STM32F407 usart tx shows non-digital signal on pin PA9

[Build-A-Burger]

I'm using Atollic True Studio and CubeMX to program a STM32F407 Discovery board and using 1 pin (shown in yellow) to trigger the scope. The signal that's supposed to be TX from the usart doesn't look right. I've tried it powering it with the USB cable and using a separate 5v power supply.

Can't see that I'm doing anything wrong.
Here's the code from usart.c

void MX_USART1_UART_Init(void)
{
  huart1.Instance = USART1;
  huart1.Init.BaudRate = 9600;
  huart1.Init.WordLength = UART_WORDLENGTH_8B;
  huart1.Init.StopBits = UART_STOPBITS_1;
  huart1.Init.Parity = UART_PARITY_NONE;
  huart1.Init.Mode = UART_MODE_TX_RX;
  huart1.Init.HwFlowCtl = UART_HWCONTROL_NONE;
  huart1.Init.OverSampling = UART_OVERSAMPLING_8;
  if (HAL_UART_Init(&huart1) != HAL_OK)
  {
    Error_Handler();
  }
}
void HAL_UART_MspInit(UART_HandleTypeDef* uartHandle)
{
  GPIO_InitTypeDef GPIO_InitStruct = {0};
  if(uartHandle->Instance==USART1)
  {
  /* USER CODE BEGIN USART1_MspInit 0 */

  /* USER CODE END USART1_MspInit 0 */
    /* USART1 clock enable */
    __HAL_RCC_USART1_CLK_ENABLE();
 
    __HAL_RCC_GPIOA_CLK_ENABLE();
    /**USART1 GPIO Configuration   
    PA9     ------> USART1_TX
    PA10     ------> USART1_RX
    */
    GPIO_InitStruct.Pin = TX1_Pin;
    GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
    GPIO_InitStruct.Pull = GPIO_PULLUP;
    GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_MEDIUM;
    GPIO_InitStruct.Alternate = GPIO_AF7_USART1;
    HAL_GPIO_Init(TX1_GPIO_Port, &GPIO_InitStruct);

    GPIO_InitStruct.Pin = RX1_Pin;
    GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
    GPIO_InitStruct.Pull = GPIO_PULLUP;
    GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
    GPIO_InitStruct.Alternate = GPIO_AF7_USART1;
    HAL_GPIO_Init(RX1_GPIO_Port, &GPIO_InitStruct);

  /* USER CODE BEGIN USART1_MspInit 1 */

  /* USER CODE END USART1_MspInit 1 */
  }
}

And here's where I call the usart transmit function:

for(;;)
    {
        vTaskDelay(10);
        HAL_GPIO_WritePin(GPIOB, TRIG_Pin, GPIO_PIN_SET);
        vTaskDelay(1);
        HAL_GPIO_WritePin(GPIOB, TRIG_Pin, GPIO_PIN_RESET);
        ret = HAL_UART_Transmit(&huart1, pData, Size, 100);
        data[0]++;
   }

 

[KlausST]

Hi,

Which pin number is the yellow signal? I understand pin1, but USART_Tx is pin 68.

If the yellow signal is from pin68, then please interchange your scope probes, just to check if it's not a probe problem.

The shown signal
* either shows low drive strength (no push pull, or series resistance, or weak solder joint)
* or high capacitive load

Klaus

 

[Build-A-Burger]

Hey, thanks for the quick reply!
The TX pin is what CubeMX assigned: PA9 and I'm just using PB7 as the trigger pin.

--- Updated Feb 4, 2022 ---

OK, I tried changing the scope probes and it still does the same thing.

 

[KlausST]

Hi,

PA9 is pin 68
PB7 is pin 93
****

Usually the cube generated code should be correct.
But I don't what piece of code is from you and what is from cube

What woiries me, it seems Tx is defined as Push-pull, but also the Rx pin, which makes no sense.

Klaus

 

[Build-A-Burger]

CubeMX doesn't give you any other choice except 'pull-up'.