The other day, I came across this interesting lil guy called the KidiJamz Studio from VTech. Apart from it actually having some interesting voices and stock effects, I noticed that it had a docking port for what appears be an MP3 player peripheral.
I was bummed that this thing didn't come with the MP3 player, as it seems to be included when you buy it. I was interested in figuring out how it actually sent data to the MP3 player. I was thinking about trying to use it purely as a digital output, or possibly even a way to access the board's microcontroller.
The pin connections to the various daughter boards are neatly labeled, allowing me to map out the connections. I was looking for wires connecting the MP3 player connector to the board, and found a port with 7 pins attached labeled TO-24. For this board, it seemed that the red wire was pin 1, connected to Vcc, and the next wire, pin 2, was connected to ground on pretty much every attachment. This leaves 5 pins to handle data, device selection, and other functions.
I also found that there were some unused connections that were still connected to the main processor on the board. Interestingly, TO-27 seemed to trigger a little steel drum melody that you can't hear from any of the other function buttons if you short out pin 4 with pins 1, 2 , 5, or 6, and crash the board if you short pin 3 or 5. Some of the ports that should logically exist by their numbering scheme are mysteriously absent.
The board is pretty standard with late 90s/early 00s toy synths. The keys are divided in left and right connections on the port TO-05. The way that keys are triggered is by shorting any of the pins on that channel to Pins 1 or 2 on their respective port, L or R. This allows for 24 notes to be played using only 14.
Still have no idea how this sends data to the MP3 player. I'll need to do some bus sniffing on the pins which are easy enough to access.
Board Connections TO-01 Power Switch TO-02 8p. Speed TO-03 7p, Style Selection TO-04 18p, Keyboard LEDs, Divided into L/R TO-05 14p, Keys, Divided into L/R, Short to 1 or 2 TO-06 4p, Rhythm Selection TO-07 TO-08 4p, Filler sounds TO-09 3p, Stereo Line In TO-10 3p, Stereo Headphones TO-11 8p, Voice select TO-12 TO-13 TO-14 8p, Demo songs TO-15 TO-16 TO-17 4P Unknown TO-18 4p, SFX TO-19 3p, Volume TO-20 TO-21 TO-22 TO-23 4p, Mic w/ volume control TO-24 7p, MP3 Player TO-25 3p, MP3 Player stop/record buttons TO-26 TO-27 7p, unused, Pin 1 is linked to the Vcc of U2? TO-28 2p, unused, one pin looks connected via R107 to the red wire on TO-14, other pin looks like it would've been attached to D15 if it was actually there. D15 Looks like it would've been attached to P2 of TO-04L, the keys. TO-29 3p, unused, middle connects to scratch TRY_ME 2p, Related to first demo state? SCRATCH 2p SPK Mono Speaker