4_arduino_counter_EN.ino

#define BUTTON 8

int counter = 0; //We store the number 0 in an integer type variable named counter
String msg; //We declare the variable msg of type String (characheteres chain)
boolean sign = true; //We declare a boolean variable (true or false) named sign that will determine whether to add or remove 1
//Other common types of variables are float (decimal number) and char (characteres)

void setup() {
  // put your setup code here, to run once:

  pinMode(BUTTON, INPUT); // Set BUTTON as an INPUT

  Serial.begin(9600); //Initializes serial communication at 9600 baud
}

void loop() {
  // put your main code here, to run repeatedly:
  if (Serial.available() )
  {
    //If a message has been received do this
    msg = Serial.readString();  //Stores the received message in the msg variable
    
    Serial.print("--> ");
    Serial.println(msg);
    
    if(msg == "+")//If the message is equal to +
    { 
      sign = true; //Then we set sign to true.
    }
    else if (msg == "-") //Otherwise if the message is equal to +
    {
      sign = false;
    }
    else //If not (if not a + or -) do
    {
      Serial.println("Type + or -");
    }
  }

  if(digitalRead(BUTTON) == HIGH) //If the input is at 5V = button pressed then do
  { 
    while(digitalRead(BUTTON) == HIGH) //As long as the condition (button pressed) is true do:
    { //This loop is used to wait until the button is released to avoid counting a number of times
      delay(100); //Wait 100ms
    } 

    if(sign == true) // If sign = true (if we sent a +)
    {
      counter++; //Add 1 (it's like doing: counter = counter +1;)
    }
    
    if(sign == false) // If sign = false (if we sent a -)
    {
      counter--; //Remove 1 (it's like doing: counter = counter -1;)
    }
    
    Serial.println(counter); //Display the counter
  }

}