jacdac.usb_bridge

Submodules

Package Contents

Classes

UsbBridgeClient

This service is normally not announced or otherwise exposed on the serial bus.
class jacdac.usb_bridge.UsbBridgeClient(bus: jacdac.bus.Bus, role: str)

Bases: jacdac.bus.Client

This service is normally not announced or otherwise exposed on the serial bus.

  • It is used to communicate with a USB-Jacdac bridge at the USB layer.

  • The host sends broadcast packets to this service to control the link layer.

  • The device responds with broadcast reports (no-one else does that).

  • These packets are not forwarded to the UART Jacdac line.

  • Packets are sent over USB Serial (CDC).

  • The host shall set the CDC to 1Mbaud 8N1

  • (even though in some cases the USB interface is connected directly to the MCU and line settings are

  • ignored).

  • The CDC line carries both Jacdac frames and serial logging output.

  • Jacdac frames have valid CRC and are framed by delimeter characters and possibly fragmented.

  • 0xFE is used as a framing byte.

  • Note that bytes 0xF8-0xFF are always invalid UTF-8.

  • 0xFF occurs relatively often in Jacdac packets, so is not used for framing.

  • The following sequences are supported:

    • 0xFE 0xF8 - literal 0xFE

    • 0xFE 0xF9 - reserved; ignore

    • 0xFE 0xFA - indicates that some serial logs were dropped at this point

    • 0xFE 0xFB - indicates that some Jacdac frames were dropped at this point

    • 0xFE 0xFC - Jacdac frame start

    • 0xFE 0xFD - Jacdac frame end

  • 0xFE followed by any other byte:

    • in serial, should be treated as literal 0xFE (and the byte as itself, unless it’s 0xFE)

    • in frame data, should terminate the current frame fragment,

  • and ideally have all data (incl. fragment start) in the current frame fragment treated as serial

Implements a client for the USB Bridge service.

disable_packets() → None

Disables forwarding of Jacdac packets.

enable_packets() → None

Enables forwarding of Jacdac packets.

disable_log() → None

Disables forwarding of serial log messages.

enable_log() → None

Enables forwarding of serial log messages.