ADB Test Host

A host for testing Apple Desktop Bus devices.

HOWTO

Requirements

• PIC
  • Microchip MPASM (bundled with MPLAB)
    • Note that you must use MPLAB X version 5.35 or earlier or MPLAB 8 as later versions of MPLAB X have removed MPASM
  • A PIC12F1840 microcontroller
  • A device to program the PIC with
• Python
  • Python 3.x
  • PySerial

Steps

• Build the code using Microchip MPASM and download the result into a PIC12F1840.
• Connect the Tx and Rx lines to a UART on a PC.
• Run the Python code.

Example

$ python3 -i testhost.py
>>> import serial
>>> serial_obj = serial.Serial(port='/dev/ttyS0', baudrate=115200, timeout=1)
>>> adb = AdbTestHost(serial_obj)
>>> # Press and release 'S' key on ADB keyboard
>>> adb.talk(2, 0)
b'\x01\x81'

Serial Protocol

• Uses 8-N-1 at 115200 baud.
• User sends ADB command byte as it is to be transmitted
  • For a Listen (0bXXXX10XX) command, user follows with:
    • Payload length (1 byte, should be 2-8 but this is not enforced)
    • Payload
• Host sends the ADB command and then responds
  • Result code:
    • 0x00: Normal
    • 0x01: A device is requesting service (SRQ)
    • 0x02: ADB is stuck low by a misbehaving device
  • For a Talk (0bXXXX11XX) command, this is followed with:
    • Payload length (1 byte, should be 2-8 but this is not enforced)
    • Payload
• Break characters are interpreted as reset conditions; they do not have result codes