I need to build an (apparently) extremely simple device which is basically a pushbutton that pauses and restarts the playback on an iPhone.
This is exactly what the central button does, on the remote control that can be found along the cable of iPhone headsets - both the official Apple ones, delivered with the iPhone, or commercially available compatibles.
I've spent the past half hour researching around (including this site) to no avail. As I am writing this, I am at the office, without any instrumentation, so I cannot probe the TRRS 3.5 mm jack connector to see what happens as I press buttons.
Just to make it perfectly clear why I need this: I need to build a pedal control for the pause/play function of any audio app. Let's say I've given a half-improvised lecture, which I have recorded on my iPhone, then I want to replay it and transcribe it. As a ten-fingered typist I type fast enough, but not so fast as to keep up pace with speech, so I want to pause and restart playback without lifting my hands from the keyboard.
This is a function which existed on good ol' Dictaphones, including - if I remember correctly - the very first one, invented by A.G.Bell in the 1880s, but apparently I cannot find a way to do the same with an iPhone.