Ultibo Canbus Library

This is a port of the MCP_CAN library written by Cory J. Fowler for Arduino. The original library is on github here: https://github.com/coryjfowler/MCP_CAN_lib

Please see the above github for examples on how to use the library in the /examples folder. I have succesfully ported one of the examples and it required very little change. Note that some of the functions have been changed to use var parameters but most have retained the original C style pointers, so you need to be careful when passing buffers etc.

The library talks to an MCP2515 SPI based canbus controller.

Basic example. This code will not compile until you implement 'log()' or delete that code;

var
  MyCanBus : MCP_CAN;
  Res : longword;
  buf : array[0..7] of byte;

begin
  MyCanBus := MCP_CAN.Create(0);  // 0 or 1 i.e. which of the two SPI enable pins you want to use.

  // this is as fast as you can go on a chinese MCP2515 board.
  Res := MyCanBus.BeginCan(MCP_ANY, CAN_1000KBPS, MCP_16MHZ);

  if (res = CAN_OK) then
    log('MCP2515 Initialized Successfully.')
  else
    log('Error Initializing MCP2515...');

  // the lib defaults to loopback mode if you don't change it.
  // in loopback mode any message you send is received by the same node and
  // a canbus does not have to be connected.

  // Change from loopback to normal mode to allow messages to be transmitted
  if (FCanBus.setMode(MCP_NORMAL) <> CAN_OK) then
    log('Error setting canbus mode to normal');

  buf[0] := 0;
  buf[1] := 1;
  buf[2] := 2;
  buf[3] := 3;
  buf[4] := 4;
  buf[5] := 5;
  buf[6] := 6;
  buf[7] := 7;

  // send the above buffer onto the canbus with can id $100, length 8.
  // note you do not have to send 8 bytes, but you must send at least 1 byte.
  res := FCanBus.sendMsgBuf($100, 8, @buf[0]);

  // check res here for CAN_OK
end.

This library will work with the multitude of Arduino SPI canbus boards you can buy on eBay for couple of quid. However, when using one of these boards with Raspberry PI you must either use a level shifter or modify the board because the PI is a 3.3v device and all of the boards are 5v devices. Luckily the board only requires 5v for the Canbus transceiver so it is possible to get the right voltage levels on the SPI pins with a small modification. This is easier and neater, and details can be found here;

https://www.raspberrypi.org/forums/viewtopic.php?t=141052 or here; https://vimtut0r.com/2017/01/17/can-bus-with-raspberry-pi-howtoquickstart-mcp2515-kernel-4-4-x/

My boards are mostly like that second one but in my case I cut a trace on the back of the board and soldered to the capacitor on the front.

Note that if you do not either modify the board or use a level shifter you will blow the input pins on your PI.