tinySA/os/hal/platforms/SPC5xx/DSPI_v1/spi_lld.c

/*
 * Licensed under ST Liberty SW License Agreement V2, (the "License");
 * You may not use this file except in compliance with the License.
 * You may obtain a copy of the License at:
 *
 *        http://www.st.com/software_license_agreement_liberty_v2
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * @file    templates/spi_lld.c
 * @brief   SPI Driver subsystem low level driver source template.
 *
 * @addtogroup SPI
 * @{
 */

#include "ch.h"
#include "hal.h"

#if HAL_USE_SPI || defined(__DOXYGEN__)

/* Some forward declarations.*/
static void spi_serve_rx_irq(edma_channel_t channel, void *p);
static void spi_serve_dma_error_irq(edma_channel_t channel,
                                    void *p,
                                    uint32_t esr);

/*===========================================================================*/
/* Driver local definitions.                                                 */
/*===========================================================================*/

/* Enforced MCR bits.*/
#define DSPI_MCR_ENFORCED_BITS      (SPC5_MCR_MSTR)

/* Excluded MCR bits.*/
#define DSPI_MCR_EXCLUDED_BITS      (SPC5_MCR_CONT_SCKE     |               \
                                     SPC5_MCR_DCONF_MASK    |               \
                                     SPC5_MCR_ROOE          |               \
                                     SPC5_MCR_MDIS          |               \
                                     SPC5_MCR_DIS_TXF       |               \
                                     SPC5_MCR_DIS_RXF       |               \
                                     SPC5_MCR_CLR_TXF       |               \
                                     SPC5_MCR_CLR_RXF       |               \
                                     SPC5_MCR_HALT)

/* Excluded PUSHR bits.*/
#define DSPI_PUSHR_EXCLUDED_BITS    (SPC5_PUSHR_CTAS_MASK   |               \
                                     SPC5_PUSHR_EOQ         |               \
                                     SPC5_PUSHR_TXDATA_MASK)

#define DSPI_PUSHR8_ADDRESS(spip)   (((uint32_t)&(spip)->dspi->PUSHR.R) + 3)
#define DSPI_PUSHR16_ADDRESS(spip)  (((uint32_t)&(spip)->dspi->PUSHR.R) + 2)
#define DSPI_POPR8_ADDRESS(spip)    (((uint32_t)&(spip)->dspi->POPR.R) + 3)
#define DSPI_POPR16_ADDRESS(spip)   (((uint32_t)&(spip)->dspi->POPR.R) + 2)

/*===========================================================================*/
/* Driver exported variables.                                                */
/*===========================================================================*/

/**
 * @brief   SPID1 driver identifier.
 */
#if SPC5_SPI_USE_DSPI0 || defined(__DOXYGEN__)
SPIDriver SPID1;
#endif

/**
 * @brief   SPID2 driver identifier.
 */
#if SPC5_SPI_USE_DSPI1 || defined(__DOXYGEN__)
SPIDriver SPID2;
#endif

/**
 * @brief   SPID3 driver identifier.
 */
#if SPC5_SPI_USE_DSPI2 || defined(__DOXYGEN__)
SPIDriver SPID3;
#endif

/**
 * @brief   SPID4 driver identifier.
 */
#if SPC5_SPI_USE_DSPI3 || defined(__DOXYGEN__)
SPIDriver SPID4;
#endif

/*===========================================================================*/
/* Driver local variables and types.                                         */
/*===========================================================================*/

#if SPC5_SPI_USE_DSPI0 || defined(__DOXYGEN__)
/**
 * @brief   DMA configuration for DSPI0 TX.
 */
static const edma_channel_config_t spi_dspi0_tx_dma_config = {
  SPC5_DSPI0_TX_DMA_DEV_ID, SPC5_SPI_DSPI0_DMA_PRIO, SPC5_SPI_DSPI0_DMA_PRIO,
  NULL, spi_serve_dma_error_irq, &SPID1
};

/**
 * @brief   DMA configuration for DSPI0 RX.
 */
static const edma_channel_config_t spi_dspi0_rx_dma_config = {
  SPC5_DSPI0_RX_DMA_DEV_ID, SPC5_SPI_DSPI0_DMA_PRIO, SPC5_SPI_DSPI0_DMA_PRIO,
  spi_serve_rx_irq, spi_serve_dma_error_irq, &SPID1
};
#endif /* SPC5_SPI_USE_DSPI0 */

#if SPC5_SPI_USE_DSPI1 || defined(__DOXYGEN__)
/**
 * @brief   DMA configuration for DSPI1 TX.
 */
static const edma_channel_config_t spi_dspi1_tx_dma_config = {
  SPC5_DSPI1_TX_DMA_DEV_ID, SPC5_SPI_DSPI1_DMA_PRIO, SPC5_SPI_DSPI1_DMA_PRIO,
  NULL, spi_serve_dma_error_irq, &SPID2
};

/**
 * @brief   DMA configuration for DSPI1 RX.
 */
static const edma_channel_config_t spi_dspi1_rx_dma_config = {
  SPC5_DSPI1_RX_DMA_DEV_ID, SPC5_SPI_DSPI1_DMA_PRIO, SPC5_SPI_DSPI1_DMA_PRIO,
  spi_serve_rx_irq, spi_serve_dma_error_irq, &SPID2
};
#endif /* SPC5_SPI_USE_DSPI1 */

#if SPC5_SPI_USE_DSPI2 || defined(__DOXYGEN__)
/**
 * @brief   DMA configuration for DSPI2 TX.
 */
static const edma_channel_config_t spi_dspi2_tx_dma_config = {
  SPC5_DSPI2_TX_DMA_DEV_ID, SPC5_SPI_DSPI2_DMA_PRIO, SPC5_SPI_DSPI2_DMA_PRIO,
  NULL, spi_serve_dma_error_irq, &SPID3
};

/**
 * @brief   DMA configuration for DSPI2 RX.
 */
static const edma_channel_config_t spi_dspi2_rx_dma_config = {
  SPC5_DSPI2_RX_DMA_DEV_ID, SPC5_SPI_DSPI2_DMA_PRIO, SPC5_SPI_DSPI2_DMA_PRIO,
  spi_serve_rx_irq, spi_serve_dma_error_irq, &SPID3
};
#endif /* SPC5_SPI_USE_DSPI2 */

#if SPC5_SPI_USE_DSPI3 || defined(__DOXYGEN__)
/**
 * @brief   DMA configuration for DSPI3 TX.
 */
static const edma_channel_config_t spi_dspi3_tx_dma_config = {
  SPC5_DSPI3_TX_DMA_DEV_ID, SPC5_SPI_DSPI3_DMA_PRIO, SPC5_SPI_DSPI3_DMA_PRIO,
  NULL, spi_serve_dma_error_irq, &SPID4
};

/**
 * @brief   DMA configuration for DSPI3 RX.
 */
static const edma_channel_config_t spi_dspi3_rx_dma_config = {
  SPC5_DSPI3_RX_DMA_DEV_ID, SPC5_SPI_DSPI3_DMA_PRIO, SPC5_SPI_DSPI3_DMA_PRIO,
  spi_serve_rx_irq, spi_serve_dma_error_irq, &SPID4
};
#endif /* SPC5_SPI_USE_DSPI3 */

/*===========================================================================*/
/* Driver local functions.                                                   */
/*===========================================================================*/

/**
 * @brief   Starts eception using DMA for frames up to 8 bits.
 *
 * @param[in] spip      pointer to the @p SPIDriver object
 * @param[in] n         number of words to be exchanged
 * @param[out] rxbuf    the pointer to the receive buffer
 *
 * @notapi
 */
static void spi_start_dma_rx8(SPIDriver *spip,
                              size_t n,
                              uint8_t *rxbuf) {

  edmaChannelSetup(spip->rx_channel,            /* channel.                 */
                   DSPI_POPR8_ADDRESS(spip),    /* src.                     */
                   rxbuf,                       /* dst.                     */
                   0,                           /* soff, do not advance.    */
                   1,                           /* doff, advance by one.    */
                   0,                           /* ssize, 8 bits transfers. */
                   0,                           /* dsize, 8 bits transfers. */
                   1,                           /* nbytes, always one.      */
                   n,                           /* iter.                    */
                   0,                           /* slast.                   */
                   0,                           /* dlast.                   */
                   EDMA_TCD_MODE_DREQ | EDMA_TCD_MODE_INT_END);     /* mode.*/

  edmaChannelStart(spip->rx_channel);
}

/**
 * @brief   Starts reception using DMA for frames up to 16 bits.
 *
 * @param[in] spip      pointer to the @p SPIDriver object
 * @param[in] n         number of words to be exchanged
 * @param[out] rxbuf    the pointer to the receive buffer
 *
 * @notapi
 */
static void spi_start_dma_rx16(SPIDriver *spip,
                               size_t n,
                               uint16_t *rxbuf) {

  edmaChannelSetup(spip->rx_channel,            /* channel.                 */
                   DSPI_POPR16_ADDRESS(spip),   /* src.                     */
                   rxbuf,                       /* dst.                     */
                   0,                           /* soff, do not advance.    */
                   2,                           /* doff, advance by two.    */
                   1,                           /* ssize, 16 bits transfers.*/
                   1,                           /* dsize, 16 bits transfers.*/
                   2,                           /* nbytes, always two.      */
                   n,                           /* iter.                    */
                   0,                           /* slast, no source adjust. */
                   0,                           /* dlast.                   */
                   EDMA_TCD_MODE_DREQ | EDMA_TCD_MODE_INT_END);     /* mode.*/

  edmaChannelStart(spip->rx_channel);
}

/**
 * @brief   Starts transmission using DMA for frames up to 8 bits.
 *
 * @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
 *
 * @notapi
 */
static void spi_start_dma_tx8(SPIDriver *spip,
                              size_t n,
                              const uint8_t *txbuf) {
  uint32_t cmd = spip->config->pushr & ~DSPI_PUSHR_EXCLUDED_BITS;
  uint8_t *cp = (uint8_t *)DSPI_PUSHR8_ADDRESS(spip);

  /* The first frame is pushed by the CPU, then the DMA is activated to
     send the following frames.*/
  spip->dspi->PUSHR.R = cmd | (uint32_t)*txbuf++;
  *cp = 0x55;

  /* Setting up TX DMA TCD parameters for 8 bits transfers.*/
  edmaChannelSetup(spip->tx_channel,            /* channel.                 */
                   txbuf,                       /* src.                     */
                   DSPI_PUSHR8_ADDRESS(spip),   /* dst.                     */
                   1,                           /* soff, advance by 1.      */
                   0,                           /* doff, do not advance.    */
                   0,                           /* ssize, 8 bits transfers. */
                   0,                           /* dsize, 8 bits transfers. */
                   1,                           /* nbytes, always one.      */
                   n - 1,                       /* iter.                    */
                   0,                           /* slast, no source adjust. */
                   0,                           /* dlast, no dest.adjust.   */
                   EDMA_TCD_MODE_DREQ);         /* mode.                    */

  edmaChannelStart(spip->tx_channel);
}

/**
 * @brief   Starts transmission using DMA for frames up to 16 bits.
 *
 * @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
 *
 * @notapi
 */
static void spi_start_dma_tx16(SPIDriver *spip,
                               size_t n,
                               const uint16_t *txbuf) {
  uint32_t cmd = spip->config->pushr & ~DSPI_PUSHR_EXCLUDED_BITS;

  /* The first frame is pushed by the CPU, then the DMA is activated to
     send the following frames.*/
  spip->dspi->PUSHR.R = cmd | (uint32_t)*txbuf++;

  /* Setting up TX DMA TCD parameters for 16 bits transfers.*/
  edmaChannelSetup(spip->tx_channel,            /* channel.                 */
                   txbuf,                       /* src.                     */
                   DSPI_PUSHR16_ADDRESS(spip),  /* dst.                     */
                   2,                           /* soff, advance by 2.      */
                   0,                           /* doff, do not advance.    */
                   1,                           /* ssize, 16 bits transfers.*/
                   1,                           /* dsize, 16 bits transfers.*/
                   2,                           /* nbytes, always two.      */
                   n - 1,                       /* iter.                    */
                   0,                           /* slast, no source adjust. */
                   0,                           /* dlast, no dest.adjust.   */
                   EDMA_TCD_MODE_DREQ);         /* mode.                    */

  edmaChannelStart(spip->tx_channel);
}

/**
 * @brief   Starts transmission using FIFO pre-filling for frames up to 8 bits.
 *
 * @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
 *
 * @notapi
 */
static void spi_tx_prefill8(SPIDriver *spip,
                            size_t n,
                            const uint8_t *txbuf) {
  uint32_t cmd = spip->config->pushr & ~DSPI_PUSHR_EXCLUDED_BITS;

  do {
    if (--n == 0) {
      spip->dspi->PUSHR.R = SPC5_PUSHR_EOQ | cmd | (uint32_t)*txbuf;
      break;
    }
    spip->dspi->PUSHR.R = cmd | (uint32_t)*txbuf;
    txbuf++;
  } while (TRUE);
}

/**
 * @brief   Starts transmission using FIFO pre-filling for frames up to 16 bits.
 *
 * @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
 *
 * @notapi
 */
static void spi_tx_prefill16(SPIDriver *spip,
                             size_t n,
                             const uint16_t *txbuf) {
  uint32_t cmd = spip->config->pushr & ~DSPI_PUSHR_EXCLUDED_BITS;

  do {
    if (--n == 0) {
      spip->dspi->PUSHR.R = SPC5_PUSHR_EOQ | cmd | (uint32_t)*txbuf;
      break;
    }
    spip->dspi->PUSHR.R = cmd | (uint32_t)*txbuf;
    txbuf++;
  } while (TRUE);
}

static void spi_serve_rx_irq(edma_channel_t channel, void *p) {
  SPIDriver *spip = (SPIDriver *)p;

  (void)channel;

  /* Stops the DSPI and clears the queues.*/
  spip->dspi->MCR.R = SPC5_MCR_MSTR    | SPC5_MCR_HALT    |
                      SPC5_MCR_CLR_TXF | SPC5_MCR_CLR_RXF;

  /* Portable SPI ISR code defined in the high level driver, note, it is
     a macro.*/
  _spi_isr_code(spip);
}

static void spi_serve_dma_error_irq(edma_channel_t channel,
                                    void *p,
                                    uint32_t esr) {
  SPIDriver *spip = (SPIDriver *)p;

  (void)channel;
  (void)esr;

  /* Stops the DSPI and clears the queues.*/
  spip->dspi->MCR.R = SPC5_MCR_MSTR    | SPC5_MCR_HALT    |
                      SPC5_MCR_CLR_TXF | SPC5_MCR_CLR_RXF;

  SPC5_SPI_DMA_ERROR_HOOK(spip);
}

/*===========================================================================*/
/* Driver interrupt handlers.                                                */
/*===========================================================================*/

/*===========================================================================*/
/* Driver exported functions.                                                */
/*===========================================================================*/

/**
 * @brief   Low level SPI driver initialization.
 *
 * @notapi
 */
void spi_lld_init(void) {

#if SPC5_SPI_USE_DSPI0
  /* Driver initialization.*/
  spiObjectInit(&SPID1);
  SPID1.dspi = &SPC5_DSPI0;
  SPID1.tx_channel = EDMA_ERROR;
  SPID1.rx_channel = EDMA_ERROR;
#endif /* SPC5_SPI_USE_DSPI0 */

#if SPC5_SPI_USE_DSPI1
  /* Driver initialization.*/
  spiObjectInit(&SPID2);
  SPID2.dspi = &SPC5_DSPI1;
  SPID2.tx_channel = EDMA_ERROR;
  SPID2.rx_channel = EDMA_ERROR;
#endif /* SPC5_SPI_USE_DSPI1 */

#if SPC5_SPI_USE_DSPI2
  /* Driver initialization.*/
  spiObjectInit(&SPID3);
  SPID3.dspi = &SPC5_DSPI2;
  SPID3.tx_channel = EDMA_ERROR;
  SPID3.rx_channel = EDMA_ERROR;
#endif /* SPC5_SPI_USE_DSPI2 */

#if SPC5_SPI_USE_DSPI03
  /* Driver initialization.*/
  spiObjectInit(&SPID4);
  SPID4.dspi = &SPC5_DSPI3;
  SPID4.tx_channel = EDMA_ERROR;
  SPID4.rx_channel = EDMA_ERROR;
#endif /* SPC5_SPI_USE_DSPI3 */
}

/**
 * @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->state == SPI_STOP) {
    /* Enables the peripheral.*/

#if SPC5_SPI_USE_DSPI0
    if (&SPID1 == spip) {
      SPC5_DSPI0_ENABLE_CLOCK();
      spip->tx_channel = edmaChannelAllocate(&spi_dspi0_tx_dma_config);
      spip->rx_channel = edmaChannelAllocate(&spi_dspi0_rx_dma_config);
    }
#endif /* SPC5_SPI_USE_DSPI0 */

#if SPC5_SPI_USE_DSPI1
    if (&SPID2 == spip) {
      SPC5_DSPI1_ENABLE_CLOCK();
      spip->tx_channel = edmaChannelAllocate(&spi_dspi1_tx_dma_config);
      spip->rx_channel = edmaChannelAllocate(&spi_dspi1_rx_dma_config);
    }
#endif /* SPC5_SPI_USE_DSPI1 */

#if SPC5_SPI_USE_DSPI2
    if (&SPID3 == spip) {
      SPC5_DSPI2_ENABLE_CLOCK();
      spip->tx_channel = edmaChannelAllocate(&spi_dspi2_tx_dma_config);
      spip->rx_channel = edmaChannelAllocate(&spi_dspi2_rx_dma_config);
    }
#endif /* SPC5_SPI_USE_DSPI2 */

#if SPC5_SPI_USE_DSPI3
    if (&SPID4 == spip) {
      SPC5_DSPI3_ENABLE_CLOCK();
      spip->tx_channel = edmaChannelAllocate(&spi_dspi3_tx_dma_config);
      spip->rx_channel = edmaChannelAllocate(&spi_dspi3_rx_dma_config);
    }
#endif /* SPC5_SPI_USE_DSPI3 */

    chDbgAssert((spip->tx_channel != EDMA_ERROR) &&
                (spip->rx_channel != EDMA_ERROR),
                "spi_lld_start(), #1", "channel cannot be allocated");
  }

  /* Configures the peripheral.*/
  spip->dspi->MCR.R     = SPC5_MCR_MSTR | SPC5_MCR_HALT | spip->config->mcr;
  spip->dspi->CTAR[0].R = spip->config->ctar0;
  spip->dspi->RSER.R    = SPC5_RSER_TFFF_RE | SPC5_RSER_TFFF_DIRS |
                          SPC5_RSER_RFDF_RE | SPC5_RSER_RFDF_DIRS;
  spip->dspi->SR.R      = spip->dspi->SR.R;
}

/**
 * @brief   Deactivates the SPI peripheral.
 *
 * @param[in] spip      pointer to the @p SPIDriver object
 *
 * @notapi
 */
void spi_lld_stop(SPIDriver *spip) {

  if (spip->state == SPI_READY) {
    /* Releases the allocated EDMA channels.*/
    edmaChannelRelease(spip->tx_channel);
    edmaChannelRelease(spip->rx_channel);

    /* Resets the peripheral.*/
    spip->dspi->CTAR[0].R = 0;
    spip->dspi->RSER.R    = 0;
    spip->dspi->SR.R      = spip->dspi->SR.R;
    spip->dspi->MCR.R     = SPC5_MCR_MSTR    | SPC5_MCR_MDIS    |
                            SPC5_MCR_CLR_TXF | SPC5_MCR_CLR_RXF |
                            SPC5_MCR_HALT;

#if SPC5_SPI_USE_DSPI0
    if (&SPID1 == spip) {
      SPC5_DSPI0_DISABLE_CLOCK();
    }
#endif /* SPC5_SPI_USE_DSPI0 */

#if SPC5_SPI_USE_DSPI1
    if (&SPID2 == spip) {
      SPC5_DSPI1_DISABLE_CLOCK();
    }
#endif /* SPC5_SPI_USE_DSPI1 */

#if SPC5_SPI_USE_DSPI2
    if (&SPID3 == spip) {
      SPC5_DSPI2_DISABLE_CLOCK();
    }
#endif /* SPC5_SPI_USE_DSPI2 */

#if SPC5_SPI_USE_DSPI3
    if (&SPID4 == spip) {
      SPC5_DSPI3_DISABLE_CLOCK();
    }
#endif /* SPC5_SPI_USE_DSPI3 */
  }
}

/**
 * @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) {

  (void)spip;

}

/**
 * @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) {

  (void)spip;

}

/**
 * @brief   Ignores data on the SPI bus.
 * @details This asynchronous function starts the transmission of a series of
 *          idle words on the SPI bus and ignores the received data.
 * @post    At the end of the operation the configured callback is invoked.
 *
 * @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;
  (void)n;

}

/**
 * @brief   Exchanges data on the SPI bus.
 * @details This asynchronous function starts a simultaneous transmit/receive
 *          operation.
 * @post    At the end of the operation the configured callback is invoked.
 * @note    The buffers are organized as uint8_t arrays for data sizes below or
 *          equal to 8 bits else it is organized as uint16_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) {

  /* Starting transfer.*/
  spip->dspi->MCR.B.HALT = 0;

  /* DMAs require a different setup depending on the frame size.*/
  if (spip->dspi->CTAR[0].B.FMSZ < 8) {
    /* Setting up the RX DMA channel.*/
    spi_start_dma_rx8(spip, n, rxbuf);

    if (n <= SPC5_DSPI_FIFO_DEPTH) {
      /* If the total transfer size is smaller than the TX FIFO size then
         the whole transmitted data is pushed here and the TX DMA is not
         activated.*/
      spi_tx_prefill8(spip, n, txbuf);
    }
    else {
      spi_start_dma_tx8(spip, n, txbuf);
    }
  }
  else {
    /* Setting up the RX DMA channel.*/
    spi_start_dma_rx16(spip, n, rxbuf);

    if (n <= SPC5_DSPI_FIFO_DEPTH) {
      /* If the total transfer size is smaller than the TX FIFO size then
         the whole transmitted data is pushed here and the TX DMA is not
         activated.*/
      spi_tx_prefill16(spip, n, txbuf);
    }
    else {
      spi_start_dma_tx16(spip, n, txbuf);
    }
  }
}

/**
 * @brief   Sends data over the SPI bus.
 * @details This asynchronous function starts a transmit operation.
 * @post    At the end of the operation the configured callback is invoked.
 * @note    The buffers are organized as uint8_t arrays for data sizes below or
 *          equal to 8 bits else it is organized as uint16_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;
  (void)n;
  (void)txbuf;

}

/**
 * @brief   Receives data from the SPI bus.
 * @details This asynchronous function starts a receive operation.
 * @post    At the end of the operation the configured callback is invoked.
 * @note    The buffers are organized as uint8_t arrays for data sizes below or
 *          equal to 8 bits else it is organized as uint16_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;
  (void)n;
  (void)rxbuf;

}

/**
 * @brief   Exchanges one frame using a polled wait.
 * @details This synchronous function exchanges one frame using a polled
 *          synchronization method. This function is useful when exchanging
 *          small amount of data on high speed channels, usually in this
 *          situation is much more efficient just wait for completion using
 *          polling than suspending the thread waiting for an interrupt.
 *
 * @param[in] spip      pointer to the @p SPIDriver object
 * @param[in] frame     the data frame to send over the SPI bus
 * @return              The received data frame from the SPI bus.
 */
uint16_t spi_lld_polled_exchange(SPIDriver *spip, uint16_t frame) {

  (void)spip;
  (void)frame;

  return 0;
}

#endif /* HAL_USE_SPI */

/** @} */