STM32F407 SPI TXE flag Interrupt problem.

Posted on June 04, 2015 at 13:39

> But, after the last data is transmitted, the TXE flag still remains HIGH and the execution keeps reentering the ISR over and over.

That's how it's supposed to work - it is an indicator of tx (holding) register empty. Disable the interrupt after last byte.

> Furthermore, the RXNE flag is never SET. So no data is received.

Don't look at it in the debugger.

JW

Posted on June 04, 2015 at 13:55

Hi Jan,

Thank you for replying.

I didn't understand the second part > Don't look at it in the debugger.

Here's my interrupt routine:-

void SPI2_IRQHandler(void)

{

  if(SPI_I2S_GetITStatus(My_SPI, SPI_I2S_IT_TXE) == SET)

  {

    if(TxDiffPtr > 0)

    {

      SPI_I2S_SendData(My_SPI, gu8a_Tx[TxRdPtr]);

      TxRdPtr++;

      TxDiffPtr--;

      if(TxRdPtr >= TX_RX_SIZE)

      {

        TxRdPtr = 0;

      }

    }

    else

    {

      SPI_I2S_ITConfig(My_SPI, SPI_I2S_IT_TXE, DISABLE);

    }

  }

  if(SPI_I2S_GetITStatus(My_SPI, SPI_I2S_IT_RXNE) == SET)

  {

      gu8a_Rx[RxWrPtr] = SPI_I2S_ReceiveData(My_SPI);

      RxWrPtr++;

      RxDiffPtr++;

      if(RxWrPtr >= TX_RX_SIZE)

      {

        RxWrPtr = 0;

      }

      SPI_I2S_ITConfig(My_SPI, SPI_I2S_IT_RXNE, DISABLE);

  }

}

Posted on June 05, 2015 at 13:26

and the routines to send data to the slave and read data from it...

For sending data:-

 CS_LOW();      //Slave enabled

  for (int i = 0; i < length; i++)

  {

    gu8a_Tx[TxWrPtr] = data[i];

    TxWrPtr++;

    TxDiffPtr++;

    if(TxWrPtr >= TX_RX_SIZE)

    {

      TxWrPtr = 0;

    }

  }

For receiving data:-

  CS_LOW();

  for (int j = 0; j < length; j++)

  {

    if(RxDiffPtr > 0)

    {

      data[j] =  gu8a_Rx[RxRdPtr];

      RxRdPtr++;

      RxDiffPtr--;

      if(RxRdPtr >= TX_RX_SIZE)

      {

        RxRdPtr = 0;

      }

    }

  }

I get the interrupts, but no communication though.

Regards,

Abhishek.

Posted on June 05, 2015 at 18:07

I didn't understand the second part > Don't look at it in the debugger.

 

The debugger will change the behaviour of the peripheral if you park a register view over it. So DON'T do that, because it's invasive.

Check also that you are using volatile keyword for variables changed under interrupt, and the wisdom of using non-atomic operations to manage content.

Posted on June 06, 2015 at 06:53

Hi Clive,

Thank you very much for replying.

I declared the variables used in interrupt as volatile.

I probed the SPI clock when SPI_I2S_SendData(My_SPI, gu8a_Tx[TxRdPtr]); is called from interrupt, and clock is generated.

In order to keep record of read, write and difference pointers, i am using for loop(atomic operation of copying byte one-by-one into buffer) rather than non-atomic operation(memcpy), if that is what you meant.

To summarize upto now, i get the TXE interrupts, and spi clock is generated when data is transmitted to the slave. But still unable to receive any data. So i suppose that actually the slave is not receiving any data at all.

Regards,

Abhishek.