After a quick evaluation of the Hackaday audience demographics, we requirement to state the late 90s were weird. Even portable audio players were downright bizarre: MP3 players existed, however you packed up your tunes (all eight of them) over your PC’s parallel port. While assisting a cousin relocation some furniture, [Ch00f] discovered a big collection of one of the oddest music styles ever: HitClips, a small plastic encapsulated bit of circuitry that stores 60 seconds of terrible-sounding mono audio. Yes, this was a thing, however so was the pet rock. without any HitClips player, [Ch00f] chose he would take a swing at reverse engineering these tiny, tinny songs.
After taking apart the plastic enclosure, [Ch00f] discovered a extremely easy circuit: a few resistors, a cap, as well as an epoxy blob that enclosed an die with the musical data. On the back of the clip, there are eight pads for linking to the player. With nothing to go on, [Ch00f] started poking around as well as discovered linking one of these pins to ground triggered circuit to draw 300uA of present for about 60 seconds – the exact same length of time as the recorded sample.
[Ch00f] originally believed the HitClip would offer audio data over an SPI or other digital protocol. What he discovered was much much more interesting: two of the pins on the HitClip correspond to the push as well as pull FETs of a class D amplifier. The audio on the HitClip is digital audio, however it’s encoded so it can directly drive an analog circuit. quite smart engineering for a pleased meal toy, if you ask us.
After disposing this data with a logic analyzer, [Ch00f] turned all the values in to .WAV file. It was, amazingly, music. A bit refinement to the process to nail down the timing resulted in a 60-second clip seen (heard?) after the break.
Since [Ch00f] doesn’t want to spend $40 on eBay for a vintage HitClips player, he’s best about at the limit of what he can reverse engineer out of these cheap, crappy music chips. He has put up all his documentation, though, so if you’re up for improving on [Ch00f]’s methods, have a go.
