SPI Communication Issue with STM32G431K8T6

[sqyq]

Hello,

I am working with an STM32G431K8T6and using the LL library to configure SPI in master mode.
The issue is with the MISO pin (PB4).

• The pin is configured as SPI input, with no pull-up or pull-down.

• When PB4 is left unconnected, the voltage is measured at 3.3v.

• If I short PB4 directly to GND, the current goes up to about 65mA, which looks like the pin is driving strongly,similar to push-pull output.

• Because of this, the SPI slave cannot pull the line low enough, and communication fails.

Configuration Details:

void MX_SPI1_Init(void)
{

  /* USER CODE BEGIN SPI1_Init 0 */

  /* USER CODE END SPI1_Init 0 */

  LL_SPI_InitTypeDef SPI_InitStruct = {0};

  LL_GPIO_InitTypeDef GPIO_InitStruct = {0};

  /* Peripheral clock enable */
  LL_APB2_GRP1_EnableClock(LL_APB2_GRP1_PERIPH_SPI1);

  LL_AHB2_GRP1_EnableClock(LL_AHB2_GRP1_PERIPH_GPIOA);
  LL_AHB2_GRP1_EnableClock(LL_AHB2_GRP1_PERIPH_GPIOB);
  /**SPI1 GPIO Configuration
  PA7   ------> SPI1_MOSI
  PB3   ------> SPI1_SCK
  PB4   ------> SPI1_MISO
  */
  GPIO_InitStruct.Pin = LL_GPIO_PIN_7;
  GPIO_InitStruct.Mode = LL_GPIO_MODE_ALTERNATE;
  GPIO_InitStruct.Speed = LL_GPIO_SPEED_FREQ_LOW;
  GPIO_InitStruct.OutputType = LL_GPIO_OUTPUT_PUSHPULL;
  GPIO_InitStruct.Pull = LL_GPIO_PULL_NO;
  GPIO_InitStruct.Alternate = LL_GPIO_AF_5;
  LL_GPIO_Init(GPIOA, &GPIO_InitStruct);

  GPIO_InitStruct.Pin = LL_GPIO_PIN_3;
  GPIO_InitStruct.Mode = LL_GPIO_MODE_ALTERNATE;
  GPIO_InitStruct.Speed = LL_GPIO_SPEED_FREQ_LOW;
  GPIO_InitStruct.OutputType = LL_GPIO_OUTPUT_PUSHPULL;
  GPIO_InitStruct.Pull = LL_GPIO_PULL_NO;
  GPIO_InitStruct.Alternate = LL_GPIO_AF_5;
  LL_GPIO_Init(GPIOB, &GPIO_InitStruct);

  GPIO_InitStruct.Pin = LL_GPIO_PIN_4;
  GPIO_InitStruct.Mode = LL_GPIO_MODE_ALTERNATE;
  GPIO_InitStruct.Speed = LL_GPIO_SPEED_FREQ_LOW;
  GPIO_InitStruct.OutputType = LL_GPIO_OUTPUT_PUSHPULL;
  GPIO_InitStruct.Pull = LL_GPIO_PULL_NO;
  GPIO_InitStruct.Alternate = LL_GPIO_AF_5;
  LL_GPIO_Init(GPIOB, &GPIO_InitStruct);

  /* USER CODE BEGIN SPI1_Init 1 */

  /* USER CODE END SPI1_Init 1 */
  SPI_InitStruct.TransferDirection = LL_SPI_FULL_DUPLEX;
  SPI_InitStruct.Mode = LL_SPI_MODE_MASTER;
  SPI_InitStruct.DataWidth = LL_SPI_DATAWIDTH_8BIT;
  SPI_InitStruct.ClockPolarity = LL_SPI_POLARITY_HIGH;
  SPI_InitStruct.ClockPhase = LL_SPI_PHASE_2EDGE;
  SPI_InitStruct.NSS = LL_SPI_NSS_SOFT;
  SPI_InitStruct.BaudRate = LL_SPI_BAUDRATEPRESCALER_DIV8;
  SPI_InitStruct.BitOrder = LL_SPI_MSB_FIRST;
  SPI_InitStruct.CRCCalculation = LL_SPI_CRCCALCULATION_DISABLE;
  SPI_InitStruct.CRCPoly = 7;
  LL_SPI_Init(SPI1, &SPI_InitStruct);
  LL_SPI_SetStandard(SPI1, LL_SPI_PROTOCOL_MOTOROLA);
  LL_SPI_DisableNSSPulseMgt(SPI1);
  /* USER CODE BEGIN SPI1_Init 2 */

  /* USER CODE END SPI1_Init 2 */

}

 Any help would be appreciated.