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April 9, 2007
MiniROM for the Blacet Miniwave
Jason Proctor asked me a while back to burn some PPG wavetables into some ROMs for the Blacet Miniwave. I was a little concerned about how he was going to sweep through the 64 waves per bank. This isn't real easy as the Miniwave only has 16 waves per bank whereas the PPG had 64 waves per bank. I opened my big mouth and said it wouldn't be that difficult to build a PCB with surface mount FLASH that crams all of the PPG wavetables into a nice small plug and play package. With a little bit of swizzling of the address lines of the bank and wave A/D converters it'd be trivial to drive with no external CV processing.
The end result is a 1.2" x .7" PCB that has 32 banks of 64 waves each, which allows for smoother transitions between waves than a stock Miniwave with the previously available ROM waves. It installs in a socket just like a regular ROM but has four wires that are tack soldered to the back of the board to pick up extra bits of resolution from the wave and bank A/Ds. Pictures of the first unit are here:
http://www.retrosynth.com/gear/minirom/minirom_rev1/
I've built five beta units (in addition to a single wire wrap prototype) and they work just fine although my intended method for programming them didn't pan out. I'll have to come up with another scheme for bypassing the onboard logic while programming the FLASH and spin another board.
I have a demo up on youtube:
http://www.youtube.com/watch?v=qm9m_G0efdI
Posted by cary at 9:43 AM