#include <SPI.h>

int rx = 0;

// The setup() function runs after reset.
void setup() {
  // Initialize serial for DEBUG.
  Serial.begin(9600);

  SPI.begin();
}
// The loop() function runs continuously after setup().
void loop() {
   digitalWrite(SS, LOW);
   delay(20);
   // Send check
   SPI.transfer("check");

   // Wait for slave.
   delay(20);
   // Get slave response.
  rx = SPI.transfer(0);
  Serial.println (rx);
}