Deciphering SPI commands given to RF module of RC heli

Projects Networking, Protocols, and Devices
2 
// SPI interrupt routine
ISR (SPI_STC_vect)
{  
  byte thisByte = SPDR;
  
  Serial.print(thisByte);
  Serial.print(" ");
  
  if ( thisByte == 255 )
    Serial.println();
}

Writing something to the serial interface inside an interrupt handler is a bad idea. You'll end in a dead lock in no time. Save the data in a buffer and write it to the serial interface in the standard loop() routine.