Post
by Sweetfoot Studios » Sat May 23, 2015 4:57 pm
I've had some success retrofitting my synare PS-2 with midi, kinda. I say kinda because it's super buggy, and I don't really understand the system well enough to know why.
I had to reverse engineer the keyboard/note generation interface somewhat, though, so maybe I can help you. What I found was that the "pads", contrary to my original theory, are not piezo triggers in the style of the synare 3, but rather momentary switches. The board that the pads are mounted to connects to another board via serial plug. This second board, I'll call it the brain board, features a microprocessor and some memory that I believe serves to convert the on/off info from the pads to CV/gate signals, which it in turn passes on to the analog voice circuitry on yet a third board mounted under the control panel via a ribbon cable.
I realized I could use some old ribbon cables to interrupt the connection between the pads and the brain board, and trick the brain into thinking pads were being pushed. The new ribbon cable has 3 terminals; 2 female, and one male, which I had to make from a breadboard with jumpers soldered in to make pins. The terminals are wired in parallel, so that one female terminal plugs onto the pins on the pad board, the other female terminal plugs onto the midi retrofit, and the male terminal plugs into the brain board. This configuration allows the pads to still function when they are feeling cooperative, but also allows my midi retrofit to make the momentary connections instead.
I could give you more info on the arduino and relay based midi retrofit if you are interested, but if you just want a keyboard, I bet you could get a cheap momentary keyboard from a toy or an old organ, and wire the ribbon cable to that instead of a midi retrofit.
The trick is understanding the pin layout coming from the pad board. I don't remember the specifics, but I do remember the serial plug pins on the pad board are arranged in a row with a gap dividing the row into two unequal groups. The smaller group of pins control the octave, and the larger group controls the note. Both groups have a "ground" pin; you can find it with a multimeter if you put one probe on the nut in the middle of the pad board that has a green ground wire going to it, and touch the other probe to each pin until your meter indicates continuity (assuming none of your pads are shorted out). A note selection is made by briefly connecting the note's corresponding pin to the "note section" ground pin. The same goes for octave selection.
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