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ADB(4) Device Drivers Manual (macppc) ADB(4)

adbintroduction to Apple Desktop Bus support

adb0 at macobio?
abtn* at adb?
akbd* at adb?
ams* at adb?
apm0 at adb?
piic0 at adb?

The Apple Desktop Bus (ADB) is the single-master, multiple-slave, low-speed serial bus interface used by Macintosh computers to connect input devices such as keyboards, mice, trackballs, and graphics tablets to the machine.

Originally developed for the Mac68K port, the adb driver was heavily modified when it was ported to the PowerPC architecture. During this port it seems that the original adb event device was split into many smaller subsystems, namely:

  1. Apple Keyboard driver (akbd(4)).
  2. Apple Mouse Support driver (ams(4)).

New adb devices such as the Apple Brightness / Volume Control Button (abtn(4)), some energy control (apm(4)), and I2C controller (piic(4)) were added to the PowerPC port later to complement the ADB system.

OpenBSD provides support for the following devices:

Apple brightness/volume/eject button control
Apple Keyboard Device
Apple Mouse Support
advanced power management device interface
Apple via-pmu I2C controller


The adb interface first appeared in NetBSD 0.9. It has been under development ever since. The original adb manpage was written by Colin Wood for NetBSD/Mac68K.

Original ADB support was written by Bradley A. Grantham. The direct ADB routines were written by John P. Wittkoski.

January 10, 2009 OpenBSD-5.5