CAN-Bus Implementation Issue

Projects Networking, Protocols, and Devices
1

Hi! I have been having issues over the past few days with implementing a CAN-bus shield and would really appreciate help. I am using the MCP2515 module with an Arduino UNO. I have tried the following libraries and used the example code provided by those libraries:

  1. mcp_can by coryjfowler
  2. CAN by Sandeep Mistry

The ultimate goal is to read and send messages to and from a Victron Energy Battery Management System which is implementing CAN 2.0A.

I have tried communicating between two Arduino's, and have managed to do this successfully, however, I fail to receive any messages when I try connect the Arduino to CAN hi and CAN lo of the device. I will show the code I am using to receive messages below:

/* 
  MCP2515 Setup
  VCC - 5V
  GND - GND
  SCK - SCK (PIN13)
  SO - MISO (PIN12)
  SI - MOSI (PIN11)
  CS - PIN10
  INT - PIN2
*/

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

long unsigned int rxId;
unsigned char len = 0;
unsigned char rxBuf[8];                         
char msgString[128];                        // Array to store serial string

#define CAN0_INT 2                              // Set INT to pin 2
MCP_CAN CAN0(10);                               // Set CS to pin 10


void setup()
{
  Serial.begin(115200);
  // Initialize MCP2515 running at 16MHz with a baudrate of 500kb/s and the masks and filters disabled.
  if(CAN0.begin(MCP_ANY, CAN_500KBPS, MCP_16MHZ) == CAN_OK)
    Serial.println("MCP2515 Initialized Successfully!");
  else
    Serial.println("Error Initializing MCP2515...");
  
  CAN0.setMode(MCP_NORMAL);                     // Set operation mode to normal so the MCP2515 sends acks to received data.

  pinMode(CAN0_INT, INPUT);                            // Configuring pin for /INT input
}

void loop()
{
  if(!digitalRead(CAN0_INT))                         // If CAN0_INT pin is low, read receive buffer
  {
    CAN0.readMsgBuf(&rxId, &len, rxBuf);      // Read data: len = data length, buf = data byte(s)
    
    if((rxId & 0x80000000) == 0x80000000)     // Determine if ID is standard (11 bits) or extended (29 bits)
      sprintf(msgString, "Extended ID: 0x%.8lX  DLC: %1d  Data:", (rxId & 0x1FFFFFFF), len);
    else
      sprintf(msgString, "Standard ID: 0x%.3lX       DLC: %1d  Data:", rxId, len);
  
    Serial.print(msgString);
  
    if((rxId & 0x40000000) == 0x40000000){    // Determine if message is a remote request frame.
      sprintf(msgString, " REMOTE REQUEST FRAME");
      Serial.print(msgString);
    } else {
      for(byte i = 0; i<len; i++){
        sprintf(msgString, " 0x%.2X", rxBuf[i]);
        Serial.print(msgString);
      }
    }
        
    Serial.println();
  }
}

All it indicates is that the MCP2515 has successfully initialized but there are no interrupts and thus I believe no messages are being received. I am wondering if perhaps messages are being sent too fast for the MCP2515 to be able to register it, or if there's a synchronization issue. I currently have not implemented any masks or filters. I have read the datasheet and I know exactly the messages I am expected to receive but I am unable to receive any. If anyone knows what the issue may be or if there's any other place I can go to for further help on this issue I would appreciate the assistance! Thanks in advance.

2

Does your "MCP2515 module" have a 16 MHz crystal?

4

Yes it does

5

Either the BMS is using a baud rate other than 500k, or it's not sending any data.

Hire or buy an oscilloscope to investigate.

Alternatively, if you have good soldering skills, attach a wire to the transceiver Rx pin and use a spare pin on the Arduino to look for a digital signal by using pulseIn(). The shortest pulse that you detect can be used to calculate the baud rate. (4 micro sec resolution on the Uno R3)

6

Try reversing the CAN Hi and Low pins on your connection.

7

This topic was automatically closed 180 days after the last reply. New replies are no longer allowed.