CAN over Serial

A text based interface. For example use over serial ports like /dev/ttyS1 or /dev/ttyUSB0 on Linux machines or COM1 on Windows. The interface is a simple implementation that has been used for recording CAN traces.

Note

The properties extended_id, is_remote_frame and is_error_frame from the class can.Message are not in use. These interface will not send or receive flags for this properties.

Bus

class can.interfaces.serial.serial_can.SerialBus(channel, baudrate=115200, timeout=0.1, *args, **kwargs)[source]

Bases: can.bus.BusABC

Enable basic can communication over a serial device.

Note

See can.interfaces.serial.SerialBus._recv_internal() for some special semantics.

Parameters:
  • channel (str) – The serial device to open. For example “/dev/ttyS1” or “/dev/ttyUSB0” on Linux or “COM1” on Windows systems.
  • baudrate (int) –

    Baud rate of the serial device in bit/s (default 115200).

    Warning

    Some serial port implementations don’t care about the baudrate.

  • timeout (float) – Timeout for the serial device in seconds (default 0.1).
send(msg, timeout=None)[source]

Send a message over the serial device.

Parameters:
  • msg (can.Message) –

    Message to send.

    Note

    Flags like extended_id, is_remote_frame and is_error_frame will be ignored.

    Note

    If the timestamp is a float value it will be converted to an integer.

  • timeout – This parameter will be ignored. The timeout value of the channel is used instead.
shutdown()[source]

Close the serial interface.

Internals

The frames that will be sent and received over the serial interface consist of six parts. The start and the stop byte for the frame, the timestamp, DLC, arbitration ID and the payload. The payload has a variable length of between 0 and 8 bytes, the other parts are fixed. Both, the timestamp and the arbitration ID will be interpreted as 4 byte unsigned integers. The DLC is also an unsigned integer with a length of 1 byte.

Serial frame format

  Start of frame Timestamp DLC Arbitration ID Payload End of frame
Length (Byte) 1 4 1 4 0 - 8 1
Data type Byte Unsigned 4 byte integer Unsigned 1 byte integer Unsigned 4 byte integer Byte Byte
Byte order - Little-Endian Little-Endian Little-Endian - -
Description Must be 0xAA Usually s, ms or µs since start of the device Length in byte of the payload - - Must be 0xBB

Examples of serial frames

CAN message with 8 byte payload

CAN message
Arbitration ID Payload
1 0x11 0x22 0x33 0x44 0x55 0x66 0x77 0x88
Serial frame
Start of frame Timestamp DLC Arbitration ID Payload End of frame
0xAA 0x66 0x73 0x00 0x00 0x08 0x01 0x00 0x00 0x00 0x11 0x22 0x33 0x44 0x55 0x66 0x77 0x88 0xBB

CAN message with 1 byte payload

CAN message
Arbitration ID Payload
1 0x11
Serial frame
Start of frame Timestamp DLC Arbitration ID Payload End of frame
0xAA 0x66 0x73 0x00 0x00 0x01 0x01 0x00 0x00 0x00 0x11 0xBB

CAN message with 0 byte payload

CAN message
Arbitration ID Payload
1 None
Serial frame
Start of frame Timestamp DLC Arbitration ID End of frame
0xAA 0x66 0x73 0x00 0x00 0x00 0x01 0x00 0x00 0x00 0xBBS