GPIO19=BCK(pad31), GPIO18=WS(pad30), GPIO22=DATA(pad36)
+    (net (code "20") (name "GPIO5")
+      (node (ref "U1") (pin "29"))
+      (node (ref "JP1") (pin "1")))
+    (net (code "21") (name "GPIO25")
+      (node (ref "U1") (pin "10"))
+      (node (ref "JP2") (pin "1")))
+    (net (code "22") (name "GPIO23")
+      (node (ref "U1") (pin "37"))
+      (node (ref "JP3") (pin "1")))
+    (net (code "23") (name "GPIO19")
+      (node (ref "U1") (pin "31"))
+      (node (ref "JP4") (pin "1")))
+    (net (code "24") (name "GPIO18")
+      (node (ref "U1") (pin "30"))
+      (node (ref "JP5") (pin "1")))
+    (net (code "25") (name "GPIO22")
+      (node (ref "U1") (pin "36"))
+      (node (ref "JP6") (pin "1")))
+
+    ;; I2S bus nets: jumper outputs from BOTH columns land on the same bus node,
+    ;; then through optional series term R1/R2/R3 to the stacking connector.
+    (net (code "26") (name "I2S_BCK_PRE")
+      (node (ref "JP1") (pin "2"))
+      (node (ref "JP4") (pin "2"))
+      (node (ref "R1") (pin "1")))
+    (net (code "27") (name "I2S_BCK")
+      (node (ref "R1") (pin "2"))
+      (node (ref "J1") (pin "8")))
+    (net (code "28") (name "I2S_WS_PRE")
+      (node (ref "JP2") (pin "2"))
+      (node (ref "JP5") (pin "2"))
+      (node (ref "R2") (pin "1")))
+    (net (code "29") (name "I2S_WS")
+      (node (ref "R2") (pin "2"))
+      (node (ref "J1") (pin "10")))
+    (net (code "30") (name "I2S_DATA_PRE")
+      (node (ref "JP3") (pin "2"))
+      (node (ref "JP6") (pin "2"))
+      (node (ref "R3") (pin "1")))
+    (net (code "31") (name "I2S_DATA")
+      (node (ref "R3") (pin "2"))
+      (node (ref "J1") (pin "12")))
+
+    ;; ================= I2C =================
+    ;; GPIO32=SDA(pad8), GPIO33=SCL(pad9)
+    (net (code "40") (name "I2C_SDA")
+      (node (ref "U1") (pin "8"))
+      (node (ref "R4") (pin "2"))
+      (node (ref "J1") (pin "15"))
+      (node (ref "J3") (pin "3")))
+    (net (code "41") (name "I2C_SCL")
+      (node (ref "U1") (pin "9"))
+      (node (ref "R5") (pin "2"))
+      (node (ref "J1") (pin "16"))
+      (node (ref "J3") (pin "4")))
+
+    ;; ================= UART (bus, GPIO17=TX pad28 / GPIO16=RX pad27) =================
+    (net (code "50") (name "UART_TX")
+      (node (ref "U1") (pin "28"))
+      (node (ref "J1") (pin "17")))
+    (net (code "51") (name "UART_RX")
+      (node (ref "U1") (pin "27"))
+      (node (ref "J1") (pin "18")))
+
+    ;; ================= UART2 second bus pair (19,20 on connector) =================
+    ;; No dedicated second hardware UART pins routed from MCU on this rev; bus pass-through
+    ;; for daisy-chained boards. Left as connector-only nets (flag for EE if MCU tap needed).
+    (net (code "52") (name "UART2_TX")
+      (node (ref "J1") (pin "19")))
+    (net (code "53") (name "UART2_RX")
+      (node (ref "J1") (pin "20")))
+
+    ;; ================= LED (APA102) =================
+    ;; CAVEAT: original note said GPIO13 but GPIO13 is an ADDR strap. Reassigned to spare GPIOs:
+    ;; LED_DAT = GPIO21 (pad33), LED_CLK = GPIO4 (pad26). EE to confirm.
+    (net (code "60") (name "LED_DAT")
+      (node (ref "U1") (pin "33"))
+      (node (ref "J1") (pin "21")))
+    (net (code "61") (name "LED_CLK")
+      (node (ref "U1") (pin "26"))
+      (node (ref "J1") (pin "22")))
+
+    ;; ================= ADDRESS STRAPS =================
+    ;; Each GPIO -> two strap pads: R(10k) to 3V3 OR R(0R) to GND. Populate exactly one.
+    ;; ADDR0 GPIO13 = pad16
+    (net (code "70") (name "ADDR0_GPIO13")
+      (node (ref "U1") (pin "16"))
+      (node (ref "R10") (pin "2"))
+      (node (ref "R11") (pin "1")))
+    ;; ADDR1 GPIO14 = pad13
+    (net (code "71") (name "ADDR1_GPIO14")
+      (node (ref "U1") (pin "13"))
+      (node (ref "R12") (pin "2"))
+      (node (ref "R13") (pin "1")))
+    ;; ADDR2 GPIO27 = pad12
+    (net (code "72") (name "ADDR2_GPIO27")
+      (node (ref "U1") (pin "12"))
+      (node (ref "R14") (pin "2"))
+      (node (ref "R15") (pin "1")))
+    ;; ADDR3 GPIO26 = pad11
+    (net (code "73") (name "ADDR3_GPIO26")
+      (node (ref "U1") (pin "11"))
+      (node (ref "R16") (pin "2"))
+      (node (ref "R17") (pin "1")))
+
+    ;; ================= ADDR CHAIN (connector pass-through 23/24) =================
+    (net (code "74") (name "ADDR_CHAIN_IN")
+      (node (ref "J1") (pin "23")))
+    (net (code "75") (name "ADDR_CHAIN_OUT")
+      (node (ref "J1") (pin "24")))
+
+    ;; ================= SPARE =================
+    (net (code "80") (name "SPARE_CONN25")
+      (node (ref "J1") (pin "25"))
+      (node (ref "J3") (pin "5")))
+    ;; J3 pin6 = NC (HUD), intentionally unconnected
+  )
+)
--- a/platformio.ini
+++ b/platformio.ini
@ -0,0 +1,75 @@
+; BikeAudio — split-board Bluetooth audio relay.
+;
+; Roles (one ESP32 can't be A2DP sink+source, and a source reaches one speaker,
+; so the work is split across boards sharing an I2S audio bus + an I2C control bus):
+;   SINK        - iPhone connects here (A2DP in) -> drives the I2S bus as master
+;   BROADCASTER - reads I2S -> A2DP-streams to ONE speaker (one per channel)
+;   HUD         - ESP32-S3 round touch LCD; control panel over I2C
+;
+; Channels are brand-agnostic: Headset / Speaker 1 / Guest (discovery picks the
+; real device per channel). Build one: pio run -e sink | -e broadcaster_headset
+; | -e broadcaster_speaker1 | -e broadcaster_guest | -e hud
+;
+; Audio boards: ESP32 core 2.0.x via espressif32 ~6.6.0, esp32dev, huge_app (BT stack).
+
+[platformio]
+default_envs = sink, broadcaster_headset, broadcaster_speaker1, broadcaster_guest
+
+[env]
+platform = espressif32 @ ~6.6.0
+board = esp32dev
+framework = arduino
+board_build.partitions = huge_app.csv
+monitor_speed = 115200
+; pschatzmann libs pinned to exact commits (ESP32-A2DP 1.8.11, audio-tools 1.2.4)
+lib_deps =
+    https://github.com/pschatzmann/ESP32-A2DP#42601717cd70d5300c9b519f3c2bf1d64d77ea2b
+    https://github.com/pschatzmann/arduino-audio-tools#64b64dcb9bde18a0a17766eeb6529c3a53d920a8
+
+; --- SINK: A2DP sink (iPhone) -> I2S master ----------------------------------
+[env:sink]
+build_src_filter = +<sink.cpp>
+
+; --- BROADCASTER "Headset" -> Cardo (I2C 0x11) -------------------------------
+[env:broadcaster_headset]
+build_src_filter = +<broadcaster.cpp>
+build_flags = '-DTARGET_SPEAKER="Tangerine EDGE"' -DHUB_I2C_ADDR=0x11
+
+; --- BROADCASTER "Speaker 1" -> JBL (I2C 0x10) -------------------------------
+[env:broadcaster_speaker1]
+build_src_filter = +<broadcaster.cpp>
+build_flags = '-DTARGET_SPEAKER="JBL Charge 5"' -DHUB_I2C_ADDR=0x10
+
+; --- BROADCASTER "Guest" -> antenna board, occasional passenger (I2C 0x12) ---
+;     No hardcoded device — pick the speaker via the HUD scan UI (discovery).
+[env:broadcaster_guest]
+build_src_filter = +<broadcaster.cpp>
+build_flags = '-DTARGET_SPEAKER="Guest"' -DHUB_I2C_ADDR=0x12
+
+; --- HUD: ESP32-S3-Touch-LCD-1.28 (round GC9A01 LCD + CST816S touch) ----------
+;     Different chip (esp32s3); LVGL UI + I2C master to the audio boards.
+;     NOT in default_envs — build with: pio run -e hud
+[env:hud]
+platform = espressif32 @ ~6.6.0
+board = esp32-s3-devkitc-1
+framework = arduino
+board_upload.flash_size = 4MB
+board_build.partitions = default.csv
+monitor_speed = 115200
+build_src_filter = +<hud.cpp>
+lib_deps =
+    lovyan03/LovyanGFX@^1.1.16
+    lvgl/lvgl@^8.3.11
+; LVGL via build flags (LV_CONF_SKIP -> defaults + overrides); no lv_conf.h.
+; Keep flag values free of shell-special chars (parens/spaces). Tick via
+; lv_tick_inc() in loop() (no LV_TICK_CUSTOM, which needs a parenthesised expr).
+build_flags =
+    -DLV_CONF_SKIP=1
+    -DLV_COLOR_DEPTH=16
+    -DLV_COLOR_16_SWAP=1
+    -DLV_MEM_SIZE=49152
+    -DLV_FONT_MONTSERRAT_14=1
+    -DLV_FONT_MONTSERRAT_20=1
+    -DLV_FONT_MONTSERRAT_28=1
+    -DLV_FONT_MONTSERRAT_48=1
+    -DLV_USE_LOG=0
--- a/src/broadcaster.cpp
+++ b/src/broadcaster.cpp
@ -0,0 +1,469 @@
+/**
+ * Resound — Boards B & C : I2S SLAVE -> [FIFO delay] -> A2DP SOURCE
+ *
+ * Reads PCM from the shared I2S bus (clocked by Board A) into a FIFO, and an
+ * A2DP source drains the FIFO to one Bluetooth speaker. The FIFO sits a fixed
+ * jitter cushion (BASE_DELAY_MS) plus an adjustable trim behind the I2S write
+ * head; the trim (0..MAX_DELAY_MS) is set live BY EAR with two capacitive-touch
+ * pads to align this speaker against the other one, and is saved to flash.
+ *
+ * No Wi-Fi: Wi-Fi + Bluetooth + buffer don't fit in RAM on the classic ESP32.
+ *
+ * Per-env build flag: TARGET_SPEAKER ("JBL Charge 5" / "Tangerine EDGE").
+ *
+ * Wiring:
+ *   I2S in (from Board A): BCK=GPIO19  WS=GPIO18  DATA=GPIO22  + GND
+ *   Touch "+" : GPIO4 (T0)    Touch "-" : GPIO27 (T7)   (attach a wire/pad)
+ */
+
+#include <Arduino.h>
+#include <string.h>
+
+#include "AudioTools.h"
+#include "BluetoothA2DPSource.h"
+#include <Preferences.h>
+#include <Wire.h>
+
+#include "bus_proto.h"
+
+#ifndef TARGET_SPEAKER
+#define TARGET_SPEAKER "Resound-Speaker"
+#endif
+
+// I2C slave address (which speaker this board controls). Set per-env via build
+// flag; default to the JBL address if unspecified.
+#ifndef HUB_I2C_ADDR
+#define HUB_I2C_ADDR HUB_I2C_ADDR_JBL
+#endif
+
+#define I2C_SDA_PIN     32
+#define I2C_SCL_PIN     33
+
+#define I2S_BCK_PIN     19
+#define I2S_WS_PIN      18
+#define I2S_DATA_PIN    22
+
+#define TOUCH_PLUS      T0      // GPIO4
+#define TOUCH_MINUS     T7      // GPIO27
+#define TOUCH_THRESH    40      // touchRead below this = touched
+
+#define SR_HZ           44100
+#define BASE_DELAY_MS   40      // fixed jitter cushion (applied to both speakers)
+#define MAX_DELAY_MS    200     // adjustable trim on top of the cushion
+#define DELAY_STEP_MS   5
+#define TOUCH_REPEAT_MS 150
+#define RING_MS         (BASE_DELAY_MS + MAX_DELAY_MS + 40)   // + headroom
+#define RING_FRAMES     ((uint32_t)SR_HZ * RING_MS / 1000)
+#define BASE_FRAMES     ((uint32_t)SR_HZ * BASE_DELAY_MS / 1000)
+
+I2SStream           i2s;
+BluetoothA2DPSource source;
+Preferences         prefs;
+
+// FIFO of interleaved L,R int16. Producer = i2s_task, consumer = A2DP callback.
+static int16_t           ring[RING_FRAMES * 2];
+static volatile uint32_t write_frames = 0;     // producer position (monotonic)
+static volatile uint32_t read_frames  = 0;     // consumer position (monotonic)
+static volatile uint32_t trim_frames  = 0;     // adjustable delay (frames)
+static volatile bool     primed       = false; // FIFO has reached target fill
+static volatile uint16_t delay_ms_current = 0;
+static bool              save_pending = false;
+static unsigned long     last_change_ms = 0;
+
+// Current playback volume (0..100). Mirrored into status_buf for the hub.
+static uint8_t           current_volume = 100;
+static bool              vol_save_pending = false;
+
+// --- I2C slave control bus (hub = master) -------------------------------
+// Callbacks run in ISR/Wire context: they must be LIGHT — no Serial, NVS, or
+// blocking calls. They only stash requests into volatile globals; loop() acts.
+static volatile bool     have_delay   = false;
+static volatile uint16_t pending_delay = 0;
+static volatile bool     have_volume  = false;
+static volatile uint8_t  pending_volume = 0;
+
+// Status snapshot served on HUB_CMD_GET_STATUS reads; refreshed by loop().
+//   [0]=connected [1]=delay lo [2]=delay hi [3]=volume
+//   [4]=scanning  [5]=scan_count [6]=has_device              (Phase 3)
+static volatile uint8_t  status_buf[HUB_STATUS_LEN] = {0, 0, 0, 100, 0, 0, 0};
+
+// --- Phase 3: BT speaker discovery / selection --------------------------
+// A discovered device collected during an inquiry scan.
+struct ScanDev {
+    char    name[HUB_NAME_MAX + 1];
+    uint8_t mac[6];
+    int8_t  rssi;
+};
+static ScanDev           scan_list[HUB_MAX_SCAN];
+static volatile uint8_t  scan_count = 0;
+static volatile bool     scanning   = false;
+
+// Currently selected / saved speaker.
+static char              cur_name[HUB_NAME_MAX + 1] = {0};
+static uint8_t           cur_mac[6] = {0};
+static bool              has_device = false;
+
+// I2C request flags set by the Wire callbacks, applied in loop().
+static volatile bool     req_scan_start = false;
+static volatile bool     req_scan_stop  = false;
+static volatile bool     req_select     = false;
+static volatile uint8_t  pending_select = 0;
+static volatile bool     req_forget     = false;
+
+// Which read buffer the next onRequest should serve. The master sets it by
+// writing the read command byte just before issuing the read. Multiplexed in
+// on_i2c_request() so GET_STATUS / GET_SCANITEM / GET_CURNAME can share the bus.
+static volatile uint8_t  last_read_cmd = HUB_CMD_GET_STATUS;
+static volatile uint8_t  pending_scanitem = 0;   // index requested via GET_SCANITEM
+// Pre-filled in the callback (light memcpy) and handed back on the read.
+static volatile uint8_t  scanitem_buf[HUB_SCANITEM_LEN] = {0};
+
+// Per-device callback fired during a scan (plain C fn ptr — no captures).
+// Stash discovered audio sinks into scan_list; never connect (return false).
+static bool on_ssid(const char *ssid, esp_bd_addr_t addr, int rssi) {
+    if (!scanning) return false;
+    if (scan_count >= HUB_MAX_SCAN) return false;
+    // Dedupe by MAC.
+    for (uint8_t i = 0; i < scan_count; i++) {
+        if (memcmp(scan_list[i].mac, addr, 6) == 0) return false;
+    }
+    ScanDev &d = scan_list[scan_count];
+    if (ssid) {
+        strncpy(d.name, ssid, HUB_NAME_MAX);
+        d.name[HUB_NAME_MAX] = 0;
+    } else {
+        d.name[0] = 0;
+    }
+    memcpy(d.mac, addr, 6);
+    if (rssi >  127) rssi =  127;
+    if (rssi < -128) rssi = -128;
+    d.rssi = (int8_t)rssi;
+    scan_count++;
+    return false;   // keep scanning; collect everything
+}
+
+// Discovery state changes. The library auto-restarts discovery after STOPPED if
+// nothing matched, so explicitly cancel to halt the loop.
+static void on_disc_state(esp_bt_gap_discovery_state_t state) {
+    if (state == ESP_BT_GAP_DISCOVERY_STOPPED) {
+        scanning = false;
+        source.cancel_discovery();
+    }
+}
+
+// Master wrote [cmd][args...]; parse into request flags only.
+static void on_i2c_receive(int n) {
+    if (n < 1) return;
+    uint8_t cmd = Wire.read();
+    last_read_cmd = cmd;        // remember for the following onRequest (if any)
+    switch (cmd) {
+        case HUB_CMD_SET_DELAY:
+            if (Wire.available() >= 2) {
+                uint8_t lo = Wire.read();
+                uint8_t hi = Wire.read();
+                pending_delay = (uint16_t)lo | ((uint16_t)hi << 8);
+                have_delay = true;
+            }
+            break;
+        case HUB_CMD_SET_VOLUME:
+            if (Wire.available() >= 1) {
+                pending_volume = Wire.read();
+                have_volume = true;
+            }
+            break;
+        case HUB_CMD_SCAN_START:
+            req_scan_start = true;
+            break;
+        case HUB_CMD_SCAN_STOP:
+            req_scan_stop = true;
+            break;
+        case HUB_CMD_SELECT:
+            if (Wire.available() >= 1) {
+                pending_select = Wire.read();
+                req_select = true;
+            }
+            break;
+        case HUB_CMD_FORGET:
+            req_forget = true;
+            break;
+        case HUB_CMD_GET_SCANITEM: {
+            // Prep scanitem_buf NOW from the list (light memcpy is OK here).
+            uint8_t idx = Wire.available() >= 1 ? Wire.read() : 0xFF;
+            pending_scanitem = idx;
+            uint8_t *b = (uint8_t *)scanitem_buf;
+            memset(b, 0, HUB_SCANITEM_LEN);
+            if (idx < scan_count) {
+                ScanDev &d = scan_list[idx];
+                b[0] = 1;                          // valid
+                b[1] = (uint8_t)d.rssi;            // rssi (int8)
+                memcpy(&b[2], d.mac, 6);           // MAC
+                uint8_t nl = (uint8_t)strnlen(d.name, HUB_NAME_MAX);
+                b[8] = nl;                         // name length
+                memcpy(&b[9], d.name, nl);         // name bytes
+            }
+            break;
+        }
+        case HUB_CMD_GET_CURNAME:
+            // Nothing to do: onRequest serves cur_name (NUL-padded).
+            break;
+        case HUB_CMD_GET_STATUS:
+            // Nothing to do: onRequest serves the pre-filled status_buf.
+            break;
+        default:
+            break;
+    }
+    while (Wire.available()) Wire.read();   // drain any extra bytes
+}
+
+// Master issued a read; pick the buffer keyed by the last command byte.
+static void on_i2c_request() {
+    if (last_read_cmd == HUB_CMD_GET_SCANITEM) {
+        Wire.write((uint8_t *)scanitem_buf, HUB_SCANITEM_LEN);
+    } else if (last_read_cmd == HUB_CMD_GET_CURNAME) {
+        uint8_t nbuf[HUB_NAME_MAX];
+        uint8_t nl = (uint8_t)strnlen(cur_name, HUB_NAME_MAX);
+        memcpy(nbuf, cur_name, nl);
+        if (nl < HUB_NAME_MAX) memset(nbuf + nl, 0, HUB_NAME_MAX - nl);
+        Wire.write(nbuf, HUB_NAME_MAX);
+    } else {
+        Wire.write((uint8_t *)status_buf, HUB_STATUS_LEN);
+    }
+}
+
+// Continuously pull I2S into the FIFO (paced by Board A's master clock).
+// Carry any partial frame across reads so L/R never slips out of alignment.
+static void i2s_task(void *arg) {
+    static uint8_t buf[1024];
+    static int     rem = 0;
+    for (;;) {
+        size_t got = i2s.readBytes(buf + rem, sizeof(buf) - rem);
+        int    total  = rem + (int)got;
+        int    frames = total / 4;
+        int16_t *s = (int16_t *)buf;
+        for (int i = 0; i < frames; i++) {
+            uint32_t w = write_frames % RING_FRAMES;
+            ring[w * 2]     = s[i * 2];
+            ring[w * 2 + 1] = s[i * 2 + 1];
+            write_frames++;
+        }
+        rem = total - frames * 4;
+        if (rem > 0) memmove(buf, buf + frames * 4, rem);
+        if (got == 0) vTaskDelay(1);   // no clock yet (Board A down) — don't spin
+    }
+}
+
+// A2DP drains the FIFO sequentially, kept (BASE_FRAMES + trim) behind the write head.
+int32_t read_delayed(Frame *data, int32_t fc) {
+    uint32_t w      = write_frames;
+    uint32_t target = BASE_FRAMES + trim_frames;     // desired gap behind write head
+
+    if (!primed) {
+        if (w < target + (uint32_t)fc) {             // not buffered enough yet -> silence
+            for (int32_t i = 0; i < fc; i++) { data[i].channel1 = 0; data[i].channel2 = 0; }
+            return fc;
+        }
+        read_frames = w - target;
+        primed = true;
+    }
+
+    uint32_t avail = w - read_frames;                // frames available to read
+    if (avail > RING_FRAMES) {                        // producer lapped us (big drift) -> resync
+        read_frames = (w > target) ? (w - target) : 0;
+        avail = w - read_frames;
+    }
+
+    int32_t n = ((uint32_t)fc <= avail) ? fc : (int32_t)avail;
+    for (int32_t i = 0; i < n; i++) {
+        uint32_t idx = (read_frames + i) % RING_FRAMES;
+        data[i].channel1 = ring[idx * 2];
+        data[i].channel2 = ring[idx * 2 + 1];
+    }
+    read_frames += n;
+    for (int32_t i = n; i < fc; i++) { data[i].channel1 = 0; data[i].channel2 = 0; }  // pad underrun
+    return fc;
+}
+
+static void set_delay(int ms) {
+    if (ms < 0) ms = 0;
+    if (ms > MAX_DELAY_MS) ms = MAX_DELAY_MS;
+    if ((uint16_t)ms == delay_ms_current) return;
+    delay_ms_current = (uint16_t)ms;
+    trim_frames      = ((uint32_t)ms * SR_HZ) / 1000;
+    primed           = false;                 // re-establish the FIFO gap at the new delay
+    save_pending     = true;
+    last_change_ms   = millis();
+    Serial.printf("[SRC %s] delay = %d ms\n", TARGET_SPEAKER, ms);
+}
+
+void on_conn_state(esp_a2d_connection_state_t state, void *obj) {
+    if (state == ESP_A2D_CONNECTION_STATE_CONNECTED)
+        Serial.printf("[SRC %s] CONNECTED\n", TARGET_SPEAKER);
+    else if (state == ESP_A2D_CONNECTION_STATE_DISCONNECTED)
+        Serial.printf("[SRC %s] disconnected — will retry\n", TARGET_SPEAKER);
+}
+
+void setup() {
+    Serial.begin(115200);
+    delay(500);
+    Serial.printf("=== Resound Source -> '%s' (FIFO delay, %ums cushion) ===\n",
+                  TARGET_SPEAKER, BASE_DELAY_MS);
+
+    prefs.begin("bikeaudio", false);
+    set_delay(prefs.getUShort("delay_ms", 0));
+    save_pending = false;
+    current_volume = (uint8_t)prefs.getUShort("vol", 100);
+    if (current_volume > 100) current_volume = 100;
+
+    // I2C control bus: slave at HUB_I2C_ADDR on SDA=32 / SCL=33.
+    Wire.begin((uint8_t)HUB_I2C_ADDR, I2C_SDA_PIN, I2C_SCL_PIN, 100000);
+    Wire.onReceive(on_i2c_receive);
+    Wire.onRequest(on_i2c_request);
+    Serial.printf("[SRC %s] I2C slave @ 0x%02X (SDA=%d SCL=%d), vol=%u\n",
+                  TARGET_SPEAKER, (unsigned)HUB_I2C_ADDR, I2C_SDA_PIN, I2C_SCL_PIN,
+                  current_volume);
+
+    auto cfg = i2s.defaultConfig(RX_MODE);
+    cfg.pin_bck = I2S_BCK_PIN; cfg.pin_ws = I2S_WS_PIN; cfg.pin_data = I2S_DATA_PIN;
+    cfg.sample_rate = SR_HZ; cfg.channels = 2; cfg.bits_per_sample = 16;
+    cfg.is_master = false; cfg.buffer_count = 8; cfg.buffer_size = 512;
+    i2s.begin(cfg);
+
+    xTaskCreatePinnedToCore(i2s_task, "i2s_reader", 4096, nullptr, 5, nullptr, 0);
+
+    source.set_data_callback_in_frames(read_delayed);
+    source.set_on_connection_state_changed(on_conn_state);
+    source.set_volume(current_volume);
+
+    // Load any saved/selected speaker (Phase 3). "spk_mac" is a 6-byte blob.
+    uint8_t savedMac[6];
+    size_t  got = prefs.getBytes("spk_mac", savedMac, 6);
+    if (got == 6) {
+        memcpy(cur_mac, savedMac, 6);
+        String sn = prefs.getString("spk_name", "");
+        strncpy(cur_name, sn.c_str(), HUB_NAME_MAX);
+        cur_name[HUB_NAME_MAX] = 0;
+        has_device = true;
+        source.set_auto_reconnect(cur_mac);   // remember + auto-reconnect to it
+        source.start();
+        Serial.printf("[SRC] Reconnecting to saved '%s' (%02X:%02X:%02X:%02X:%02X:%02X) — trim %u ms\n",
+                      cur_name, cur_mac[0], cur_mac[1], cur_mac[2],
+                      cur_mac[3], cur_mac[4], cur_mac[5], delay_ms_current);
+    } else {
+        // No saved device — fall back to the hardcoded target by name.
+        has_device = false;
+        cur_name[0] = 0;
+        source.set_auto_reconnect(true, 5);
+        source.start(TARGET_SPEAKER);
+        Serial.printf("[SRC] Connecting to fallback '%s' — trim %u ms; touch + GPIO4, - GPIO27\n",
+                      TARGET_SPEAKER, delay_ms_current);
+    }
+}
+
+void loop() {
+    unsigned long now = millis();
+
+    // Apply I2C requests stashed by the Wire callbacks (heavy work runs here).
+    if (have_delay) {
+        have_delay = false;
+        set_delay((int)pending_delay);
+    }
+    if (have_volume) {
+        have_volume = false;
+        uint8_t v = pending_volume;
+        if (v > 100) v = 100;
+        if (v != current_volume) {
+            current_volume = v;
+            source.set_volume(current_volume);
+            vol_save_pending = true;
+            last_change_ms   = now;
+            Serial.printf("[SRC %s] volume = %u\n", TARGET_SPEAKER, current_volume);
+        }
+    }
+
+    // --- Phase 3: apply discovery / selection requests (heavy work here) ---
+    if (req_scan_start) {
+        req_scan_start = false;
+        scan_count = 0;
+        memset(scan_list, 0, sizeof(scan_list));
+        scanning = true;
+        source.disconnect();
+        source.set_auto_reconnect(false);          // force a fresh discovery
+        source.set_ssid_callback(on_ssid);
+        source.set_discovery_mode_callback(on_disc_state);
+        source.start();                            // begin inquiry scan
+        Serial.printf("[SRC %s] scan started\n", TARGET_SPEAKER);
+    }
+    if (req_scan_stop) {
+        req_scan_stop = false;
+        source.cancel_discovery();
+        scanning = false;
+        Serial.printf("[SRC %s] scan stopped (%u found)\n", TARGET_SPEAKER, scan_count);
+    }
+    if (req_select) {
+        req_select = false;
+        uint8_t idx = pending_select;
+        if (idx < scan_count) {
+            source.cancel_discovery();
+            scanning = false;
+            memcpy(cur_mac, scan_list[idx].mac, 6);
+            strncpy(cur_name, scan_list[idx].name, HUB_NAME_MAX);
+            cur_name[HUB_NAME_MAX] = 0;
+            source.connect_to(cur_mac);
+            source.set_auto_reconnect(cur_mac);
+            prefs.putBytes("spk_mac", cur_mac, 6);
+            prefs.putString("spk_name", cur_name);
+            has_device = true;
+            Serial.printf("[SRC %s] selected '%s' (%02X:%02X:%02X:%02X:%02X:%02X)\n",
+                          TARGET_SPEAKER, cur_name, cur_mac[0], cur_mac[1], cur_mac[2],
+                          cur_mac[3], cur_mac[4], cur_mac[5]);
+        }
+    }
+    if (req_forget) {
+        req_forget = false;
+        source.disconnect();
+        prefs.remove("spk_mac");
+        prefs.remove("spk_name");
+        has_device = false;
+        cur_name[0] = 0;
+        memset(cur_mac, 0, 6);
+        Serial.printf("[SRC %s] forgot saved device\n", TARGET_SPEAKER);
+    }
+
+    // Refresh the status snapshot served on GET_STATUS reads.
+    status_buf[0] = source.is_connected() ? 1 : 0;
+    status_buf[1] = (uint8_t)(delay_ms_current & 0xFF);
+    status_buf[2] = (uint8_t)(delay_ms_current >> 8);
+    status_buf[3] = current_volume;
+    status_buf[4] = scanning ? 1 : 0;
+    status_buf[5] = scan_count;
+    status_buf[6] = has_device ? 1 : 0;
+
+    static unsigned long last_touch = 0;
+    if (now - last_touch >= TOUCH_REPEAT_MS) {
+        bool plus  = touchRead(TOUCH_PLUS)  < TOUCH_THRESH;
+        bool minus = touchRead(TOUCH_MINUS) < TOUCH_THRESH;
+        if (plus && !minus)      { set_delay(delay_ms_current + DELAY_STEP_MS); last_touch = now; }
+        else if (minus && !plus) { set_delay(delay_ms_current - DELAY_STEP_MS); last_touch = now; }
+    }
+
+    if (save_pending && now - last_change_ms > 1500) {
+        prefs.putUShort("delay_ms", delay_ms_current);
+        save_pending = false;
+        Serial.printf("[SRC %s] saved %u ms to flash\n", TARGET_SPEAKER, delay_ms_current);
+    }
+
+    if (vol_save_pending && now - last_change_ms > 1500) {
+        prefs.putUShort("vol", current_volume);
+        vol_save_pending = false;
+        Serial.printf("[SRC %s] saved vol %u to flash\n", TARGET_SPEAKER, current_volume);
+    }
+
+    static unsigned long last_st = 0;
+    if (now - last_st > 5000) {
+        Serial.printf("[SRC %s] connected=%s trim=%ums fill=%u heap=%u\n",
+                      TARGET_SPEAKER, source.is_connected() ? "YES" : "no", delay_ms_current,
+                      (unsigned)(write_frames - read_frames), ESP.getFreeHeap());
+        last_st = now;
+    }
+    delay(20);
+}
--- a/src/bus_proto.h
+++ b/src/bus_proto.h
@ -0,0 +1,53 @@
+/**
+ * Resound — control-bus protocol shared by the S3 hub (I2C master) and the
+ * source Boards B/C (I2C slaves). Included by both hub_s3.cpp and board_source.cpp.
+ *
+ * Bus: I2C. Hub = master. Each source board = a slave at a fixed address.
+ *   S3:  SDA=GPIO15  SCL=GPIO16   (board expansion header)
+ *   B/C: SDA=GPIO32  SCL=GPIO33   (free pins; I2S=19/18/22, touch=4/27)
+ *   Shared GND + two ~4.7k pull-ups (SDA->3V3, SCL->3V3).
+ */
+#pragma once
+#include <stdint.h>
+
+#define HUB_I2C_ADDR_JBL    0x10
+#define HUB_I2C_ADDR_CARDO  0x11
+#define HUB_I2C_ADDR_GUEST  0x12   // antenna board: source for an occasional guest speaker
+
+// Master -> slave WRITE: first byte = command, then args (little-endian).
+#define HUB_CMD_SET_DELAY   0x01   // arg: uint16 delay_ms (0..HUB_MAX_DELAY_MS)
+#define HUB_CMD_SET_VOLUME  0x02   // arg: uint8  volume (0..100)
+#define HUB_CMD_GET_STATUS  0x10   // master then issues a READ of HUB_STATUS_LEN bytes
+
+#define HUB_MAX_DELAY_MS    200
+
+// Slave -> master status payload (returned on the read after HUB_CMD_GET_STATUS):
+//   [0] connected (0/1)
+//   [1] delay_ms low byte
+//   [2] delay_ms high byte
+//   [3] volume (0..100)
+//   [4] scanning (0/1)         (Phase 3)
+//   [5] scan device count      (Phase 3)
+//   [6] has a saved/selected device (0/1)   (Phase 3)
+#define HUB_STATUS_LEN      7
+
+// --- Phase 3: speaker discovery / selection -------------------------------
+// The source board runs a BT inquiry scan (audio pauses during a scan),
+// collects nearby audio sinks (name+MAC), and connects to a chosen one.
+#define HUB_CMD_SCAN_START   0x03  // write: clear list + begin a fresh discovery scan
+#define HUB_CMD_SCAN_STOP    0x04  // write: cancel scanning
+#define HUB_CMD_SELECT       0x05  // write [uint8 index]: connect to scan item + persist (NVS)
+#define HUB_CMD_FORGET       0x06  // write: forget saved device (disconnect + erase)
+#define HUB_CMD_GET_SCANITEM 0x14  // write [uint8 index]; THEN read HUB_SCANITEM_LEN bytes
+#define HUB_CMD_GET_CURNAME  0x15  // read HUB_NAME_MAX bytes: current/selected device name (NUL-padded)
+
+#define HUB_MAX_SCAN         12     // max devices reported
+#define HUB_NAME_MAX         24     // max device-name length carried over the bus
+
+// Scan-item payload (fixed length), returned on the read after GET_SCANITEM[index]:
+//   [0] valid (0/1 — 0 if index >= count)
+//   [1] rssi (int8)
+//   [2..7] MAC (6 bytes)
+//   [8] name length (<= HUB_NAME_MAX)
+//   [9 ..] name bytes
+#define HUB_SCANITEM_LEN    (9 + HUB_NAME_MAX)   // 33
--- a/src/hud.cpp
+++ b/src/hud.cpp
@ -0,0 +1,929 @@
+/**
+ * Resound — Hub (ESP32-S3-Touch-LCD-1.28) : PHASE 3 discovery + control
+ *
+ * Round GC9A01 LCD + CST816S touch, wired as an I2C MASTER to the source
+ * boards. Three brand-agnostic channels are controlled (discovery picks the
+ * actual device per channel):
+ *   index 0 "Headset"   @ 0x11
+ *   index 1 "Speaker 1" @ 0x10
+ *   index 2 "Guest"     @ 0x12  (occasional; usually offline)
+ * The UI is built with LVGL 8.3 (rendered THROUGH the LovyanGFX `lcd` device),
+ * tuned to be glanceable on a 240x240 ROUND screen for use on a motorcycle
+ * handlebar: big high-contrast type, large tap targets, bold connection colours.
+ *
+ * Screens (separate lv_obj_create(NULL) screens, switched with lv_scr_load):
+ *   HOME     : big master-volume arc (drag -> set ALL channels), three labeled
+ *              connection dots (Headset / Speaker 1 / Guest) at top, "SPEAKERS"
+ *              button at the bottom.
+ *   SPEAKERS : three buttons (Headset / Speaker 1 / Guest) showing connect state
+ *              + current device name; tap -> that channel's DETAIL.  BACK -> HOME.
+ *   DETAIL   : per-speaker. Volume arc (this speaker), Delay -/+ control,
+ *              SCAN button, BACK -> SPEAKERS.
+ *   SCAN     : starts a scan on entry; spinner while scanning; an lv_list of
+ *              discovered devices (name + rssi). Tap a row -> SELECT + DETAIL.
+ *              RESCAN re-issues the scan; BACK cancels + returns to DETAIL.
+ *
+ * Two I2C buses are in use, on separate ports:
+ *   - port 0 (Wire1's underlying peripheral via LovyanGFX): CST816S touch SDA=6 SCL=7
+ *   - "Wire1" (this code, I2C master): source boards  SDA=15 SCL=16
+ *
+ * Board pins (Waveshare ESP32-S3-Touch-LCD-1.28):
+ *   GC9A01 SPI: SCLK=10 MOSI=11 MISO=12 CS=9 DC=8 RST=14   backlight=2
+ *   CST816S touch (I2C): SDA=6 SCL=7  (polled; INT left unused)
+ *   Control bus (I2C master): SDA=15 SCL=16
+ *
+ * Build: pio run -e hub_s3   |   flash: esp32s3, bootloader@0x0
+ */
+
+#define LGFX_USE_V1
+#include <Arduino.h>
+#include <Wire.h>
+#include <string.h>
+#include <LovyanGFX.hpp>
+#include <lvgl.h>
+#include "bus_proto.h"
+
+class LGFX : public lgfx::LGFX_Device {
+    lgfx::Panel_GC9A01    _panel;
+    lgfx::Bus_SPI         _bus;
+    lgfx::Light_PWM       _light;
+    lgfx::Touch_CST816S   _touch;
+public:
+    LGFX() {
+        { auto c = _bus.config();
+          c.spi_host   = SPI2_HOST;
+          c.spi_mode   = 0;
+          c.freq_write = 40000000;
+          c.pin_sclk   = 10;
+          c.pin_mosi   = 11;
+          c.pin_miso   = 12;
+          c.pin_dc     = 8;
+          _bus.config(c); _panel.setBus(&_bus); }
+
+        { auto c = _panel.config();
+          c.pin_cs        = 9;
+          c.pin_rst       = 14;
+          c.panel_width   = 240;
+          c.panel_height  = 240;
+          c.offset_x      = 0;
+          c.offset_y      = 0;
+          c.readable      = false;
+          c.invert        = true;     // GC9A01 typically needs inversion
+          c.rgb_order     = false;
+          _panel.config(c); }
+
+        { auto c = _light.config();
+          c.pin_bl      = 2;
+          c.freq        = 12000;
+          c.pwm_channel = 7;
+          _light.config(c); _panel.setLight(&_light); }
+
+        { auto c = _touch.config();
+          c.i2c_port = 0;
+          c.pin_sda  = 6;
+          c.pin_scl  = 7;
+          c.pin_int  = -1;            // poll over I2C (avoid INT-pin ambiguity)
+          c.pin_rst  = -1;
+          c.i2c_addr = 0x15;
+          c.freq     = 400000;
+          c.x_min = 0; c.x_max = 239; c.y_min = 0; c.y_max = 239;
+          _touch.config(c); _panel.setTouch(&_touch); }
+
+        setPanel(&_panel);
+    }
+};
+
+LGFX lcd;
+
+// ---------------------------------------------------------------------------
+// Control-bus (I2C master) config
+// ---------------------------------------------------------------------------
+#define CTRL_I2C_SDA   15
+#define CTRL_I2C_SCL   16
+#define CTRL_I2C_HZ    100000
+
+#define DELAY_STEP     5     // ms per delay +/- press
+#define POLL_PERIOD_MS 1000  // status poll cadence per speaker
+
+// Per-speaker model. delay_ms/volume are the values we display & command;
+// "connected" is reported by the board, "online" is whether the I2C
+// transaction itself succeeded (board present on the bus at all).
+struct Speaker {
+    uint8_t     addr;
+    const char *name;       // role label (Headset / Speaker 1 / Guest), not the BT device name
+    bool        online;     // I2C transaction succeeded this poll
+    bool        connected;  // board says its BT sink is connected
+    uint16_t    delay_ms;
+    uint8_t     volume;
+    // Phase 3 discovery state (from the 7-byte status payload).
+    bool        scanning;   // board is currently running a BT inquiry scan
+    uint8_t     scan_count; // devices found so far in the current scan
+    bool        has_device; // a device is saved/selected on the board
+    char        cur_name[HUB_NAME_MAX + 1]; // selected BT device name (NUL-term)
+};
+
+#define NUM_SPK 3
+
+static Speaker speakers[NUM_SPK] = {
+    // Brand-agnostic channels; discovery picks the actual device per channel.
+    { HUB_I2C_ADDR_CARDO, "Headset",   false, false, 0, 0, false, 0, false, {0} },
+    { HUB_I2C_ADDR_JBL,   "Speaker 1", false, false, 0, 0, false, 0, false, {0} },
+    { HUB_I2C_ADDR_GUEST, "Guest",     false, false, 0, 0, false, 0, false, {0} },
+};
+
+// A discovered scan item, mirrored from the board over GET_SCANITEM.
+struct ScanItem {
+    uint8_t index;                  // index on the board (passed back in SELECT)
+    int8_t  rssi;
+    uint8_t mac[6];
+    char    name[HUB_NAME_MAX + 1]; // NUL-terminated
+};
+
+// Local mirror of the current scan list (for the speaker being configured).
+static ScanItem scanItems[HUB_MAX_SCAN];
+static int      scanItemCount = 0;
+
+// Which speaker DETAIL / SCAN is operating on (0..NUM_SPK-1).
+static int      activeSpeaker = 0;
+
+// ===========================================================================
+// I2C helpers (DATA LAYER — unchanged transactions, all on Wire1)
+// ===========================================================================
+
+// Poll one speaker for status. Updates s.online/connected/delay_ms/volume.
+// On any bus failure the speaker is marked offline.
+// NOTE: the control bus uses Wire1 (I2C peripheral 1). Peripheral 0 is already
+// owned by the LovyanGFX CST816S touch (GPIO6/7), so we must not touch it here.
+static void pollStatus(Speaker &s) {
+    Wire1.beginTransmission(s.addr);
+    Wire1.write(HUB_CMD_GET_STATUS);
+    if (Wire1.endTransmission(true) != 0) {
+        s.online = false;
+        return;
+    }
+    int n = Wire1.requestFrom((int)s.addr, (int)HUB_STATUS_LEN);
+    if (n < HUB_STATUS_LEN) {
+        s.online = false;
+        return;
+    }
+    uint8_t b[HUB_STATUS_LEN];
+    for (int i = 0; i < HUB_STATUS_LEN; i++) b[i] = Wire1.read();
+    s.online     = true;
+    s.connected  = (b[0] != 0);
+    s.delay_ms   = (uint16_t)(b[1] | (b[2] << 8));
+    s.volume     = b[3];
+    s.scanning   = (b[4] != 0);
+    s.scan_count = b[5];
+    s.has_device = (b[6] != 0);
+}
+
+// Fetch the board's current/selected device name into out (HUB_NAME_MAX+1).
+// On failure out is left empty. The name comes back NUL-padded.
+static void getCurName(Speaker &s, char *out) {
+    out[0] = '\0';
+    Wire1.beginTransmission(s.addr);
+    Wire1.write(HUB_CMD_GET_CURNAME);
+    if (Wire1.endTransmission(true) != 0) return;
+    int n = Wire1.requestFrom((int)s.addr, (int)HUB_NAME_MAX);
+    if (n < HUB_NAME_MAX) {
+        while (Wire1.available()) Wire1.read();
+        return;
+    }
+    for (int i = 0; i < HUB_NAME_MAX; i++) {
+        out[i] = (char)Wire1.read();
+    }
+    out[HUB_NAME_MAX] = '\0';
+}
+
+// Begin a fresh discovery scan on speaker s.
+static void startScan(Speaker &s) {
+    Wire1.beginTransmission(s.addr);
+    Wire1.write(HUB_CMD_SCAN_START);
+    Wire1.endTransmission(true);
+}
+
+// Cancel an in-progress scan on speaker s.
+static void sendScanStop(Speaker &s) {
+    Wire1.beginTransmission(s.addr);
+    Wire1.write(HUB_CMD_SCAN_STOP);
+    Wire1.endTransmission(true);
+}
+
+// Select scan item `index` on speaker s (connect + persist on the board).
+static void sendSelect(Speaker &s, uint8_t index) {
+    Wire1.beginTransmission(s.addr);
+    Wire1.write(HUB_CMD_SELECT);
+    Wire1.write(index);
+    Wire1.endTransmission(true);
+}
+
+// Read scan item `index` from speaker s into `out`. Returns true if valid.
+static bool getScanItem(Speaker &s, uint8_t index, ScanItem &out) {
+    Wire1.beginTransmission(s.addr);
+    Wire1.write(HUB_CMD_GET_SCANITEM);
+    Wire1.write(index);
+    if (Wire1.endTransmission(true) != 0) return false;
+    int n = Wire1.requestFrom((int)s.addr, (int)HUB_SCANITEM_LEN);
+    if (n < HUB_SCANITEM_LEN) {
+        while (Wire1.available()) Wire1.read();
+        return false;
+    }
+    uint8_t valid = Wire1.read();
+    int8_t  rssi  = (int8_t)Wire1.read();
+    uint8_t mac[6];
+    for (int i = 0; i < 6; i++) mac[i] = Wire1.read();
+    uint8_t namelen = Wire1.read();
+    if (namelen > HUB_NAME_MAX) namelen = HUB_NAME_MAX;
+    char name[HUB_NAME_MAX + 1];
+    for (int i = 0; i < HUB_NAME_MAX; i++) {
+        char c = (char)Wire1.read();
+        if (i < namelen) name[i] = c;
+    }
+    name[namelen] = '\0';
+    if (!valid) return false;
+    out.index = index;
+    out.rssi  = rssi;
+    memcpy(out.mac, mac, 6);
+    strncpy(out.name, name, sizeof(out.name));
+    out.name[HUB_NAME_MAX] = '\0';
+    return true;
+}
+
+// Refresh the local scan-list mirror for speaker `i` from the board. Reads up
+// to scan_count items (capped to HUB_MAX_SCAN) and stores the valid ones,
+// sorted strongest-RSSI first so the cap keeps the best candidates.
+static void pollScanList(int i) {
+    Speaker &s = speakers[i];
+    int want = s.scan_count;
+    if (want > HUB_MAX_SCAN) want = HUB_MAX_SCAN;
+    int got = 0;
+    for (int idx = 0; idx < want && got < HUB_MAX_SCAN; idx++) {
+        ScanItem it;
+        if (getScanItem(s, (uint8_t)idx, it)) {
+            scanItems[got++] = it;
+        }
+    }
+    // Strongest RSSI first (simple insertion sort; list is tiny).
+    for (int a = 1; a < got; a++) {
+        ScanItem key = scanItems[a];
+        int b = a - 1;
+        while (b >= 0 && scanItems[b].rssi < key.rssi) {
+            scanItems[b + 1] = scanItems[b];
+            b--;
+        }
+        scanItems[b + 1] = key;
+    }
+    scanItemCount = got;
+}
+
+// Command a new delay (ms) to a speaker.
+static void sendDelay(const Speaker &s, uint16_t ms) {
+    Wire1.beginTransmission(s.addr);
+    Wire1.write(HUB_CMD_SET_DELAY);
+    Wire1.write(ms & 0xFF);
+    Wire1.write((ms >> 8) & 0xFF);
+    Wire1.endTransmission();
+}
+
+// Command a new volume (0..100) to a speaker.
+static void sendVolume(const Speaker &s, uint8_t vol) {
+    Wire1.beginTransmission(s.addr);
+    Wire1.write(HUB_CMD_SET_VOLUME);
+    Wire1.write(vol);
+    Wire1.endTransmission();
+}
+
+// ===========================================================================
+// LVGL <-> LovyanGFX glue
+// ===========================================================================
+static lv_color_t lvbuf1[240 * 40];
+static lv_color_t lvbuf2[240 * 40];
+static lv_disp_draw_buf_t draw_buf;
+static lv_disp_drv_t disp_drv;
+static lv_indev_drv_t indev_drv;
+
+static void disp_flush(lv_disp_drv_t *drv, const lv_area_t *area, lv_color_t *px) {
+    uint32_t w = area->x2 - area->x1 + 1, h = area->y2 - area->y1 + 1;
+    lcd.startWrite();
+    lcd.setAddrWindow(area->x1, area->y1, w, h);
+    lcd.writePixels((uint16_t *)&px->full, w * h);
+    lcd.endWrite();
+    lv_disp_flush_ready(drv);
+}
+
+static void touch_read(lv_indev_drv_t *drv, lv_indev_data_t *data) {
+    int32_t x, y;
+    if (lcd.getTouch(&x, &y)) {
+        data->state = LV_INDEV_STATE_PR;
+        data->point.x = x;
+        data->point.y = y;
+    } else {
+        data->state = LV_INDEV_STATE_REL;
+    }
+}
+
+// ===========================================================================
+// UI palette / helpers
+// ===========================================================================
+#define COL_BG       lv_color_black()
+#define COL_GREEN    lv_color_hex(0x00D26A)   // connected
+#define COL_RED      lv_color_hex(0xE0322B)   // online but not connected
+#define COL_GREY     lv_color_hex(0x555555)   // offline
+#define COL_CYAN     lv_color_hex(0x18C0E0)
+#define COL_ACCENT   lv_color_hex(0x18C0E0)   // arc indicator
+#define COL_TRACK    lv_color_hex(0x303030)   // arc background
+#define COL_WHITE    lv_color_white()
+#define COL_BTN      lv_color_hex(0x1B2A3A)
+#define COL_BACK     lv_color_hex(0x4A1414)
+
+// Pick the connection colour for a speaker's state.
+static lv_color_t connColor(const Speaker &s) {
+    if (!s.online) return COL_GREY;
+    return s.connected ? COL_GREEN : COL_RED;
+}
+
+// ===========================================================================
+// Screen objects + the widget pointers we update from the poll timer
+// ===========================================================================
+static lv_obj_t *scrHome;
+static lv_obj_t *scrSpeakers;
+static lv_obj_t *scrDetail;
+static lv_obj_t *scrScan;
+
+// HOME widgets
+static lv_obj_t *homeArc;
+static lv_obj_t *homePctLabel;
+static lv_obj_t *homeDot[NUM_SPK];   // per-channel connection dots (Headset/Speaker 1/Guest)
+
+// SPEAKERS widgets
+static lv_obj_t *spkBtnDot[NUM_SPK];   // dot inside each speaker button
+static lv_obj_t *spkBtnLabel[NUM_SPK]; // "<role>\n<device>" text inside each button
+
+// DETAIL widgets
+static lv_obj_t *detHeading;
+static lv_obj_t *detArc;
+static lv_obj_t *detArcPct;
+static lv_obj_t *detDelayLabel;
+
+// SCAN widgets
+static lv_obj_t *scanHeading;
+static lv_obj_t *scanSpinner;
+static lv_obj_t *scanList;
+
+// Master volume tracked on the hub (drives both speakers from HOME).
+static uint8_t masterVolume = 0;
+
+// Forward declarations of builders/refreshers.
+static void buildHome();
+static void buildSpeakers();
+static void buildDetail();
+static void buildScan();
+static void refreshHome();
+static void refreshSpeakers();
+static void refreshDetail();
+static void refreshScanList();
+static void enterScan();
+
+// ===========================================================================
+// HOME screen
+// ===========================================================================
+static void home_arc_cb(lv_event_t *e) {
+    lv_obj_t *arc = lv_event_get_target(e);
+    uint8_t v = (uint8_t)lv_arc_get_value(arc);
+    masterVolume = v;
+    lv_label_set_text_fmt(homePctLabel, "%d", v);
+    // Drive ALL channels from the master arc.
+    for (int i = 0; i < NUM_SPK; i++) {
+        speakers[i].volume = v;
+        sendVolume(speakers[i], v);
+    }
+}
+
+static void home_to_speakers_cb(lv_event_t *e) {
+    refreshSpeakers();
+    lv_scr_load(scrSpeakers);
+}
+
+static void buildHome() {
+    scrHome = lv_obj_create(NULL);
+    lv_obj_set_style_bg_color(scrHome, COL_BG, 0);
+    lv_obj_clear_flag(scrHome, LV_OBJ_FLAG_SCROLLABLE);
+
+    // Big master-volume arc nearly filling the screen.
+    homeArc = lv_arc_create(scrHome);
+    lv_obj_set_size(homeArc, 220, 220);
+    lv_obj_center(homeArc);
+    lv_arc_set_rotation(homeArc, 135);
+    lv_arc_set_bg_angles(homeArc, 0, 270);
+    lv_arc_set_range(homeArc, 0, 100);
+    lv_arc_set_value(homeArc, masterVolume);
+    lv_obj_set_style_arc_width(homeArc, 16, LV_PART_MAIN);
+    lv_obj_set_style_arc_color(homeArc, COL_TRACK, LV_PART_MAIN);
+    lv_obj_set_style_arc_width(homeArc, 16, LV_PART_INDICATOR);
+    lv_obj_set_style_arc_color(homeArc, COL_ACCENT, LV_PART_INDICATOR);
+    lv_obj_set_style_bg_color(homeArc, COL_ACCENT, LV_PART_KNOB);
+    lv_obj_set_style_pad_all(homeArc, 8, LV_PART_KNOB);  // larger, glove-friendly knob
+    lv_obj_add_event_cb(homeArc, home_arc_cb, LV_EVENT_VALUE_CHANGED, NULL);
+
+    // Center: big % number + "VOLUME" caption.
+    homePctLabel = lv_label_create(scrHome);
+    lv_obj_set_style_text_font(homePctLabel, &lv_font_montserrat_48, 0);
+    lv_obj_set_style_text_color(homePctLabel, COL_WHITE, 0);
+    lv_label_set_text_fmt(homePctLabel, "%d", masterVolume);
+    lv_obj_align(homePctLabel, LV_ALIGN_CENTER, 0, -4);
+
+    lv_obj_t *cap = lv_label_create(scrHome);
+    lv_obj_set_style_text_font(cap, &lv_font_montserrat_14, 0);
+    lv_obj_set_style_text_color(cap, COL_GREY, 0);
+    lv_label_set_text(cap, "VOLUME");
+    lv_obj_align(cap, LV_ALIGN_CENTER, 0, 34);
+
+    // Top: three compact connection indicators (dot + short label), evenly
+    // spaced in a row near the top. Kept within the round screen's safe area:
+    // the labels sit at y~28-44 where the chord is wide enough for the text.
+    const char *roles[NUM_SPK] = { "Headset", "Speaker 1", "Guest" };
+    const int xoff[NUM_SPK] = { -64, 0, 64 };
+    for (int i = 0; i < NUM_SPK; i++) {
+        homeDot[i] = lv_obj_create(scrHome);
+        lv_obj_set_size(homeDot[i], 14, 14);
+        lv_obj_set_style_radius(homeDot[i], LV_RADIUS_CIRCLE, 0);
+        lv_obj_set_style_border_width(homeDot[i], 0, 0);
+        lv_obj_set_style_bg_color(homeDot[i], COL_GREY, 0);
+        lv_obj_align(homeDot[i], LV_ALIGN_TOP_MID, xoff[i], 26);
+        lv_obj_clear_flag(homeDot[i], LV_OBJ_FLAG_SCROLLABLE);
+
+        lv_obj_t *l = lv_label_create(scrHome);
+        lv_obj_set_style_text_font(l, &lv_font_montserrat_14, 0);
+        lv_obj_set_style_text_color(l, COL_WHITE, 0);
+        lv_label_set_text(l, roles[i]);
+        lv_obj_align_to(l, homeDot[i], LV_ALIGN_OUT_BOTTOM_MID, 0, 2);
+    }
+
+    // Bottom: "SPEAKERS" button.
+    lv_obj_t *btn = lv_btn_create(scrHome);
+    lv_obj_set_size(btn, 130, 46);
+    lv_obj_align(btn, LV_ALIGN_BOTTOM_MID, 0, -22);
+    lv_obj_set_style_bg_color(btn, COL_BTN, 0);
+    lv_obj_set_style_radius(btn, 12, 0);
+    lv_obj_add_event_cb(btn, home_to_speakers_cb, LV_EVENT_CLICKED, NULL);
+    lv_obj_t *bl = lv_label_create(btn);
+    lv_obj_set_style_text_font(bl, &lv_font_montserrat_20, 0);
+    lv_label_set_text(bl, "SPEAKERS");
+    lv_obj_center(bl);
+}
+
+static void refreshHome() {
+    for (int i = 0; i < NUM_SPK; i++) {
+        lv_obj_set_style_bg_color(homeDot[i], connColor(speakers[i]), 0);
+    }
+}
+
+// ===========================================================================
+// SPEAKERS screen
+// ===========================================================================
+static void speakers_back_cb(lv_event_t *e) {
+    refreshHome();
+    lv_scr_load(scrHome);
+}
+
+static void speakers_select_cb(lv_event_t *e) {
+    activeSpeaker = (int)(intptr_t)lv_event_get_user_data(e);
+    refreshDetail();
+    lv_scr_load(scrDetail);
+}
+
+static void buildSpeakers() {
+    scrSpeakers = lv_obj_create(NULL);
+    lv_obj_set_style_bg_color(scrSpeakers, COL_BG, 0);
+    lv_obj_clear_flag(scrSpeakers, LV_OBJ_FLAG_SCROLLABLE);
+
+    // Three channel buttons stacked in the center column. Heights kept >=48px
+    // (glove-friendly tap target) and widths narrowed so they stay inside the
+    // round bezel where the top/bottom buttons hit the narrower chords.
+    const char *roles[NUM_SPK] = { "Headset", "Speaker 1", "Guest" };
+    const int ypos[NUM_SPK] = { -58, 0, 58 };  // relative to vertical center
+    for (int i = 0; i < NUM_SPK; i++) {
+        lv_obj_t *btn = lv_btn_create(scrSpeakers);
+        lv_obj_set_size(btn, 168, 50);
+        lv_obj_align(btn, LV_ALIGN_CENTER, 0, ypos[i]);
+        lv_obj_set_style_bg_color(btn, COL_BTN, 0);
+        lv_obj_set_style_radius(btn, 12, 0);
+        lv_obj_set_style_pad_left(btn, 8, 0);
+        lv_obj_clear_flag(btn, LV_OBJ_FLAG_SCROLLABLE);
+        lv_obj_add_event_cb(btn, speakers_select_cb, LV_EVENT_CLICKED,
+                            (void *)(intptr_t)i);
+
+        // Connection dot inside the button (left of content area).
+        spkBtnDot[i] = lv_obj_create(btn);
+        lv_obj_set_size(spkBtnDot[i], 14, 14);
+        lv_obj_set_style_radius(spkBtnDot[i], LV_RADIUS_CIRCLE, 0);
+        lv_obj_set_style_border_width(spkBtnDot[i], 0, 0);
+        lv_obj_set_style_bg_color(spkBtnDot[i], COL_GREY, 0);
+        lv_obj_align(spkBtnDot[i], LV_ALIGN_LEFT_MID, 0, 0);
+        lv_obj_clear_flag(spkBtnDot[i], LV_OBJ_FLAG_SCROLLABLE);
+
+        // Role + device name (smaller font so two lines fit in 50px).
+        spkBtnLabel[i] = lv_label_create(btn);
+        lv_obj_set_style_text_font(spkBtnLabel[i], &lv_font_montserrat_14, 0);
+        lv_obj_set_style_text_color(spkBtnLabel[i], COL_WHITE, 0);
+        lv_label_set_text_fmt(spkBtnLabel[i], "%s", roles[i]);
+        lv_obj_align(spkBtnLabel[i], LV_ALIGN_LEFT_MID, 24, 0);
+    }
+
+    // BACK button at the bottom.
+    lv_obj_t *back = lv_btn_create(scrSpeakers);
+    lv_obj_set_size(back, 110, 44);
+    lv_obj_align(back, LV_ALIGN_BOTTOM_MID, 0, -16);
+    lv_obj_set_style_bg_color(back, COL_BACK, 0);
+    lv_obj_set_style_radius(back, 12, 0);
+    lv_obj_add_event_cb(back, speakers_back_cb, LV_EVENT_CLICKED, NULL);
+    lv_obj_t *bl = lv_label_create(back);
+    lv_obj_set_style_text_font(bl, &lv_font_montserrat_20, 0);
+    lv_label_set_text(bl, "BACK");
+    lv_obj_center(bl);
+}
+
+static void refreshSpeakers() {
+    for (int i = 0; i < NUM_SPK; i++) {
+        lv_obj_set_style_bg_color(spkBtnDot[i], connColor(speakers[i]), 0);
+        const char *dev = speakers[i].cur_name[0] ? speakers[i].cur_name
+                                                  : "(no device)";
+        lv_label_set_text_fmt(spkBtnLabel[i], "%s\n%s", speakers[i].name, dev);
+    }
+}
+
+// ===========================================================================
+// DETAIL screen (per speaker)
+// ===========================================================================
+static void detail_arc_cb(lv_event_t *e) {
+    lv_obj_t *arc = lv_event_get_target(e);
+    uint8_t v = (uint8_t)lv_arc_get_value(arc);
+    Speaker &s = speakers[activeSpeaker];
+    s.volume = v;
+    sendVolume(s, v);
+    lv_label_set_text_fmt(detArcPct, "%d", v);
+}
+
+static void detail_delay_step(int dir) {
+    Speaker &s = speakers[activeSpeaker];
+    int d = (int)s.delay_ms + dir * DELAY_STEP;
+    if (d < 0) d = 0;
+    if (d > HUB_MAX_DELAY_MS) d = HUB_MAX_DELAY_MS;
+    s.delay_ms = (uint16_t)d;
+    sendDelay(s, s.delay_ms);
+    lv_label_set_text_fmt(detDelayLabel, "Delay %u ms", s.delay_ms);
+}
+static void detail_delay_minus_cb(lv_event_t *e) { detail_delay_step(-1); }
+static void detail_delay_plus_cb(lv_event_t *e)  { detail_delay_step(+1); }
+
+static void detail_scan_cb(lv_event_t *e) { enterScan(); }
+
+static void detail_back_cb(lv_event_t *e) {
+    refreshSpeakers();
+    lv_scr_load(scrSpeakers);
+}
+
+static void buildDetail() {
+    scrDetail = lv_obj_create(NULL);
+    lv_obj_set_style_bg_color(scrDetail, COL_BG, 0);
+    lv_obj_clear_flag(scrDetail, LV_OBJ_FLAG_SCROLLABLE);
+
+    // Heading (role + device name).
+    detHeading = lv_label_create(scrDetail);
+    lv_obj_set_style_text_font(detHeading, &lv_font_montserrat_20, 0);
+    lv_obj_set_style_text_color(detHeading, COL_CYAN, 0);
+    lv_label_set_long_mode(detHeading, LV_LABEL_LONG_DOT);
+    lv_obj_set_width(detHeading, 170);
+    lv_obj_set_style_text_align(detHeading, LV_TEXT_ALIGN_CENTER, 0);
+    lv_label_set_text(detHeading, "");
+    lv_obj_align(detHeading, LV_ALIGN_TOP_MID, 0, 26);
+
+    // Per-speaker volume arc.
+    detArc = lv_arc_create(scrDetail);
+    lv_obj_set_size(detArc, 150, 150);
+    lv_obj_align(detArc, LV_ALIGN_CENTER, 0, -8);
+    lv_arc_set_rotation(detArc, 135);
+    lv_arc_set_bg_angles(detArc, 0, 270);
+    lv_arc_set_range(detArc, 0, 100);
+    lv_obj_set_style_arc_width(detArc, 12, LV_PART_MAIN);
+    lv_obj_set_style_arc_color(detArc, COL_TRACK, LV_PART_MAIN);
+    lv_obj_set_style_arc_width(detArc, 12, LV_PART_INDICATOR);
+    lv_obj_set_style_arc_color(detArc, COL_ACCENT, LV_PART_INDICATOR);
+    lv_obj_set_style_bg_color(detArc, COL_ACCENT, LV_PART_KNOB);
+    lv_obj_set_style_pad_all(detArc, 6, LV_PART_KNOB);
+    lv_obj_add_event_cb(detArc, detail_arc_cb, LV_EVENT_VALUE_CHANGED, NULL);
+
+    detArcPct = lv_label_create(scrDetail);
+    lv_obj_set_style_text_font(detArcPct, &lv_font_montserrat_28, 0);
+    lv_obj_set_style_text_color(detArcPct, COL_WHITE, 0);
+    lv_label_set_text(detArcPct, "0");
+    lv_obj_align(detArcPct, LV_ALIGN_CENTER, 0, -8);
+
+    // Delay control: "-"  "Delay NNN ms"  "+".
+    lv_obj_t *minus = lv_btn_create(scrDetail);
+    lv_obj_set_size(minus, 46, 46);
+    lv_obj_align(minus, LV_ALIGN_CENTER, -70, 54);
+    lv_obj_set_style_bg_color(minus, COL_BTN, 0);
+    lv_obj_add_event_cb(minus, detail_delay_minus_cb, LV_EVENT_CLICKED, NULL);
+    lv_obj_t *ml = lv_label_create(minus);
+    lv_obj_set_style_text_font(ml, &lv_font_montserrat_28, 0);
+    lv_label_set_text(ml, "-");
+    lv_obj_center(ml);
+
+    detDelayLabel = lv_label_create(scrDetail);
+    lv_obj_set_style_text_font(detDelayLabel, &lv_font_montserrat_14, 0);
+    lv_obj_set_style_text_color(detDelayLabel, COL_WHITE, 0);
+    lv_label_set_text(detDelayLabel, "Delay 0 ms");
+    lv_obj_align(detDelayLabel, LV_ALIGN_CENTER, 0, 54);
+
+    lv_obj_t *plus = lv_btn_create(scrDetail);
+    lv_obj_set_size(plus, 46, 46);
+    lv_obj_align(plus, LV_ALIGN_CENTER, 70, 54);
+    lv_obj_set_style_bg_color(plus, COL_BTN, 0);
+    lv_obj_add_event_cb(plus, detail_delay_plus_cb, LV_EVENT_CLICKED, NULL);
+    lv_obj_t *pl = lv_label_create(plus);
+    lv_obj_set_style_text_font(pl, &lv_font_montserrat_28, 0);
+    lv_label_set_text(pl, "+");
+    lv_obj_center(pl);
+
+    // SCAN (left) and BACK (right) at the bottom.
+    lv_obj_t *scan = lv_btn_create(scrDetail);
+    lv_obj_set_size(scan, 90, 44);
+    lv_obj_align(scan, LV_ALIGN_BOTTOM_MID, -50, -14);
+    lv_obj_set_style_bg_color(scan, COL_BTN, 0);
+    lv_obj_add_event_cb(scan, detail_scan_cb, LV_EVENT_CLICKED, NULL);
+    lv_obj_t *sl = lv_label_create(scan);
+    lv_obj_set_style_text_font(sl, &lv_font_montserrat_20, 0);
+    lv_label_set_text(sl, "SCAN");
+    lv_obj_center(sl);
+
+    lv_obj_t *back = lv_btn_create(scrDetail);
+    lv_obj_set_size(back, 90, 44);
+    lv_obj_align(back, LV_ALIGN_BOTTOM_MID, 50, -14);
+    lv_obj_set_style_bg_color(back, COL_BACK, 0);
+    lv_obj_add_event_cb(back, detail_back_cb, LV_EVENT_CLICKED, NULL);
+    lv_obj_t *bl = lv_label_create(back);
+    lv_obj_set_style_text_font(bl, &lv_font_montserrat_20, 0);
+    lv_label_set_text(bl, "BACK");
+    lv_obj_center(bl);
+}
+
+static void refreshDetail() {
+    Speaker &s = speakers[activeSpeaker];
+    const char *dev = s.cur_name[0] ? s.cur_name : "(no device)";
+    lv_label_set_text_fmt(detHeading, "%s  %s", s.name, dev);
+    // Don't fight the user's drag: only set the arc when not being touched.
+    if (!lv_obj_has_state(detArc, LV_STATE_PRESSED)) {
+        lv_arc_set_value(detArc, s.volume);
+        lv_label_set_text_fmt(detArcPct, "%d", s.volume);
+    }
+    lv_label_set_text_fmt(detDelayLabel, "Delay %u ms", s.delay_ms);
+}
+
+// ===========================================================================
+// SCAN screen
+// ===========================================================================
+static void scan_row_cb(lv_event_t *e) {
+    int listIdx = (int)(intptr_t)lv_event_get_user_data(e);
+    if (listIdx < 0 || listIdx >= scanItemCount) return;
+    const ScanItem &it = scanItems[listIdx];
+    Speaker &s = speakers[activeSpeaker];
+    Serial.printf("[scan] select %s idx=%u for %s\n",
+                  it.name, it.index, s.name);
+    sendSelect(s, it.index);
+    // Optimistically show it as the current device.
+    strncpy(s.cur_name, it.name, sizeof(s.cur_name));
+    s.cur_name[HUB_NAME_MAX] = '\0';
+    refreshDetail();
+    lv_scr_load(scrDetail);
+}
+
+static void scan_rescan_cb(lv_event_t *e) {
+    scanItemCount = 0;
+    startScan(speakers[activeSpeaker]);
+    Serial.printf("[scan] rescan for %s\n", speakers[activeSpeaker].name);
+    refreshScanList();
+}
+
+static void scan_back_cb(lv_event_t *e) {
+    sendScanStop(speakers[activeSpeaker]);
+    refreshDetail();
+    lv_scr_load(scrDetail);
+}
+
+static void buildScan() {
+    scrScan = lv_obj_create(NULL);
+    lv_obj_set_style_bg_color(scrScan, COL_BG, 0);
+    lv_obj_clear_flag(scrScan, LV_OBJ_FLAG_SCROLLABLE);
+
+    scanHeading = lv_label_create(scrScan);
+    lv_obj_set_style_text_font(scanHeading, &lv_font_montserrat_20, 0);
+    lv_obj_set_style_text_color(scanHeading, COL_CYAN, 0);
+    lv_label_set_text(scanHeading, "Scanning");
+    lv_obj_align(scanHeading, LV_ALIGN_TOP_MID, 0, 24);
+
+    // Spinner shown while scanning.
+    scanSpinner = lv_spinner_create(scrScan, 1000, 60);
+    lv_obj_set_size(scanSpinner, 44, 44);
+    lv_obj_align(scanSpinner, LV_ALIGN_TOP_MID, 0, 52);
+    lv_obj_set_style_arc_color(scanSpinner, COL_TRACK, LV_PART_MAIN);
+    lv_obj_set_style_arc_color(scanSpinner, COL_ACCENT, LV_PART_INDICATOR);
+
+    // Device list (scrolls natively). Kept inside the round safe area.
+    scanList = lv_list_create(scrScan);
+    lv_obj_set_size(scanList, 184, 96);
+    lv_obj_align(scanList, LV_ALIGN_CENTER, 0, 8);
+    lv_obj_set_style_bg_color(scanList, COL_BG, 0);
+    lv_obj_set_style_border_width(scanList, 0, 0);
+
+    // RESCAN (left) / BACK (right).
+    lv_obj_t *rescan = lv_btn_create(scrScan);
+    lv_obj_set_size(rescan, 92, 44);
+    lv_obj_align(rescan, LV_ALIGN_BOTTOM_MID, -50, -12);
+    lv_obj_set_style_bg_color(rescan, COL_BTN, 0);
+    lv_obj_add_event_cb(rescan, scan_rescan_cb, LV_EVENT_CLICKED, NULL);
+    lv_obj_t *rl = lv_label_create(rescan);
+    lv_obj_set_style_text_font(rl, &lv_font_montserrat_14, 0);
+    lv_label_set_text(rl, "RESCAN");
+    lv_obj_center(rl);
+
+    lv_obj_t *back = lv_btn_create(scrScan);
+    lv_obj_set_size(back, 92, 44);
+    lv_obj_align(back, LV_ALIGN_BOTTOM_MID, 50, -12);
+    lv_obj_set_style_bg_color(back, COL_BACK, 0);
+    lv_obj_add_event_cb(back, scan_back_cb, LV_EVENT_CLICKED, NULL);
+    lv_obj_t *bl = lv_label_create(back);
+    lv_obj_set_style_text_font(bl, &lv_font_montserrat_20, 0);
+    lv_label_set_text(bl, "BACK");
+    lv_obj_center(bl);
+}
+
+// Rebuild the scan list rows from the local mirror; toggle spinner/heading by
+// the scanning state. Called from the poll timer while SCAN is active.
+static void refreshScanList() {
+    Speaker &s = speakers[activeSpeaker];
+
+    if (s.scanning) {
+        lv_label_set_text_fmt(scanHeading, "%s: scanning", s.name);
+        lv_obj_clear_flag(scanSpinner, LV_OBJ_FLAG_HIDDEN);
+    } else {
+        lv_label_set_text_fmt(scanHeading, "%s: %d found", s.name, scanItemCount);
+        lv_obj_add_flag(scanSpinner, LV_OBJ_FLAG_HIDDEN);
+    }
+
+    // Rebuild the rows from scratch (avoids leaking / stale entries).
+    lv_obj_clean(scanList);
+
+    if (scanItemCount == 0) {
+        if (!s.scanning) {
+            lv_obj_t *btn = lv_list_add_btn(scanList, NULL, "(none found)");
+            lv_obj_set_style_text_color(btn, COL_GREY, 0);
+        }
+        return;
+    }
+
+    for (int i = 0; i < scanItemCount; i++) {
+        const ScanItem &it = scanItems[i];
+        char row[HUB_NAME_MAX + 16];
+        snprintf(row, sizeof(row), "%s  %ddB",
+                 it.name[0] ? it.name : "(unnamed)", it.rssi);
+        lv_obj_t *btn = lv_list_add_btn(scanList, LV_SYMBOL_BLUETOOTH, row);
+        lv_obj_set_style_text_font(btn, &lv_font_montserrat_14, 0);
+        lv_obj_set_style_bg_color(btn, COL_BTN, 0);
+        lv_obj_set_style_text_color(btn, COL_WHITE, 0);
+        lv_obj_set_style_min_height(btn, 44, 0);   // glove-friendly tap target
+        lv_obj_add_event_cb(btn, scan_row_cb, LV_EVENT_CLICKED,
+                            (void *)(intptr_t)i);
+    }
+}
+
+// Enter SCAN for the active speaker: kick off a scan + show the screen.
+static void enterScan() {
+    scanItemCount = 0;
+    startScan(speakers[activeSpeaker]);
+    Serial.printf("[scan] start for %s\n", speakers[activeSpeaker].name);
+    refreshScanList();
+    lv_scr_load(scrScan);
+}
+
+// ===========================================================================
+// Periodic I2C poll, driven by an lv_timer (~1 Hz, main context — safe).
+// ===========================================================================
+static void poll_timer_cb(lv_timer_t *t) {
+    lv_obj_t *cur = lv_scr_act();
+
+    if (cur == scrScan) {
+        // While scanning, poll the active speaker + pull the list as it grows.
+        Speaker &s = speakers[activeSpeaker];
+        bool wasScanning = s.scanning;
+        uint8_t prevCount = s.scan_count;
+        pollStatus(s);
+        if ((s.scan_count > 0 && s.scan_count != prevCount) ||
+            (wasScanning && !s.scanning)) {
+            pollScanList(activeSpeaker);
+        }
+        refreshScanList();
+        return;
+    }
+
+    // Otherwise poll all channels for status + device name.
+    for (int i = 0; i < NUM_SPK; i++) {
+        pollStatus(speakers[i]);
+        getCurName(speakers[i], speakers[i].cur_name);
+    }
+
+    if (cur == scrHome) {
+        refreshHome();
+    } else if (cur == scrSpeakers) {
+        refreshSpeakers();
+    } else if (cur == scrDetail) {
+        refreshDetail();
+    }
+
+    // Heartbeat.
+    static unsigned long lastBeat = 0;
+    unsigned long now = millis();
+    if (now - lastBeat >= 5000) {
+        lastBeat = now;
+        Serial.printf("[hub] alive heap=%u", ESP.getFreeHeap());
+        for (int i = 0; i < NUM_SPK; i++) {
+            const Speaker &s = speakers[i];
+            const char *st = s.online ? (s.connected ? "on" : "idle") : "off";
+            Serial.printf("  %s[%s D%u V%u]", s.name, st, s.delay_ms, s.volume);
+        }
+        Serial.println();
+    }
+}
+
+// ===========================================================================
+// setup() / loop()
+// ===========================================================================
+void setup() {
+    Serial.begin(115200);
+    delay(300);
+    Serial.println("=== Resound Hub — S3 LVGL UI ===");
+
+    // Control bus: I2C master to the source boards on Wire1 (peripheral 1).
+    // Peripheral 0 is used by the LovyanGFX CST816S touch (GPIO6/7).
+    Wire1.begin(CTRL_I2C_SDA, CTRL_I2C_SCL, CTRL_I2C_HZ);
+    Serial.printf("[i2c] master up SDA=%d SCL=%d @%dHz\n",
+                  CTRL_I2C_SDA, CTRL_I2C_SCL, CTRL_I2C_HZ);
+
+    lcd.init();
+    lcd.setRotation(0);
+    lcd.setBrightness(200);
+
+    // LVGL core + display + touch input.
+    lv_init();
+    lv_disp_draw_buf_init(&draw_buf, lvbuf1, lvbuf2, 240 * 40);
+    lv_disp_drv_init(&disp_drv);
+    disp_drv.hor_res  = 240;
+    disp_drv.ver_res  = 240;
+    disp_drv.flush_cb = disp_flush;
+    disp_drv.draw_buf = &draw_buf;
+    lv_disp_drv_register(&disp_drv);
+
+    lv_indev_drv_init(&indev_drv);
+    indev_drv.type    = LV_INDEV_TYPE_POINTER;
+    indev_drv.read_cb = touch_read;
+    lv_indev_drv_register(&indev_drv);
+
+    // Seed device names + status once so the UI starts populated.
+    for (int i = 0; i < NUM_SPK; i++) {
+        pollStatus(speakers[i]);
+        getCurName(speakers[i], speakers[i].cur_name);
+    }
+    // Seed the master arc from the loudest channel that's online (best effort;
+    // the Guest is usually offline, so don't let it drag the seed).
+    masterVolume = 0;
+    for (int i = 0; i < NUM_SPK; i++) {
+        if (speakers[i].online && speakers[i].volume > masterVolume) {
+            masterVolume = speakers[i].volume;
+        }
+    }
+
+    // Build all screens, then show HOME.
+    buildHome();
+    buildSpeakers();
+    buildDetail();
+    buildScan();
+    refreshHome();
+    lv_scr_load(scrHome);
+
+    // 1 Hz I2C poll, driven from LVGL's timer (runs in main context).
+    lv_timer_create(poll_timer_cb, POLL_PERIOD_MS, NULL);
+
+    Serial.println("[LCD] LVGL UI up");
+}
+
+void loop() {
+    // Drive LVGL's tick manually (we don't use LV_TICK_CUSTOM — its millis()
+    // expr can't go through build flags cleanly).
+    static uint32_t last_tick = 0;
+    uint32_t now = millis();
+    lv_tick_inc(now - last_tick);
+    last_tick = now;
+
+    lv_timer_handler();
+    delay(5);
+}
--- a/src/sink.cpp
+++ b/src/sink.cpp
@ -0,0 +1,96 @@
+/**
+ * Resound — Board A : A2DP SINK  ->  I2S MASTER
+ *
+ * Part of the 3-board relay. The iPhone connects to this board over Bluetooth
+ * (A2DP name "Resound"). This board decodes the audio to PCM and clocks it
+ * out on a shared I2S bus as the MASTER. Boards B and C (A2DP sources) listen
+ * to this same bus as slaves and stream it to the JBL / Cardo speakers.
+ *
+ *   iPhone  ))BT))  [Board A: sink] ==I2S==> [Board B: src] ))BT)) JBL
+ *                                      \====> [Board C: src] ))BT)) Cardo
+ *
+ * Why a separate board: one ESP32 cannot be an A2DP sink and source at once
+ * (single Bluedroid A2DP role), and an A2DP source can hold only one outgoing
+ * link — so the sink and each speaker need their own chip. See README.
+ *
+ * I2S OUTPUT pins (this board DRIVES the bus — wire these to B and C):
+ *   BCK  = GPIO5   WS/LRCK = GPIO25   DATA(out) = GPIO23   + common GND
+ *
+ * Build: pio run -e sink   (compiled via build_src_filter in platformio.ini)
+ */
+
+#include <Arduino.h>
+
+#include "AudioTools.h"
+#include "BluetoothA2DPSink.h"
+
+#define I2S_BCK_PIN    5
+#define I2S_WS_PIN     25
+#define I2S_DATA_PIN   23
+
+I2SStream         i2s;
+BluetoothA2DPSink sink;
+
+static uint16_t current_sample_rate = 0;
+
+// Configure / reconfigure the I2S bus as master TX at the given rate.
+static void start_i2s(uint16_t rate) {
+    if (rate == 0) rate = 44100;          // SBC default before negotiation
+    auto cfg = i2s.defaultConfig(TX_MODE);
+    cfg.pin_bck         = I2S_BCK_PIN;
+    cfg.pin_ws          = I2S_WS_PIN;
+    cfg.pin_data        = I2S_DATA_PIN;
+    cfg.sample_rate     = rate;
+    cfg.channels        = 2;
+    cfg.bits_per_sample = 16;
+    cfg.is_master       = true;           // Board A clocks the whole bus
+    cfg.buffer_count    = 8;
+    cfg.buffer_size     = 512;
+    i2s.begin(cfg);
+    current_sample_rate = rate;
+    Serial.printf("[SINK] I2S master @ %u Hz / 16-bit / stereo\n", rate);
+}
+
+// Called from the BT task with decoded PCM. Keep it cheap — just push to I2S.
+void write_pcm_to_i2s(const uint8_t *data, uint32_t len) {
+    i2s.write(data, len);
+}
+
+void on_conn_state(esp_a2d_connection_state_t state, void *obj) {
+    if (state == ESP_A2D_CONNECTION_STATE_CONNECTED)        Serial.println("[SINK] iPhone CONNECTED");
+    else if (state == ESP_A2D_CONNECTION_STATE_DISCONNECTED) Serial.println("[SINK] iPhone disconnected");
+}
+
+void setup() {
+    Serial.begin(115200);
+    delay(500);
+    Serial.println("=== Resound Board A — A2DP SINK -> I2S master ===");
+
+    start_i2s(44100);
+
+    // false  => the sink does NOT run its own I2S; we forward PCM ourselves.
+    sink.set_stream_reader(write_pcm_to_i2s, false);
+    sink.set_on_connection_state_changed(on_conn_state);
+    sink.set_auto_reconnect(true);
+    sink.start("Resound");
+
+    Serial.println("[SINK] Advertising 'Resound' — connect from iPhone");
+}
+
+void loop() {
+    // Follow the negotiated sample rate (iPhone usually 44100; reconfigure if not).
+    uint16_t sr = sink.sample_rate();
+    if (sr != 0 && sr != current_sample_rate) {
+        Serial.printf("[SINK] sample rate changed %u -> %u, reconfiguring I2S\n",
+                      current_sample_rate, sr);
+        start_i2s(sr);
+    }
+
+    static unsigned long last = 0;
+    if (millis() - last > 5000) {
+        Serial.printf("[SINK] iPhone=%s  heap=%u\n",
+                      sink.is_connected() ? "YES" : "no", ESP.getFreeHeap());
+        last = millis();
+    }
+    delay(100);
+}
Author	SHA1	Message	Date
blue	2c6e7e8762	hardware: KiCad bootstrap for the Resound carrier PCB (Small Build) Netlist-first KiCad-import package for the single carrier PCB (ESP32-WROOM-32E, SINK/BROADCASTER assembly variants): - hardware/carrier/resound-carrier.net : KiCad s-expr netlist, 44 components / 40 nets, real library footprints (RF_Module:ESP32-WROOM-32, 2x13 stacking header, 0402 passives, SOT-23 auto-reset, JST-SH HUD conn). Parens balanced. - hardware/carrier/BOM.csv : 44 parts (ref/value/footprint/MPN/DNP/notes). - hardware/carrier/LAYOUT.md : 45x45 4-layer stackup, 15mm antenna keep-out, placement, JLCPCB DRC, SINK-vs-BROADCASTER variant + address-strap table. - hardware/carrier/README.md : KiCad import steps + caveats. Agent decisions flagged for EE: LED moved off the GPIO13 strap to LED_DAT=GPIO21 / LED_CLK=GPIO4; verify WROOM footprint pad numbering; UART2 is connector-only this rev. Deliverable is import-ready netlist+BOM+spec, not a finished .kicad_pcb. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>	2026-06-11 15:10:15 -04:00
blue	b5d1169392	Rename: product -> "Resound"; firmware roles -> hud/sink/broadcaster Product name BikeAudio -> "Resound" (the device isn't bike-specific — works at home, backyard, camping, parties, group rides). This is the A2DP advertise name the phone connects to: sink.start("Resound"). All banners/comments + README updated. (After reflashing the sink, the phone must forget "BikeAudio" and connect to "Resound".) Firmware vocabulary clarified (the old hub/sink/source was confusing — "source" read backwards since those boards SEND audio): hub_s3.cpp / env hub_s3 -> hud.cpp / env hud board_sink.cpp -> sink.cpp (env sink) board_source.cpp -> broadcaster.cpp (envs broadcaster_headset 0x11, broadcaster_speaker1 0x10, broadcaster_guest 0x12) hub_proto.h -> bus_proto.h default_envs = sink + the three broadcasters. All envs build clean. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>	2026-06-11 14:14:16 -04:00
blue	dca7d3ba46	Phase 4 LVGL UI + guest channel + brand-agnostic naming - LVGL 8.3 round-screen UI (replaces the LovyanGFX direct-draw functional UI): master volume arc, per-channel connection dots, SPEAKERS list, per-channel DETAIL (volume arc + delay -/+ + scan), SCAN list. Rendered through LovyanGFX; configured via build flags (LV_CONF_SKIP); tick via lv_tick_inc in loop. - Third channel "Guest" @ I2C 0x12 (the onboard-antenna ESP32 — the long-range link to an occasional passenger speaker). New [env:source_guest]. - Channels are now brand-agnostic, in order: index0 "Headset" (0x11), index1 "Speaker 1" (0x10), index2 "Guest" (0x12). Discovery picks the real device per channel, so labels stay generic. - hub_proto.h: HUB_I2C_ADDR_GUEST 0x12. Built clean: hub_s3 (LVGL, 3 channels) + source_guest. LVGL render verified on hardware (basic); guest board needs flashing + wiring into the I2S/I2C buses. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>	2026-06-11 13:06:10 -04:00
blue	de61905e9c	Phase 3: BT speaker discovery + selection (no more hardcoded names) The source boards now scan for nearby Bluetooth speakers and connect to a user-chosen one; the hub screen drives it. Hardcoded TARGET_SPEAKER remains only as a first-boot fallback when nothing is saved. - hub_proto.h: status payload -> 7 bytes (adds scanning, scan_count, has_device). New cmds: SCAN_START/STOP, SELECT(index), FORGET, GET_SCANITEM(index)->33-byte item (valid,rssi,mac,namelen,name), GET_CURNAME->24-byte name. - board_source.cpp: set_ssid_callback collects nearby sinks (dedupe by MAC, COD-filtered to audio), set_discovery_mode_callback stops the scan loop, connect_to(mac) + set_auto_reconnect(mac) on SELECT, MAC+name persisted to NVS (spk_mac/spk_name). Boot connects to saved MAC or falls back to the name. onRequest multiplexes status/scanitem/curname by last read command. - hub_s3.cpp: MAIN screen now shows each speaker's selected device name + a "pick" button; SCREEN_SCAN shows the live discovery list (RSSI-sorted, scrollable) with tap-to-select, Rescan, Back. All I2C on Wire1. Built by two parallel sub-agents against hub_proto.h; all three envs build clean first try. Needs the I2C bus wired to test on hardware. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>	2026-06-11 11:57:48 -04:00
blue	4b432c6123	Phase 2: I2C control bus (S3 hub master <-> B/C slaves) Wired control path so the S3 hub can set delay/volume on the source boards and read their status, over an I2C bus (separate from the audio I2S bus). - src/hub_proto.h: shared protocol — addresses (JBL 0x10, Cardo 0x11), commands SET_DELAY (u16), SET_VOLUME (u8), GET_STATUS (4-byte payload: connected, delay LE, volume). - board_source.cpp (B/C): I2C slave on GPIO32/33 (addr via -DHUB_I2C_ADDR). Light onReceive/onRequest callbacks stash requests; loop() applies them (reuses set_delay; adds current_volume -> source.set_volume, NVS-persisted). Relay/FIFO/touch untouched. - hub_s3.cpp: I2C master on Wire1 (GPIO15/16) — peripheral 1, since the CST816S touch owns peripheral 0. Polls both boards ~1Hz; LovyanGFX UI shows each speaker's connect/delay/volume with touch +/- zones that send commands. - platformio.ini: -DHUB_I2C_ADDR per source env. Written by two parallel sub-agents (one per side) against hub_proto.h; fixed the Wire->Wire1 peripheral conflict. All three envs build clean. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>	2026-06-11 10:44:45 -04:00
blue	9ed1899285	S3 hub Phase 1: round LCD + touch bring-up (LovyanGFX) ESP32-S3-Touch-LCD-1.28 first light: GC9A01 round display + backlight + CST816S touch working via LovyanGFX. Draws a label and red dots on touch. - src/hub_s3.cpp: LovyanGFX LGFX config for this board (GC9A01 SPI SCLK10/MOSI11/MISO12/CS9/DC8/RST14, backlight GPIO2; CST816S touch I2C SDA6/SCL7 polled, addr 0x15). - platformio.ini: new [env:hub_s3] (esp32-s3-devkitc-1, 4MB, LovyanGFX). Not in default_envs. Flash: esp32s3, bootloader@0x0 +boot_app0@0xe000. Foundation for the on-device UI hub. PSRAM not yet enabled (not needed for bring-up; will enable for LVGL). Next: I2C control bus to Boards B/C. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>	2026-06-11 10:12:17 -04:00
blue	0b1c34074f	Fix robotic audio + crash: proper FIFO delay line The previous delay buffer re-derived the read position from the write head on every A2DP pull (read = write - delay), so it sampled the buffer at the Bluetooth pull-rate while positioning by the I2S write-rate — skipping/ repeating samples (robotic) and, with no cushion at delay=0, constantly under/overrunning until it destabilized and crashed. Replace with a real FIFO: a sequential read pointer that advances by the frames consumed, held BASE_DELAY_MS (40 ms jitter cushion) + the touch trim behind the I2S write head, with underrun (pad silence) and overrun (resync) handling. Also carry partial frames across I2S reads so L/R never slips. Verified on hardware: clean audio to both speakers, stable for hours, touch-pad sync aligns JBL and Cardo. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>	2026-06-10 16:07:49 -04:00
blue	66f56f1e09	docs: document touch-pad sync (GPIO4/27), no WiFi UI Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>	2026-06-10 14:18:05 -04:00
blue	2a34ed5abe	Sync via capacitive touch (drop Wi-Fi) — fixes BT starvation The Wi-Fi/web/ESP-NOW sync approach was unviable: Wi-Fi + Bluetooth-A2DP + the delay buffer exhausted RAM on the classic ESP32 (~20 KB free), and the Bluetooth stack was so starved the source boards couldn't even connect to a speaker. Confirmed on hardware: with Wi-Fi up the JBL would not connect; with Wi-Fi removed it connects instantly (~65 KB free). - board_source.cpp: remove Wi-Fi/ESP-NOW. Keep the I2S-reader-task + ring delay line (now 200 ms; plenty of RAM without Wi-Fi). Adjust delay live by ear via two capacitive-touch pads — "+" on GPIO4 (T0), "-" on GPIO27 (T7); tap = 5 ms step, hold = ramp. Persisted to flash (debounced). - board_sink.cpp: reverted to the simple A2DP sink + I2S master (no Wi-Fi). - platformio.ini: drop SPEAKER_ID. Remove relay_config.h. All three boards connect reliably with healthy heap. Touch pins read ~120 untouched; threshold 40. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>	2026-06-10 14:07:43 -04:00
blue	0b474b172b	Add per-speaker delay sync with Wi-Fi/web UI + ESP-NOW Adds runtime speaker-sync control to the relay: - src/relay_config.h: shared Wi-Fi AP creds + ESP-NOW RelayDelayMsg (delay_ms[JBL], delay_ms[Cardo]) on a fixed channel. - board_sink.cpp (Board A): hosts a Wi-Fi AP "BikeAudio-Setup" + a small web UI (two sliders, no app) at 192.168.4.1, and broadcasts the chosen per-speaker delays to the source boards over ESP-NOW. Still A2DP sink + I2S master. (Tune while parked — Wi-Fi/BT coexist on one radio.) - board_source.cpp (Boards B/C): inserts an adjustable delay line between I2S in and A2DP out — a dedicated reader task fills a ring buffer (up to ~250 ms) and the A2DP callback reads delay_frames behind the write head. Delay arrives via ESP-NOW (per SPEAKER_ID) and is persisted to flash (Preferences), so it survives power cycles. - platformio.ini: source envs get -DSPEAKER_ID (0=JBL, 1=Cardo). Lets the rider trim JBL vs Cardo timing to sync the two speakers. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>	2026-06-10 13:11:41 -04:00
blue	baa3ef7690	3-board relay firmware: sink + I2S + dual source Implements the only architecture that can relay iPhone audio to two BT speakers at once (one ESP32 cannot be A2DP sink+source, and a source holds only one link): iPhone ))BT)) [Board A: A2DP sink -> I2S master] ==I2S bus==> [Board B: I2S slave -> A2DP source] ))BT)) JBL ==I2S bus==> [Board C: I2S slave -> A2DP source] ))BT)) Cardo - src/board_sink.cpp : A2DP sink "BikeAudio", forwards decoded PCM to an I2S master bus (BCK=5, WS=25, DATA=23); follows negotiated sample rate. - src/board_source.cpp : I2S slave (BCK=19, WS=18, DATA=22) -> A2DP source, target speaker via TARGET_SPEAKER build flag; pads silence on underrun. - platformio.ini : 3 envs (sink, source_jbl, source_cardo) sharing an [env] base; sources differ only by TARGET_SPEAKER. build_src_filter selects the per-board source file. Libs pinned as before. - README_RELAY.md : wiring table, I2S bus topology, flash order, pairing, and the speaker-sync limitation. Replaces the single-board src/main.cpp (architecturally impossible). All three envs build clean. Hardware flash + wiring next. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>	2026-06-10 11:35:12 -04:00
blue	04e7f20430	Convert Arduino sketch to PlatformIO project Restructure BikeAudio for PlatformIO while preserving the original build specs from the .ino header: - platform espressif32 @ ~6.6.0 -> ESP32 Arduino core 2.0.17 - board esp32dev (ESP32 DevKitC v4) - board_build.partitions = huge_app.csv (Huge APP, required for BT stack) - monitor_speed = 115200 Changes: - BikeAudio.ino -> src/main.cpp (+ #include <Arduino.h>, print_status() forward declaration; PlatformIO compiles .cpp directly and does not auto-generate prototypes like the Arduino IDE). - Add platformio.ini with pschatzmann ESP32-A2DP + arduino-audio-tools pinned to exact commits (ESP32-A2DP 1.8.11, audio-tools 1.2.4) for reproducible builds. - Adapt three spots to the current library API (behavior preserved): * RingBuffer<uint8_t>::read() -> bool read(T&) * connection-state callbacks: drop esp_bd_addr_t arg -> (esp_a2d_connection_state_t, void) BluetoothA2DPSource::start(name, bool) -> start(name) (auto-reconnect already configured via set_auto_reconnect(true)) Verified: pio run -e esp32dev succeeds. RAM 14.5% (47.6 KB), Flash 42.0% (1.32 MB / 3 MB). Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>	2026-06-10 09:44:09 -04:00