File content as of revision 164:2e7515f8c45d:

/* mbed Microcontroller Library 
 *******************************************************************************
 * Copyright (c) 2015 WIZnet Co.,Ltd. All rights reserved.
 * 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.
 * 3. Neither the name of ARM Limited nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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 COPYRIGHT HOLDER 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.
 *******************************************************************************
 */
 
#include "mbed_assert.h"
#include <math.h>

#include "spi_api.h"
#include "cmsis.h"
#include "pinmap.h"
#include "mbed_error.h"
#include "PeripheralPins.h"

static inline int ssp_disable(spi_t *obj);
static inline int ssp_enable(spi_t *obj);

void spi_init(spi_t *obj, PinName mosi, PinName miso, PinName sclk, PinName ssel) {
    // determine the SPI to use
    SPIName spi_mosi = (SPIName)pinmap_peripheral(mosi, PinMap_SPI_MOSI);
    SPIName spi_miso = (SPIName)pinmap_peripheral(miso, PinMap_SPI_MISO);
    SPIName spi_sclk = (SPIName)pinmap_peripheral(sclk, PinMap_SPI_SCLK);
    SPIName spi_ssel = (SPIName)pinmap_peripheral(ssel, PinMap_SPI_SSEL);
    SPIName spi_data = (SPIName)pinmap_merge(spi_mosi, spi_miso);
    SPIName spi_cntl = (SPIName)pinmap_merge(spi_sclk, spi_ssel);
    obj->spi = (SSP_TypeDef*)pinmap_merge(spi_data, spi_cntl);
    MBED_ASSERT((int)obj->spi != NC);
    
    // enable power and clocking
    switch ((int)obj->spi) {
        case SPI_0: CRG->SSPCLK_SSR   = CRG_SSPCLK_SSR_MCLK; break; //PLL output clock
        case SPI_1: CRG->SSPCLK_SSR   = CRG_SSPCLK_SSR_MCLK; break;
    }
    
    // set default format and frequency
    if (ssel == NC) {
        spi_format(obj, 8, 0, 0);  // 8 bits, mode 0, master
    } else {
        spi_format(obj, 8, 0, 1);  // 8 bits, mode 0, slave
    }
    spi_frequency(obj, 1000000);
    
    // enable the ssp channel
    ssp_enable(obj);

    // pin out the spi pins
    pinmap_pinout(mosi, PinMap_SPI_MOSI);
    pinmap_pinout(miso, PinMap_SPI_MISO);
    pinmap_pinout(sclk, PinMap_SPI_SCLK);
    if (ssel != NC) {
        pinmap_pinout(ssel, PinMap_SPI_SSEL);
    }
}

void spi_free(spi_t *obj) {}

void spi_format(spi_t *obj, int bits, int mode, int slave) {
    ssp_disable(obj);
    MBED_ASSERT(((bits >= 4) && (bits <= 16)) && (mode >= 0 && mode <= 3));
    
    int polarity = (mode & 0x2) ? 1 : 0;
    int phase = (mode & 0x1) ? 1 : 0;
    
    // set it up
    int DSS = bits - 1;            // DSS (data select size)
    int SPO = (polarity) ? 1 : 0;  // SPO - clock out polarity
    int SPH = (phase) ? 1 : 0;     // SPH - clock out phase
    
    int FRF = 0;                   // FRF (frame format) = SPI
    uint32_t tmp = obj->spi->CR0;
    tmp &= ~(0xFFFF);
    tmp |= DSS << 0
        | FRF << 4
        | SPO << 6
        | SPH << 7;
    obj->spi->CR0 = tmp;
    
    tmp = obj->spi->CR1;
    tmp &= ~(0xD);
    tmp |= 0 << 0                   // LBM - loop back mode - off
        | ((slave) ? 1 : 0) << 2   // MS - master slave mode, 1 = slave
        | 0 << 3;                  // SOD - slave output disable - na
    obj->spi->CR1 = tmp;
    
    ssp_enable(obj);
}

void spi_frequency(spi_t *obj, int hz) {
    ssp_disable(obj);
    
    // setup the spi clock diveder to /1
    switch ((int)obj->spi) {
        case SPI_0:
            CRG->SSPCLK_PVSR  = CRG_SSPCLK_PVSR_DIV1; //1/1 (bypass) 
            break;
        case SPI_1:
            CRG->SSPCLK_PVSR  = CRG_SSPCLK_PVSR_DIV1; //1/1 (bypass)
            break;
    }
    
    uint32_t HCLK = SystemCoreClock; 
    
    int prescaler;
    
    for (prescaler = 2; prescaler <= 254; prescaler += 2) {
        int prescale_hz = HCLK / prescaler;
        
        // calculate the divider
        int divider = floor(((float)prescale_hz / (float)hz) + 0.5f);
        
        // check we can support the divider
        if (divider < 256) {
            // prescaler
            obj->spi->CPSR = prescaler;
            
            // divider
            obj->spi->CR0 &= ~(0xFFFF << 8);
            obj->spi->CR0 |= (divider - 1) << 8;
            ssp_enable(obj);
            return;
        }
    }
    error("Couldn't setup requested SPI frequency");
}

static inline int ssp_disable(spi_t *obj) {
    return obj->spi->CR1 &= ~(1 << 1);
}

static inline int ssp_enable(spi_t *obj) {
    return obj->spi->CR1 |= (1 << 1);
}

static inline int ssp_readable(spi_t *obj) {
    return obj->spi->SR & (1 << 2);
}

static inline int ssp_writeable(spi_t *obj) {
    return obj->spi->SR & (1 << 1);
}

static inline void ssp_write(spi_t *obj, int value) {
    while (!ssp_writeable(obj));
    obj->spi->DR = value;
}

static inline int ssp_read(spi_t *obj) {
    while (!ssp_readable(obj));
    return obj->spi->DR;
}

static inline int ssp_busy(spi_t *obj) {
    return (obj->spi->SR & (1 << 4)) ? (1) : (0);
}

int spi_master_write(spi_t *obj, int value) {
    ssp_write(obj, value);
    return ssp_read(obj);
}

int spi_slave_receive(spi_t *obj) {
    return (ssp_readable(obj) && !ssp_busy(obj)) ? (1) : (0);
}

int spi_slave_read(spi_t *obj) {
    return obj->spi->DR;
}

void spi_slave_write(spi_t *obj, int value) {
    while (ssp_writeable(obj) == 0) ;
    obj->spi->DR = value;
}

int spi_busy(spi_t *obj) {
    return ssp_busy(obj);
}