Reverse Engineering Apple’s Mikey Chip

What happened

As [Hemant] discovered after finding a single archived blog post from 16 years ago about it, the chip is relatively simple by modern standards. On the old iPods, generally referred to here in the future as iPod Classic, there lives a tiny, undocumented chip called Mikey.

It sits at the headphone output and performs only two functions: powering the Apple wired headset microphone and handling button presses from the three buttons. Despite these headphones and iPods having existed for nearly two decades, no one in the open source community has figured out the protocol Apple used for these buttons until now . Besides handling microphone bias, it sits on an I2C bus and monitors presses from the three buttons on the headset.