library

/*! \file spi.c \brief SPI interface driver. */
//*****************************************************************************
//
// File Name    : 'spi.c'
// Title                : SPI interface driver
// Author               : Pascal Stang - Copyright (C) 2000-2002
// Created              : 11/22/2000
// Revised              : 06/06/2002
// Version              : 0.6
// Target MCU   : Atmel AVR series
// Editor Tabs  : 4
//
// NOTE: This code is currently below version 1.0, and therefore is considered
// to be lacking in some functionality or documentation, or may not be fully
// tested.  Nonetheless, you can expect most functions to work.
//
// This code is distributed under the GNU Public License
//              which can be found at http://www.gnu.org/licenses/gpl.txt
//
//*****************************************************************************

#include <avr/io.h>
#include <avr/interrupt.h>

#include "spi.h"

// Define the SPI_USEINT key if you want SPI bus operation to be
// interrupt-driven.  The primary reason for not using SPI in
// interrupt-driven mode is if the SPI send/transfer commands
// will be used from within some other interrupt service routine
// or if interrupts might be globally turned off due to of other
// aspects of your program
//
// Comment-out or uncomment this line as necessary
//#define SPI_USEINT

// global variables
volatile u08 spiTransferComplete;

// SPI interrupt service handler
#ifdef SPI_USEINT
SIGNAL(SIG_SPI)
{
        spiTransferComplete = TRUE;
}
#endif

// access routines
void spiInit()
{
#ifdef __AVR_ATmega128__
        // setup SPI I/O pins
        sbi(PORTB, 1);  // set SCK hi
        sbi(DDRB, 1);   // set SCK as output
        cbi(DDRB, 3);   // set MISO as input
        sbi(DDRB, 2);   // set MOSI as output
        sbi(DDRB, 0);   // SS must be output for Master mode to work
#elif __AVR_ATmega8__
    // setup SPI I/O pins
    sbi(PORTB, 5);  // set SCK hi
    sbi(DDRB, 5);   // set SCK as output
    cbi(DDRB, 4);   // set MISO as input
    sbi(DDRB, 3);   // set MOSI as output
    sbi(DDRB, 2);   // SS must be output for Master mode to work
#else
        // setup SPI I/O pins
        sbi(PORTB, 7);  // set SCK hi
        sbi(DDRB, 7);   // set SCK as output
        cbi(DDRB, 6);   // set MISO as input
        sbi(DDRB, 5);   // set MOSI as output
        sbi(DDRB, 4);   // SS must be output for Master mode to work
#endif
        
        // setup SPI interface :
        // master mode
        sbi(SPCR, MSTR);
        // clock = f/4
//      cbi(SPCR, SPR0);
//      cbi(SPCR, SPR1);
        // clock = f/16
        cbi(SPCR, SPR0);
        sbi(SPCR, SPR1);
        // select clock phase positive-going in middle of data
        cbi(SPCR, CPOL);
        // Data order MSB first
        cbi(SPCR,DORD);
        // enable SPI
        sbi(SPCR, SPE);
                
        
        // some other possible configs
        //outp((1<<MSTR)|(1<<SPE)|(1<<SPR0), SPCR );
        //outp((1<<CPHA)|(1<<CPOL)|(1<<MSTR)|(1<<SPE)|(1<<SPR0)|(1<<SPR1), SPCR );
        //outp((1<<CPHA)|(1<<MSTR)|(1<<SPE)|(1<<SPR0), SPCR );
        
        // clear status
        inb(SPSR);
        spiTransferComplete = TRUE;

        // enable SPI interrupt
        #ifdef SPI_USEINT
        sbi(SPCR, SPIE);
        #endif
}
/*
void spiSetBitrate(u08 spr)
{
        outb(SPCR, (inb(SPCR) & ((1<<SPR0)|(1<<SPR1))) | (spr&((1<<SPR0)|(1<<SPR1)))));
}
*/
void spiSendByte(u08 data)
{
        // send a byte over SPI and ignore reply
        #ifdef SPI_USEINT
                while(!spiTransferComplete);
                spiTransferComplete = FALSE;
        #else
                while(!(inb(SPSR) & (1<<SPIF)));
        #endif

        outb(SPDR, data);
}

u08 spiTransferByte(u08 data)
{
        #ifdef SPI_USEINT
        // send the given data
        spiTransferComplete = FALSE;
        outb(SPDR, data);
        // wait for transfer to complete
        while(!spiTransferComplete);
        #else
        // send the given data
        outb(SPDR, data);
        // wait for transfer to complete
        while(!(inb(SPSR) & (1<<SPIF)));
        #endif
        // return the received data
        return inb(SPDR);
}

u16 spiTransferWord(u16 data)
{
        u16 rxData = 0;

        // send MS byte of given data
        rxData = (spiTransferByte((data>>8) & 0x00FF))<<8;
        // send LS byte of given data
        rxData |= (spiTransferByte(data & 0x00FF));

        // return the received data
        return rxData;
}