firmware: use verified sensor settings

docs/CHANGELOG.md

@@ -6,6 +6,7 @@
 - Added XIAO-side persistent level calibration with stability checking and RS485 start/clear commands; no dashboard behavior changed.
 - Prevented echoed or oversized RS485 frames from starving the XIAO sensor loop.
 - Silently discard malformed partial RS485 echoes instead of emitting recursive `invalid_json` responses.
+- Replaced sensor auto-detection with the verified installation settings: BNO086 address `0x4B` and MAX-M10S UART at 38400 baud.
 
 ## Unreleased
 

firmware/xiao-esp32c6-sensor-node/README.md

@@ -9,9 +9,9 @@ This Arduino sketch reads a BNO086 IMU and MAX-M10S GPS and publishes versioned,
 | GPS TX to XIAO RX | D9 |
 | GPS RX from XIAO TX | D10 |
 
-Power both sensors from 3.3V with shared ground. Required Arduino libraries are Adafruit BNO08x, TinyGPSPlus, and ArduinoJson 6.x. Enable **USB CDC On Boot** for diagnostics. GPS uses hardware UART0 and RS485 uses hardware UART1. Startup probes 9600, 38400, 115200, and 4800 baud and reports the first rate producing checksum-valid NMEA.
+Power both sensors from 3.3V with shared ground. Required Arduino libraries are Adafruit BNO08x, TinyGPSPlus, and ArduinoJson 6.x. Enable **USB CDC On Boot** for diagnostics. GPS uses hardware UART0 at the verified 38400 baud; RS485 uses hardware UART1.
 
-At startup the firmware scans D7/D8 and accepts either valid BNO08x address, `0x4A` or `0x4B`. If neither appears in the scan, verify 3.3V/GND, swap-check SDA and SCL, and confirm the breakout's PS0/PS1 jumpers are configured for I2C.
+The BNO086 uses the verified `0x4B` I2C address on D7/D8. If initialization fails, verify 3.3V/GND, SDA/SCL wiring, and the breakout's PS0/PS1 configuration.
 
 The node sends `sensor_status` at 115200 baud every 200 ms. See `docs/SENSOR_NODE_PROTOCOL.md`. The initial firmware is transmit-only; add a dashboard receiver after bench-testing the node, RS485 polarity, and sensor axes.
 

firmware/xiao-esp32c6-sensor-node/gps.cpp

@@ -4,39 +4,13 @@
 namespace { TinyGPSPlus parser; }
 
 namespace {
-uint32_t activeBaud = GPS_FALLBACK_BAUD;
+uint32_t activeBaud = GPS_BAUD;
-
-bool baudHasValidNmea(HardwareSerial& serial, uint32_t baud) {
-    TinyGPSPlus probe;
-    serial.end();
-    serial.begin(baud, SERIAL_8N1, GPS_RX_PIN, GPS_TX_PIN);
-    unsigned long started = millis();
-    while (millis() - started < GPS_BAUD_DETECT_MS) {
-        while (serial.available()) probe.encode(serial.read());
-        if (probe.passedChecksum() > 0) return true;
-        delay(1);
-    }
-    return false;
-}
 }
 
 void initGps(HardwareSerial& serial) {
-    const uint32_t candidates[] = {9600, 38400, 115200, 4800};
-    Serial.println("Detecting GPS UART baud...");
-    for (uint32_t baud : candidates) {
-        Serial.print("Trying GPS baud ");
-        Serial.println(baud);
-        if (!baudHasValidNmea(serial, baud)) continue;
-        activeBaud = baud;
-        Serial.print("Valid GPS NMEA detected at ");
-        Serial.println(activeBaud);
-        return;
-    }
-
-    activeBaud = GPS_FALLBACK_BAUD;
-    serial.end();
     serial.begin(activeBaud, SERIAL_8N1, GPS_RX_PIN, GPS_TX_PIN);
-    Serial.println("No valid GPS NMEA detected; falling back to 9600 baud");
+    Serial.print("Starting GPS UART at ");
+    Serial.println(activeBaud);
 }
 
 void updateGps(HardwareSerial& serial, GpsState& s) {

firmware/xiao-esp32c6-sensor-node/imu.cpp

@@ -9,26 +9,6 @@ Adafruit_BNO08x bno086(-1);
 sh2_SensorValue_t value;
 bool initialized = false;
 float radiansToDegrees(float r) { return r * 180.0f / PI; }
-bool addressResponds(uint8_t address) {
-    Wire.beginTransmission(address);
-    return Wire.endTransmission() == 0;
-}
-
-uint8_t findBnoAddress() {
-    Serial.println("Scanning I2C bus on D7 SDA / D8 SCL...");
-    uint8_t bnoAddress = 0;
-    for (uint8_t address = 1; address < 127; address++) {
-        if (!addressResponds(address)) continue;
-        Serial.print("I2C device found at 0x");
-        if (address < 0x10) Serial.print('0');
-        Serial.println(address, HEX);
-        if (address == BNO086_I2C_ADDRESS || address == BNO086_I2C_ADDRESS_ALTERNATE) {
-            bnoAddress = address;
-        }
-    }
-    return bnoAddress;
-}
-
 void updateEuler(ImuState& s) {
     float sinr = 2 * (s.real * s.i + s.j * s.k);
     float cosr = 1 - 2 * (s.i * s.i + s.j * s.j);
@@ -45,16 +25,9 @@ bool initImu() {
     Wire.begin(BNO086_SDA_PIN, BNO086_SCL_PIN);
     Wire.setClock(BNO086_I2C_CLOCK_HZ);
     delay(100);
-
-    uint8_t address = findBnoAddress();
-    if (address == 0) {
-        Serial.println("No BNO086 found at 0x4A or 0x4B");
-        return false;
-    }
-
     Serial.print("Starting BNO086 at 0x");
-    Serial.println(address, HEX);
+    Serial.println(BNO086_I2C_ADDRESS, HEX);
-    initialized = bno086.begin_I2C(address, &Wire);
+    initialized = bno086.begin_I2C(BNO086_I2C_ADDRESS, &Wire);
     if (initialized) initialized = bno086.enableReport(SH2_ROTATION_VECTOR, IMU_REPORT_INTERVAL_US);
     return initialized;
 }

firmware/xiao-esp32c6-sensor-node/sensor_node_config.h

@@ -11,11 +11,9 @@
 #define BNO086_SCL_PIN D8
 #define GPS_RX_PIN D9
 #define GPS_TX_PIN D10
-#define BNO086_I2C_ADDRESS 0x4A
+#define BNO086_I2C_ADDRESS 0x4B
-#define BNO086_I2C_ADDRESS_ALTERNATE 0x4B
 #define BNO086_I2C_CLOCK_HZ 100000
-#define GPS_FALLBACK_BAUD 9600
+#define GPS_BAUD 38400
-#define GPS_BAUD_DETECT_MS 2500
 #define RS485_BAUD 115200
 #define IMU_REPORT_INTERVAL_US 20000
 #define TELEMETRY_INTERVAL_MS 200

tests/test_xiao_sensor_node_contract.py

@@ -30,19 +30,17 @@ def test_imu_does_not_redeclare_arduino_degrees_macro():
     assert "float degrees(" not in imu
     assert "radiansToDegrees" in imu
 
-def test_imu_scans_both_bno08x_i2c_addresses():
+def test_imu_uses_verified_i2c_address():
     config = source("sensor_node_config.h")
     imu = source("imu.cpp")
-    assert "BNO086_I2C_ADDRESS 0x4A" in config
+    assert "BNO086_I2C_ADDRESS 0x4B" in config
-    assert "BNO086_I2C_ADDRESS_ALTERNATE 0x4B" in config
+    assert "findBnoAddress" not in imu
-    assert "findBnoAddress()" in imu
-    assert "Wire.endTransmission()" in imu
 
-def test_gps_auto_detects_common_nmea_baud_rates():
+def test_gps_uses_verified_uart_baud():
+    config = source("sensor_node_config.h")
     gps = source("gps.cpp")
-    assert "baudHasValidNmea" in gps
+    assert "GPS_BAUD 38400" in config
-    assert "{9600, 38400, 115200, 4800}" in gps
+    assert "baudHasValidNmea" not in gps
-    assert "passedChecksum() > 0" in gps
 
 def test_level_calibration_is_persistent_and_non_blocking():
     calibration = source("calibration.cpp")