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/*
ChibiOS/RT - Copyright (C) 2006,2007,2008,2009,2010 Giovanni Di Sirio.
This file is part of ChibiOS/RT.
ChibiOS/RT is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
ChibiOS/RT 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
/**
* @file AT91SAM7/spi_lld.c
* @brief AT91SAM7 low level SPI driver code.
*
* @addtogroup AT91SAM7_SPI
* @{
*/
#include "ch.h"
#include "hal.h"
#if CH_HAL_USE_SPI || defined(__DOXYGEN__)
/*===========================================================================*/
/* Driver exported variables. */
/*===========================================================================*/
#if USE_AT91SAM7_SPI || defined(__DOXYGEN__)
/** @brief SPI driver identifier.*/
SPIDriver SPID;
#endif
/*===========================================================================*/
/* Driver local variables. */
/*===========================================================================*/
/*===========================================================================*/
/* Driver local functions. */
/*===========================================================================*/
/**
* @brief Synchronous SPI transfer.
*
* @param[in] n number of bytes to be exchanged
*
* @param[in] txbuf the pointer to the transmit buffer or @p NULL
* @param[out] rxbuf the pointer to the receive buffer or @p NULL
*/
void rw8(size_t n, const uint8_t *txbuf, uint8_t *rxbuf) {
size_t ntx = n;
while (n > 0) {
uint32_t sr = AT91C_BASE_SPI->SPI_SR;
if (sr & AT91C_SPI_RDRF) {
uint8_t w = AT91C_BASE_SPI->SPI_RDR;
if (rxbuf != NULL)
*rxbuf++ = w;
n--;
continue; /* Priority over transmission. */
}
if ((ntx > 0) && (sr & AT91C_SPI_TDRE)) {
if (txbuf != NULL)
AT91C_BASE_SPI->SPI_TDR = *txbuf++;
else
AT91C_BASE_SPI->SPI_TDR = 0xFF;
ntx--;
}
}
}
/*===========================================================================*/
/* Driver interrupt handlers. */
/*===========================================================================*/
/*===========================================================================*/
/* Driver exported functions. */
/*===========================================================================*/
/**
* @brief Low level SPI driver initialization.
*
* @notapi
*/
void spi_lld_init(void) {
#if USE_AT91SAM7_SPI
spiObjectInit(&SPID);
#endif
}
/**
* @brief Configures and activates the SPI peripheral.
*
* @param[in] spip pointer to the @p SPIDriver object
*
* @notapi
*/
void spi_lld_start(SPIDriver *spip) {
if (spip->spd_state == SPI_STOP) {
/* disable general-purpose I/O for SPI pins */
AT91C_BASE_PIOA->PIO_PDR = SPI_MISO | SPI_MOSI | SPI_SCK;
/* select perepheral A for SPI pins*/
AT91C_BASE_PIOA->PIO_ASR = SPI_MISO | SPI_MOSI | SPI_SCK;
/* Clock activation.*/
AT91C_BASE_PMC->PMC_PCER = (1 << AT91C_ID_SPI);
}
/* software reset must be written twice (errata for revision B parts) */
AT91C_BASE_SPI->SPI_CR = AT91C_SPI_SWRST;
AT91C_BASE_SPI->SPI_CR = AT91C_SPI_SWRST;
/* Configuration.*/
AT91C_BASE_SPI->SPI_MR = spip->spd_config->spc_mr;
AT91C_BASE_SPI->SPI_CSR[MMC_CSR_NUM] = spip->spd_config->spc_csr;
/* Enable SPI */
AT91C_BASE_SPI->SPI_CR = AT91C_SPI_SPIEN;
}
/**
* @brief Deactivates the SPI peripheral.
*
* @param[in] spip pointer to the @p SPIDriver object
*
* @notapi
*/
void spi_lld_stop(SPIDriver *spip) {
if (spip->spd_state != SPI_STOP) {
/* disable SPI */
AT91C_BASE_SPI->SPI_CR = AT91C_SPI_SPIDIS;
/* disable clocks to SPI perepheral */
AT91C_BASE_PMC->PMC_PCDR = (1 << AT91C_ID_SPI);
}
}
/**
* @brief Asserts the slave select signal and prepares for transfers.
*
* @param[in] spip pointer to the @p SPIDriver object
*
* @notapi
*/
void spi_lld_select(SPIDriver *spip) {
palClearPad(spip->spd_config->spc_ssport, spip->spd_config->spc_sspad);
}
/**
* @brief Deasserts the slave select signal.
* @details The previously selected peripheral is unselected.
*
* @param[in] spip pointer to the @p SPIDriver object
*
* @notapi
*/
void spi_lld_unselect(SPIDriver *spip) {
palSetPad(spip->spd_config->spc_ssport, spip->spd_config->spc_sspad);
}
/**
* @brief Ignores data on the SPI bus.
* @details This function transmits a series of idle words on the SPI bus and
* ignores the received data. This function can be invoked even
* when a slave select signal has not been yet asserted.
*
* @param[in] spip pointer to the @p SPIDriver object
* @param[in] n number of words to be ignored
*
* @notapi
*/
void spi_lld_ignore(SPIDriver *spip, size_t n) {
(void)spip;
rw8(n, NULL, NULL);
}
/**
* @brief Exchanges data on the SPI bus.
* @details This function performs a simultaneous transmit/receive operation.
* @note The buffers are organized as uint8_t arrays.
*
* @param[in] spip pointer to the @p SPIDriver object
* @param[in] n number of words to be exchanged
* @param[in] txbuf the pointer to the transmit buffer
* @param[out] rxbuf the pointer to the receive buffer
*
* @notapi
*/
void spi_lld_exchange(SPIDriver *spip, size_t n,
const void *txbuf, void *rxbuf) {
(void)spip;
rw8(n, txbuf, rxbuf);
}
/**
* @brief Sends data over the SPI bus.
* @note The buffers are organized as uint8_t arrays.
*
* @param[in] spip pointer to the @p SPIDriver object
* @param[in] n number of words to send
* @param[in] txbuf the pointer to the transmit buffer
*
* @notapi
*/
void spi_lld_send(SPIDriver *spip, size_t n, const void *txbuf) {
(void)spip;
rw8(n, txbuf, NULL);
}
/**
* @brief Receives data from the SPI bus.
* @note The buffers are organized as uint8_t arrays.
*
* @param[in] spip pointer to the @p SPIDriver object
* @param[in] n number of words to receive
* @param[out] rxbuf the pointer to the receive buffer
*
* @notapi
*/
void spi_lld_receive(SPIDriver *spip, size_t n, void *rxbuf) {
(void)spip;
rw8(n, NULL, rxbuf);
}
#endif /* CH_HAL_USE_SPI */
/** @} */
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