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How to receive bytes from SPI with interrupts using HAL?

Question asked by Michel Keijzers on May 25, 2018
Latest reply on May 27, 2018 by Michel Keijzers

Background

(note I asked this question too at https://electronics.stackexchange.com/questions/376282/how-to-receive-bytes-from-spi-with-interrupts-using-hal-on-stm32 , but no answers yet).

 

I am trying to make a SPI connection between two STM32F103C8T6's.

 

Measurements

According to my logic analyzer I get a signal that looks ok (sending 10 bytes with values 0x55):

 

 

Results

My receiver's callback function for RX Complete also stops in the breakpoint (last line in code below):

 

    void HAL_SPI_RxCpltCallback(SPI_HandleTypeDef *hspi)
    {
      /* Prevent unused argument(s) compilation warning */
      if (hspi1.RxXferCount == 10)

 

Problem

I sent 10 bytes, however, the RxXferCount has value 0. Instead, RxXferSize has value 10, but pRxBuffPtr is empty.

 

Question

How can I receive the correct bytes?

 

**Values from the register SPI1 and variable hspi1**

 

 

Relevant code

 

Initialization (using a GPIO for defining Master and Slave):

 

    /* SPI1 init function */
    static void MX_SPI1_Init(void)
    {

      hspi1.Instance = SPI1;
      hspi1.Init.Mode = (HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_12) == GPIO_PIN_SET ?
        SPI_MODE_MASTER : SPI_MODE_SLAVE);
      hspi1.Init.Direction = SPI_DIRECTION_2LINES;
      hspi1.Init.DataSize = SPI_DATASIZE_8BIT;
      hspi1.Init.CLKPolarity = SPI_POLARITY_LOW;
      hspi1.Init.CLKPhase = SPI_PHASE_1EDGE;
      hspi1.Init.NSS = SPI_NSS_SOFT;
      hspi1.Init.BaudRatePrescaler = SPI_BAUDRATEPRESCALER_256;
      hspi1.Init.FirstBit = SPI_FIRSTBIT_MSB;
      hspi1.Init.TIMode = SPI_TIMODE_DISABLE;
      hspi1.Init.CRCCalculation = SPI_CRCCALCULATION_DISABLE;
      hspi1.Init.CRCPolynomial = 10;
      if (HAL_SPI_Init(&hspi1) != HAL_OK)
      {
        _Error_Handler(__FILE__, __LINE__);
      }
    }


Main function:

 

   int main(void)
    {
       ...
       MX_SPI1_Init();
       ...

       _transmitter = (HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_12) == GPIO_PIN_SET ?
                      SPI_MODE_MASTER : SPI_MODE_SLAVE);

       while (1)
       {
       if (_transmitter)
       {
       uint8_t data[] = { 0x55, 0x55, 0x55, 0x55, 0x55,
                                 0x55, 0x55, 0x55, 0x55, 0x55 };
              HAL_SPI_Transmit_IT(&hspi1, data, 10);
       }
       else
       {
          HAL_SPI_Receive_IT(&hspi1, _spi_data, 10);
          }
       }
    }

Outcomes