Going to STOP while waiting for UART TX DMA to complete

[hmc]

Posted on July 04, 2016 at 04:06

Dear forum, I am trying to transfer a block of bytes from RAM to UART2 using DMA on STM32F042.  I found the HAL function HAL_UART_Transmit_DMA, so I want to go to stop right after that, like this:

    int_disable();

    while ((block = getBlock(&n))) { /* while not End-Of-Data... */         int_enable();         extern UART_HandleTypeDef huart2;         HAL_UART_Transmit_DMA(&huart2, (uint8_t*)block, n);         HAL_PWR_EnterSTOPMode(PWR_MAINREGULATOR_ON, PWR_STOPENTRY_WFI);         int_disable();     }     int_enable(); I read the reference manual DMA section, but I cannot figure out whether I need to enable the UART2 before going to sleep.  I would imagine that going to WFI will work fine, since DMA interrupt is getting fired... Thanks for reading. #low-power #dma

[Walid FTITI_O]

Posted on July 04, 2016 at 11:32

Hi choi.henry,

What you want to achieve exactly ? The problem that you faced is not clearly mentionned here. Please , reformulate to help you. -Hannibal-

[hmc]

Posted on July 04, 2016 at 21:38

Hi Hannibal, can you please confirm whether my code looks right for sending a block of bytes over UART2 using DMA?  I am the UART state is stuck at HAL_UART_STATE_BUSY_TX...

HAL_StatusTypeDef dma_status;

do {    dma_status = HAL_UART_Transmit_DMA(&huart2, (uint8_t*)block, n);    assert(dma_status == HAL_OK || dma_status == HAL_BUSY);

   HAL_UART_StateTypeDef uart_state;

   do { // <-- stuck in this loop     HAL_PWR_EnterSLEEPMode(PWR_MAINREGULATOR_ON, PWR_STOPENTRY_WFI);     uart_state = HAL_UART_GetState(&huart2);    } while (uart_state & (HAL_UART_STATE_BUSY | HAL_UART_STATE_ERROR)); } while (dma_status == HAL_BUSY);