# 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, *args, **kwargs)

  Enable basic can communication over a serial device.

## 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