fix: correct XIAO RS485 UART pin mapping

docs/SENSOR_NODE_PROTOCOL.md

@@ -2,7 +2,7 @@
 
 The XIAO sensor node reads the BNO086 and MAX-M10S and publishes vehicle telemetry over half-duplex RS485 at 115200 8-N-1, one JSON object per line at 4 Hz. It owns no control state. Cargo remains the controller, HTTP server, and `/api/v1` source of truth; JBD/NimBLE behavior is unchanged.
 
-The expansion-board pins are D2 driver enable, D4 TX, and D5 RX. Only physical bus ends should be terminated. Confirm A/B polarity because vendor labels vary.
+The expansion-board pins are D2 driver enable, D4 RX, and D5 TX, matching Seeed's XIAO RS485 expansion-board wiring. Only physical bus ends should be terminated. Confirm A/B polarity because vendor labels vary.
 
 ## Schema version 1
 

firmware/esp32-s3-dashboard/dashboard_config.h

@@ -1,6 +1,6 @@
 #pragma once
 
-static const char *DASHBOARD_VERSION = "0.1.131-rs485-sensor-stats";
+static const char *DASHBOARD_VERSION = "0.1.132-rs485-raw-diagnostics";
 
 // First-boot defaults. Credentials are stored in Preferences/NVS after setup.
 static const char *DASHBOARD_DEFAULT_CARGO_WIFI_SSID = "OverlandController";

firmware/esp32-s3-dashboard/esp32-s3-dashboard.ino

@@ -687,6 +687,12 @@ static void update_diagnostics_overlay()
     text += String(sensor_node.framesDropped);
     text += "/";
     text += String(sensor_node.parseErrors + sensor_node.oversizedFrames);
+    text += "\n  Raw bytes/age: ";
+    text += String(sensor_node.bytesReceived);
+    text += "/";
+    text += sensor_node.bytesReceived
+        ? String(millis() - sensor_node.lastByteMs) + " ms"
+        : String("--");
     text += "\n  Frame age: ";
     text += sensor_node.frameReceived
         ? String(millis() - sensor_node.lastFrameMs) + " ms"

firmware/esp32-s3-dashboard/sensor_node_receiver.cpp

@@ -117,6 +117,8 @@ void initSensorNodeRs485() {
 void processSensorNodeRs485() {
     while (sensorNodeSerial.available() > 0) {
         char value = (char)sensorNodeSerial.read();
+        sensorNodeStatus.bytesReceived++;
+        sensorNodeStatus.lastByteMs = millis();
         if (value == '\r') continue;
 
         if (value != '\n') {

firmware/esp32-s3-dashboard/sensor_node_receiver.h

@@ -16,6 +16,7 @@ struct SensorNodeDashboardStatus {
     uint32_t framesDropped = 0;
     uint32_t parseErrors = 0;
     uint32_t oversizedFrames = 0;
+    uint32_t bytesReceived = 0;
     uint32_t nodeRestarts = 0;
     uint32_t satellites = 0;
     float pitchDegrees = 0;
@@ -29,6 +30,7 @@ struct SensorNodeDashboardStatus {
     String stability = "unknown";
     String firmwareVersion;
     String utcTime;
+    unsigned long lastByteMs = 0;
     unsigned long lastFrameMs = 0;
 };
 

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

@@ -4,7 +4,7 @@ This Arduino sketch reads a BNO086 IMU and MAX-M10S GPS and publishes versioned,
 
 | Function | XIAO pin |
 | --- | --- |
-| RS485 DE / TX / RX | D2 / D4 / D5 |
+| RS485 DE / RX / TX | D2 / D4 / D5 |
 | BNO086 SDA / SCL | D7 / D8 |
 | GPS TX to XIAO RX | D9 |
 | GPS RX from XIAO TX | D10 |

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

@@ -2,11 +2,11 @@
 #include <Arduino.h>
 
 #define SENSOR_NODE_NAME "xiao_c6_sensor_node"
-#define SENSOR_NODE_FIRMWARE_VERSION "0.2.0"
+#define SENSOR_NODE_FIRMWARE_VERSION "0.2.1"
 #define SENSOR_NODE_SCHEMA_VERSION 1
 #define RS485_DE_PIN D2
-#define RS485_TX_PIN D4
-#define RS485_RX_PIN D5
+#define RS485_RX_PIN D4
+#define RS485_TX_PIN D5
 #define BNO086_SDA_PIN D7
 #define BNO086_SCL_PIN D8
 #define GPS_RX_PIN D9

tests/test_dashboard_source_contract.py

@@ -44,6 +44,8 @@ def test_dashboard_receives_sensor_node_rs485_for_diagnostics():
     assert 'strcmp(type, "sensor_status")' in receiver
     assert 'doc["frame_sequence"]' in receiver
     assert "framesDropped" in receiver
+    assert "bytesReceived++" in receiver
+    assert r'text += "\n  Raw bytes/age: "' in dashboard
     assert 'imu["yaw_degrees"]' in receiver
     assert 'gps["altitude_meters"]' in receiver
     assert 'JsonObject utc = gps["utc"]' in receiver

tests/test_xiao_sensor_node_contract.py

@@ -7,7 +7,7 @@ def source(name): return (NODE / name).read_text()
 
 def test_wiring_matches_assembly():
     config = source("sensor_node_config.h")
-    expected = {"RS485_DE_PIN":"D2", "RS485_TX_PIN":"D4", "RS485_RX_PIN":"D5",
+    expected = {"RS485_DE_PIN":"D2", "RS485_RX_PIN":"D4", "RS485_TX_PIN":"D5",
                 "BNO086_SDA_PIN":"D7", "BNO086_SCL_PIN":"D8", "GPS_RX_PIN":"D9", "GPS_TX_PIN":"D10"}
     for name, pin in expected.items(): assert re.search(rf"#define\s+{name}\s+{pin}\b", config)