unable to recieve messages via canbus Sheild

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1

Hello,

I am trying to demonstrate can bus communication using arduino uno(2 units) and sparkfun canbus sheild(2 units). I am trying to send the basic examples given in sparkfun canbus library.

i am getting “Can init Ok” message on serial monitor but no message is being displayed. can anyone help me in this?

thanks in advance

my code for transmitter:

#include <Canbus.h>
#include <defaults.h>
#include <global.h>
#include <mcp2515.h>
#include <mcp2515_defs.h>

//********************************Setup Loop*********************************//

void setup() {
  Serial.begin(9600);
  Serial.println("CAN Write - Testing transmission of CAN Bus messages");
  delay(1000);
  
  if(Canbus.init(CANSPEED_500))  //Initialise MCP2515 CAN controller at the specified speed
    Serial.println("CAN Init ok");
  else
    Serial.println("Can't init CAN");
    
  delay(1000);
}

//********************************Main Loop*********************************//

void loop() 
{
tCAN message;

        message.id = 0x631; //formatted in HEX
        message.header.rtr = 0;
        message.header.length = 8; //formatted in DEC
        message.data[0] = 0x40;
	message.data[1] = 0x05;
	message.data[2] = 0x30;
	message.data[3] = 0xFF; //formatted in HEX
	message.data[4] = 0x00;
	message.data[5] = 0x40;
	message.data[6] = 0x00;
	message.data[7] = 0x00;

mcp2515_bit_modify(CANCTRL, (1<<REQOP2)|(1<<REQOP1)|(1<<REQOP0), 0);
mcp2515_send_message(&message);

delay(1000);
}

my code for reciever is:

#include <Canbus.h>
#include <defaults.h>
#include <global.h>
#include <mcp2515.h>
#include <mcp2515_defs.h>

//********************************Setup Loop*********************************//

void setup() {
  Serial.begin(9600); // For debug use
  Serial.println("CAN Read - Testing receival of CAN Bus message");  
  delay(1000);
  
  if(Canbus.init(CANSPEED_500))  //Initialise MCP2515 CAN controller at the specified speed
    Serial.println("CAN Init ok");
  else
    Serial.println("Can't init CAN");
    
  delay(1000);
}

//********************************Main Loop*********************************//

void loop(){

  tCAN message;
if (mcp2515_check_message()) 
	{
    if (mcp2515_get_message(&message)) 
	{
        //if(message.id == 0x620 and message.data[2] == 0xFF)  //uncomment when you want to filter
             //{
               
               Serial.print("ID: ");
               Serial.print(message.id,HEX);
               Serial.print(", ");
               Serial.print("Data: ");
               Serial.print(message.header.length,DEC);
               for(int i=0;i<message.header.length;i++) 
                {	
                  Serial.print(message.data[i],HEX);
                  Serial.print(" ");
                }
               Serial.println("");
             //}
           }}

}

my pin connection are:

Transmitter side:

Arduino uno ---- canbus sheild

D8-D13 ------------ D8-D13

Gnd ----------------- gnd

5v ------------------- 5v

D2 ------------------ D2

ioref ------------- ioref

reset ------------ reset

Reciever side:

Arduino uno ---- canbus sheild

D8-D13 ------------ D8-D13

Gnd ----------------- gnd

5v ------------------- 5v

D2 ------------------ D2

ioref ------------- ioref

reset ------------ reset

connections between transmitter can to reciever can is via CAN_L and CAN_H and Gnd.

I am using sparkfun canbus library.

Thanks in Advance

2

You need a 120 ohm bus termination resistor across CAN_H and CAN_L on both ends of your bus.

https://support.maxongroup.com/hc/en-us … ermination

3

I have tried connecting 120 OHM resistor across can_h and can_l but the problem still persists