Arduino frameworks

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

arduino/main/imu.h

@@ -0,0 +1,31 @@
+#ifndef IMU_H
+#define IMU_H
+
+#include <Arduino.h>
+
+// WT61 IMU data structure
+struct ImuData {
+  // Acceleration (g)
+  float ax, ay, az;
+  // Angular velocity (deg/s)
+  float gx, gy, gz;
+  // Euler angles (degrees)
+  float roll, pitch, yaw;
+  // Timestamp of last valid packet (millis)
+  unsigned long lastUpdate;
+};
+
+// Initialize IMU serial (call in setup)
+void imu_init();
+
+// Process incoming bytes - call frequently in loop
+// Returns true if new complete packet was parsed
+bool imu_update();
+
+// Get latest IMU data
+const ImuData& imu_get_data();
+
+// Check if IMU data is fresh (updated within timeout_ms)
+bool imu_is_fresh(unsigned long timeout_ms = 200);
+
+#endif