MSCanBus

ESP32-based GPS, Accelerometer, and etc. CAN Bus implementation for MegaSquirt ECUs.

Overview

This project leverages the ESP32 microcontroller to interface with MegaSquirt open-source engine controllers and Race Technology data loggers via CAN bus. It provides real-time GPS data including coordinates, time, altitude, and vehicle speed and acceleration to both systems for logging and display.

Features

• Dual CAN Bus Protocol Support:
  • MegaSquirt extended frame protocol (29-bit) at 500 kbps
  • Race Technology 11-bit CAN message format
• GPS Integration: u-blox binary protocol with multi-constellation support (GPS, GLONASS, Galileo, Beidou)
• Accelerometer Integration: 3-axis IMU data with automatic calibration (MPU6050)
• EGT Integration: MAX31855 thermocouple sensor for exhaust gas temperature measurement
• Real-time Data: GPS coordinates, UTC time, altitude, course, speed, acceleration, and exhaust gas temperature
• JBPerf Compatible: Uses same block/offset scheme as JBPerf IO Extender Board
• Race Technology Compatible: Broadcasts GPS position, speed, and accelerometer data using Race Technology 11-bit CAN message format
• Debug Output: Comprehensive serial logging for troubleshooting

Hardware Required

Core Components

• ESP-WROOM-32 + Expansion Board - ESP32 development board
• HGLRC Mini M100 - u-blox compatible 10Hz GPS module
• SN65HVD230 - CAN Bus Transceiver Module
• MPU6050 IMU Module - 6-axis accelerometer/gyroscope
• MAX31855 Module - K-type thermocouple amplifier for EGT measurement

Libraries Required

FastIMU

• Purpose: IMU/accelerometer data processing (MPU6050 support)
• Repository: FastIMU
• Features Used: Accelerometer calibration, real-time sensor data

Included Libraries (Custom and modified)

qqqlab_GPS_UBLOX (Included in project)

• Purpose: u-blox GPS binary (UBX) protocol handler with added date/time support
• Origin: Ported from ArduPilot AP_GPS_UBLOX (v4.5.7)
• Modifications: Platform agnostic, removed ArduPilot dependencies, no float usage
• Supported GPS: u-blox M8N, M9N, M10, F9P series modules
• Features: GNSS configuration, real-time positioning

MAX31855-library (Git submodule)

• Purpose: K-type thermocouple temperature measurement via MAX31855 amplifier
• Repository: MAX31855-library
• Features Used: Temperature reading, fault detection with error codes
• Installation: Automatically included as git submodule

Installation & Setup

1. Arduino IDE Setup

1. Install ESP32 board package:

   • File → Preferences → Additional Board Manager URLs
   • Add: https://dl.espressif.com/dl/package_esp32_index.json
   • Tools → Board → Boards Manager → Search "ESP32" → Install

2. Select board: ESP32 Dev Module

3. Install required libraries:

   Method 1: Arduino Library Manager (Recommended)

   • Tools → Manage Libraries
   • Search "FastIMU" → Install by LiquidCGS
   • Search "MAX31855-library" → Install by Moarbue

   Method 2: Manual Installation

   • FastIMU: Download from GitHub → Add .ZIP Library
   • MAX31855-library: Download from GitHub → Add .ZIP Library

2. Hardware Connections

ESP32 to GPS Module

ESP32    GPS Module
-----    ----------
GPIO16 → RX (GPS receives)
GPIO17 → TX (GPS transmits)
3.3V   → VCC
GND    → GND

ESP32 to IMU (MPU6050)

ESP32    MPU6050
-----    -------
GPIO26 → SDA
GPIO27 → SCL
3.3V   → VCC
GND    → GND
AD0    → GND (sets I2C address to 0x68)

ESP32 to EGT Sensor (MAX31855)

ESP32    MAX31855
-----    --------
GPIO14 → SCK
GPIO33 → CS
GPIO25 → MISO (DO)
3.3V   → VCC
GND    → GND

ESP32 to CAN Transceiver (SN65HVD230)

ESP32    SN65HVD230
-----    ----------
GPIO21 → RX (CAN RX)
GPIO22 → TX (CAN TX)
3.3V   → VCC
GND    → GND

CAN Bus Wiring

SN65HVD230    CAN Bus
----------    -------
CANH       → CAN High
CANL       → CAN Low

Technical Specifications

CAN Bus Configuration

• Speed: 500 kbps (configurable in code)
• Define: Set via CAN_SPEED constant in MSCanBus.ino
• Protocol: MegaSquirt extended frame format (29-bit identifier)
• Target ID: 0 (MegaSquirt ECU, configurable as MS_CAN_ID)
• Device ID: 10 (configurable as MY_CAN_ID)
• CAN Table ID: 7 (configurable as MS_CAN_TBL)

GPS Configuration

• Baud Rate: 230,400 bps (auto-negotiated)
• Update Rate: 100ms (10 Hz)
• Protocol: u-blox UBX binary
• GNSS Systems: GPS, SBAS, Galileo, Beidou, IMES, QZSS, GLONASS (bitmask: 77)
• Save Config: Auto-save when needed

Supported Data Requests (JBPerf IO Extender Compatible)

Offset	Data Type	Description	Response When
2	Accelerometer	3-axis accelerometer data (12-bit normalized)	IMU available
110	Real-time Clock	GPS UTC time	GPS time valid
128	GPS Coordinates	Lat/Lng in deg/min format	GPS fix available
136	GPS Status	Fix status, altitude, speed, course	GPS fix available

Race Technology CAN Broadcasts

Message ID	Define	Broadcast Rate	Description	Data Format
0x300	CAN_ID_ACCEL_XYZ	25Hz	Accelerometer XYZ	16-bit signed, g×1000, little-endian
0x302	CAN_ID_GPS_LLH1	5Hz	GPS Position LLH1	Validity flags, accuracy, latitude (degrees×1e-7)
0x303	CAN_ID_GPS_LLH2	5Hz	GPS Position LLH2	Longitude (degrees×1e-7), altitude (mm)
0x310	CAN_ID_GPS_SPEED	10Hz	GPS Speed 2D/3D	Validity flags, accuracy, speed (m/s×1e-4)

Custom CANEGT Protocol Broadcasts

Message ID	Define	Broadcast Rate	Description	Data Format
0x690	CAN_ID_EGT	3Hz	EGT Temperature	Scaled EGT value (12-bit normalized for 0-1250°C range)

Configuration

Pin Configuration

Edit these defines in MSCanBus.ino to match your wiring:

// Debug Output
#define DEBUG true    // Enable detailed serial logging

// Hardware pins
#define CAN_RX    21  // ESP32 pin connected to CAN transceiver RX
#define CAN_TX    22  // ESP32 pin connected to CAN transceiver TX

#define GPS_RX    16  // ESP32 pin connected to GPS TX
#define GPS_TX    17  // ESP32 pin connected to GPS RX

#define SCK_PIN   14  // ESP32 pin connected to MAX31855 SCK
#define MISO_PIN  25  // ESP32 pin connected to MAX31855 MISO
#define CS_PIN    33  // ESP32 pin connected to MAX31855 CS

#define IMU_SDA   26  // ESP32 pin connected to IMU SDA
#define IMU_SCL   27  // ESP32 pin connected to IMU SCL

// Race Technology CAN Message IDs
#define CAN_ID_ACCEL_XYZ     0x300  // Accelerometer XYZ data
#define CAN_ID_GPS_LLH1      0x302  // GPS Position LLH1 (latitude)
#define CAN_ID_GPS_LLH2      0x303  // GPS Position LLH2 (longitude/altitude)
#define CAN_ID_GPS_SPEED     0x310  // GPS Speed 2D/3D

// Custom CANEGT Protocol Message IDs
#define CAN_ID_EGT           0x690  // EGT Temperature (1680 decimal)

// MegaSquirt CAN IDs
#define MS_CAN_ID 0   // MegaSquirt ECU CAN ID (usually 0)
#define MY_CAN_ID 10  // This device's CAN ID (must match TunerStudio)
#define MS_CAN_TBL 7  // This device's Table number (must match TunerStudio)

// IMU Configuration
#define IMU_GEOMETRY 0    //Set IMU geometry (check the reference [picture](https://github.com/LiquidCGS/FastIMU/raw/main/MountIndex.png)).
MPU6050 IMU;              //Set to a supported by [FastIMU](https://github.com/LiquidCGS/FastIMU) IMU

// Race Technology broadcast timing
#define RT_GPS_POSITION_INTERVAL_MS 200  // 5Hz for GPS position (LLH1/LLH2)
#define RT_GPS_SPEED_INTERVAL_MS 100     // 10Hz for GPS speed
#define RT_ACCEL_INTERVAL_MS 40          // 25Hz for accelerometer
#define RT_EGT_INTERVAL_MS 333           // 3Hz for EGT data

TunerStudio Setup

Configure TunerStudio to enable necessary settings: CAN-bus / Testmodes → CAN EGO,GPS

Poll GPS data

1. Fetch GPS Data: JBPerf GPS
2. Remote CAN Id: 10
3. Table: 7
4. Offset(bytes): 128

Listen to GPS broadcasts

1. Fetch GPS Data: Race Technology 11bit
2. CAN base address: 769 (0x301 = CAN_ID_GPS_LLH1)

Accelerometer Data Via CAN

1. Fetch Accelerometer Data: Race Technology 11bit
2. CAN base address: 768 (0x300 = CAN_ID_ACCEL_XYZ)

For detailed EGT configuration in TunerStudio, see: EGT Documentation

Usage

Serial Monitor Output

Open Arduino IDE Serial Monitor (115200 baud) to view debug information:

GPS Status (every 1 second when DEBUG enabled)

Fix: 3D_FIX | Satellites: 8 | Time Valid: YES
Position: 37.7749000°, -122.4194000° | Altitude: 52.3m
Speed: 0.00m/s | Course: 0.0° | H.Acc: 1500mm
Time: 14:30:25 25/12/2024 (GPS Week: 2345)

Accelerometer Status (every 1 second when DEBUG enabled)

AccelX: 0.002991 AccelY: -0.003235 AccelZ: 0.997864
GyroX: 0.084204 GyroY: 0.151900 GyroZ: -0.265331
IMU Temp: 24.774117

EGT Status (every 1 second)

EGT1: 852.25 °C

or if thermocouple fault detected:

Thermocouple 1 fault: ERROR_OPEN_CIRCUIT
Thermocouple 1 fault: ERROR_GND_SHORT
Thermocouple 1 fault: ERROR_VCC_SHORT
Thermocouple 1 fault: ERROR_READ
Thermocouple 1 fault: ERROR_NOT_INITIALIZED

CAN Communication Examples

Got a CAN Frame for: 10 Got CAN Req
[CAN TX] Time Req: Block=7 Offset=110 Data=[19 1E 0E 00 19 0C 07 E8]
[CAN TX] GPS1 Req: Block=7 Offset=128 Data=[25 2E A5 1C 7A 0C 4B 8F]
[CAN TX] GPS2 Req: Block=7 Offset=136 Data=[02 00 00 CE 00 00 00 00]

Data Format Details

MegaSquirt Protocol (Request/Response)

Accelerometer Data (Offset 2)

• Bytes 0-1: X-axis acceleration (12-bit, big-endian, ±4G normalized to 0-4095)
• Bytes 2-3: Y-axis acceleration (12-bit, big-endian, ±4G normalized to 0-4095)
• Bytes 4-5: Z-axis acceleration (12-bit, big-endian, ±4G normalized to 0-4095)
• Bytes 6-7: Reserved (0x00)

Time Data (Offset 110)

• Byte 0: Seconds (0-59)
• Byte 1: Minutes (0-59)
• Byte 2: Hours (0-23)
• Byte 3: Reserved (0)
• Byte 4: Day (1-31)
• Byte 5: Month (1-12)
• Bytes 6-7: Year (big-endian, e.g., 2024 = 0x07E8)

GPS Coordinates (Offset 128)

• Bytes 0-3: Latitude (degrees, minutes, milli-minutes)
• Bytes 4-7: Longitude (degrees, minutes, milli-minutes)

GPS Status (Offset 136)

• Byte 0: Status flags (bit 0: longitude sign, bit 1: GPS fix)
• Bytes 1-3: Altitude in cm (signed, big-endian)
• Bytes 4-5: Ground speed in cm/s (big-endian)
• Bytes 6-7: Course in 0.01° (big-endian)

Race Technology Protocol (Broadcast)

Accelerometer Data (0x300)

• Byte 0: Validity flag (0x01 = valid accelerometer data)
• Byte 1: Accuracy (0x00 = perfect accuracy)
• Bytes 2-3: X-axis acceleration (16-bit signed, g×1000, little-endian)
• Bytes 4-5: Y-axis acceleration (16-bit signed, g×1000, little-endian)
• Bytes 6-7: Z-axis acceleration (16-bit signed, g×1000, little-endian)

GPS Position LLH1 (0x302)

• Byte 0: GPS fix status (0x01 = valid GPS fix)
• Byte 1: Latitude accuracy (0.1m units, mm÷100)
• Byte 2: Longitude accuracy (0.1m units, mm÷100)
• Byte 3: Altitude accuracy (0.1m units, mm÷100)
• Bytes 4-7: Latitude (32-bit signed, degrees×1e-7, little-endian)

GPS Position LLH2 (0x303)

• Bytes 0-3: Longitude (32-bit signed, degrees×1e-7, little-endian)
• Bytes 4-7: Altitude (32-bit signed, mm, little-endian)

GPS Speed (0x310)

• Byte 0: GPS fix status (0x01 = valid GPS fix)
• Byte 1: Speed accuracy (cm/s units, mm/s÷100)
• Bytes 2-4: 2D speed (24-bit, m/s×1e-4, little-endian)
• Bytes 5-7: 3D speed (24-bit, m/s×1e-4, little-endian)

Custom CANEGT Protocol (Broadcast)

EGT Temperature (0x690)

• Bytes 0-1: Scaled EGT value (16-bit, big-endian, 12-bit normalized for 0-1250°C range)
• Bytes 2-7: Reserved for future use (0x00)

Project Structure

MSCanBus/
├── MSCanBus.ino          # Main Arduino sketch
├── MSCanBus.h            # MegaSquirt protocol definitions
├── qqqlab_GPS_UBLOX.h    # GPS driver header
├── qqqlab_GPS_UBLOX.cpp  # GPS driver implementation
└── README.md             # This documentation

Troubleshooting

Common Issues

1. CAN Bus Not Working

• Check wiring: Verify CAN transceiver connections (especially CANH/CANL)
• Termination: Ensure 120Ω resistors on both ends of CAN bus
• Speed: Confirm CAN speed matches MegaSquirt (default 500 kbps)
• MegaSquirt warning: If you see The following error was reported by the MegaSquirt: CAN transceiver broken? or wrong CAN baud rate?! Wait 20 seconds, then start engine., recheck that CAN_SPEED is 500 kbps and that CAN_TX=GPIO22/CAN_RX=GPIO21 match the latest hardware pinout.
• Power: Verify 3.3V/5V compatibility with your CAN transceiver

2. GPS Not Getting Fix

• Antenna placement: GPS needs clear view of sky (outdoors recommended)
• Power: Check GPS module voltage requirements (3.3V vs 5V)
• Time: Allow 30-60 seconds for initial fix (cold start)
• Serial: Verify GPS TX/RX connections and baud rate

3. No CAN Responses in TunerStudio

• Device ID: Verify MY_CAN_ID matches TunerStudio configuration
• MegaSquirt setup: Enable CAN broadcasting in MegaSquirt settings
• Frame format: Confirm extended frame (29-bit) format enabled
• Block/Offset: Use JBPerf IO Extender settings (CAN Table 7)

4. GPS Time/Position Invalid

• Fix status: GPS must have valid fix for coordinate requests
• Time validity: Real-time clock requires GPS time synchronization
• Satellite count: Need 4+ satellites for 3D fix

Debug Information

• Serial Monitor: 115200 baud for debug output
• GPS Status: Check fix type and satellite count
• Accelerometer/Gyro Status: Check X Y Z acceleration
• CAN Frames: Monitor transmitted data for correctness
• Error Messages: Look for validation failures or timeouts

License & Attribution

This project includes code from:

• ArduPilot Project: qqqlab_GPS_UBLOX based on AP_GPS_UBLOX (GPL v3)
• FastIMU Library: IMU sensor integration by LiquidCGS (MIT License)
• MAX31855-library: Temperature sensor integration by Moarbue (MIT License)
• MSCan_Gauge: MegaSquirt CAN protocol implementation (merkur2k/MSCan_Gauge)

Compatible with JBPerf IO Extender protocol for MegaSquirt integration. Compatible with Race Technology CAN protocol for data logger integration.