Hello !
Do you have any idea of alternatives for such hardwares ? The V2 is quite interesting with its 64 analog inputs.
You can use the Teensy + 74HC4067 16:1 analog MUXs + 74HC595 shift registers to create your own. That's the combo of hardware I used in my TeensyMIDIPolySynth (
https://forum.pjrc.com/threads/60690-TeensyMIDIPolySynth?p=237404&viewfull=1#post237404). My project took analog inputs (pots) & digital inputs (pushbuttons) thru the MUXs, & used that to adjust settings as a MIDI-to-sound instrument. It sends the current selection states thru the shift registers to display on LEDs. That's slightly different from what you seem to want to do (take inputs & generate MIDI outputs), but the point of my post is to pass along that with the Teensy & some minimal additional hardware (74HC4067 MUXs & 74HC595 shift registers), you could probably create an equivalent fairly quickly & easily.
The MUXs require one analog input/output & 4 digital addressing pins. You can cascade the MUXs (I used this approach in the TeensyMIDIPolySynth), so the primary MUX would use these 5 pins as described. The secondary MUX input/output pin would be wired to the 16 input/output pins on the primary MUX. Doing it this way, you would need an additional 4 addressing pins for the secondary MUXs. Therefore, you would only need 9 pins (4 primary addressing, 4 secondary addressing, & 1 input/output) to give you 256 analog inputs/outputs. The MUXs work for both analog signals & digital signals. You can use the 16 side of any MUX for either input or output, or any mix of both.
The shift registers require only 2 pins (clock & data). Or if you want, you might add a third pin for the output enable. I tied the output enable pin on the shift registers to a PWM pin from the Teensy & used the PWM duty cycle to control the brightness of the LEDs. You can cascade as many 74HC595s as you might need for your LED outputs (I am using seven 74HC595s, for a total of 56 outputs from only 3 pins in my case).
Feel free to ask any other related questions.
Good luck & have fun !!
Mark J Culross
KD5RXT