ESP CAN Sniffer

A simple ESP32-based CAN bus sniffer for BMS traffic using an MCP2515 CAN controller.

Overview

This project reads CAN frames from a BMS network and prints packet details over serial. It supports both standard and extended CAN IDs and scans common baud rates for MCP2515 initialization.

Features

• ESP32 + MCP2515 CAN bus sniffer
• Auto-detects CAN baud rate from 500 kbps, 250 kbps, and 125 kbps
• Supports standard and extended CAN IDs
• Prints frame metadata, data bytes in HEX, and decimal representation
• Periodic summary of unique IDs seen

Hardware

• ESP32 development board
• MCP2515 CAN controller module with TJA1050 or similar transceiver
• CAN bus from BMS

MCP2515 wiring

This is an example wiring for the MCP2515 module to the ESP32:

ESP32 pin	MCP2515 pin	Notes
GPIO18	SCK	SPI clock
GPIO19	MISO (SO)	SPI data in
GPIO23	MOSI (SI)	SPI data out
GPIO5	CS	SPI chip select
GPIO4	INT	MCP2515 interrupt
5V	VCC	Use 5V supply as indicated
GND	GND	Common ground

Software

Required library

The project depends on the MCP_CAN_lib library.

Build and upload

1. Open the project in PlatformIO.
2. Select the esp32dev environment.
3. Build and upload to the ESP32.

Serial monitor

Open the serial monitor at 115200 baud.

The output includes:

• connection status
• detected CAN frames
• frame type (STD/EXT)
• CAN ID
• DLC
• data bytes in HEX and DEC

Notes

• The MCP2515 module is initialized with an 8 MHz crystal.
• If initialization fails, verify power, ground, and SPI wiring.
• The module will attempt 500 kbps, 250 kbps, then 125 kbps.

License

This project is licensed under the MIT License.