#include<SoftwareSerial.h>// serial library

int bp = 3;// declare that bp(pushbutton)is in pin 3

SoftwareSerial myserial(0, 1); // define the serial and the TX=1 and RX=0

void setup() {
  pinMode(bp,INPUT_PULLUP) ;// Declare that pudhbutton is an input

 
  myserial.begin(9600);
}

void loop() {

  int bps = 0;
  bps = digitalRead(bp);
  if (bps == LOW) //if the pushbutton is pressed this condition will be true
  {

    myserial.write('1');// send this char
   

  }
  else
  { myserial.write('0');//if the pushbutton is not pressed sen this char

  }

  delay(100);

}