LIN BUS non blocking HAL_LIN_SendBreak?

[JBond.1]

Hi, HAL_LIN_SendBreak seems to be blocking CPU, is there a way to bring UART TX pin down then wait for timer and bring it up? I have done it making GPIO pin GPIO_MODE_OUTPUT_PP then back to GPIO_MODE_AF_PP but init after takes long time. I was wondering is it possible to do it within UART without changing pin mode? Or reducing the time pin mode init is required?

void LIN_SendFrame_IT(void)
{
    __HAL_UART_DISABLE(&huart2);

    GPIO_InitTypeDef g = {0};
    g.Pin = LIN_TX_Pin;
    g.Mode = GPIO_MODE_OUTPUT_PP;
    g.Speed = GPIO_SPEED_FREQ_HIGH;
    HAL_GPIO_Init(LIN_TX_GPIO_Port, &g);

    HAL_GPIO_WritePin(LIN_TX_GPIO_Port, LIN_TX_Pin, GPIO_PIN_RESET);

    TIM2->ARR = 900;          // 900us break
    TIM2->CNT = 0;
    TIM2->CR1 |= TIM_CR1_OPM;
    HAL_TIM_Base_Start_IT(&htim2);
}

void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef *htim)
{
    if (htim != &htim2) return;

    HAL_GPIO_WritePin(LIN_TX_GPIO_Port, LIN_TX_Pin, GPIO_PIN_SET);

    GPIO_InitTypeDef g = {0};
    g.Pin = LIN_TX_Pin;
    g.Mode = GPIO_MODE_AF_PP;

    // This takes way too long to retunt to UART
    HAL_GPIO_Init(LIN_TX_GPIO_Port, &g);
    __HAL_UART_ENABLE(&huart2);

    HAL_UART_Transmit_DMA(&huart2, &DATA, 1); //Transmit
}

[Andrew Neil · Accepted solution]

---

@JBond.1 wrote:

HAL_LIN_SendBreak seems to be blocking CPU

What makes you say that?

The source doesn't seem to suggest it:

/**
  * @brief  Transmits break characters.
  * @PAram  huart  Pointer to a UART_HandleTypeDef structure that contains
  *                the configuration information for the specified UART module.
  * @retval HAL status
  */
HAL_StatusTypeDef HAL_LIN_SendBreak(UART_HandleTypeDef *huart)
{
  /* Check the parameters */
  assert_param(IS_UART_INSTANCE(huart->Instance));

  /* Process Locked */
  __HAL_LOCK(huart);

  huart->gState = HAL_UART_STATE_BUSY;

  /* Send break characters */
  ATOMIC_SET_BIT(huart->Instance->CR1, USART_CR1_SBK);

  huart->gState = HAL_UART_STATE_READY;

  /* Process Unlocked */
  __HAL_UNLOCK(huart);

  return HAL_OK;
}

https://github.com/STMicroelectronics/stm32l1xx-hal-driver/blob/master/Src/stm32l1xx_hal_uart.c#L2774

[JBond.1]

Seems to be my bad, looks like its not blocking, which is ok, just maybe wanted longer pause at start than 13 bits