MIDIfying a Yamaha cs-01

[der.warst]

Hey there,

I've been a lurker on this forum for quite a time, but now switched to active mode because I'd really like to MIDIfy my Yamaha CS01 Synth.

For a start it would be enough for me to have it receive notes, but maybe some control for the sliders could be added, too.

As far as I can see on its schematic: http://freenet-homepage.de/kirdneh/yamaha_cs01_schematic.pdf, the keyboard matrix is pretty simple:

By seeing the vast amount of projects that this forum is filled up with, I'm a little unsure which application would fit the best and if I could just use something "as is" for that task or if I have to write/modify some code.

Anyway, Thanks for any hint in the right direction.

Simon

[Wilba]

Looks like an interesting project... I wish I had a vintage synth worthy of MIDIfication...

The main problem you have with this circuit is the keyboard switches are in a matrix.

At a guess, N2-N7 are outputs from IC1, one of these will be high, the rest low. When one is high, then any closed switches (pressed keys) connected to that output will conduct the high signal into B11,B12,B21,B22,B31,B32. You can view this as a group of six keys being "sampled" as each of the N2-N7 outputs is cycled. (Also, some other switches are sampled this way, like the waveform switch).

Now perhaps the easiest (but rather brute force) method of adding MIDI In would be to connect something like a 4066 chip, i.e. bilateral switches, in parallel with each switch of the keyboard, and then connecting the control pin to a DOUT pin, and running the MIDIIO128 application. The application should be easy to configure and not require any real coding to get things working. One 4066 chip could drive four keys. See here: http://www.fairchildsemi.com/ds/CD/CD4066BC.pdf

The other more elegant way (which would involve a lot of custom programming) is to work out when N2-N7 is being turned on, and insert your own high signals into B11,B12,B21,B22,B31,B32. This is probably a lot more effort than you'd expect. It's been done before with other synths (see http://www.maxmidi.com/diy/sk1/article.html). Also, it probably won't be possible with MIOS because you'd need a dedicated processor just to make sure B11,B12,B21,B22,B31,B32 are driven high within microseconds of N2-N7 changing, you can't have MIOS interrupting this process.

So I'd go for plan A. Watch out for the very bizarre voltages! It looks like everything works on GND being "high" and -9V being "low"... this complicates everything, as I would suspect that IC1 also is running on a 9V difference between high and low... perhaps a 4066 won't work then... and you'll need some other solution to control the switches (i.e. relays). Someone with more experience with MIDIfication could help you there.

[ilmenator]

You could also try reed relais, see this thread, very similar to solution A, but no hassle with strange voltages.

Best regards, ilmenator

[Shum]

Hi Simon,

The Yamaha cs-01 is an analogue synth as seen from the schematic. As such it does not receive or send midi messages. In other words it cannot receive notes as you would want it to. Not very sure what you really wish to do.

If the keyboard can be isolated from the synth, a simple midi interface can be built to make it a midi keyboard. However, you no longer be able to play the Yamaha cs-01.

Regards

Shum

[drsyncenstein]

@Shum: he's trying to control an analog synth with midi messages.

That is not so weird is it? Lot's of people doing that.

Very cool project if he succeeds!