6.1 KiB
CAN API
Include Library
#include <CAN.h>
Setup
Begin
Initialize the library with the specified bit rate.
CAN.begin(bitrate);
bitrate
- bit rate in bits per seconds (bps) (1000E3
,500E3
,250E3
,200E3
,125E3
,100E3
,80E3
,50E3
,40E3
,20E3
,10E3
,5E3
)
Returns 1
on success, 0
on failure.
Set pins
MCP2515
Override the default CS
and INT
pins used by the library. Must be called before CAN.begin(...)
.
CAN.setPins(cs, irq);
cs
- new chip select pin to use, defaults to10
irq
- new INT pin to use, defaults to2
. Must be interrupt capable via attachInterrupt(...).
This call is optional and only needs to be used if you need to change the default pins used.
ESP32
Override the default CTX
and CRX
pins used by the library. Must be called before CAN.begin(...)
.
CAN.setPins(rx, tx);
rx
- new CRX pin to use, defaults to4
tx
- new CTX pin to use, defaults to5
.
This call is optional and only needs to be used if you need to change the default pins used.
Set SPI Frequency
MCP2515 only
Override the default SPI frequency of 10 MHz used by the library. Must be called before CAN.begin(...)
.
CAN.setSPIFrequency(frequency);
frequency
- new SPI frequency to use, defaults to10E6
This call is optional and only needs to be used if you need to change the default SPI frequency used. Some logic level converters cannot support high speeds such as 10 MHz, so a lower SPI frequency can be selected with CAN.setSPIFrequency(frequency)
.
Set Clock Frequency
MCP2515 only
Override the default clock source frequency that is connected to the MCP2515. Must be called before CAN.begin(...)
.
CAN.setClockFrequency(clockFrequency);
clockFrequency
- new clock frequency to use (8E6
,16E6
) connected to MCP2515, defaults to16 Mhz
This call is optional and only needs to be used if you need to change the clock source frequency connected to the MCP2515. Most shields have a 16 MHz clock source on board, some breakout boards have a 8 MHz source.
End
Stop the library
CAN.end()
Sending data
Begin packet
Start the sequence of sending a packet.
CAN.beginPacket(id);
CAN.beginPacket(id, dlc);
CAN.beginPacket(id, dlc, rtr);
CAN.beginExtendedPacket(id);
CAN.beginExtendedPacket(id, dlc);
CAN.beginExtendedPacket(id, dlc, rtr);
id
- 11-bit id (standard packet) or 29-bit packet id (extended packet)dlc
- (optional) value of Data Length Code (DLC) field of packet, default is size of data written in packetrtr
- (optional) value of Remote Transmission Request (RTR) field of packet (false
ortrue
), defaults tofalse
. RTR packets contain no data, the DLC field of the packet represents the requested length.
Returns 1
on success, 0
on failure.
Writing
Write data to the packet. Each packet can contain up to 8 bytes.
CAN.write(byte);
CAN.write(buffer, length);
byte
- single byte to write to packet
or
buffer
- data to write to packetlength
- size of data to write
Returns the number of bytes written.
Note: Other Arduino Print
API's can also be used to write data into the packet
End packet
End the sequence of sending a packet.
CAN.endPacket()
Returns 1
on success, 0
on failure.
Receiving data
Parsing packet
Check if a packet has been received.
int packetSize = CAN.parsePacket();
Returns the packet size in bytes or 0
if no packet was received. For RTR packets the size reflects the DLC field of the packet.
Register callback
Register a callback function for when a packet is received.
CAN.onReceive(onReceive);
void onReceive(int packetSize) {
// ...
}
onReceive
- function to call when a packet is received.
Packet ID
long id = CAN.packetId();
Returns the id (11-bit or 29 bit) of the received packet. Standard packets have an 11-bit id, extended packets have an 29-bit id.
Packet Extended
bool extended = CAN.packetExtended();
Returns true
if the received packet is extended, false
otherwise.
Packet RTR
bool rtr = CAN.packetRtr();
Returns the value of the Remote Transmission Request (RTR) field of the packet true
/false
. RTR packets contain no data, the DLC field is the requested data length.
Packet DLC
int DLC = CAN.packetDlc();
Returns the value of the Data Length Code (DLC) field of the packet.
Available
int availableBytes = CAN.available()
Returns number of bytes available for reading.
Peeking
Peek at the next byte in the packet.
int b = CAN.peek();
Returns the next byte in the packet or -1
if no bytes are available.
Reading
Read the next byte from the packet.
int b = CAN.read();
Returns the next byte in the packet or -1
if no bytes are available.
Note: Other Arduino Stream
API's can also be used to read data from the packet
Filtering
Filter packets that meet the desired criteria.
CAN.filter(id);
CAN.filter(id, mask);
CAN.filterExtended(id);
CAN.filterExtended(id, mask);
id
- 11-bit id (standard packet) or 29-bit packet id (extended packet)mask
- (optional) 11-bit mask (standard packet) or 29-bit mask (extended packet), defaults to0x7ff
or0x1fffffff
(extended)
Only packets that meet the following criteria are acknowleged and received, other packets are ignored:
if ((packetId & mask) == id) {
// acknowleged and received
} else {
// ignored
}
Returns 1
on success, 0
on failure.
Other modes
Loopback mode
Put the CAN controller in loopback mode, any outgoing packets will also be received.
CAN.loopback();
Sleep mode
Put the CAN contoller in sleep mode.
CAN.sleep();
Wake up the CAN contoller if it was previously in sleep mode.
CAN.wakeup();