SPI Timeout problem

Posted on February 28, 2016 at 16:15

Hi,

I'm using ST's driver for SPI in full -duplex, 8 bit, master mode. The function HAL_SPI_TransmitReceive() returns sometimes HAL_TIMEOUT. After inspecting code I don't understand the following:

The code below at line marked A===>: Waits for RXNE to get set. Then DR is read. this should clear the RXNE flag.

When this is last read operation in loop, we continue to B===>.

In B===> we again wait for RXNE to get set.

My questions are:

1. How can RXNE be set if data was not sent on TX?

2. Sometimes the check of RXNE in B===> passes. I can't understand how RXNE was set if prior to B we read DR (and therefore I would expect the flag to be cleared)?

Thanks,

Ari

===========================================

/* Transmit and Receive data in 8 Bit mode */

    else

    {

      hspi->Instance->DR = (*hspi->pTxBuffPtr++);

      hspi->TxXferCount--;

      if(hspi->TxXferCount == 0)

      {

        /* Enable CRC Transmission */

        if(hspi->Init.CRCCalculation == SPI_CRCCALCULATION_ENABLED)

        {

          hspi->Instance->CR1 |= SPI_CR1_CRCNEXT;

        }

        /* Wait until RXNE flag is set */

        if(SPI_WaitOnFlagUntilTimeout(hspi, SPI_FLAG_RXNE, RESET, Timeout) != HAL_OK)

        {

          return HAL_TIMEOUT;

        }

        (*hspi->pRxBuffPtr) = hspi->Instance->DR;

        hspi->RxXferCount--;

      }

      else

      {

        while(hspi->TxXferCount > 0)

        {

          /* Wait until TXE flag is set to send data */

          if(SPI_WaitOnFlagUntilTimeout(hspi, SPI_FLAG_TXE, RESET, Timeout) != HAL_OK)

          {

            return HAL_TIMEOUT;

          }

          hspi->Instance->DR = (*hspi->pTxBuffPtr++);

          hspi->TxXferCount--;

          /* Enable CRC Transmission */

          if((hspi->TxXferCount == 0) && (hspi->Init.CRCCalculation == SPI_CRCCALCULATION_ENABLED))

          {

            hspi->Instance->CR1 |= SPI_CR1_CRCNEXT;

          }

A===>     /* Wait until RXNE flag is set */

          if(SPI_WaitOnFlagUntilTimeout(hspi, SPI_FLAG_RXNE, RESET, Timeout) != HAL_OK)

          {

            return HAL_TIMEOUT;

          }

          (*hspi->pRxBuffPtr++) = hspi->Instance->DR;

          hspi->RxXferCount--;

        }

B===>  /* Wait until RXNE flag is set */

       if(SPI_WaitOnFlagUntilTimeout(hspi, SPI_FLAG_RXNE, RESET, Timeout) != HAL_OK)

        {

          return HAL_TIMEOUT;

        }

        (*hspi->pRxBuffPtr++) = hspi->Instance->DR;

        hspi->RxXferCount--;

      }

    }