Pulse a LED

LED_pulse.ino

// Source: https://www.sparkfun.com/tutorials/329
// To understand the code you need to look at the sinus curve in the toturial.


const int LED = 0;

void setup() {
}

void loop()
{
  // prevent LED to light on max brightness by stoping before the curve reaches the top plane
  float trimBrightnessMax = 0.854;
  
  // optional: modify sinus curve. 
  // use the same options for rising and falling fade to prevent a missmatch of max/min brightness
  float sinRange = 127.5;
  float sinOffset = 127.5;
  
  // modify step length to change the transition speed
  float stepLength, start, end, out;

  // rising (start from zero and go to max brightness)
  // start value is at bottom of the curve
  // end value is the top of the sinus curve
  start = 4.712; //pi*1.5
  end = 7.854; //pi*2.5
  end -= trimBrightnessMax;
  stepLength = .001;
  fade(start, end, stepLength, sinRange, sinOffset);

  // pause at peak brightness
  delay(500); 

  // falling (start from max brightness and go to zero)
  // start value is the top of the sinus curve
  // end value is at bottom of the curve
  start = 1.570; //pi*0.5
  start += trimBrightnessMax;
  end = 4.712; //pi*1.5
  stepLength = .0008;
  fade(start, end, stepLength, sinRange, sinOffset);

  // pause when LED is off
  delay(2000);
}

void fade(float start, float end, float stepLength, float sinRange, float sinOffset) {
  float out;
  while (start < end)
  {
    start = start + stepLength;
    out = sin(start) * sinRange + sinOffset;
    analogWrite(LED, out);
    delay(1);
  }
}

sinus-wave-255-range.png

sinus-wave-range.png

Source - SparkFun Electronics.pdf