RXNE Flag of STM32F302R8 is never SET

[WM_IR]

Hi, I have a problem where my SPI SR RXNE in STM32F302R8 is never SET, causing my program always halt in while loop, waiting the RXNE status to become SET, when receive data.

how I set the RXNE flag is below:

#define SPI_SR_RXNE 0

#define SPI_RXNE_FLAG   (1 << SPI_SR_RXNE)

Here is my main code:

MAIN CODE: In the main code, I stuck at the SPI_ReceiveData() because after I send my desired data to slave, I received a dummy byte. So, to clear the dummy byte, I need to read the RXNE first. But, my code was stuck at that line which is Read the dummy byte.

 while(1)

  {

while(GPIO_ReadFromInputPin(GPIOC,GPIO_PIN_NO_13));

delay();

//enable SPI peripheral (SPE in SPI Control register 1)

SPI_PeripheralControl(SPI2,ENABLE);

//declare variable untuk command code

uint8_t commandcode = COMMAND_LED_CTRL; //0x50

//define ackbyte

uint8_t ackbyte;

//create array

uint8_t args[2];

//Send data

SPI_SendData(SPI2,&commandcode,1);

SPI_ReceiveData(SPI2,&dummy_read,1); MY CODE STUCK RIGHT HERE

SPI_SendData(SPI2,&dummy_write,1);

//then, lets call SPI_ReceiveData untuk receive data from slave.

SPI_ReceiveData(SPI2,&ackbyte,1);

}

THEN, INSIDE SPI_ReceiveData function: When my code execute the SPI_Receive data, it will check the status flag first, if RESET, then it will stuck in the while loop until it SET. As I bold the line below. But, I stuck at here.

void SPI_ReceiveData(SPI_RegDef_t *pSPIx, uint8_t *pRxBuffer, uint32_t Len)

{

while(Len > 0)

  {

   //1. wait until RXNE is SET

   while(SPI_GetFlagStatus(pSPIx, SPI_RXNE_FLAG) == FLAG_RESET);

   //2. TXE set, check dff or CRCL

   if(pSPIx->CR1 & (1 << SPI_CR1_CRCL))

   {

   //16 bit data frame format

   //1. load the data from Data Register(DR) to Rx Buffer address

   *((uint16_t*)pRxBuffer) = pSPIx->DR ; 

   //2. kene decrease len

   Len--;

   Len--; 

   (uint16_t*)pRxBuffer++; 

   }

   else

   {

   //8 bit data frame format

   //1. Load the data into Data Register(DR)

   *(pRxBuffer) = *((volatile uint8_t *)&pSPIx->DR);

   //2.decrease len

   Len--;

   //3.increment pTxBuffer in order to make it point to next data item

   pRxBuffer++;

   }

  }   

}

SPI_GetFlagStatus() function: Here is the code that I check the status flag. here I detected my RXNE flag is not SET.

uint8_t SPI_GetFlagStatus(SPI_RegDef_t *pSPIx, uint32_t FlagName)

{

if(pSPIx->SR & FlagName)

{

return FLAG_SET;

}

return FLAG_RESET;

}

Anyone could help me in this issue? Im using STM32F302R8 nucleo board

[waclawek.jan]

Observe the SCK pin using oscilloscope or logic analyzer.

JW

[WM_IR]

Here is the clock, during the first send data,it produce normally, but when to clear the RXNE, it could not produce the SCK.

[waclawek.jan]

What is in SPI_SendData()?

Maybe SPI_SendData already clears the RXNE, doesn't it?

JW

[WM_IR]

Here is what inside the SPI_SendData():

void SPI_SendData(SPI_RegDef_t *pSPIx, uint8_t *pTxBuffer, uint32_t Len)

{

  while(Len > 0)

  {

   //1. wait until TXE is SET

   while(SPI_GetFlagStatus(pSPIx, SPI_TXE_FLAG) == FLAG_RESET);

   //2. lepas TXE set, check dff or CRCL

   if(pSPIx->CR1 & (1 << SPI_CR1_CRCL))

   {

   //16 bit data frame format

   //1. Load the data into Data Register(DR)

   pSPIx->DR = *((uint16_t*)pTxBuffer);

   //2. decrease len

   Len--;

   Len--;

   //3. increment pTxBuffer in order to make it point to next data item

   (uint16_t*)pTxBuffer++;

   }

   else

   {

   //8 bit data frame format

   //1. Load the data into Data Register(DR)

   *((volatile uint8_t *)&pSPIx->DR) = *pTxBuffer;

   //2. decrease len

   Len--;

   //3. increment pTxBuffer in order to make it point to next data item

   pTxBuffer++;

   }

  }

}

But, I suspect that the hardware automatically, clear the RXNE based on this:

But, Im not really understand what this means, can you explain it to me?

[Tesla DeLorean]

Watch that reading/viewing DR in the debugger will auto-clear SR.RXNE

[waclawek.jan]

RXNE works as a watermark on the Rx FIFO. When a byte arrives, it is stored to FIFO, and it's "level" increments by 1; when your read out a byte from FIFO, it's "level" decrements by 1.

If FRXTH=1, if "level">=1, RXNE=1; if "level" < 1 (i.e. "level" == 0, FIFO empty), RXNE = 0.

If FRXTH=0, if "level" >=2, RXNE=1; if "level"<2 (i.e. there is zero or one byte in FIFO), RXNE=0.

You probably want to have FRXTH set to 1.

JW

[WM_IR]

So, do I need to set the FRXTH manually? If I want to set it, during the SPI want to send data or to read data?

[waclawek.jan]

Normally, you would set it once, when you set up the SPI at the beginning of your program.

JW

[WM_IR]

I have managed to SET the FRXTH bit. After the data is sent, the RXNE goes HIGH. But, after it execute next code line which is SPI_receiveData(), It automatically clear the RXNE. Is this means that the hardware clear the RXNE automatically?

If I want the RXNE stays HIGH, I do not understand what do you mean by the "level" If you could elaborate more, I am very appreciated.

Thank you