Question

Microcontroller programming exercises by practice on Arduino:

Write a program that lights a green LED attached to pin 3. The green LED should turn off after a button attached to pin4 has been pushed and released 3 times. Each time the button is pushed it will turn on a red LED attached to pin 7 and turn off a yellow LED attached to pin 9. When the button is not pushed the red LED will be off and the yellow LED will turn on. Assume the button is wired active low.

Answer 1

/* sketch 1 
turn on a LED when the button is pressed
turn it off when the button is not pressed (or released)
*/
int pinButton = 4; //the pin where we connect the button
int LED = 3; //the pin we connect the LED

void setup()
 {
  pinMode(pinButton, INPUT); //set the button pin as INPUT
  pinMode(LED, OUTPUT); //set the LED pin as OUTPUT
}

void loop() 
{
  int stateButton = digitalRead(pinButton); //read the state of the button
  if(stateButton == 1) { //if is pressed
     digitalWrite(LED, HIGH); //write 1 or HIGH to led pin
  } else { //if not pressed
     digitalWrite(LED, LOW);  //write 0 or low to led pin
  }
}

/* sketch 2 
turn on a LED when the button is pressed and let it on when the button is released
*/
int pinButton = 4; //the pin where we connect the button
int LED = 3; //the pin we connect the LED

void setup() {
  pinMode(pinButton, INPUT); //set the button pin as INPUT
  pinMode(LED, OUTPUT); //set the LED pin as OUTPUT
}

void loop() {
  int stateButton = digitalRead(pinButton); //read the state of the button
  if(stateButton == 1) { //if is pressed
     digitalWrite(LED, HIGH); //write 1 or HIGH to led pin
  }
}

/* sketch 3 
turn on a LED when the button is pressed and let it on 
until the button is pressed again
*/
int LED = 7;
int stateLED = LOW;
int stateButton;
int previous = LOW;
long time = 0;
long debounce = 200;

int LED = 9; 
int stateLED = LOW; 
int stateButton; 
int previous = LOW; 
long time = 0; 
long debounce = 200;

void setup() {
  pinMode(pinButton, INPUT);
  pinMode(LED, OUTPUT);
}

void loop() {
  stateButton = digitalRead(pinButton);  
  if(stateButton == HIGH && previous == LOW && millis() - time > debounce) {
    if(stateLED == HIGH){
      stateLED = LOW; 
    } else {
       stateLED = HIGH; 
    }
    time = millis();
  }
  digitalWrite(LED, stateLED);
  previous == stateButton;
}