spike: BLE+A2DP coexistence test on Board A (throwaway)

Proves dual-mode BLE+A2DP fit in RAM (~110KB free) but BLE radio activity
shreds the A2DP audio (clicks, no music) even when only advertising. Conclusion:
move BLE control to a dedicated ESP32-S3 hub; keep Board A a pure sink.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/board_sink.cpp

@@ -1,96 +1,109 @@
 /**
- * BikeAudio — Board A : A2DP SINK  ->  I2S MASTER
+ * BLE-COEXISTENCE SPIKE (throwaway) — Board A : A2DP SINK + I2S master + BLE GATT
  *
- * Part of the 3-board relay. The iPhone connects to this board over Bluetooth
+ * Purpose: prove the classic ESP32 can run the A2DP sink (iPhone audio) AND a
- * (A2DP name "BikeAudio"). This board decodes the audio to PCM and clocks it
+ * BLE GATT server at the same time, in dual mode (BTDM), with healthy heap.
- * out on a shared I2S bus as the MASTER. Boards B and C (A2DP sources) listen
+ * This is the gate for the phone-app control channel. NOT final firmware.
- * 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
+ * Checks at runtime: BLE advertises ("BikeAudio-Ctl"), iPhone still connects to
- *                                      \====> [Board C: src] ))BT)) Cardo
+ * A2DP "BikeAudio", I2S master clocks, and heap stays sane.
- *
- * 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"
+#include <BLEDevice.h>
+#include <BLEServer.h>
+#include <BLEUtils.h>
 
 #define I2S_BCK_PIN    5
 #define I2S_WS_PIN     25
 #define I2S_DATA_PIN   23
 
+#define SVC_UUID  "a1000001-b10e-4c2a-9b00-000000000001"
+#define CHR_UUID  "a1000002-b10e-4c2a-9b00-000000000002"
+
 I2SStream         i2s;
 BluetoothA2DPSink sink;
+static uint16_t   current_sample_rate = 0;
+static BLECharacteristic *ctl_char = nullptr;
+static volatile bool ble_connected = false;
 
-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
+    if (rate == 0) rate = 44100;
     auto cfg = i2s.defaultConfig(TX_MODE);
-    cfg.pin_bck         = I2S_BCK_PIN;
+    cfg.pin_bck = I2S_BCK_PIN; cfg.pin_ws = I2S_WS_PIN; cfg.pin_data = I2S_DATA_PIN;
-    cfg.pin_ws          = I2S_WS_PIN;
+    cfg.sample_rate = rate; cfg.channels = 2; cfg.bits_per_sample = 16;
-    cfg.pin_data        = I2S_DATA_PIN;
+    cfg.is_master = true; cfg.buffer_count = 8; cfg.buffer_size = 512;
-    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);
+    Serial.printf("[SINK] I2S master @ %u Hz\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 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");
 }
 
+class SrvCB : public BLEServerCallbacks {
+    void onConnect(BLEServer *) override { ble_connected = true;  Serial.println("[BLE] central connected"); }
+    void onDisconnect(BLEServer *s) override { ble_connected = false; Serial.println("[BLE] central disconnected"); s->getAdvertising()->start(); }
+};
+
+class ChrCB : public BLECharacteristicCallbacks {
+    void onWrite(BLECharacteristic *c) override {
+        Serial.printf("[BLE] write: '%s'\n", c->getValue().c_str());
+    }
+};
+
 void setup() {
     Serial.begin(115200);
     delay(500);
-    Serial.println("=== BikeAudio Board A — A2DP SINK -> I2S master ===");
+    Serial.println("=== BLE SPIKE — A2DP sink + BLE GATT (BTDM) ===");
+    Serial.printf("[boot] heap=%u\n", ESP.getFreeHeap());
 
+    // BLE first: btStart() brings the controller up in dual mode (BTDM), then
+    // bluedroid + BLE host. A2DP (also bluedroid) then registers on top.
+    BLEDevice::init("BikeAudio-Ctl");
+    Serial.printf("[BLE] init done heap=%u\n", ESP.getFreeHeap());
+    BLEServer *srv = BLEDevice::createServer();
+    srv->setCallbacks(new SrvCB());
+    BLEService *svc = srv->createService(SVC_UUID);
+    ctl_char = svc->createCharacteristic(
+        CHR_UUID,
+        BLECharacteristic::PROPERTY_READ | BLECharacteristic::PROPERTY_WRITE | BLECharacteristic::PROPERTY_NOTIFY);
+    ctl_char->setValue("ready");
+    svc->start();
+    BLEAdvertising *adv = BLEDevice::getAdvertising();
+    adv->addServiceUUID(SVC_UUID);
+    adv->setScanResponse(true);
+    BLEDevice::startAdvertising();
+    Serial.printf("[BLE] advertising 'BikeAudio-Ctl' heap=%u\n", ESP.getFreeHeap());
+
+    // Now the A2DP sink in dual mode.
     start_i2s(44100);
-
+    sink.set_default_bt_mode(ESP_BT_MODE_BTDM);
-    // 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("BikeAudio");
-
+    Serial.printf("[SINK] A2DP started heap=%u\n", ESP.getFreeHeap());
-    Serial.println("[SINK] Advertising 'BikeAudio' — connect from iPhone");
+    Serial.println("[SINK] Advertising 'BikeAudio' — connect 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) {
+    if (sr != 0 && sr != current_sample_rate) start_i2s(sr);
-        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",
+        Serial.printf("[STATUS] iPhone=%s BLE=%s heap=%u\n",
-                      sink.is_connected() ? "YES" : "no", ESP.getFreeHeap());
+                      sink.is_connected() ? "YES" : "no",
+                      ble_connected ? "YES" : "no", ESP.getFreeHeap());
         last = millis();
     }
-    delay(100);
+    delay(50);
 }