HAL_SPI_TransmitReceive_DMA read before write

[dominik]

Hi

I'm using the HAL_SPI_TransmitReceive_DMA to write to an external Flash. On a delte command for the external flash I need to wait for until the busy flag of the flash is zero. So I use this function to check the busy flag.

 spi_read(&command, sizeof (command), &SPI_RX_BUFFER, 2);
 
 if ((SPI_RX_BUFFER[1] & 1) == 0)
        return true;
    else
        return false;

void spi_read(const void *txdata, size_t txsize, void *rxdata, size_t rxsize)
{
    HAL_GPIO_WritePin(Flash_NSS_GPIO_Port, Flash_NSS_Pin, GPIO_PIN_RESET);
    //reset the TX_RX complete Indication
    SPI_TXRX_Complete (true, false);
    SPI_TXRX_Status_Complete (true, false);
 
    HAL_SPI_TransmitReceive_DMA (&hspi3, (uint8_t *)txdata, (uint8_t *)rxdata, rxsize);
}

The problem is, that the RX of the DMA is not ready when I check the busy flag:

SPI_RX_BUFFER[1] & 1

How can I fix this issue?

[waclawek.jan]

Observe the communication on the SPI pins using logic analyzer.

JW

[dominik · Accepted solution]

It's running, problem was that with high optimization debugger I got wrong and inpossible results. I changed the icf file to a bigger range ange disabled the optimization, now it works like it should.

[KnarfB]

If your MCU has a data cache, the observed behaviour at high optimzation could be due to cache incoherency.

[dominik]

I changed my icf file to a 1 image Debug config, now I can debug without optimization