CAN-Communication.md

CAN Communication

This section describes the hardware and system architecture of the PiRacer instrument cluster.

Materials

The following materials are used for this section. The Speed Sensor (LM393) is connected with Arduino Nano/Uno and the Arduino Nano/Uno is connected with MCP2515. The CAN BUS is stablished between the MCP2515 and the 2CH CAN BUS FD HAT. The 2CH CAN BUS FD HAT is connected with Raspberry Pi 4. The drivetrain of the PiRacer is connected via I2C with the Raspberry Pi 4.

PiRacer	Raspberry Pi 4	2CH CAN-BUS FD HAT	MCP2515	Arduino Nano	SpeedSensor

This is how the assembled PiRacer looks like:

Wiring

The following picture shows the wiring of the PiRacer instrument cluster.

Sensor Sensor (LM393) -> Arduino Nano

LM393	Arduino
VCC	5V
GND	GND
OUT	D2
A0	A0

Note: A0 is Analog Input Pin Which is not mandatory to connect.

Arduino Nano -> MCP2515

Arduino	MCP2515
5V	VCC
GND	GND
D10	CS
D11	SI
D12	SO
D13	SCK
D2 or D3	INT

Note: D2 or D3 is optional. If you want to use interrupt, connect D2 or D3 to INT pin of MCP2515.

Set Up

Raspberry Pi with Rasbian OS and 2CH-CAN-FD-HAT.
How to set up 2CH-CAN-FD-HAT

Note Use Dual SPI Mode. Sometimes can0 and can01 is swapped, so please keep this in mind. If they are swapped, you have to rename can0 can1.

Code Example for testing

Transmitter Code Example (Arduino Nano)

Note: We used to try to use MCP2515 Library, but it didn't work. So we used MCP_CAN Library instead of MCP2515 Library. Maybe it might work depending on the external environment such as OS, Arduino version, etc. so please try it to use MCP2515 Library.

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

#define SENSOR_PIN 2

MCP_CAN CAN(10);
uint8_t count = 0;

void rpmCounter() {
 count++;
 Serial.println(count);
}

void setup() {

  Serial.begin(9600);

  CAN.begin(MCP_ANY, CAN_125KBPS, MCP_8MHZ);
  CAN.setMode(MCP_NORMAL);

  pinMode(SENSOR_PIN, INPUT);
  attachInterrupt(digitalPinToInterrupt(SENSOR_PIN), rpmCounter, RISING);
}

void loop() {

  uint8_t data[8];
  int can_id = 0x125; // optional can id
  int can_dlc = 8; // data length you want to send
  memcpy(data, &count, 8); // copy count to data array

  int status = CAN.sendMsgBuf(can_id, 0, can_dlc, data);

  if (status == CAN_OK)
    Serial.println("Success");
  else 
    Serial.println("Error");
  delay(1000);
}

Reference:

1. MCP_CAN Library
2. MCP2515 Library

Receiver Code Example (Raspberry Pi)

import can
import time

can_interface = 'can0'

def receive_can_messages():
    bus = can.interface.Bus(channel=can_interface, bustype='socketcan')

    while True:
        message = bus.recv()
        print(f"recieve ID={message.arbitration_id}, data={message.data}")
        time.sleep(1);

if __name__ == "__main__":
    receive_can_messages()

Reference:

1. python-can Library