#include <SPI.h>

const int slaveSelectPin = 10;

void setup() {
  pinMode(slaveSelectPin, OUTPUT);
  SPI.begin();
  Serial.begin(9600);
  pinMode(2, INPUT_PULLUP);
}

void loop() {
  digitalWrite(slaveSelectPin, LOW);
  delay(100);
  if( !digitalRead(2)==0 ) SPI.transfer('0');
  if( !digitalRead(2)==1 ) SPI.transfer('1');
  Serial.println( !digitalRead(2) );
  delay(100);
  digitalWrite(slaveSelectPin, HIGH);
}