Euclidian sequencer proof-of-concept for Ardcore

euclid.ino

/*
  A simple two-channel euclidian sequencer (work-in-progress).

  Currently supports one channel. Caveat: there may be bugs. I just got my Ardcore
  and I started developing this before it arrived.

  Given an input like (A), it should send out something like (B) in a loop:

  (A) * * * * * * * *
  (B) *     *     *
  

  TODO:

  * Make length settable from first knob
  * Make offset for the second channel settable from the second knob
  * Make length for first channel settable from third knob
  * Make length for second channel settable from fourth knob
*/

const int clkIn  = 2;
const int digPin = 3;

volatile int clkState = LOW;
volatile int digState = LOW;

int n      = 0; // current input ping count
int count  = 3; // number of pings to output per measure
int offset = 0; // number of pings at start of measure to wait
int length = 8; // length of measure in pings

void setup() {
  pinMode(clkIn, INPUT);
  
  pinMode(digPin, OUTPUT);
  digitalWrite(digPin, LOW);
  
  attachInterrupt(0, isr, RISING);
}

void loop() {
  if(clkState == HIGH) {
    clkState = LOW;
    digState = hit(n, count, offset, length) ? HIGH : LOW;
    
    digitalWrite(digPin, digState);
  }

  n++;
}

void isr() {
  clkState = HIGH;
}

// calculate whether to send an output ping or not
boolean hit(int n, int count, int offset, int length) {
  return ( (n + offset) * count ) % length < count;
}