Arduino frameworks

- AltSoftSerial UART with WT61 IMU
- UART with Pi on TX0/RX0 (and USB)

arduino/main/main.ino

@@ -2,24 +2,77 @@
 // Motorcycle telemetry hub
 
 #include "voltage.h"
+#include "imu.h"
+#include "comms.h"
+
+// Timing
+static const unsigned long TELEMETRY_INTERVAL_MS = 100;  // 10Hz telemetry
+static unsigned long lastTelemetryTime = 0;
 
 void setup() {
-  Serial.begin(9600);
   pinMode(LED_BUILTIN, OUTPUT);
 
   voltage_init();
+  imu_init();      // AltSoftSerial on pins 8(RX)/9(TX)
+  comms_init();    // Hardware Serial to Pi at 115200
 }
 
 void loop() {
-  // Report battery voltage
-  Serial.print("V_bat: ");
-  Serial.print(voltage_read(), 2);
-  Serial.println("V");
+  // Always poll IMU - it's streaming at 20Hz
+  imu_update();
 
-  // Heartbeat blink
-  digitalWrite(LED_BUILTIN, HIGH);
-  delay(50);
-  digitalWrite(LED_BUILTIN, LOW);
+  // Process any commands from Pi
+  if (comms_update()) {
+    const char* cmd = comms_get_command();
+    // Future: handle commands like "PING", "SET_RATE", etc.
+    // For now, echo back as acknowledgment
+    if (cmd[0] != '\0') {
+      comms_send("ACK", cmd);
+    }
+  }
 
-  delay(1000);  // 1Hz update rate
+  // Send telemetry at fixed interval
+  unsigned long now = millis();
+  if (now - lastTelemetryTime >= TELEMETRY_INTERVAL_MS) {
+    lastTelemetryTime = now;
+    sendTelemetry();
+  }
+
+  // Heartbeat - quick blink if IMU fresh, slow blink if stale
+  static unsigned long lastBlink = 0;
+  unsigned long blinkInterval = imu_is_fresh() ? 500 : 2000;
+  if (now - lastBlink >= blinkInterval) {
+    lastBlink = now;
+    digitalWrite(LED_BUILTIN, !digitalRead(LED_BUILTIN));
+  }
+}
+
+void sendTelemetry() {
+  // Battery voltage
+  comms_send("V_bat", voltage_read());
+
+  // IMU data (only if we have fresh data)
+  if (imu_is_fresh()) {
+    const ImuData& imu = imu_get_data();
+
+    // Acceleration (g)
+    comms_send("Ax", imu.ax);
+    comms_send("Ay", imu.ay);
+    comms_send("Az", imu.az);
+
+    // Angular velocity (deg/s)
+    comms_send("Gx", imu.gx);
+    comms_send("Gy", imu.gy);
+    comms_send("Gz", imu.gz);
+
+    // Euler angles (degrees)
+    comms_send("Roll", imu.roll);
+    comms_send("Pitch", imu.pitch);
+    comms_send("Yaw", imu.yaw);
+  } else {
+    comms_send("IMU", "STALE");
+
+    // flip LED to indicate main cycle
+    digitalWrite(LED_BUILTIN, !digitalRead(LED_BUILTIN));
+  }
 }