#include <SPI.h>
#include "pins_arduino.h"

const int button = A0;
int spi_receiver = 0;

void setup() {
  Serial.begin(9600);
  SPI.begin();
  pinMode(button, INPUT_PULLUP);
  pinMode(SS, OUTPUT);
  digitalWrite(SS, HIGH);
}

void loop() {
  if(digitalRead(button) == LOW) {
    digitalWrite(SS, LOW);
    spi_receiver = SPI.transfer(100);
    digitalWrite(SS, HIGH);
    Serial.println(spi_receiver);
  }
}