breath.ino

#include <SPI.h>
#include "LPD8806.h"

// LED parameters:
#define LED_COUNT 16
#define DATA_PIN 6
#define CLOCK_PIN 12

LPD8806 strip;

void setup() {
  strip = LPD8806(LED_COUNT, DATA_PIN, CLOCK_PIN);
  
  // Turn the strip on.
  strip.begin();
  
  // Refresh the strip.
  strip.show();
}

void loop() {
  breath();
}

const int  CYCLE_MILLISECONDS = 5000; // 5 second breathing cycle.
const uint8_t KEYFRAMES[]  = {
  // Rising
  20, 21, 22, 24, 26, 28, 31, 34, 38, 41, 45, 50, 55, 60, 66, 73, 80, 87, 95,
  103, 112, 121, 131, 141, 151, 161, 172, 182, 192, 202, 211, 220, 228, 236,
  242, 247, 251, 254, 255,

  // Falling
  254, 251, 247, 242, 236, 228, 220, 211, 202, 192, 182, 172, 161, 151, 141,
  131, 121, 112, 103, 95, 87, 80, 73, 66, 60, 55, 50, 45, 41, 38, 34, 31, 28,
  26, 24, 22, 21, 20,
  20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 
};

unsigned long lastBreath = 0.0;
int keyframePointer = 0;

void breath() {
  int numKeyframes = sizeof(KEYFRAMES) - 1;
  float period = CYCLE_MILLISECONDS / numKeyframes;
  unsigned long now = millis();
  
  if ((now - lastBreath) > period) {
    lastBreath = now;

    for (int i = 0; i < strip.numPixels(); i++) {
      uint8_t color = (127 * KEYFRAMES[keyframePointer]) / 256;
      strip.setPixelColor(i, color, 0, 0);
    }
    strip.show();   

    // Increment the keyframe pointer.
    if (++keyframePointer > numKeyframes) {
      // Reset to 0 after the last keyframe.
      keyframePointer = 0;
    }   
  }
}