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slLIN

License

What is this?

This is project slLIN. A LIN protocol inspired by Lawicel's serial line CAN protocol.

How do I use it?

Linux

Configure for master mode, 19200 baud.

sudo slcand -o -F -b 4b00 /dev/ttyACM1

Configure for slave mode, 19200 baud.

sudo slcand -l -F -b 4b00 /dev/ttyACM1

Configure Response

Configure response for ID 'b' using classic checksum. Note, the -x suppresses echoing of the CAN frame.

cangen slcan1 -x -e -L 4 -n 1 -D deadbeef -I 31000b

Configure response for ID '23' using enhanced checksum.

cangen slcan1 -x -e -L 8 -n 1 -D f00f00AA55AA55AA -I 320017

Frame Request

Send header for ID 'b'. Again, the -x suppresses the local echo of the RTR frame.

cangen slcan0  -x -R -I b -n 1

Master Transmission

To send a master request frame, first configure the frame data as you would for a response, then send the header.

Serial Line CAN (slcan) Protocol

The protocol for CAN is decribed here.

Serial Line LIN (slLIN) Protocol

slLIN mostly follows Lawicel's protocol with a few modifications for LIN:

Command                Direction            Description
L\r host to device Open device in slave mode
O\r host to device Open device in master mode
C\r host to device Close device
TIIIIIIIILDD...\r both See next section for CAN-ID decoding
rIIIL\r host to device Only valid in master mode. Send LIN header
n\r both Request device name
Yn\r
(where n is 0 or 1)		 host to device Enable / disable periodic time stamp transmission.
If enabled, the device sends the current time stamp approx. once per second as YTTTT\r.
The format of the time stamp follows the Lawicel format, c.f. documentation of Zn\r command.
shhhh\r
(hex values)		 host to device Set device baud rate, e.g 4b00 sets 19200 Baud/s
Sn\r host to device Set sleep timeout in seconds, i.e. S0 sets 4 seconds, S1 5 seconds...
v\r both Query firmware version

Frame Coding

LIN frames

Start Bit Length Description
0 6 LIN-ID
8 8 CRC

Device to Host Frames

A length of 0 implies an unanswered request.

Bitmask Description
0x00010000 bad sync field (not 0x55). This is typically the only flag
0x00020000 bad PID received, LIN-ID carries recovered ID
0x00040000 bit error in some fixed part of the frame e.g. start bit wasn't 0, stop bit wasn't 1, ...
0x00080000 more than 9 bytes on bus
0x00100000 request was not answered by this node

Host to Device Frames

Length and data of the carrying CAN frame must be valid.

Bitmask Description
0x00100000 Enables frame response if set, else disables.
0x00200000 store LIN frame data. The CAN frames length and data must be valid
Start Bit Length Description
16 2 CRC computation
CRC Computation
Value Description
0x00 take CRC field as is
0x01 ignore CRC field, compute classic CRC
0x02 ignore CRC field, compute enhanced CRC

Bus Error and State Frame

These are always from from device to host and do not carry any LIN frame data.

Bitmask Description
0x10000000 bus status bits are valid
0x08000000 bus error bits are valid
Start Bit Length Description
0 2 Bus State
2 2 Bus Error

Bus State

Value Description
0x00 bus is asleep
0x01 bus is awake
0x02 bus is in error state

Bus Error

Value Description
0x00 no error
0x01 bus shorted to GND
0x02 bus shorted to VBAT

Master Transmission

To put a LIN header on the bus, send a remote request (RTR) CAN frame. Encode the LIN-ID as CAN-ID. The protected identifier is computed by the device. The length part of the RTR frame is ignored.

To send only the break BREAK field only send a RTR frame with an ID of 0x100.

To send a master request frame, store the target payload as response on the device, then send a header with the master request ID.