isuck.c

void rgblight_effect_breathing(uint8_t interval) {
  static uint8_t pos = 0;
  static uint16_t last_timer = 0;
  float val;

  if (timer_elapsed(last_timer) < pgm_read_byte(&RGBLED_BREATHING_INTERVALS[interval])) {
    return;
  }
  last_timer = timer_read();


  // http://sean.voisen.org/blog/2011/10/breathing-led-with-arduino/
  val = (exp(sin((pos/255.0)*M_PI)) - RGBLIGHT_EFFECT_BREATHE_CENTER/M_E)*(RGBLIGHT_EFFECT_BREATHE_MAX/(M_E-1/M_E));
  rgblight_sethsv_noeeprom(rgblight_config.hue, rgblight_config.sat, val);
  pos = (pos + 1) % 256;
}