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STM32L053C8Tx HAL UART DMA Bug at Overrun Error

Question asked by Till Rachow on Jan 25, 2018
Latest reply on Apr 4, 2018 by Till Rachow

Hi,

 

i found a bug in the HAL library for STM32L053C8Tx, when using UART with DMA. STMCube says its version STM32Cube FW_L0 V1.10.0

 

It seems that, in HAL_UART_IRQHandler the DMA should be reset when an Error occurs.

 

In a first step, the DMA request is disabled with CLEAR_BIT(huart->Instance->CR3, USART_CR3_DMAR); in line 1704 in stm32l0xx_har_uart.c

The program then jumps to HAL_DMA_Abort_IT at line 487 in stm32l0xx_hal_dma.c to reset the DMA.

It will only reset the DMA if hdma->State is HAL_DMA_STATE_BUSY. In my case, hdma->State is HAL_DMA_STATE_HALF_READY, which in my eyes qualifies as busy, but of course HAL_DMA_Abort_IT returns with HAL_ERROR, because its not HAL_DMA_STATE_BUSY. Thats why the DMA never gets reset, the Lock is still locked and state is still HAL_DMA_STATE_HALF_READY.

 

This results in very strange behaviour when using DMA after the error, as Rxcount, destination and source can't be changed. Calls to HAL_UART_DMAStop or HAL_UART_Abort won't do the trick, as USART_CR3_DMAR was cleared, making the program assume that DMA was properly reset.

 

I also use an STM32F0, which in my understanding has a slightly different HAL lib. In my STM32F0 project i couldn't find HAL_DMA_STATE_HALF_READY. It seems to me like that state was removed from some part of the HAL universe, but surely it was not done properly.

 

I hope this error gets fixed, either by eliminating HAL_DMA_STATE_HALF_READY or allowing HAL_DMA_Abort_IT to abort with state = HAL_DMA_STATE_HALF_READY.

Also i think it problematic to rely on USART_CR3_DMAR only to check if any DMA changes are needed, though there are many other variables that need to be changed to make the HAL lib work..

 

Maybe Erwan LE SAINT or any member of the HAL development team can help here?

 

Thanks,

 

Till

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