---
name: "adb"
section: "4"
platform: "openbsd"
package: "man"
version: "8.0-current-20261101"
release: "OpenBSD 8.0-current (2026-11-01)"
platforms: ["freebsd", "openbsd"]
url: "https://new.carta.tech/adb/4"
---

# adb(4)

introduction to Apple Desktop Bus support

## NAME

**adb** – introduction to Apple Desktop Bus support

## SYNOPSIS

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

## DESCRIPTION

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)](/akbd/4.md)).

2. Apple Mouse Support driver ([ams(4)](/ams/4.md)).

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

OpenBSD provides support for the following devices:

- [abtn(4)](/abtn/4.md)

  Apple brightness/volume/eject button control

- [akbd(4)](/akbd/4.md)

  Apple Keyboard Device

- [ams(4)](/ams/4.md)

  Apple Mouse Support

- [apm(4)](/apm/4.md)

  advanced power management device interface

- [piic(4)](/piic/4.md)

  Apple via-pmu I2C controller

## SEE ALSO

[intro(4)](/intro/4.md)

## HISTORY

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.

## AUTHORS

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