Hackaday · Creativity & design

Apple's Mikey Chip Protocol Deciphered

After nearly two decades, the communication protocol for Apple's undocumented Mikey chip, found in older iPod Classics, has been reverse-engineered.

The Mikey chip, located at the headphone output, is responsible for powering the wired headset microphone and processing button presses from the headset's three buttons.

The chip operates on an I2C bus. Button presses are detected by a drop in voltage on a line, with each button having a unique resistive load.

A significant part of the reverse engineering involved understanding a "chirp" signal, which acts as a handshake between the headset and the iPod.

This handshake was deciphered using a custom debugger built into Rockbox firmware.

The discovered protocol has been integrated into an existing version of Rockbox and submitted for official builds.

This feature is beneficial for users still utilizing wired headphones and older iPod models, some of which remain functional under specific cold conditions.

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