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Hardware setup

Required components

Component Recommended model
Microcontroller Arduino Mega 2560
CAN module MCP2515 + TJA1050 breakout board
Bus terminators 2× 120 Ω resistor
Wiring Twisted pair for CAN_H / CAN_L

Wiring diagram

The MCP2515 communicates with the Arduino over SPI. On the Arduino Mega, the hardware SPI pins are:

Arduino Mega MCP2515 module
5V VCC
GND GND
pin 52 SCK (SPI clock)
pin 51 SI (MOSI)
pin 50 SO (MISO)
pin 53 CS (Chip Select)
pin 2 INT (interrupt, optional)

The CS pin is configurable in code. This implementation uses pin 53, the hardware SPI CS on the Mega.

Initialization code

cpp
#include <SPI.h>
#include <mcp_can.h>

const int SPI_CS_PIN = 53;
MCP_CAN CAN(SPI_CS_PIN);

void setup() {
    while (CAN_OK != CAN.begin(MCP_ANY, CAN_250KBPS, MCP_8MHZ)) {
        delay(100);
    }
    CAN.setMode(MCP_NORMAL);
}

CAN.begin() parameters:

Parameter Value Description
MCP_ANY — No mask filter (receive all)
CAN_250KBPS 250 kbps Standard J1939 speed for heavy vehicles
MCP_8MHZ 8 MHz Crystal frequency on the module

Installing the library

Install mcp_can by Cory Fowler from the Arduino IDE library manager, or clone directly:

bash
cd ~/Documents/Arduino/libraries
git clone https://github.com/coryjfowler/MCP_CAN_lib

Important

Always place a 120 Ω resistor between CAN_H and CAN_L at each end of the bus. Without terminators, signal reflections will make the bus unstable.

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