Multipli if statements in one

Projects General Guidance
1

Hello,

Im making a binairy counter with the MultiFunction Shield

This is my code so far:

// this constant won't change:
const int  buttonPin = A1;    // the pin that the pushbutton is attached to
const int ledPin0 = 13;       // the pin that the LED is attached to
const int ledPin1 = 12;       // the pin that the LED is attached to
const int ledPin2 = 11;       // the pin that the LED is attached to
const int ledPin3 = 10;       // the pin that the LED is attached to

// Variables will change:
int buttonPushCounter = 0;   // counter for the number of button presses
int buttonState = 0;         // current state of the button
int lastButtonState = 0;     // previous state of the button

void setup() {
  // initialize the button pin as a input:
  pinMode(buttonPin, INPUT);
  // initialize the LED as an output:
  pinMode(ledPin0, OUTPUT);
  pinMode(ledPin1, OUTPUT);
  pinMode(ledPin2, OUTPUT);
  pinMode(ledPin3, OUTPUT);
  
  // initialize serial communication:
  Serial.begin(9600);
}


void loop() {
  buttonPushCounter = 0;
  while(buttonPushCounter <= 15){
  
  
  // read the pushbutton input pin:
  buttonState = !digitalRead(buttonPin);

  // compare the buttonState to its previous state
  if (buttonState != lastButtonState) {
    // if the state has changed, increment the counter
    if (buttonState == HIGH) {
      // if the current state is HIGH then the button went from off to on:
      buttonPushCounter++;
      Serial.println("on");
      Serial.print("number of button pushes: ");
      Serial.println(buttonPushCounter);
    } else {
      // if the current state is LOW then the button went from on to off:
      Serial.println("off");
    }
    // Delay a little bit to avoid bouncing
    delay(50);
  }
  // save the current state as the last state, for next time through the loop
  lastButtonState = buttonState;


  // turns on the LED every four button pushes by checking the modulo of the
  // button push counter. the modulo function gives you the remainder of the
  // division of two numbers:
  if (buttonPushCounter == 1) {
    digitalWrite(ledPin0, LOW);
  } else {
    digitalWrite(ledPin0, HIGH);
  }


   if (buttonPushCounter == 2) {
    digitalWrite(ledPin1, LOW);
  } else {
    digitalWrite(ledPin1, HIGH);
  }


   if (buttonPushCounter == 3) {
    digitalWrite(ledPin0, LOW);
    digitalWrite(ledPin1, LOW);
  } else {
    digitalWrite(ledPin0, HIGH);
    digitalWrite(ledPin1, HIGH);
  }


   if (buttonPushCounter == 4) {
    digitalWrite(ledPin2, LOW);
  } else {
    digitalWrite(ledPin2, HIGH);
  }


   if (buttonPushCounter == 5) {
    digitalWrite(ledPin0, LOW);
    digitalWrite(ledPin2, LOW);
  } else {
    digitalWrite(ledPin0, HIGH);
    digitalWrite(ledPin2, HIGH);
  }
  

   if (buttonPushCounter == 6) {
    digitalWrite(ledPin1, LOW);
    digitalWrite(ledPin2, LOW);
  } else {
    digitalWrite(ledPin1, HIGH);
    digitalWrite(ledPin2, HIGH);
  }


  if (buttonPushCounter == 7) {
    digitalWrite(ledPin0, LOW);
    digitalWrite(ledPin1, LOW);
    digitalWrite(ledPin2, LOW);
  } else {
    digitalWrite(ledPin0, HIGH);
    digitalWrite(ledPin1, HIGH);
    digitalWrite(ledPin2, HIGH);
  }


    if (buttonPushCounter == 8) {
    digitalWrite(ledPin3, LOW);
  } else {
    digitalWrite(ledPin3, HIGH);
  }

    if (buttonPushCounter == 9) {
    digitalWrite(ledPin0, LOW);
    digitalWrite(ledPin3, LOW);
  } else {
    digitalWrite(ledPin0, HIGH);
    digitalWrite(ledPin3, HIGH);
  }


   if (buttonPushCounter == 10) {
    digitalWrite(ledPin1, LOW);
    digitalWrite(ledPin3, LOW);
  } else {
    digitalWrite(ledPin1, HIGH);
    digitalWrite(ledPin3, HIGH);
  }


   if (buttonPushCounter == 11) {
    digitalWrite(ledPin0, LOW);
    digitalWrite(ledPin1, LOW);
    digitalWrite(ledPin3, LOW);
  } else {
    digitalWrite(ledPin0, HIGH);
    digitalWrite(ledPin1, HIGH);
    digitalWrite(ledPin3, HIGH);
  }


     if (buttonPushCounter == 12) {
    digitalWrite(ledPin2, LOW);
    digitalWrite(ledPin3, LOW);
  } else {
    digitalWrite(ledPin2, HIGH);
    digitalWrite(ledPin3, HIGH);
  }


     if (buttonPushCounter == 13) {
    digitalWrite(ledPin0, LOW);
    digitalWrite(ledPin1, LOW);
    digitalWrite(ledPin3, LOW);
  } else {
    digitalWrite(ledPin0, HIGH);
    digitalWrite(ledPin1, HIGH);
    digitalWrite(ledPin3, HIGH);
  }


     if (buttonPushCounter == 14) {
    digitalWrite(ledPin1, LOW);
    digitalWrite(ledPin2, LOW);
    digitalWrite(ledPin3, LOW);
  } else {
    digitalWrite(ledPin1, HIGH);
    digitalWrite(ledPin2, HIGH);
    digitalWrite(ledPin3, HIGH);
  }


   if (buttonPushCounter == 15) {
    digitalWrite(ledPin0, LOW);
    digitalWrite(ledPin1, LOW);
    digitalWrite(ledPin2, LOW);
    digitalWrite(ledPin3, LOW);
  } else {
    digitalWrite(ledPin0, HIGH);
    digitalWrite(ledPin1, HIGH);
    digitalWrite(ledPin2, HIGH);
    digitalWrite(ledPin3, HIGH);
  }
  }
}

But I now use the if statement 16 times is there a way to write this shorter?

2

Use a switch statement.

3

You could use the case/switch statement instead.

The else statements here don't make much sense, as (unless counter == 15) all four pins will end up being HIGH. That can't be right. It appears you want to make specific pins LOW, and have everything else HIGH.
To prevent flickering you probably best set a flag in your switch statements, and in the end set all the pins according to those flags. Also you may use arrays instead of separate variables for the LED pins.

Your code would start to look like this:

byte ledPin[4] = {13, 12, 11, 10};
bool ledPinState[4];

loop {
  // other statements

  // Set all pins to HIGH.
  for (byte i=0; i++; i<4) {
    ledPinState[i] = HIGH;
  }
 
  switch (buttonPushCounter) {
  case 1: 
    ledPinState[0] = LOW;
    break;

  case 2:
    ledPinState[1] = LOW;
    break;
  };

  for (byte i=0; i++; i<4) {
    digitalWrite(ledPin[i], ledPinState[i]);
  }
}

In fact, as you're trying to output a digital state, you can do it even simpler. When you have your pins in the array, this bit of code can replace all your if/else statements with this:

  for (byte i=0; i++; i<4) {
    digitalWrite(ledPin[i], (pushButtonCounter && (1 << i)) == 0);
  }

The brackets may not be necessary; added them to make sure the statement is processed in the correct order.

Explanation is likely in order, as this is bit magic.

1 << i means "1 binary left-shift by i places". So for i = 0, 1, 2 and 3 respectively, the result is 0b0001, 0b0010, 0b0100 and 0b1000 (decimal: 1, 2, 4, 8) respectively.

&& is the binary and operator, so the result of pushButtonCounter && (1 << i) is either 0 (if bit i in pushButtonCounter is zero), or 1 << i if that specific bit is 1.

Based on your list of if statements, you want a binary output, where the LEDs are HIGH if that specific bit is 0, and that's what the == 0 part takes care of.