diff --git a/esp32/uwb_anchor/platformio.ini b/esp32/uwb_anchor/platformio.ini
new file mode 100644
index 0000000..9d88d5f
--- /dev/null
+++ b/esp32/uwb_anchor/platformio.ini
@@ -0,0 +1,30 @@
+; SaltyBot UWB Anchor Firmware — Issue #544
+; Target: Makerfabs ESP32 UWB Pro (DW3000 chip)
+;
+; Library: Makerfabs MaUWB_DW3000
+;   https://github.com/Makerfabs/MaUWB_DW3000
+;
+; Flash:
+;   pio run -e anchor0 --target upload   (port-side anchor)
+;   pio run -e anchor1 --target upload   (starboard anchor)
+; Monitor:
+;   pio device monitor -e anchor0 -b 115200
+
+[common]
+platform     = espressif32
+board        = esp32dev
+framework    = arduino
+monitor_speed = 115200
+upload_speed  = 921600
+lib_deps =
+    https://github.com/Makerfabs/MaUWB_DW3000.git
+build_flags =
+    -DCORE_DEBUG_LEVEL=0
+
+[env:anchor0]
+extends     = common
+build_flags = ${common.build_flags} -DANCHOR_ID=0
+
+[env:anchor1]
+extends     = common
+build_flags = ${common.build_flags} -DANCHOR_ID=1
diff --git a/esp32/uwb_anchor/src/main.cpp b/esp32/uwb_anchor/src/main.cpp
new file mode 100644
index 0000000..e022ee2
--- /dev/null
+++ b/esp32/uwb_anchor/src/main.cpp
@@ -0,0 +1,413 @@
+/*
+ * uwb_anchor — SaltyBot ESP32 UWB Pro anchor firmware (TWR responder)
+ * Issue #544
+ *
+ * Hardware: Makerfabs ESP32 UWB Pro (DW3000 chip)
+ *
+ * Role
+ * ────
+ *   Anchor sits on SaltyBot body, USB-connected to Jetson Orin.
+ *   Two anchors per robot (anchor-0 port side, anchor-1 starboard).
+ *   Person-worn tags initiate ranging; anchors respond.
+ *
+ * Protocol: Double-Sided TWR (DS-TWR)
+ * ────────────────────────────────────
+ *   Tag → Anchor   POLL   (msg_type 0x01)
+ *   Anchor → Tag   RESP   (msg_type 0x02, payload: T_poll_rx, T_resp_tx)
+ *   Tag → Anchor   FINAL  (msg_type 0x03, payload: Ra, Da, Db timestamps)
+ *   Anchor computes range via DS-TWR formula, emits +RANGE on Serial.
+ *
+ * Serial output (115200 8N1, USB-CDC to Jetson)
+ * ──────────────────────────────────────────────
+ *   +RANGE:<anchor_id>,<range_mm>,<rssi_dbm>\r\n   (on each successful range)
+ *
+ * AT commands (host → anchor)
+ * ───────────────────────────
+ *   AT+RANGE?                  → returns last buffered +RANGE line
+ *   AT+RANGE_ADDR=<hex_addr>   → pair with specific tag (filter others)
+ *   AT+RANGE_ADDR=             → clear pairing (accept all tags)
+ *   AT+ID?                     → returns +ID:<anchor_id>
+ *
+ * Pin mapping — Makerfabs ESP32 UWB Pro
+ * ──────────────────────────────────────
+ *   SPI SCK   18    SPI MISO  19    SPI MOSI  23
+ *   DW CS     21    DW RST    27    DW IRQ    34
+ *
+ * Build
+ * ──────
+ *   pio run -e anchor0 --target upload   (port side)
+ *   pio run -e anchor1 --target upload   (starboard)
+ */
+
+#include <Arduino.h>
+#include <SPI.h>
+#include <math.h>
+#include "dw3000.h"   // Makerfabs MaUWB_DW3000 library
+
+/* ── Configurable ───────────────────────────────────────────────── */
+
+#ifndef ANCHOR_ID
+#  define ANCHOR_ID  0          /* 0 = port, 1 = starboard */
+#endif
+
+#define SERIAL_BAUD  115200
+
+/* ── Pin map (Makerfabs ESP32 UWB Pro) ─────────────────────────── */
+
+#define PIN_SCK   18
+#define PIN_MISO  19
+#define PIN_MOSI  23
+#define PIN_CS    21
+#define PIN_RST   27
+#define PIN_IRQ   34
+
+/* ── DW3000 channel / PHY config ───────────────────────────────── */
+
+static dwt_config_t dw_cfg = {
+    5,                 /* channel 5 (6.5 GHz, best penetration) */
+    DWT_PLEN_128,      /* preamble length                       */
+    DWT_PAC8,          /* PAC size                              */
+    9,                 /* TX preamble code                      */
+    9,                 /* RX preamble code                      */
+    1,                 /* SFD type (IEEE 802.15.4z)             */
+    DWT_BR_6M8,        /* data rate 6.8 Mbps                    */
+    DWT_PHR_MODE_STD,  /* standard PHR                          */
+    DWT_PHR_RATE_DATA,
+    (129 + 8 - 8),     /* SFD timeout                           */
+    DWT_STS_MODE_OFF,  /* STS off — standard TWR                */
+    DWT_STS_LEN_64,
+    DWT_PDOA_M0,       /* no PDoA                               */
+};
+
+/* ── Frame format ──────────────────────────────────────────────── */
+
+/* Byte layout for all frames:
+ *   [0]     frame_type  (FTYPE_*)
+ *   [1]     src_id      (tag 8-bit addr, or ANCHOR_ID)
+ *   [2]     dst_id
+ *   [3..]   payload
+ *   (FCS appended automatically by DW3000 — 2 bytes)
+ */
+
+#define FTYPE_POLL   0x01
+#define FTYPE_RESP   0x02
+#define FTYPE_FINAL  0x03
+
+#define FRAME_HDR   3
+#define FCS_LEN     2
+
+/* RESP payload: T_poll_rx(5 B) + T_resp_tx(5 B) */
+#define RESP_PAYLOAD   10
+#define RESP_FRAME_LEN (FRAME_HDR + RESP_PAYLOAD + FCS_LEN)
+
+/* FINAL payload: Ra(5 B) + Da(5 B) + Db(5 B) */
+#define FINAL_PAYLOAD   15
+#define FINAL_FRAME_LEN (FRAME_HDR + FINAL_PAYLOAD + FCS_LEN)
+
+/* ── Timing ────────────────────────────────────────────────────── */
+
+/* Turnaround delay: anchor waits 500 µs after poll_rx before tx_resp.
+ * DW3000 tick = 1/(128×499.2e6) ≈ 15.65 ps  →  500 µs = ~31.95M ticks.
+ * Stored as uint32 shifted right 8 bits for dwt_setdelayedtrxtime. */
+#define RESP_TX_DLY_US      500UL
+#define DWT_TICKS_PER_US    63898UL          /* 1µs in DW3000 ticks (×8 prescaler) */
+#define RESP_TX_DLY_TICKS   (RESP_TX_DLY_US * DWT_TICKS_PER_US)
+
+/* How long anchor listens for FINAL after sending RESP */
+#define FINAL_RX_TIMEOUT_US  3000
+
+/* Speed of light (m/s) */
+#define SPEED_OF_LIGHT  299702547.0
+
+/* DW3000 40-bit timestamp mask */
+#define DWT_TS_MASK  0xFFFFFFFFFFULL
+
+/* Antenna delay (factory default; calibrate per unit for best accuracy) */
+#define ANT_DELAY  16385
+
+/* ── Interrupt flags (set in ISR, polled in main) ──────────────── */
+
+static volatile bool g_rx_ok   = false;
+static volatile bool g_tx_done = false;
+static volatile bool g_rx_err  = false;
+static volatile bool g_rx_to   = false;
+
+static uint8_t  g_rx_buf[128];
+static uint32_t g_rx_len = 0;
+
+/* ── State ──────────────────────────────────────────────────────── */
+
+/* Last successful range (serves AT+RANGE? queries) */
+static int32_t g_last_range_mm = -1;
+static char    g_last_range_line[72] = {};
+
+/* Optional tag pairing: 0 = accept all tags */
+static uint8_t g_paired_tag_id = 0;
+
+/* ── DW3000 ISR callbacks ───────────────────────────────────────── */
+
+static void cb_tx_done(const dwt_cb_data_t *) { g_tx_done = true; }
+
+static void cb_rx_ok(const dwt_cb_data_t *d) {
+    g_rx_len = d->datalength;
+    if (g_rx_len > sizeof(g_rx_buf)) g_rx_len = sizeof(g_rx_buf);
+    dwt_readrxdata(g_rx_buf, g_rx_len, 0);
+    g_rx_ok = true;
+}
+
+static void cb_rx_err(const dwt_cb_data_t *) { g_rx_err = true; }
+static void cb_rx_to(const dwt_cb_data_t  *) { g_rx_to  = true; }
+
+/* ── Timestamp helpers ──────────────────────────────────────────── */
+
+static uint64_t ts_read(const uint8_t *p) {
+    uint64_t v = 0;
+    for (int i = 4; i >= 0; i--) v = (v << 8) | p[i];
+    return v;
+}
+
+static void ts_write(uint8_t *p, uint64_t v) {
+    for (int i = 0; i < 5; i++, v >>= 8) p[i] = (uint8_t)(v & 0xFF);
+}
+
+static inline uint64_t ts_diff(uint64_t later, uint64_t earlier) {
+    return (later - earlier) & DWT_TS_MASK;
+}
+
+static inline double ticks_to_s(uint64_t t) {
+    return (double)t / (128.0 * 499200000.0);
+}
+
+/* Estimate receive power from CIR diagnostics (dBm) */
+static float rx_power_dbm(void) {
+    dwt_rxdiag_t d;
+    dwt_readdiagnostics(&d);
+    if (d.maxGrowthCIR == 0 || d.rxPreamCount == 0) return 0.0f;
+    float f = (float)d.maxGrowthCIR;
+    float n = (float)d.rxPreamCount;
+    return 10.0f * log10f((f * f) / (n * n)) - 121.74f;
+}
+
+/* ── AT command handler ─────────────────────────────────────────── */
+
+static char g_at_buf[64];
+static int  g_at_idx = 0;
+
+static void at_dispatch(const char *cmd) {
+    if (strcmp(cmd, "AT+RANGE?") == 0) {
+        if (g_last_range_mm >= 0)
+            Serial.println(g_last_range_line);
+        else
+            Serial.println("+RANGE:NO_DATA");
+
+    } else if (strcmp(cmd, "AT+ID?") == 0) {
+        Serial.printf("+ID:%d\r\n", ANCHOR_ID);
+
+    } else if (strncmp(cmd, "AT+RANGE_ADDR=", 14) == 0) {
+        const char *v = cmd + 14;
+        if (*v == '\0') {
+            g_paired_tag_id = 0;
+            Serial.println("+OK:UNPAIRED");
+        } else {
+            g_paired_tag_id = (uint8_t)strtoul(v, nullptr, 0);
+            Serial.printf("+OK:PAIRED=0x%02X\r\n", g_paired_tag_id);
+        }
+    } else {
+        Serial.println("+ERR:UNKNOWN_CMD");
+    }
+}
+
+static void serial_poll(void) {
+    while (Serial.available()) {
+        char c = (char)Serial.read();
+        if (c == '\r') continue;
+        if (c == '\n') {
+            g_at_buf[g_at_idx] = '\0';
+            if (g_at_idx > 0) at_dispatch(g_at_buf);
+            g_at_idx = 0;
+        } else if (g_at_idx < (int)(sizeof(g_at_buf) - 1)) {
+            g_at_buf[g_at_idx++] = c;
+        }
+    }
+}
+
+/* ── DS-TWR anchor state machine ────────────────────────────────── */
+
+/*
+ * DS-TWR responder (one shot):
+ *   1. Wait for POLL from tag
+ *   2. Delayed-TX RESP (carry T_poll_rx + scheduled T_resp_tx)
+ *   3. Wait for FINAL from tag  (tag embeds Ra, Da, Db)
+ *   4. Compute: Rb = T_final_rx − T_resp_tx
+ *               tof = (Ra·Rb − Da·Db) / (Ra+Rb+Da+Db)
+ *               range_m = tof × c
+ *   5. Print +RANGE line
+ */
+static void twr_cycle(void) {
+
+    /* --- 1. Listen for POLL --- */
+    dwt_setrxtimeout(0);
+    dwt_rxenable(DWT_START_RX_IMMEDIATE);
+
+    g_rx_ok = g_rx_err = false;
+    uint32_t deadline = millis() + 2000;
+    while (!g_rx_ok && !g_rx_err) {
+        serial_poll();
+        if (millis() > deadline) {
+            /* restart RX if we've been stuck */
+            dwt_rxenable(DWT_START_RX_IMMEDIATE);
+            deadline = millis() + 2000;
+        }
+        yield();
+    }
+    if (!g_rx_ok || g_rx_len < FRAME_HDR) return;
+
+    /* validate POLL */
+    if (g_rx_buf[0] != FTYPE_POLL) return;
+    uint8_t tag_id = g_rx_buf[1];
+    if (g_paired_tag_id != 0 && tag_id != g_paired_tag_id) return;
+
+    /* --- 2. Record T_poll_rx --- */
+    uint8_t  poll_rx_raw[5];
+    dwt_readrxtimestamp(poll_rx_raw);
+    uint64_t T_poll_rx = ts_read(poll_rx_raw);
+
+    /* Compute delayed TX time: poll_rx + turnaround, aligned to 512-tick grid */
+    uint64_t resp_tx_sched = (T_poll_rx + RESP_TX_DLY_TICKS) & ~0x1FFULL;
+
+    /* Build RESP frame */
+    uint8_t resp[RESP_FRAME_LEN];
+    resp[0] = FTYPE_RESP;
+    resp[1] = ANCHOR_ID;
+    resp[2] = tag_id;
+    ts_write(&resp[3], T_poll_rx);      /* T_poll_rx  (tag uses this) */
+    ts_write(&resp[8], resp_tx_sched);  /* scheduled T_resp_tx */
+
+    dwt_writetxdata(RESP_FRAME_LEN - FCS_LEN, resp, 0);
+    dwt_writetxfctrl(RESP_FRAME_LEN, 0, 1 /*ranging*/);
+    dwt_setdelayedtrxtime((uint32_t)(resp_tx_sched >> 8));
+
+    /* Enable RX after TX to receive FINAL */
+    dwt_setrxaftertxdelay(300);
+    dwt_setrxtimeout(FINAL_RX_TIMEOUT_US);
+
+    /* Fire delayed TX */
+    g_tx_done = g_rx_ok = g_rx_err = g_rx_to = false;
+    if (dwt_starttx(DWT_START_TX_DELAYED | DWT_RESPONSE_EXPECTED) != DWT_SUCCESS) {
+        dwt_forcetrxoff();
+        return; /* TX window missed — try next cycle */
+    }
+
+    /* Wait for TX done (short wait, ISR fires fast) */
+    uint32_t t0 = millis();
+    while (!g_tx_done && millis() - t0 < 15) { yield(); }
+
+    /* Read actual T_resp_tx */
+    uint8_t resp_tx_raw[5];
+    dwt_readtxtimestamp(resp_tx_raw);
+    uint64_t T_resp_tx = ts_read(resp_tx_raw);
+
+    /* --- 3. Wait for FINAL --- */
+    t0 = millis();
+    while (!g_rx_ok && !g_rx_err && !g_rx_to && millis() - t0 < 60) {
+        serial_poll();
+        yield();
+    }
+    if (!g_rx_ok || g_rx_len < FRAME_HDR + FINAL_PAYLOAD) return;
+    if (g_rx_buf[0] != FTYPE_FINAL) return;
+    if (g_rx_buf[1] != tag_id)      return;
+
+    /* Extract DS-TWR timestamps from FINAL payload */
+    uint64_t Ra = ts_read(&g_rx_buf[3]);   /* tag: T_resp_rx − T_poll_tx */
+    uint64_t Da = ts_read(&g_rx_buf[8]);   /* tag: T_final_tx − T_resp_rx */
+    /* g_rx_buf[13..17] = Db from tag (cross-check, unused here) */
+
+    /* T_final_rx */
+    uint8_t final_rx_raw[5];
+    dwt_readrxtimestamp(final_rx_raw);
+    uint64_t T_final_rx = ts_read(final_rx_raw);
+
+    /* --- 4. DS-TWR formula --- */
+    uint64_t Rb = ts_diff(T_final_rx, T_resp_tx);  /* anchor round-trip */
+    uint64_t Db = ts_diff(T_resp_tx,  T_poll_rx);  /* anchor turnaround */
+
+    double ra = ticks_to_s(Ra), rb = ticks_to_s(Rb);
+    double da = ticks_to_s(Da), db = ticks_to_s(Db);
+
+    double denom = ra + rb + da + db;
+    if (denom < 1e-15) return;
+
+    double tof    = (ra * rb - da * db) / denom;
+    double range_m = tof * SPEED_OF_LIGHT;
+
+    /* Validity window: 0.1 m – 130 m */
+    if (range_m < 0.1 || range_m > 130.0) return;
+
+    int32_t range_mm = (int32_t)(range_m * 1000.0 + 0.5);
+    float   rssi     = rx_power_dbm();
+
+    /* --- 5. Emit +RANGE --- */
+    snprintf(g_last_range_line, sizeof(g_last_range_line),
+             "+RANGE:%d,%ld,%.1f", ANCHOR_ID, (long)range_mm, rssi);
+    g_last_range_mm = range_mm;
+    Serial.println(g_last_range_line);
+}
+
+/* ── Arduino setup ──────────────────────────────────────────────── */
+
+void setup(void) {
+    Serial.begin(SERIAL_BAUD);
+    delay(300);
+
+    Serial.printf("\r\n[uwb_anchor] anchor_id=%d  starting\r\n", ANCHOR_ID);
+
+    SPI.begin(PIN_SCK, PIN_MISO, PIN_MOSI, PIN_CS);
+
+    /* Hardware reset */
+    pinMode(PIN_RST, OUTPUT);
+    digitalWrite(PIN_RST, LOW);
+    delay(2);
+    pinMode(PIN_RST, INPUT_PULLUP);
+    delay(5);
+
+    /* DW3000 probe + init (Makerfabs MaUWB_DW3000 library) */
+    if (dwt_probe((struct dwt_probe_s *)&dw3000_probe_interf)) {
+        Serial.println("[uwb_anchor] FATAL: DW3000 probe failed — check SPI wiring");
+        for (;;) delay(1000);
+    }
+
+    if (dwt_initialise(DWT_DW_INIT) != DWT_SUCCESS) {
+        Serial.println("[uwb_anchor] FATAL: dwt_initialise failed");
+        for (;;) delay(1000);
+    }
+
+    if (dwt_configure(&dw_cfg) != DWT_SUCCESS) {
+        Serial.println("[uwb_anchor] FATAL: dwt_configure failed");
+        for (;;) delay(1000);
+    }
+
+    dwt_setrxantennadelay(ANT_DELAY);
+    dwt_settxantennadelay(ANT_DELAY);
+    dwt_settxpower(0x0E080222UL);  /* max TX power for 120 m range */
+
+    dwt_setcallbacks(cb_tx_done, cb_rx_ok, cb_rx_to, cb_rx_err,
+                     nullptr, nullptr, nullptr);
+    dwt_setinterrupt(
+        DWT_INT_TXFRS | DWT_INT_RFCG | DWT_INT_RFTO |
+        DWT_INT_RFSL  | DWT_INT_SFDT | DWT_INT_ARFE | DWT_INT_CPERR,
+        0, DWT_ENABLE_INT_ONLY);
+
+    attachInterrupt(digitalPinToInterrupt(PIN_IRQ),
+                    []() { dwt_isr(); }, RISING);
+
+    Serial.printf("[uwb_anchor] DW3000 ready  ch=%d  6.8Mbps  id=%d\r\n",
+                  dw_cfg.chan, ANCHOR_ID);
+    Serial.println("[uwb_anchor] Listening for tags...");
+}
+
+/* ── Arduino loop ───────────────────────────────────────────────── */
+
+void loop(void) {
+    serial_poll();
+    twr_cycle();
+}
diff --git a/esp32/uwb_anchor/udev/99-uwb-anchors.rules b/esp32/uwb_anchor/udev/99-uwb-anchors.rules
new file mode 100644
index 0000000..c850400
--- /dev/null
+++ b/esp32/uwb_anchor/udev/99-uwb-anchors.rules
@@ -0,0 +1,19 @@
+# SaltyBot UWB anchor USB-serial persistent symlinks
+# Install:
+#   sudo cp 99-uwb-anchors.rules /etc/udev/rules.d/
+#   sudo udevadm control --reload && sudo udevadm trigger
+#
+# Find serial numbers:
+#   udevadm info -a /dev/ttyUSB0 | grep ATTRS{serial}
+#
+# Fill ANCHOR0_SERIAL and ANCHOR1_SERIAL with the values found above.
+# Anchor 0 = port  side → /dev/uwb-anchor0
+# Anchor 1 = starboard  → /dev/uwb-anchor1
+
+SUBSYSTEM=="tty", ATTRS{idVendor}=="10c4", ATTRS{idProduct}=="ea60", \
+    ATTRS{serial}=="ANCHOR0_SERIAL", \
+    SYMLINK+="uwb-anchor0", MODE="0666"
+
+SUBSYSTEM=="tty", ATTRS{idVendor}=="10c4", ATTRS{idProduct}=="ea60", \
+    ATTRS{serial}=="ANCHOR1_SERIAL", \
+    SYMLINK+="uwb-anchor1", MODE="0666"