CCLab - Proximity Lights.ino

int led = 11, trigPin = 9, echoPin = 8;

long prevDuration = 300, realDuration, normalizedDuration;
long durationMin = 300, durationMax = 2400;
int prevBrightness;

void setup() {
  pinMode(led, OUTPUT);
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  Serial.begin(9600);
}

void loop() {
  prevDuration = realDuration;
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  realDuration = pulseIn(echoPin, HIGH);
  normalizedDuration = constrain(realDuration, durationMin, durationMax);
  Serial.print(realDuration);
  Serial.print(", ");
  Serial.print(normalizedDuration);
  Serial.print(", ");
  long durationDiff = abs(realDuration - prevDuration);
  Serial.print(durationDiff);
  Serial.print("\n");
  if (durationDiff > 50 && durationDiff < 10000) {
    int brightness = map(normalizedDuration, durationMin, durationMax, 255, 0);
    fadeTo(led, brightness);
  }
  delay(500);
}

void fadeTo(int pin, int brightness) {
  if (brightness == prevBrightness) { return; }
  int d = 5;
  if (brightness > prevBrightness) {
    for (int i = prevBrightness; i <= brightness; i++) {
      analogWrite(pin, i);
      delay(d);
    }
  } else {
    for (int i = prevBrightness; i >= brightness; i--) {
      analogWrite(pin, i);
      delay(d);
    }
  }
  prevBrightness = brightness;
}