ESP32 CAN Display Client

ESP32 CAN bus client firmware that receives sensor data from a CAN network and displays it on a 128x64 SSD1306 OLED display.

Features

• Multi-sensor CAN data reception: Receives and parses data from VEML7700 (light), BME680 (temp/humidity/pressure/IAQ), MQ-3 (alcohol), and LD2410 (presence) sensors
• Real-time OLED display: 128x64 SSD1306 I2C display with organized sensor data layout
• Modular architecture: Clean separation between CAN receiver, display driver, and UI rendering
• Thread-safe data handling: FreeRTOS tasks with mutex-protected shared data structure
• Staleness detection: Alerts when sensor data hasn't been received recently (>5 seconds)
• CAN bus health monitoring: Watchdog for CAN disconnection detection

Hardware Requirements

• ESP32-C3 SuperMini (or any ESP32 board)
• SSD1306 OLED Display (128x64, I2C, address 0x3C)
• SN65HVD230 CAN Transceiver (or compatible 3.3v CAN transceiver)
• Power supply (3.3V for ESP32-C3, 5V for CAN transceiver if needed)

Pin Connections

Function	GPIO	Description
CAN TX	4	Connect to SN65HVD230 TX pin
CAN RX	5	Connect to SN65HVD230 RX pin
I2C SDA	6	Connect to SSD1306 SDA
I2C SCL	7	Connect to SSD1306 SCL

See docs/WIRING.md for detailed wiring diagrams.

CAN Protocol

CAN Bus Speed: 500 kbps

The client receives the following CAN message IDs:

ID	Sensor	Data	Update Rate
0x100	VEML7700	Lux value (3-byte, 0-120K), status	1 Hz
0x101	BME680	Temperature, humidity, pressure	0.33 Hz
0x102	BME680	IAQ, CO2 equiv, VOC	0.33 Hz
0x109	MQ-3	Alcohol PPM, ADC, Rs/R0 ratio	1 Hz
0x107	LD2410	Presence, distance, energy levels	10 Hz
0x10F	System	Active sensors, heap, uptime	0.1 Hz

See main/can_protocol.h for complete message format definitions.

Display Layout

┌──────────────────────────────┐
│ 12345 lux           (Large)  │  ← Light level
├──────────────────────────────┤
│ 23.5C   65%   1013hPa        │  ← Environmental data
├──────────────────────────────┤
│ IAQ:120 Good                 │  ← Air quality
│ Alc:50ppm                    │  ← Alcohol level
├──────────────────────────────┤
│ P:75cm              STALE    │  ← Presence / Status
└──────────────────────────────┘

• Top: Lux value (large font)
• Middle: Temperature, Humidity, Pressure (3 columns)
• Bottom: IAQ with quality indicator, Alcohol level
• Status: Presence detection, staleness warning

Software Architecture

main.c
  ├── sensor_data.h         (Shared data structure with mutex)
  ├── can_receiver task     (Receives & parses CAN messages)
  └── display_ui task       (Renders UI at 10 Hz)

File Responsibilities

• main/main.c: Application entry point, task coordination, system monitoring
• main/can_receiver.c: TWAI driver initialization, CAN message reception and parsing
• main/display_driver.c: SSD1306 I2C driver wrapper, low-level display functions
• main/display_ui.c: UI layout and rendering logic
• main/can_protocol.h: CAN message ID and structure definitions
• main/sensor_data.h: Shared sensor data structure with thread-safe access

Build Instructions

Prerequisites

1. Install ESP-IDF v5.x
2. Set up ESP-IDF environment:

   . $HOME/esp/esp-idf/export.sh  # Or your IDF path

Build and Flash

# Clone the repository
git clone https://github.com/yourusername/Esp32-CAN-Disp-Client.git
cd Esp32-CAN-Disp-Client

# Configure the project (optional - defaults are set in sdkconfig.defaults)
idf.py menuconfig

# Build the firmware
idf.py build

# Flash to ESP32-C3
idf.py -p /dev/ttyUSB0 flash

# Monitor serial output
idf.py -p /dev/ttyUSB0 monitor

Tip: Use idf.py -p /dev/ttyUSB0 flash monitor to flash and monitor in one command.

Configuration

Default settings are in sdkconfig.defaults. You can customize:

• GPIO pin assignments in can_receiver.h and display_driver.h
• CAN bitrate (default: 500 kbps)
• Display update rate (default: 10 Hz)
• Staleness timeout (default: 5 seconds)

Usage

1. Connect the hardware according to the wiring diagram
2. Flash the firmware to the ESP32-C3
3. Connect the CAN bus to your sensor network
4. The display will show sensor data as it's received
5. Monitor serial output for debugging and CAN message logs

Expected Serial Output

I (123) MAIN: ESP32-C3 CAN Display Client
I (456) CAN_RX: Initializing TWAI (CAN) driver
I (789) DISPLAY: Initializing SSD1306 display
I (1012) MAIN: Initialization complete!
I (1234) CAN_RX: VEML7700: Lux=1234.0, Status=0
I (2345) CAN_RX: BME680 ENV: T=23.45°C, H=65%, P=1013.2hPa

Troubleshooting

No CAN messages received

• Check CAN TX/RX wiring to TJA1050
• Verify CAN bus termination resistors (120Ω at each end)
• Check CAN bitrate matches sender (500 kbps)
• Use logic analyzer or CAN bus analyzer to verify messages on bus

Display not working

• Verify I2C connections (SDA/SCL)
• Check I2C address (default 0x3C, some displays use 0x3D)
• Test display with I2C scanner
• Check power supply to display (3.3V or 5V depending on module)

Display shows "STALE"

• CAN messages not being received for >5 seconds
• Check CAN bus connection and sender status
• Verify sender is transmitting at expected rates

Build errors

• Ensure ESP-IDF v5.x is installed and activated
• Run idf.py fullclean then rebuild
• Check that all source files are present

Future Enhancements

• Auto-brightness based on lux sensor reading
• add sensor data logging in sdcard
• Button input to toggle between display screens
• Alert animations (blinking) for high alcohol detection
• WiFi configuration portal
• MQTT forwarding of sensor data
• Integrate u8g2 library for better font support

License

See LICENSE file.

Contributing

Pull requests are welcome! Please ensure:

• Code follows existing style and structure
• Comments explain CAN protocol and message formats
• Commit messages are descriptive

References

• ESP-IDF TWAI Driver Documentation
• SSD1306 Datasheet
• TJA1050 CAN Transceiver Datasheet