SPI.c

/*

    Copyright (c) 2007 Stefan Engelke <mbox@stefanengelke.de>

*/

#include "spi.h"

#include <avr/io.h>

#include <avr/interrupt.h>

#define PORT_SPI    PORTB

#define DDR_SPI     DDRB

#define DD_MISO     DDB4

#define DD_MOSI     DDB3

#define DD_SS       DDB2

#define DD_SCK      DDB5

void spi_init()

// Initialize pins for spi communication

{

    DDR_SPI &= ~((1<<DD_MOSI)|(1<<DD_MISO)|(1<<DD_SS)|(1<<DD_SCK));

    // Define the following pins as output

    DDR_SPI |= ((1<<DD_MOSI)|(1<<DD_SS)|(1<<DD_SCK));

    SPCR = ((1<<SPE)|               // SPI Enable

            (0<<SPIE)|              // SPI Interupt Enable

            (0<<DORD)|              // Data Order (0:MSB first / 1:LSB first)

            (1<<MSTR)|              // Master/Slave select   

            (0<<SPR1)|(1<<SPR0)|    // SPI Clock Rate

            (0<<CPOL)|              // Clock Polarity (0:SCK low / 1:SCK hi when idle)

            (0<<CPHA));             // Clock Phase (0:leading / 1:trailing edge sampling)

    SPSR = (0<<SPI2X);              // Double Clock Rate "1" @8MHz    

}

void spi_transfer_sync (uint8_t * dataout, uint8_t * datain, uint8_t len)

// Shift full array through target device

{

       uint8_t i;      

       for (i = 0; i < len; i++) {

             SPDR = dataout[i];

             while((SPSR & (1<<SPIF))==0);

             datain[i] = SPDR;

       }

}

void spi_transmit_sync (uint8_t * dataout, uint8_t len)

// Shift full array to target device without receiving any byte

{

       uint8_t i;      

       for (i = 0; i < len; i++) {

             SPDR = dataout[i];

             while((SPSR & (1<<SPIF))==0);

       }

}

uint8_t spi_fast_shift (uint8_t data)

// Clocks only one byte to target device and returns the received one

{

    SPDR = data;

    while((SPSR & (1<<SPIF))==0);

    return SPDR;

}