SPI_Routines.c

//**************************************************************
// ****** FUNCTIONS FOR SPI COMMUNICATION *******
//**************************************************************
//Controller: ATmega168 (Clock: 8 Mhz-internal)
//Compiler: AVR-GCC
//Version : 2.0
//Author: CC Dharmani, Chennai (India)
// www.dharmanitech.com
//With some changes by Mujda
//Date: 26 Feb 2009
//**************************************************************

//**************************************************
// ***** SOURCE FILE : SPI_routines.c ******
//**************************************************
#include <avr/io.h>
#include "SPI_routines.h"

//SPI initialize for SD card
//clock rate: 125Khz
void spi_init(void)
{
SPCR = 0x52; //setup SPI: Master mode, MSB first, SCK phase low, SCK idle low
SPSR = 0x00;
}


unsigned char SPI_transmit(unsigned char data)
{
// Start transmission
SPDR = data;

// Wait for transmission complete
while(!(SPSR & (1<<SPIF)));
  data = SPDR;

return(data);
}

unsigned char SPI_receive(void)
{
unsigned char data;
// Wait for reception complete

SPDR = 0xff;
while(!(SPSR & (1<<SPIF)));
  data = SPDR;

// Return data register
return data;
}

//******** END ****** www.dharmanitech.com *****