HAL_UART_Transmit_DMA() only work one time

[HanCheng Liu]

Posted on October 22, 2017 at 16:13

I want to use  ' HAL_UART_Transmit_DMA(); ' to send data in DMA mode like this :

    char str_Hello[]='Hello\n';

    HAL_UART_Transmit_DMA(&huart1,(unsigned char *)str_Hello,strlen(str_Hello));    HAL_Delay(500);

But transimit function only work one time(DMA is working under normal mode).

I found these in the definition of function 'HAL_UART_Transmit_DMA()' in 'stm32f1xx_hal_uart.c'

HAL_StatusTypeDef HAL_UART_Transmit_DMA(UART_HandleTypeDef *huart, uint8_t *pData, uint16_t Size)

{  uint32_t *tmp;  /* Check that a Tx process is not already ongoing */  if(huart->gState == HAL_UART_STATE_READY)

{

......

huart->gState = HAL_UART_STATE_BUSY_TX;

.....

}

}

So, I try to manually set 'huart->gState' in my while loop like this

  char str_Hello[]='Hello\n';

  HAL_UART_Transmit_DMA(&huart1,(unsigned char *)str_Hello,strlen(str_Hello));  HAL_Delay(500);

  huart1.gState = HAL_UART_STATE_READY

Although the problem was solved , but i think that it may not the correct way to solve this issue.

Anyone know how to handle it?

Thanks.

#uart #dma #hal #stm32f1

[Tesla DeLorean]

Sorry, bumping old zombie unanswered threads off my feed

[gilramon]

It's because you forgot to enable the interrupt of the UART that you work with in Cubemx.

[Karl Yamashita]

Did you assign a DMA channel to the Tx? 

Edit: Dang this is an old thread, lol.