SPI interface with other board_AVR_ESK1100 or among Arduino itself

Using Arduino Networking, Protocols, and Devices
74

Hi...!!

This code works fine with making SPDR = 0x00; at ISR but I have observed on Oscilloscope that sometime few data goes back to MISO, Slave is not able to clear SPDR perfectly, what could be the reason.

//Slave receiving data
#include <SPI.h>

void setup (void)
{
  Serial.begin(115200);
  // have to send on master in, *slave out*
  pinMode(MISO, OUTPUT);
  SPI.setBitOrder(MSBFIRST);
  SPI.setDataMode (SPI_MODE2);
  SPI.setClockDivider(SPI_CLOCK_DIV64) ;

  // turn on SPI in slave mode
  SPCR |= _BV(SPE);

  // turn on interrupts
  SPCR |= _BV(SPIE);

}  // end of setup


// SPI interrupt routine
ISR (SPI_STC_vect)
{
  byte c = SPDR;  // what we received from the master
  SPDR = 0x00;    // what to return to the master
}  // end of ISR SPI_STC_vect


void loop (void)
{
 
}  // end of loop

Just keeping bandwidth of site in mind I am attaching one oscilloscope photo for your reference.

TEK0000.BMP (76.1 KB)