Sparkfun CAN shield with Uno

Development Boards Arduino
1

Hi there,

I am trying to get the example code working with the following CAN shield: https://learn.sparkfun.com/tutorials/ca … -guide/all.

After getting the initialisation working with the Arduino UNO (actually not arduino but a knock off UNO), it doesn’t give me anything on the CAN analyser tool when I try to run the example code below:

#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);
}

Before you say the CAN analyser tool may be broken, I also tried with this code (https://github.com/coryjfowler/MCP_CAN_ … N_send.ino) from a different library and it gave me the error message in the arduino serial moniter “Error Sending Message…”.

I am using a female DB9 to DB9 cable from the CAN shield to the CAN analyser tool. Is it maybe that this is the problem? Do I have to reconfigure the jumpers in 6c here: https://learn.sparkfun.com/tutorials/ca … -guide/all ? If so, how exactly do I do that, it says something about soldering but it’s not quite clear to me how I should solder those pads.

Another idea I had was that the lack of termination resistors is causing the problem, because as far as I understand there are no termination resistors included in the shield, correct? If so, how do I add them if I want to use the DB9 cable to send receive?

Attached is a picture of my setup. There is an LCD attached, but it is not doing anything for the moment. Any help is greatly appreciated.

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thumbnail_processed.jpg1280×960 216 KB

2

Try a 120 ohm resistor between the CAN_H and CAN_L pins on the board, if that doesn’t work, you might need to skip the DB9 and wire CAN_H, CAN_L and GND directly over to your CAN analyzer tool but keep the 120 ohm resistor connected as well.

3

Hi YellowDog,

thank you very much for the reply!

Do you mean like in the second image here: https://www.instructables.com/Sparkfun- … -Tutorial/, i.e. directly connected to RX and TX pins on the shield, or the pins from the shield’s DB9 port to the CAN analyser pins directly?

Cheers.

4

Update: It worked as shown in the link (https://www.instructables.com/Sparkfun- … -Tutorial/), I also connected my CAN analyser DB9 pins 2 and 7 to my own breadboard CAN bus with termination resistors and it worked. Thanks for your suggestions!