File content as of revision 2:598d0028d5d2:

/* SWSPI, Software SPI library
 * Copyright (c) 2012-2014, David R. Van Wagner, http://techwithdave.blogspot.com
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

#include <mbed.h>
#include "SWSPI.h"

SWSPI::SWSPI(DigitalOut *mosi_pin, DigitalIn *miso_pin, DigitalOut *sclk_pin)
{
    mosi = mosi_pin;
    miso = miso_pin;
    sclk = sclk_pin;
    format(8);
    frequency();
}

SWSPI::~SWSPI()
{
    
}

void SWSPI::format(int bits, int mode)
{
    this->bits = bits;
    this->mode = mode;
    polarity = !((mode >> 1) & 1);
    phase = mode & 1;
    sclk->write(polarity);
}

void SWSPI::frequency(int hz)
{
    this->freq = hz;
}

unsigned int  SWSPI::write(unsigned int  value)
{
    int read = 0;
    //printf("SPI write %08X ",value);
    //wait(1.0/freq/2);
    for (int bit = bits-1; bit >= 0; --bit)
    {
        mosi->write(((value >> bit) & 0x01) == 0);

        if (phase == 0)
        {
            if (!miso->read())
                read |= (1 << bit);
        }

        sclk->write(!polarity);

        //wait(1.0/freq/2);

        if (phase == 1)
        {
            if (!miso->read())
                read |= (1 << bit);
        }

        sclk->write(polarity);

        //wait(1.0/freq/2);
    }
    //printf("  SPIR reads %08X \n\r" , read);
    return read;
}