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 ACAN2517 library https://github.com/pierremolinaro/acan2517, it uses a very similar API.
ACAN2517FD is a driver for the MCP2517FD and MCP2518FD CAN Controllers, in CAN FD mode. It runs on any Arduino compatible board.
The ACAN2517 library handles the MCP2517FD and MCP2518FD CAN Controller, in CAN 2.0B 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.
The demo sketch is in the
examples/LoopBackDemo
directory.
Configuration is a four-step operation.
- Instanciation of the
settings
object : the constructor has one parameter: the wished CAN bit rate. Thesettings
is fully initialized. - 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 themReceiveBufferSize
property. - 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. - 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") ;
// Arbitration bit rate: 125 kbit/s, data bit rate: 500 kbit/s
ACAN2517FDSettings settings (ACAN2517FDSettings::OSC_4MHz10xPLL,
125 * 1000, ACAN2517FDSettings::DATA_BITRATE_x4) ;
settings.mRequestedMode = ACAN2517FDSettings::InternalLoopBack ; // 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 () {
CANFDMessage 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) ;
}
}
CANFDMessage
is the class that defines a CAN FD 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 message
argument.
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):
ACAN2517FDSettings settings (ACAN2517FDSettings::OSC_4MHz10xPLL, 125 * 1000) ;
settings.mRequestedMode = ACAN2517FDSettings::InternalLoopBack ; // Select loopback mode
ACAN2517Filters 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
...
}