MCP2517FD CAN Controller Library for Arduino (in CAN 2.0B mode)

Compatibility with the other ACAN libraries

This library is fully compatible with the Teensy 3.x ACAN library https://github.com/pierremolinaro/acan, ACAN2515 library https://github.com/pierremolinaro/acan2515, and the ACAN2517FD library https://github.com/pierremolinaro/acan2517, it uses a very similar API and the same CANMessage class for handling messages.

ACAN2517 library description

ACAN2517 is a driver for the MCP2517FD CAN Controller, in CAN 2.0B mode. It runs on any Arduino compatible board.

The ACAN2517FD library handles the MCP2517FD CAN Controller, in CAN FD mode.

The library supports the 4MHz, 20 MHz and 40 MHz oscillator clock.

The driver supports many bit rates: the CAN bit timing calculator finds settings for standard 62.5 kbit/s, 125 kbit/s, 250 kbit/s, 500 kbit/s, 1 Mbit/s, but also for an exotic bit rate as 727 kbit/s. If the desired bit rate cannot be achieved, the begin method does not configure the hardware and returns an error code.

Driver API is fully described by the PDF file in the extras directory.

Demo Sketch

The demo sketch is in the examples/LoopBackDemo directory.

Configuration is a four-step operation.

1. Instanciation of the settings object : the constructor has one parameter: the wished CAN bit rate. The settings is fully initialized.
2. You can override default settings. Here, we set the mRequestedMode property to true, enabling to run demo code without any additional hardware (no CAN transceiver needed). We can also for example change the receive buffer size by setting the mReceiveBufferSize property.
3. Calling the begin method configures the driver and starts CAN bus participation. Any message can be sent, any frame on the bus is received. No default filter to provide.
4. You check the errorCode value to detect configuration error(s).

static const byte MCP2517_CS  = 20 ; // CS input of MCP2517FD, adapt to your design
static const byte MCP2517_INT = 37 ; // INT output of MCP2517FD, adapt to your design

ACAN2517FD can (MCP2517_CS, SPI, MCP2517_INT) ; // You can use SPI2, SPI3, if provided by your microcontroller

void setup () {
  Serial.begin (9600) ;
  while (!Serial) {}
  Serial.println ("Hello") ;
  ACAN2517Settings settings (ACAN2517Settings::OSC_4MHz10xPLL, 125 * 1000) ; // 125 kbit/s
  settings.mRequestedMode = ACAN2517RequestedMode::InternalLoopBackMode ; // Select loopback mode
  const uint32_t errorCode = can.begin (settings, [] { can.isr () ; }) ;
  if (0 == errorCode) {
    Serial.println ("Can ok") ;
  }else{
    Serial.print ("Error Can: 0x") ;
    Serial.println (errorCode, HEX) ;
  }
}

Now, an example of the loop function. As we have selected loop back mode, every sent frame is received.

static unsigned gSendDate = 0 ;
static unsigned gSentCount = 0 ;
static unsigned gReceivedCount = 0 ;

void loop () {
  CANMessage message ;
  if (gSendDate < millis ()) {
    message.id = 0x542 ;
    const bool ok = can.tryToSend (message) ;
    if (ok) {
      gSendDate += 2000 ;
      gSentCount += 1 ;
      Serial.print ("Sent: ") ;
      Serial.println (gSentCount) ;
    }
  }
  if (can.receive (message)) {
    gReceivedCount += 1 ;
    Serial.print ("Received: ") ;
    Serial.println (gReceivedCount) ;
  }
}

CANMessage is the class that defines a CAN message. The message object is fully initialized by the default constructor. Here, we set the id to 0x542 for sending a standard data frame, without data, with this identifier.

The can.tryToSend tries to send the message. It returns true if the message has been sucessfully added to the driver transmit buffer.

The gSendDate variable handles sending a CAN message every 2000 ms.

can.receive returns true if a message has been received, and assigned to the messageargument.

Use of Optional Reception Filtering

The MCP2517 CAN Controller implements 32 acceptance masks and 32 acceptance filters. The driver API enables you to fully manage these registers.

For example (LoopBackDemoTeensy3xWithFilters sketch):

  ACAN2517Settings settings (ACAN2517Settings::OSC_4MHz10xPLL, 125 * 1000) ;
  settings.mRequestedMode = ACAN2517 RequestedMode::LoopBackMode ; // Select loopback mode
  MCP2517Filters filters ;
// Filter #0: receive standard frame with identifier 0x123
  filters.appendFrameFilter (kStandard, 0x123, receiveFromFilter0) ;
// Filter #1: receive extended frame with identifier 0x12345678
  filters.appendFrameFilter (kExtended, 0x12345678, receiveFromFilter1) ; 
// Filter #2: receive standard frame with identifier 0x3n4
  filters.appendFilter (kStandard, 0x70F, 0x304, receiveFromFilter2) ;
  const uint32_t errorCode = can.begin (settings, [] { can.isr () ; }, filters) ;

These settings enable the acceptance of standard frames whose identifier is 0x123, extended frames whose identifier is 0x12345678, and data frames whose identifier is 0x304, 0x314, ..., 0x3E4, 0x3F4.

The receiveFromFilter0, receiveFromFilter1, receiveFromFilter2 functions are call back functions, handled by the can.dispatchReceivedMessage function:

void loop () {
  can.dispatchReceivedMessage () ; // Do not use can.receive any more
  ...
}