We need the register-based low level SPI R/W drive for STM32C031C6

[RongShengWang]

1. CubeMX only allows HAL or LL for SPI and other peripherals. STM32C031C6 itself provides the good SPI clock rate. 

   SPI LL API function only allows two-byte R/W.. The slave STPM34 Meter IC requires 4-Byte SPI R/W. So we have to choose HAL SPI API calls, such as HAL_SPI_TransmitReceive().   

    However HAL introduces a big delay (15 us or more) between two consecutive HAL SPI-API calls. We need 6 SPI-API calls within 128us for our application,  This big delay inserted by HAL makes it impossible. .

2. The only solution is to write the register low level SPI R/W functions. Is it possible to write it under the current CubeMx IDE compiler for STM32C031C6? Could you provide us the solutions?

Thanks,

Rong

[Andrew Neil]

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[Saket_Om]

Hello @RongShengWang ,

Is the data size set to greater than SPI_DATASIZE_8BIT? If yes, could you please try with this code?

void SPI_Transmit_Receive(const uint8_t *data_tx, uint8_t *data_rx, uint8_t size)
{
	uint8_t rx_size= size;
	uint8_t tx_size = size;
	
	/* Set the Rx Fifo threshold */
    if (size > 1U)
    {
      /* Set fiforxthreshold according the reception data length: 16bit */
      CLEAR_BIT(SPI1->CR2, SPI_RXFIFO_THRESHOLD);
	}
	
    /* Enable SPI */
    SPI1->CR1 |= SPI_CR1_SPE;


    while (size > 0)
    {
        /* Wait until TXE (Transmit buffer empty) flag is set */
        while (!__HAL_SPI_GET_FLAG(&hspi1, SPI_FLAG_TXE));

        /* Transmit data */
      if (tx_size > 1U)
      {
        SPI1->DR = *((uint16_t *)data_tx);
        data_tx += sizeof(uint16_t);
        tx_size -= 2U;
      }
      else
      {
        *(__IO uint8_t *)&SPI1->DR = (*data_tx);
        data_tx ++;
        tx_size --;
      }

        /* Wait until RXNE (Receive buffer not empty) flag is set */
        while (!__HAL_SPI_GET_FLAG(&hspi1, SPI_FLAG_RXNE));
		
		
		if (rx_size > 1U)
        {
          *((uint16_t *)data_rx) = (uint16_t)SPI1->DR;
          data_rx += sizeof(uint16_t);
          rx_size -= 2U;
          if (rx_size <= 1U)
          {
            /* Set RX Fifo threshold before to switch on 8 bit data size */
            SET_BIT(SPI1->CR2, SPI_RXFIFO_THRESHOLD);
          }
        }
        else
        {
          (*(uint8_t *)data_rx) = *(__IO uint8_t *)&SPI1->DR;
          data_rx++;
          rx_size --;
        }
    }

    /* Wait until the SPI is not busy */
    while (__HAL_SPI_GET_FLAG(&hspi1, SPI_FLAG_BSY));

    /* Disable SPI */
    SPI1->CR1 &= ~SPI_CR1_SPE;
}

[RongShengWang]

Hi, Omar,

     Thank you very much for your timely help. I found my setting is -

     hspi1.Init.DataSize = SPI_DATASIZE_8BIT; - Was it a big problem with my code?

     Should I change it to hspi1.Init.DataSize = SPI_DATASIZE_16BIT to run your code?

     Thank you very much!

Rong

[RongShengWang]

Hi, Omar,

     I found my setting is - hspi1.Init.DataSize = SPI_DATASIZE_8BIT; 

   I also tried to send one byte - 8 bits, rather than 16 bits, at a time. It did not work either.

     Should I change it to hspi1.Init.DataSize = SPI_DATASIZE_16BIT to run your code?

     Thank you very much!

Rong

[RongShengWang]

I need your help with my register based SPI C code which does not work.

Could you provide me with the working register based SPI C code? Thanks

[RongShengWang]

Hi, Omar,

     Your code seems working with my setting - hspi1.Init.DataSize = SPI_DATASIZE_8BIT; 

     Should I change it to hspi1.Init.DataSize = SPI_DATASIZE_16BIT to run your code?

     Thank you very much!

Rong

[Saket_Om]

Hello @RongShengWang,

Yes, you should change hspi1.Init.DataSize to SPI_DATASIZE_16BIT to run the code correctly.

I wasn't getting notified about your answer. To notify people in the forum, you need to use @username.

Thank you very much!

[RongShengWang]

Hi, Omar,

      It is strange - When I changed to SPI_DATASIZE_16BIT, your code does not work. Also "HAL_SPI_TransmitReceive" stops working - nothing works.   

    Two C files (spi.c and main.c are attached.

     When I changed it back to SPI_DATASIZE_8BIT, "HAL_SPI_TransmitReceive" works again. Your code works - but not very consistently...

     Two C files (spi.c and main.c are attached. My SPI initialization code is below. Could you explain why?  The slave SPI IC is SPTM34.

   Thank you very for your help!

Rong

hspi1.Instance = SPI1;

hspi1.Init.Mode = SPI_MODE_MASTER;

hspi1.Init.Direction = SPI_DIRECTION_2LINES;

hspi1.Init.DataSize = SPI_DATASIZE_8BIT;

hspi1.Init.CLKPolarity = SPI_POLARITY_HIGH;

hspi1.Init.CLKPhase = SPI_PHASE_2EDGE;

hspi1.Init.NSS = SPI_NSS_SOFT;

hspi1.Init.BaudRatePrescaler = SPI_BAUDRATEPRESCALER_4;

hspi1.Init.FirstBit = SPI_FIRSTBIT_MSB;

hspi1.Init.TIMode = SPI_TIMODE_DISABLE;

hspi1.Init.CRCCalculation = SPI_CRCCALCULATION_DISABLE;

hspi1.Init.CRCPolynomial = 7;

hspi1.Init.CRCLength = SPI_CRC_LENGTH_DATASIZE;

hspi1.Init.NSSPMode = SPI_NSS_PULSE_DISABLE;

[Andrew Neil]

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[RongShengWang]

Hi, Omar,

      It is strange - When I changed to SPI_DATASIZE_16BIT, your code does not work. Also "HAL_SPI_TransmitReceive" stops working - nothing works.   

    Two C files (spi.c and main.c are attached.

     When I changed it back to SPI_DATASIZE_8BIT, "HAL_SPI_TransmitReceive" works again. Your code works - but not very consistently...

     Two C files (spi.c and main.c are attached. My SPI initialization code is below. Could you explain why?  The slave SPI IC is SPTM34.

   Thank you very for your help!

Rong

hspi1.Instance = SPI1;

hspi1.Init.Mode = SPI_MODE_MASTER;

hspi1.Init.Direction = SPI_DIRECTION_2LINES;

hspi1.Init.DataSize = SPI_DATASIZE_8BIT;

hspi1.Init.CLKPolarity = SPI_POLARITY_HIGH;

hspi1.Init.CLKPhase = SPI_PHASE_2EDGE;

hspi1.Init.NSS = SPI_NSS_SOFT;

hspi1.Init.BaudRatePrescaler = SPI_BAUDRATEPRESCALER_4;

hspi1.Init.FirstBit = SPI_FIRSTBIT_MSB;

hspi1.Init.TIMode = SPI_TIMODE_DISABLE;

hspi1.Init.CRCCalculation = SPI_CRCCALCULATION_DISABLE;

hspi1.Init.CRCPolynomial = 7;

hspi1.Init.CRCLength = SPI_CRC_LENGTH_DATASIZE;

hspi1.Init.NSSPMode = SPI_NSS_PULSE_DISABLE;