HAL UART transfer with DMA keeps busy

[Lukasz Przenioslo]

Posted on September 29, 2015 at 15:28

Hello there,

I am trying to write a logger application using uart4 and DMA on STM32F4 discovery. I am usinh HAL lib and I can send through uart using regular transfer funtion without problem:

HAL_UART_Transmit(&huart4, ''mama_'', 5, 1000);

But when I try to use the DMA version:

HAL_UART_Transmit_DMA(&huart4, ''mama_'', 5);

I can only send the message once, because after that this function returns status ''HAL_UART_STATE_BUSY''. I am trying to send this message every 1 second. Why is DMA bussy in this time? I have generated my config code using Cube software and when looking at the Hyperterminal examples its pretty similar. What am I doing wrong or what did i forget? I would apreciate all help.

[Lukasz Przenioslo]

Posted on September 30, 2015 at 08:38

Anyone please?

[qwer.asdf]

Posted on September 30, 2015 at 09:50

Are you handling the interrupts? Here is the code from the STM32F4 examples in STM32Cube_FW_F4_V1.8.0\Projects\STM32F4-Discovery\Examples\UART\UART_TwoBoards_ComDMA\Src\stm32f4xx_it.c:

/**
* @brief This function handles DMA RX interrupt request. 
* @param None
* @retval None 
*/
void
USARTx_DMA_RX_IRQHandler(
void
)
{
HAL_DMA_IRQHandler(UartHandle.hdmarx);
}
/**
* @brief This function handles DMA TX interrupt request.
* @param None
* @retval None 
*/
void
USARTx_DMA_TX_IRQHandler(
void
)
{
HAL_DMA_IRQHandler(UartHandle.hdmatx);
}
/**
* @brief This function handles USARTx interrupt request.
* @param None
* @retval None
*/
void
USARTx_IRQHandler(
void
)
{
HAL_UART_IRQHandler(&UartHandle);
}

[Nickname5522_O]

Posted on September 30, 2015 at 11:06

Hi Bremen,

You should add the function that handles USART interrupts.

/** 
* @brief This function handles USARTx interrupt request. 
* @param None 
* @retval None 
*/ 
void USARTx_IRQHandler(void) 
{ 
HAL_UART_IRQHandler(&UartHandle); 
}

Indeed, the function ''HAL_UART_IRQHandler()'' calls ''UART_Transmit_IT()'' function that sets the USART state to ''HAL_UART_STATE_READY''. -Shahrzad-

[Lukasz Przenioslo]

Posted on September 30, 2015 at 18:12

Thats true, after handling interrupts the code started working. I didnt know it works like that. Thank you.