Doing some digging, until now I did not find a simple solution for digital input (gate on/off) without risking the axo to get fried.
I want to connect my axo to my eurorack drum, I figured an optocoupler would do
4 channels working at the moment, looking to expand to eight.
I'm using a CNY74-4 optocoupler
using a resistor to lower the input Voltage to something acceptable (trial, fry optocoupler, try again, i bet I should have read the data sheet) this works really well
I also put a LED in parallel over the signal cable > Xmas tree!
The panel is rather conductive. Risky business I know, I do not recommend this approach
however the cost of this solution is very low. Some Resistors a prototype panel and an optocoupler
Also, I can use them as CV and gate. CV resolution is somewhat dissappointing, I bet someone with a bit more electronics background can do better, but for triggers this works really great!
Needless to say this is still a prototype, but looking to scale it down to fit my modular.
Tips on improving this very welcome...
especially, is an optocoupler a good or a bad idea?
Patching is really straightforward using GPIO/analog-in and a math/<c object for triggering