Arduino frameworks

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

arduino/README.md

@@ -11,7 +11,58 @@ Sensor interface running on Arduino Nano, communicating with Pi via UART.
 ## Current Capabilities
 
 - Battery voltage monitoring (voltage divider on A0)
-- Serial output at 9600 baud, 1Hz update rate
+- WT61 IMU/gyro via AltSoftSerial (9-axis: accel, gyro, euler angles)
+- Duplex UART to Pi at 115200 baud, 10Hz telemetry output
+- Simple text-based protocol for easy debugging
+
+## Dependencies
+
+Install via Arduino Library Manager:
+- **AltSoftSerial** by Paul Stoffregen - for WT61 IMU serial
+
+## Pin Assignments
+
+| Pin | Function |
+|-----|----------|
+| A0 | Battery voltage (via divider) |
+| D0 (RX) | Pi UART RX ← Arduino TX |
+| D1 (TX) | Pi UART TX → Arduino RX |
+| D8 | WT61 IMU RX (AltSoftSerial) |
+| D9 | WT61 IMU TX (unused, AltSoftSerial fixed pin) |
+| D13 | Status LED (heartbeat) |
+
+## Hardware
+
+- **MCU**: Arduino Nano (ATmega328P)
+- **Pi Connection**: UART at 115200 baud (TX→RX, RX→TX, common GND)
+- **IMU**: WT61 module at 9600 baud, 20Hz output
+- **Voltage sensing**: Resistor divider (100k/47k) scaled for 0-20V input
+
+## Protocol
+
+Simple text lines, one per sensor reading:
+```
+V_bat: 12.45
+Ax: 0.02
+Ay: -0.01
+Az: 1.00
+Gx: 0.50
+Gy: -0.25
+Gz: 0.10
+Roll: 2.35
+Pitch: -1.20
+Yaw: 45.80
+```
+
+If IMU data is stale (no valid packets for 200ms):
+```
+IMU: STALE
+```
+
+Commands from Pi are echoed back:
+```
+ACK: PING
+```
 
 ## Planned
 
@@ -19,18 +70,3 @@ Sensor interface running on Arduino Nano, communicating with Pi via UART.
 - Engine temperature (thermocouple/NTC)
 - Gear position indicator
 - Turn signal / high beam status
-
-## Hardware
-
-- **MCU**: Arduino Nano (ATmega328P)
-- **Connection**: UART to Pi GPIO (TX→RX, RX→TX, common GND)
-- **Voltage sensing**: Resistor divider scaled for 0-20V input range
-
-## Protocol
-
-Simple text-based for now:
-```
-V_bat: 12.45V
-```
-
-Future: structured binary or JSON for multiple sensors.

arduino/main/comms.cpp

@@ -0,0 +1,70 @@
+#include "comms.h"
+
+// Pi communication uses hardware Serial (pins 0/1)
+// Baud rate - 115200 is reasonable for duplex with Pi
+static const long BAUD_RATE = 115200;
+
+// Command buffer
+static const int CMD_BUF_SIZE = 64;
+static char cmdBuf[CMD_BUF_SIZE];
+static int cmdIndex = 0;
+static bool cmdReady = false;
+
+// Connection tracking
+static unsigned long lastRxTime = 0;
+
+void comms_init() {
+  Serial.begin(BAUD_RATE);
+  cmdIndex = 0;
+  cmdReady = false;
+}
+
+bool comms_update() {
+  while (Serial.available()) {
+    char c = Serial.read();
+    lastRxTime = millis();
+
+    if (c == '\n' || c == '\r') {
+      if (cmdIndex > 0) {
+        cmdBuf[cmdIndex] = '\0';
+        cmdReady = true;
+        cmdIndex = 0;
+        return true;
+      }
+    } else if (cmdIndex < CMD_BUF_SIZE - 1) {
+      cmdBuf[cmdIndex++] = c;
+    }
+    // else: overflow, silently drop extra chars
+  }
+  return false;
+}
+
+void comms_send(const char* key, float value, int decimals) {
+  Serial.print(key);
+  Serial.print(": ");
+  Serial.println(value, decimals);
+}
+
+void comms_send(const char* key, int value) {
+  Serial.print(key);
+  Serial.print(": ");
+  Serial.println(value);
+}
+
+void comms_send(const char* key, const char* value) {
+  Serial.print(key);
+  Serial.print(": ");
+  Serial.println(value);
+}
+
+const char* comms_get_command() {
+  if (cmdReady) {
+    cmdReady = false;
+    return cmdBuf;
+  }
+  return "";
+}
+
+bool comms_is_connected(unsigned long timeout_ms) {
+  return (millis() - lastRxTime) < timeout_ms;
+}

arduino/main/comms.h

@@ -0,0 +1,25 @@
+#ifndef COMMS_H
+#define COMMS_H
+
+#include <Arduino.h>
+
+// Initialize Pi serial communication (call in setup)
+void comms_init();
+
+// Process incoming commands from Pi - call in loop
+// Returns true if a complete command was received
+bool comms_update();
+
+// Send telemetry line to Pi
+void comms_send(const char* key, float value, int decimals = 2);
+void comms_send(const char* key, int value);
+void comms_send(const char* key, const char* value);
+
+// Get last received command (empty if none)
+// Command buffer is cleared after reading
+const char* comms_get_command();
+
+// Check if connected (received any data recently)
+bool comms_is_connected(unsigned long timeout_ms = 5000);
+
+#endif

arduino/main/imu.cpp

@@ -0,0 +1,115 @@
+#include "imu.h"
+#include <AltSoftSerial.h>
+
+// AltSoftSerial uses fixed pins on ATmega328P:
+// RX = Pin 8, TX = Pin 9 (TX not used for WT61)
+static AltSoftSerial imuSerial;
+
+// WT61 packet structure:
+// Byte 0: 0x55 (header)
+// Byte 1: Packet type (0x51=accel, 0x52=gyro, 0x53=angle)
+// Bytes 2-9: Data (4x int16_t, little-endian)
+// Byte 10: Checksum (sum of bytes 0-9, lower 8 bits)
+static const uint8_t PACKET_HEADER = 0x55;
+static const uint8_t PACKET_ACCEL  = 0x51;
+static const uint8_t PACKET_GYRO   = 0x52;
+static const uint8_t PACKET_ANGLE  = 0x53;
+static const int PACKET_SIZE = 11;
+
+// Receive buffer
+static uint8_t rxBuf[PACKET_SIZE];
+static int rxIndex = 0;
+
+// Latest data
+static ImuData currentData = {0};
+
+// Scale factors from WT61 datasheet
+// Accel: raw / 32768 * 16g
+// Gyro:  raw / 32768 * 2000 deg/s
+// Angle: raw / 32768 * 180 deg
+static const float ACCEL_SCALE = 16.0 / 32768.0;
+static const float GYRO_SCALE  = 2000.0 / 32768.0;
+static const float ANGLE_SCALE = 180.0 / 32768.0;
+
+static int16_t parseI16(uint8_t lo, uint8_t hi) {
+  return (int16_t)((hi << 8) | lo);
+}
+
+static bool validateChecksum() {
+  uint8_t sum = 0;
+  for (int i = 0; i < PACKET_SIZE - 1; i++) {
+    sum += rxBuf[i];
+  }
+  return sum == rxBuf[PACKET_SIZE - 1];
+}
+
+static void processPacket() {
+  if (!validateChecksum()) {
+    return;  // Bad packet, ignore
+  }
+
+  uint8_t type = rxBuf[1];
+  int16_t v0 = parseI16(rxBuf[2], rxBuf[3]);
+  int16_t v1 = parseI16(rxBuf[4], rxBuf[5]);
+  int16_t v2 = parseI16(rxBuf[6], rxBuf[7]);
+  // v3 at bytes 8-9 is temperature, ignored for now
+
+  switch (type) {
+    case PACKET_ACCEL:
+      currentData.ax = v0 * ACCEL_SCALE;
+      currentData.ay = v1 * ACCEL_SCALE;
+      currentData.az = v2 * ACCEL_SCALE;
+      break;
+    case PACKET_GYRO:
+      currentData.gx = v0 * GYRO_SCALE;
+      currentData.gy = v1 * GYRO_SCALE;
+      currentData.gz = v2 * GYRO_SCALE;
+      break;
+    case PACKET_ANGLE:
+      currentData.roll  = v0 * ANGLE_SCALE;
+      currentData.pitch = v1 * ANGLE_SCALE;
+      currentData.yaw   = v2 * ANGLE_SCALE;
+      currentData.lastUpdate = millis();
+      break;
+  }
+}
+
+void imu_init() {
+  imuSerial.begin(9600);
+  rxIndex = 0;
+  currentData = {0};
+}
+
+bool imu_update() {
+  bool gotPacket = false;
+
+  while (imuSerial.available()) {
+    uint8_t c = imuSerial.read();
+
+    // State machine: look for header, then collect packet
+    if (rxIndex == 0) {
+      if (c == PACKET_HEADER) {
+        rxBuf[rxIndex++] = c;
+      }
+      // else: discard, wait for sync
+    } else {
+      rxBuf[rxIndex++] = c;
+
+      if (rxIndex >= PACKET_SIZE) {
+        processPacket();
+        rxIndex = 0;
+        gotPacket = true;
+      }
+    }
+  }
+
+  return gotPacket;
+}
+
+const ImuData& imu_get_data() {
+  return currentData;
+}
+
+bool imu_is_fresh(unsigned long timeout_ms) {
+  return (millis() - currentData.lastUpdate) < timeout_ms;
+}

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

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));
+  }
 }