spi.c

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// ----------------------------------------------------------------------------
/*
 * Copyright (c) 2008 Florian Kristen, Fabian Greif
 *  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * $Id: spi.c 6802 2008-11-12 10:25:05Z fabian $
 */
// ----------------------------------------------------------------------------

#include "mcp2515_private.h"
#ifdef  SUPPORT_FOR_MCP2515__

#include "spi.h"

#ifdef  SPI_PRESCALER
        #if (SPI_PRESCALER == 2) || (SPI_PRESCALER == 8) || (SPI_PRESCALER == 32) || (SPI_PRESCALER == 64)
                #define R_SPSR  (1<<SPI2X)
                #define SPI_PRESCALER_  (SPI_PRESCALER * 2)
        #else
                #define R_SPSR  0
                #define SPI_PRESCALER_  SPI_PRESCALER
        #endif
        
        #define SPI_CLOCK_RATE_BIT0             (1<<SPR0)
        #define SPI_CLOCK_RATE_BIT1             (1<<SPR1)
        
        #if (SPI_PRESCALER_ == 4)
                #define R_SPCR  0
        #elif (SPI_PRESCALER_ == 16)
                #define R_SPCR  SPI_CLOCK_RATE_BIT0
        #elif (SPI_PRESCALER_ == 64)
                #define R_SPCR  SPI_CLOCK_RATE_BIT1
        #elif (SPI_PRESCALER_ == 128)
                #define R_SPCR  SPI_CLOCK_RATE_BIT1 | SPI_CLOCK_RATE_BIT0
        #else
                #error   SPI_PRESCALER must be one of the values of 2^n with n = 1..7!
        #endif
#else
        #error  SPI_PRESCALER not defined!
#endif


// ----------------------------------------------------------------------------
void mcp2515_spi_init(void)
{
        #ifndef USE_SOFTWARE_SPI
                // Aktivieren des SPI Master Interfaces
                SPCR = (1<<SPE)|(1<<MSTR) | R_SPCR;
                SPSR = R_SPSR;
        #endif
}

// ----------------------------------------------------------------------------
// Schreibt/liest ein Byte ueber den Hardware SPI Bus

uint8_t spi_putc(uint8_t data)
{
        #ifdef  USE_SOFTWARE_SPI
        
        uint8_t data_in = 0;
        
        RESET(P_SCK);
        for (uint8_t i=0;i<8;i++)
        {
                data_in <<= 1;
                
                if (data & 0x80)
                        SET(P_MOSI);
                else
                        RESET(P_MOSI);
                
                SET(P_SCK);
                _delay_us(2);
                
                if (IS_SET(P_MISO))
                        data_in |= 1;
                
                data <<= 1;
                
                RESET(P_SCK);
                _delay_us(2);
        }
        
        return data_in;
        
        #else
        
        // put byte in send-buffer
        SPDR = data;
        
        // wait until byte was send
        while( !( SPSR & (1<<SPIF) ) )
                ;
        
        return SPDR;
        
        #endif
}

#endif  // SUPPORT_FOR_MCP2515__