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Experimentation

Because I am new to Arduino, I wanted to go slowly, step by step, one challenge at the time. This section contains unit tests made prior the application per se.


/*  Fading LED in a loop, speed set with a potentiometer.
*  This test involves A/D conversion and PWM
*/

int ledPin = 6;     // LED connected to D6 (pin #9)
int analogPin = 1;  // Potentiometer connected to A1 (pin #20)
int pot;            // Value read from potentiometer

void setup() {
  pinMode(ledPin, OUTPUT);      // sets the pin as output
  pot = analogRead(analogPin);  // read the analog input pin on startup.
}

void loop() {  
    
  /**
   *   Fading LED back and forth continuously
   */
  int i=0, maxval = 255;

  /** Scale **/
  int wait = pot / 4;

  /** Fade Up **/
  for(i=0;i < maxval; i++){
     delay(wait);
     analogWrite(ledPin, i);
  }

  /** Fade down **/
  for(i=maxval ; i>0; i--){
    delay(wait);
    analogWrite(ledPin, i);
  }
}


First argument in functions analogRead() and analogWrite() is the number in the pin name , not the chip pin number. For example, for pin D6 (chip pin #9) we must use:

    analogWrite(6, value); // 6 for D6, not 9 for pin#9...

The function analogWrite() will accept values greater than 255 but the result will not be as expected. So always make sure second argument will not exceed 255.

This application requires about 8 buttons and 8 LEDs plus 3 PWM outputs for a total of 19 digital pins. This count is greater than the 10 pins available in the board. Consequently, multiplexing is imperative.