#include <SoftwareSerial.h>
#define rxPin 0
#define txPin 1

SoftwareSerial Serial(rxPin, txPin);

int pressLength = 0; //the value for how long the button is pressed down  

int buttonPin = 3; // button is on pin 3

void setup() {
  
  pinMode(rxPin, INPUT); //rx is the input
  pinMode(txPin, OUTPUT); //tx is the output
  pinMode(buttonPin, INPUT_PULLUP); //the button is a input pullup (to activate internal resistor)

  Serial.begin(9600); 

}

void loop(){

  while (digitalRead(buttonPin) == LOW ){ 
 
    delay(100);  
    pressLength = pressLength + 100;   

    Serial.println(pressLength);
  }

  if (digitalRead(buttonPin) == HIGH ){ 
  }
  
  pressLength = 0; //reset the pressLength every loop 
 }