Posted on February 28, 2016 at 16:15Hi,
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--;
}
}
