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Re: Yamaha E50 has arrived :-)

Posted: Wed Jun 15, 2011 7:20 pm
by adamstan
It would be certainly possible to provide basic MIDI input (Key On/Off). However, poly pressure would be difficult, as my board is going to replace keyscan chip, but leaving old voice assigner (called "Channel processor"/"CLP" by Yamaha). So there is no way to assign pressure value to correct voice. To do that I would have to build replacement for "CLP" as well - and that would mean building much larger board to interface with rest of the circuit.

Why? As you know from the "PAS" manual, it uses time-shared parallel interface working with 1MHz clock cycling through 12 channels. It is really fast compared to 8MHz available on AVR MCU - if it had to generate these signals directly (by feeding that clock to INT pins), it would hardly have time for anything else. The solution is to build array of buffers/latches holding data for each channel, and counter/multiplexer driven by instrument's master clock, connecting these latches sequentially to data lines. It is possible, but makes MUCH larger board - especially considering weird voltage levels used by E-50/70 logic. So for now, I'm going for simpler solution of just replacing K-C chip. But maybe someday... this weird digital interface is really tempting challenge for me ;-)

Re: Yamaha E50 has arrived :-)

Posted: Wed Jun 15, 2011 9:48 pm
by dr funk
adamstan wrote:It would be certainly possible to provide basic MIDI input (Key On/Off).
Excellent! :D
adamstan wrote:However, poly pressure would be difficult, as my board is going to replace keyscan chip, but leaving old voice assigner (called "Channel processor"/"CLP" by Yamaha). So there is no way to assign pressure value to correct voice. To do that I would have to build replacement for "CLP" as well - and that would mean building much larger board to interface with rest of the circuit.
Ah, I understand. Thanks for explaining it! I've monitored the MIDI out of my Chroma in MIDI-OX, and poly pressure certainly does add a LOT of data!

Please keep me posted about your work on the E50. When you build the new key scan board, would you be interested in building a second one for my E70? I could help to fund your work and get MIDI for my E70! I'd imagine the key scanning is identical on both.

Cheers
Frank

Re: Yamaha E50 has arrived :-)

Posted: Wed Jun 15, 2011 10:41 pm
by adamstan
dr funk wrote: I'd imagine the key scanning is identical on both.
Yes, that's right, the KCA boards are identical. I can make two boards, why not?

Re: Yamaha E50 has arrived :-)

Posted: Thu Jun 16, 2011 1:41 pm
by dr funk
Excellent! Vintage Electones with MIDI - I like it! :-)

Frank

Re: Yamaha E50 has arrived :-)

Posted: Thu Jun 16, 2011 2:29 pm
by DX7Alex
The pipe organ is great, but the synth sounds demo is spectacular. Best of luck with your mods!

Re: Yamaha E50 has arrived :-)

Posted: Tue Jul 05, 2011 1:37 pm
by dr funk
Check out what this guy has done to his E70! There are 6 'Son of GX' videos... :)

E70 mods

Frank