spi_comm/arduino_slave_read/arduino_slave_read.ino


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#include<SPI.h>

volatile boolean received;
volatile byte receivedData;

ISR (SPI_STC_vect)        //Inerrrput routine function 
{
  receivedData = SPDR;   // Get the received data from SPDR register
  received = true;       // Sets received as True 
}

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

  pinMode(MISO,OUTPUT);   //Sets MISO as OUTPUT
  SPCR |= _BV(SPE);       //Turn on SPI in Slave Mode
  received = false;
  SPI.attachInterrupt();  //Activate SPI Interuupt 
}


void loop()
{ 
  if(received) {                        
    SPDR = receivedData;    // send back the received data, this is not necessary, only for demo purpose
    received = false;
    Serial.print(receivedData, HEX);
  }
}