STM32F030F4P6 - how to make UART1 TX work on PA2

[CSkil.1]

I have configured PA2 as USART1 TX in STM32CubeMX, the code it generates looks correct:

void MX_USART1_UART_Init(void)
{
 
  /* USER CODE BEGIN USART1_Init 0 */
 
  /* USER CODE END USART1_Init 0 */
 
  LL_USART_InitTypeDef USART_InitStruct = {0};
 
  LL_GPIO_InitTypeDef GPIO_InitStruct = {0};
 
  /* Peripheral clock enable */
  LL_APB1_GRP2_EnableClock(LL_APB1_GRP2_PERIPH_USART1);
 
  LL_AHB1_GRP1_EnableClock(LL_AHB1_GRP1_PERIPH_GPIOA);
  /**USART1 GPIO Configuration
  PA2   ------> USART1_TX
  PA3   ------> USART1_RX
  */
  GPIO_InitStruct.Pin = TX_Pin;
  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_1;
  LL_GPIO_Init(TX_GPIO_Port, &GPIO_InitStruct);
 
  GPIO_InitStruct.Pin = RX_Pin;
  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_1;
  LL_GPIO_Init(RX_GPIO_Port, &GPIO_InitStruct);
 
  /* USART1 DMA Init */
 
  /* USART1_TX Init */
  LL_DMA_SetDataTransferDirection(DMA1, LL_DMA_CHANNEL_2, LL_DMA_DIRECTION_MEMORY_TO_PERIPH);
 
  LL_DMA_SetChannelPriorityLevel(DMA1, LL_DMA_CHANNEL_2, LL_DMA_PRIORITY_LOW);
 
  LL_DMA_SetMode(DMA1, LL_DMA_CHANNEL_2, LL_DMA_MODE_NORMAL);
 
  LL_DMA_SetPeriphIncMode(DMA1, LL_DMA_CHANNEL_2, LL_DMA_PERIPH_NOINCREMENT);
 
  LL_DMA_SetMemoryIncMode(DMA1, LL_DMA_CHANNEL_2, LL_DMA_MEMORY_INCREMENT);
 
  LL_DMA_SetPeriphSize(DMA1, LL_DMA_CHANNEL_2, LL_DMA_PDATAALIGN_BYTE);
 
  LL_DMA_SetMemorySize(DMA1, LL_DMA_CHANNEL_2, LL_DMA_MDATAALIGN_BYTE);
 
  /* USART1 interrupt Init */
  NVIC_SetPriority(USART1_IRQn, 0);
  NVIC_EnableIRQ(USART1_IRQn);
 
  /* USER CODE BEGIN USART1_Init 1 */
 
  /* USER CODE END USART1_Init 1 */
  USART_InitStruct.BaudRate = 1000000;
  USART_InitStruct.DataWidth = LL_USART_DATAWIDTH_8B;
  USART_InitStruct.StopBits = LL_USART_STOPBITS_1;
  USART_InitStruct.Parity = LL_USART_PARITY_NONE;
  USART_InitStruct.TransferDirection = LL_USART_DIRECTION_TX_RX;
  USART_InitStruct.HardwareFlowControl = LL_USART_HWCONTROL_NONE;
  USART_InitStruct.OverSampling = LL_USART_OVERSAMPLING_16;
  LL_USART_Init(USART1, &USART_InitStruct);
  LL_USART_DisableIT_CTS(USART1);
  LL_USART_ConfigAsyncMode(USART1);
  LL_USART_Enable(USART1);
  /* USER CODE BEGIN USART1_Init 2 */
 
  /* USER CODE END USART1_Init 2 */
 
}

And then I set it up in my code as follows:

    // start uart (send/recv to/from BLE MCU)
    LL_USART_EnableIT_TC(USART1);
    LL_USART_EnableIT_RXNE(USART1);
    LL_USART_EnableDirectionTx(USART1);
    LL_USART_EnableDirectionRx(USART1);
 
    // setup uart DMA
    LL_USART_EnableDMAReq_TX(USART1);
    LL_DMA_SetPeriphAddress(DMA1, LL_DMA_CHANNEL_2, LL_USART_DMA_GetRegAddr(USART1, LL_USART_DMA_REG_DATA_TRANSMIT));
    LL_DMA_EnableIT_TC(DMA1, LL_DMA_CHANNEL_2);

It works fine if I use PA9, but using PA2 I get nothing - the GPIO is floating. Has anyone managed it and, if so, is there a trick I'm missing?

[CSkil.1]

Sorry, I hit send too soon. The code for initiating a UART transmit is this

    LL_DMA_SetDataLength(DMA1, LL_DMA_CHANNEL_2, 4);
    LL_DMA_SetMemoryAddress(DMA1, LL_DMA_CHANNEL_2, (uint32)uart_tx_buffer);
    LL_DMA_EnableChannel(DMA1, LL_DMA_CHANNEL_2);

which, as I say, works fine if I use PA9 for TX...

[MM..1]

Are you sure is your mcu F4?

[KnarfB]

are you sure that TX_Pin is LL_GPIO_PIN_2?

my CubeMX sets GPIO_InitStruct.Speed = LL_GPIO_SPEED_FREQ_HIGH;

hth

KnarfB

[waclawek.jan]

Read out and check/post content of USART and relevant GPIO registers.

Make sure physical connection is OK by setting given pin to GPIO output and toggling it.

JW