spi_common_v1.c

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/** @addtogroup spi_file SPI peripheral API
 * @ingroup peripheral_apis
 
@author @htmlonly © @endhtmlonly 2009
Uwe Hermann <uwe@hermann-uwe.de>
@author @htmlonly &copy; @endhtmlonly 2012
Ken Sarkies <ksarkies@internode.on.net>
 
Devices can have up to three SPI peripherals. The common 4-wire full-duplex
mode of operation is supported, along with 3-wire variants using unidirectional
communication modes or half-duplex bidirectional communication. A variety of
options allows many of the SPI variants to be supported. Multimaster operation
is also supported. A CRC can be generated and checked in hardware.
 
@note Some JTAG pins need to be remapped if SPI is to be used.
 
@note The I2S protocol shares the SPI hardware so the two protocols cannot be
used at the same time on the same peripheral.
 
Example: Clk/4, positive clock polarity, leading edge trigger, 8-bit words,
LSB first.
@code
        spi_init_master(SPI1, SPI_CR1_BAUDRATE_FPCLK_DIV_4, SPI_CR1_CPOL_CLK_TO_0_WHEN_IDLE,
                        SPI_CR1_CPHA_CLK_TRANSITION_1, SPI_CR1_DFF_8BIT, SPI_CR1_LSBFIRST);
        spi_write(SPI1, 0x55);          // 8-bit write
        spi_write(SPI1, 0xaa88);        // 16-bit write
        reg8 = spi_read(SPI1);          // 8-bit read
        reg16 = spi_read(SPI1);         // 16-bit read
@endcode
 
@todo need additional functions to aid ISRs in retrieving status
 
*/
 
/*
 * This file is part of the libopencm3 project.
 *
 * Copyright (C) 2009 Uwe Hermann <uwe@hermann-uwe.de>
 *
 * This library is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library.  If not, see <http://www.gnu.org/licenses/>.
 */
 
#include <libopencm3/stm32/spi.h>
#include <libopencm3/stm32/rcc.h>
 
 
/**@{*/
 
/*---------------------------------------------------------------------------*/
/** @brief Configure the SPI as Master.
 
The SPI peripheral is configured as a master with communication parameters
baudrate, data format 8/16 bits, frame format lsb/msb first, clock polarity
and phase. The SPI enable, CRC enable and CRC next controls are not affected.
These must be controlled separately.
 
To support multiple masters (dynamic switching between master and slave)
you must set SSOE to 0 and select either software or hardware control of
the NSS pin.
 
@param[in] spi Unsigned int32. SPI peripheral identifier @ref spi_reg_base.
@param[in] br Unsigned int32. Baudrate @ref spi_baudrate.
@param[in] cpol Unsigned int32. Clock polarity @ref spi_cpol.
@param[in] cpha Unsigned int32. Clock Phase @ref spi_cpha.
@param[in] dff Unsigned int32. Data frame format 8/16 bits @ref spi_dff.
@param[in] lsbfirst Unsigned int32. Frame format lsb/msb first @ref
spi_lsbfirst.
@returns int. Error code.
*/
 
int spi_init_master(uint32_t spi, uint32_t br, uint32_t cpol, uint32_t cpha,
                    uint32_t dff, uint32_t lsbfirst)
{
        uint32_t reg32 = SPI_CR1(spi);
 
        /* Reset all bits omitting SPE, CRCEN and CRCNEXT bits. */
        reg32 &= SPI_CR1_SPE | SPI_CR1_CRCEN | SPI_CR1_CRCNEXT;
 
        reg32 |= SPI_CR1_MSTR;  /* Configure SPI as master. */
 
        reg32 |= br;            /* Set baud rate bits. */
        reg32 |= cpol;          /* Set CPOL value. */
        reg32 |= cpha;          /* Set CPHA value. */
        reg32 |= dff;           /* Set data format (8 or 16 bits). */
        reg32 |= lsbfirst;      /* Set frame format (LSB- or MSB-first). */
 
        SPI_CR2(spi) |= SPI_CR2_SSOE; /* common case */
        SPI_CR1(spi) = reg32;
 
        return 0;
}
 
/*---------------------------------------------------------------------------*/
/** @brief SPI Set Data Frame Format to 8 bits
 
@param[in] spi Unsigned int32. SPI peripheral identifier @ref spi_reg_base.
*/
 
void spi_set_dff_8bit(uint32_t spi)
{
        SPI_CR1(spi) &= ~SPI_CR1_DFF;
}
 
/*---------------------------------------------------------------------------*/
/** @brief SPI Set Data Frame Format to 16 bits
 
@param[in] spi Unsigned int32. SPI peripheral identifier @ref spi_reg_base.
*/
 
void spi_set_dff_16bit(uint32_t spi)
{
        SPI_CR1(spi) |= SPI_CR1_DFF;
}
 
/**@}*/