ATTiny85 based MIDI to CV

README

Requires https://github.com/heartscrytech/DigisparkMIDI
Bootloader https://github.com/micronucleus/micronucleus
See instructions at https://janostman.wordpress.com/cheap-diy-usb-midi-to-cv-interface/

add to usbFunctionWriteOut() in DigiMIDI.h

void usbFunctionWriteOut(uchar * data, uchar len) {

uint8_t note=data[2]; //Get note for key on/off
if (note<36) note=36; //If note is lower than C2 set it to C2
note=note-36; //Subtract 36 to get into CV range
if (note>60) note=60; //If note is higher than C7 set it to C7
if (data[1] == 0x90) { //If note on
digitalWrite(5, HIGH); //Set Gate HIGH
OCR1A = note<<2; //Multiply note by 4 to set the voltage (1v/octave)
}
if (data[1] == 0x80) { //If note off
digitalWrite(5, LOW); //Set Gate LOW
OCR1A = note<<2; //Multiply note by 4 to set the voltage (1v/octave)
}

}

midi2cv.ino

#include <DigiMIDI.h>

DigiMIDIDevice midi;

void setup() {
pinMode(1,OUTPUT); //Pitch is output
pinMode(5, OUTPUT); //Gate is output
//Setup Timer1 to do PWM DAC for Pitch
TCCR1 = _BV(PWM1A) | _BV(COM1A1) | _BV(CS10);
GTCCR = 0;
OCR1C = 239;
OCR1A = 0; //Set initial Pitch to C2
digitalWrite(5,LOW); //Set initial Gate to LOW;
}

void loop() {
midi.update(); //Check if any MIDI data is received
}