#include <SPI.h>

byte data = 0;

void setup() {
  SPI.begin();           // Inisialisasi SPI
  digitalWrite(10, HIGH); // SS idle high
  Serial.begin(9600);
}

void loop() {
  digitalWrite(10, LOW);          // Pilih slave
  byte response = SPI.transfer(data);  // Kirim data ke slave
  digitalWrite(10, HIGH);         // Lepaskan slave

  Serial.print("Master kirim: ");
  Serial.print(data);
  Serial.print(" | Slave balas: ");
  Serial.println(response);

  data++;
  delay(1000);
}