Hardware Protocol Specification: Generic MCU serial bootloader (illustrative, sync-byte auto-baud)

Version: illustrative
Physical Layer: 115200 bps, 8N1.0
Framing: binary
Integrity Algorithm: sum8

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Description

Not modelling any specific vendor's exact protocol -- illustrates the auto-baud mechanism common to several real MCU ROM bootloaders.

Command Catalog & Message Signatures

Category: GENERAL

AutoBaudSync (Command ID: 0x7F) - The sync byte itself (physicalLayer.autoBaud.syncByte) -- not a normal command, just the timing reference the bootloader measures before anything else can happen.

Parameter	Type	Unit	Range / Constraints	Options
syncByte	uint8	-	-	-

GetVersion (Command ID: 0x01)

Parameter	Type	Unit	Range / Constraints	Options
opcode	uint8	-	-	-

WriteMemory (Command ID: 0x02)

Parameter	Type	Unit	Range / Constraints	Options
opcode	uint8	-	-	-
address	uint32	-	-	-
data	bytes	-	-	-

Go (Command ID: 0x03) - Jumps to application code at the given address, ending the bootloader session.

Parameter	Type	Unit	Range / Constraints	Options
opcode	uint8	-	-	-
address	uint32	-	-	-

Device-Initiated Messages

Ack (Message ID: 0x79)

Field Name	Type	Unit
controlByte	uint8	-

Nack (Message ID: 0x1F)

Field Name	Type	Unit
controlByte	uint8	-

Formal AsyncAPI 2.6.0 Specification

asyncapi: 2.6.0
info:
  title: Generic MCU serial bootloader (illustrative, sync-byte auto-baud)
  version: illustrative
  description: Not modelling any specific vendor's exact protocol -- illustrates the
    auto-baud mechanism common to several real MCU ROM bootloaders.
servers:
  serial_link:
    url: serial://tty/115200
    protocol: serial
    description: Physical UART Transport (115200 bps, 8N1.0)
    bindings:
      serial:
        baudRate: 115200
        dataBits: 8
        parity: even
        stopBits: 1.0
        framingType: binary
        integrity: sum8
channels:
  omniuart/cmd/AutoBaudSync:
    publish:
      summary: 'Send command AutoBaudSync (ID: 0x7F)'
      description: The sync byte itself (physicalLayer.autoBaud.syncByte) -- not a
        normal command, just the timing reference the bootloader measures before anything
        else can happen.
      message:
        name: AutoBaudSync_Message
        title: AutoBaudSync Command
        payload:
          $ref: '#/components/schemas/AutoBaudSync_Request'
  omniuart/cmd/GetVersion:
    publish:
      summary: 'Send command GetVersion (ID: 0x01)'
      description: Dispatch GetVersion frame to microcontroller over serial line
      message:
        name: GetVersion_Message
        title: GetVersion Command
        payload:
          $ref: '#/components/schemas/GetVersion_Request'
  omniuart/cmd/WriteMemory:
    publish:
      summary: 'Send command WriteMemory (ID: 0x02)'
      description: Dispatch WriteMemory frame to microcontroller over serial line
      message:
        name: WriteMemory_Message
        title: WriteMemory Command
        payload:
          $ref: '#/components/schemas/WriteMemory_Request'
  omniuart/cmd/Go:
    publish:
      summary: 'Send command Go (ID: 0x03)'
      description: Jumps to application code at the given address, ending the bootloader
        session.
      message:
        name: Go_Message
        title: Go Command
        payload:
          $ref: '#/components/schemas/Go_Request'
  omniuart/telemetry/Ack:
    subscribe:
      summary: 'Unsolicited telemetry message Ack (ID: 0x79)'
      description: 'Unsolicited telemetry message from device: Ack'
      message:
        name: Ack_Telemetry_Message
        title: Ack Telemetry
        payload:
          $ref: '#/components/schemas/Ack_Telemetry'
  omniuart/telemetry/Nack:
    subscribe:
      summary: 'Unsolicited telemetry message Nack (ID: 0x1F)'
      description: 'Unsolicited telemetry message from device: Nack'
      message:
        name: Nack_Telemetry_Message
        title: Nack Telemetry
        payload:
          $ref: '#/components/schemas/Nack_Telemetry'
components:
  messages: {}
  schemas:
    AutoBaudSync_Request:
      type: object
      properties:
        command_id:
          type: integer
          const: 127
          description: Opcode ID for AutoBaudSync
        syncByte:
          type: integer
          default: 127
      description: The sync byte itself (physicalLayer.autoBaud.syncByte) -- not a
        normal command, just the timing reference the bootloader measures before anything
        else can happen.
    GetVersion_Request:
      type: object
      properties:
        command_id:
          type: integer
          const: 1
          description: Opcode ID for GetVersion
        opcode:
          type: integer
          default: 1
      description: Command payload for GetVersion
    WriteMemory_Request:
      type: object
      properties:
        command_id:
          type: integer
          const: 2
          description: Opcode ID for WriteMemory
        opcode:
          type: integer
          default: 2
        address:
          type: integer
        data:
          type: string
          contentEncoding: base64
      description: Command payload for WriteMemory
    Go_Request:
      type: object
      properties:
        command_id:
          type: integer
          const: 3
          description: Opcode ID for Go
        opcode:
          type: integer
          default: 3
        address:
          type: integer
      description: Jumps to application code at the given address, ending the bootloader
        session.
    Ack_Telemetry:
      type: object
      properties:
        controlByte:
          type: integer
          default: 121
      description: Device-initiated telemetry payload for Ack
    Nack_Telemetry:
      type: object
      properties:
        controlByte:
          type: integer
          default: 31
      description: Device-initiated telemetry payload for Nack