//SPI SLAVE (ARDUINO)

//SPI COMMUNICATION BETWEEN TWO ARDUINO 

#include
    
#define LEDpin 7
#define buttonpin 2

volatile boolean received;
volatile byte Slavereceived,Slavesend;

int buttonvalue;
int x;

void setup()
{
  Serial.begin(115200);

  pinMode(buttonpin,INPUT);               // Setting pin 2 as INPUT
  pinMode(LEDpin,OUTPUT);                 // Setting pin 7 as OUTPUT
  pinMode(MISO,OUTPUT);                   //Sets MISO as OUTPUT (Have to Send data to Master IN 

  SPCR |= _BV(SPE);                       //Turn on SPI in Slave Mode
  received = false;
  SPI.attachInterrupt();                  //Interuupt ON is set for SPI commnucation
}
ISR (SPI_STC_vect)                       //Inerrrput routine function 
{
  Slavereceived = SPDR;         // Value received from master if store in variable slavereceived
  received = true;                        //Sets received as True 
}
void loop()
{ 
  if(received)                            //Logic to SET LED ON OR OFF depending upon the value recerived from master
   {
  if (Slavereceived==1) 
      {
        digitalWrite(LEDpin,HIGH);         //Sets pin 7 as HIGH LED ON
        Serial.println("Slave LED ON");
      }else
      {
        digitalWrite(LEDpin,LOW);        //Sets pin 7 as LOW LED OFF
        Serial.println("Slave LED OFF");
      }
      buttonvalue = digitalRead(buttonpin);  // Reads the status of the pin 2
      if (buttonvalue == HIGH)               //Logic to set the value of x to send to master
      {
        x=1;
      }else
      {
        x=0;
      }
  Slavesend=x;
  SPDR = Slavesend;                           //Sends the x value to master via SPDR 
  delay(1000);
}
}