Simple CV to MIDI CC converter with Arduino

EDIT: SUCCESS! Check my post below


---- original first post ----

I’ve been dabbling in video synthesis recently and needed something easier and more rewarding to do for the weekend, than straight up shader programming, which I still have no clue about So I got the Lumen macOS virtual analog video synth, reminding me of my analog video bending days a few years ago. Unfortunately it is not audio-reactive (yet?), but it can be freely controlled via MIDI CC. You know where this is going ... I checked my DIY drawer* and found a Teensy 2.0++ that I had bought years ago, the one accepting 0-5V analog inputs, which apparently is super easy to add USB MIDI functionality to. Of course I never did anything with that thing and it now turned out that I had bought a counterfeit unit that doesn’t work Luckily, I also found an Arduino Uno, which doesn’t support USB MIDI, but DIN MIDI is easy to implement with just two 220 Ohm resistors.

There are lots of Arduino MIDI tutorials out there, so writing the rather simple functionality of reading an analog input voltage and sending out appropriate MIDI CC data was quick and easy.

Here’s a first test with the Arduino Uno already powered from the AE Modular’s internal 5V bus, receiving three CV signals and sending out DIN MIDI CC to my MacBook Pro running Lumen, displayed via a tiny LED projector:

http://instagr.am/p/BsS9jyCI27D

Here’s the Arduino code from the test (works, but needs some tweaking maybe):

void setup() {
 //  Set MIDI baud rate:
 Serial.begin(31250);

 // not sure if I need this:
 pinMode(A0, INPUT_PULLUP);
 pinMode(A1, INPUT_PULLUP);
 pinMode(A2, INPUT_PULLUP);
 pinMode(A3, INPUT_PULLUP);
 pinMode(A4, INPUT_PULLUP);
 pinMode(A5, INPUT_PULLUP);
}

const int cvInputs = 6; // how many analog inputs are used
int cvLevels[cvInputs] = {0, 0, 0, 0, 0, 0};
int analogInputs[cvInputs] = {A0, A1, A2, A3, A4, A5}; // analog inputs
int midiChannel = 0; // MIDI channels 0-15 are 1-16
int midiCCnumbers[cvInputs] = {10, 11, 12, 13, 14, 15}; // define CC# for each CV input
int midiCCvalues[cvInputs] = {0, 0, 0, 0, 0, 0};

void loop() {

 for (int i = 0; i < cvInputs; i++)
 {
   cvLevels[i] = floor(analogRead(analogInputs[i])/8); // convert 10 bit analog input to 7 bit MIDI range
   
   // if cv has changed, update cv input value and send new midi cc value
   if (cvLevels[i] != midiCCvalues[i])
   {
     midiCCvalues[i] = cvLevels[i];
     sendCC(midiChannel, midiCCnumbers[i], midiCCvalues[i]);
     delay(50); // need to experiment with this delay some more, 50 is probably too long
   }  
  }
}

void sendCC(uint8_t channel, uint8_t control, uint8_t value) {
 Serial.write(0xB0 | (channel & 0xf));
 Serial.write(control & 0x7f);
 Serial.write(value & 0x7f);
}




And some general notes on the MIDI connection:


I’ve ordered a genuine Teensy 2.0++ now, as well as a bunch of Arduino Pro Micros, so that I can build a proper AE Modular module in 1U, that supports both DIN MIDI (using a 3.5mm to DIN MIDI converter) and USB MIDI.

* I mentioned my DIY drawer a few times already on this forum. As you can imagine, there has been a time when I had really lots of things in my head that I wanted to build. Even though my DIY and coding knowledge was (and is) rudimentary, I ordered various components, but apart from the Axoloti, projects never got far. Why? Because I was trying to build for Eurorack and it just occurred to me now that this was what made me fail. Having to work around the -12V to +12V power specs was too much for this electronics newbie. It is completely different now with the AE Modular, with its 0-5V range. I’m extremely happy and satisfied, as I finally can build stuff that works, without spending too many hours on projects (other adult commitments, you know).