Hardware Protocol Specification: SAE J1708

Version: J1708
Physical Layer: 9600 bps, 8N1.0
Framing: delimited
Integrity Algorithm: sum8

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Description

Heavy-vehicle diagnostic multi-drop bus. Fixed 9600 8N1 -- no parity at all, unlike M-Bus's 8E1 or G460's default -- a third distinct combination across the protocols tried so far.

Command Catalog & Message Signatures

Category: GENERAL

Message (Command ID: 0x00) - MID implies the message's format/length via an external lookup, much like LIN's identifier -- though here the boundary itself comes from bus silence, not a table (Message/data here has whatever length the specific MID's fields sum to).

Parameter	Type	Unit	Range / Constraints	Options
mid	uint8	-	-	-
data	bytes	-	-	-

Formal AsyncAPI 2.6.0 Specification

asyncapi: 2.6.0
info:
  title: SAE J1708
  version: J1708
  description: Heavy-vehicle diagnostic multi-drop bus. Fixed 9600 8N1 -- no parity
    at all, unlike M-Bus's 8E1 or G460's default -- a third distinct combination across
    the protocols tried so far.
servers:
  serial_link:
    url: serial://tty/9600
    protocol: serial
    description: Physical UART Transport (9600 bps, 8N1.0)
    bindings:
      serial:
        baudRate: 9600
        dataBits: 8
        parity: none
        stopBits: 1.0
        framingType: delimited
        integrity: sum8
channels:
  omniuart/cmd/Message:
    publish:
      summary: 'Send command Message (ID: 0x00)'
      description: MID implies the message's format/length via an external lookup,
        much like LIN's identifier -- though here the boundary itself comes from bus
        silence, not a table (Message/data here has whatever length the specific MID's
        fields sum to).
      message:
        name: Message_Message
        title: Message Command
        payload:
          $ref: '#/components/schemas/Message_Request'
components:
  messages: {}
  schemas:
    Message_Request:
      type: object
      properties:
        command_id:
          type: integer
          const: 0
          description: Opcode ID for Message
        mid:
          type: integer
        data:
          type: string
          contentEncoding: base64
      description: MID implies the message's format/length via an external lookup,
        much like LIN's identifier -- though here the boundary itself comes from bus
        silence, not a table (Message/data here has whatever length the specific MID's
        fields sum to).