UART DMA TX occasional errors

[Werner Dähn]

Once a while my Error_Callback() of the UART DMA RX/TX is triggered and I can't make sense out of it.

In the HAL_UART_ErrorCallback the values are

HAL_UART_GetState(huart) == 32 //  HAL_UART_STATE_BUSY_RX
HAL_UART_GetError(huart) == 16 // HAL_UART_ERROR_DMA 
huart->hdmarx->ErrorCode == 0 // NONE 
huart->hdmatx->ErrorCode == 2 // HAL_DMA_ERROR_FE means fifo error

Okay, so it is a FIFO error. I am not using FIFO. Any ideas?

        hdma_usart2_tx.Instance = DMA1_Stream6;
        hdma_usart2_tx.Init.Channel = DMA_CHANNEL_4;
        hdma_usart2_tx.Init.Direction = DMA_MEMORY_TO_PERIPH;
        hdma_usart2_tx.Init.PeriphInc = DMA_PINC_DISABLE;
        hdma_usart2_tx.Init.MemInc = DMA_MINC_ENABLE;
        hdma_usart2_tx.Init.PeriphDataAlignment = DMA_PDATAALIGN_BYTE;
        hdma_usart2_tx.Init.MemDataAlignment = DMA_MDATAALIGN_BYTE;
        hdma_usart2_tx.Init.Mode = DMA_NORMAL;
        hdma_usart2_tx.Init.Priority = DMA_PRIORITY_VERY_HIGH;
        hdma_usart2_tx.Init.FIFOMode = DMA_FIFOMODE_DISABLE;
        hdma_usart2_tx.Init.FIFOThreshold = DMA_FIFO_THRESHOLD_FULL;
        hdma_usart2_tx.Init.MemBurst = DMA_MBURST_INC4;
        hdma_usart2_tx.Init.PeriphBurst = DMA_PBURST_INC4;
        if (HAL_DMA_Init(&hdma_usart2_tx) != HAL_OK)
        {
          _Error_Handler(__FILE__, __LINE__);
        }
 
        __HAL_LINKDMA(huart, hdmatx, hdma_usart2_tx);

 Also I make sure that I do not call a transmit as long as the HAL_UART_TxCpltCallback() was not called and all transmits are in the main loop, not within an interrupt or callback.

[waclawek.jan]

This is a recurring question for years.

For explanation, see AN4031, chapter 4.3 Software sequence to enable DMA.

Simply ignore the error - if FIFO is not enabled, it's benign. The real solution is not to enable the FIFO error interrupt when DMA is in Direct mode; but that's probably on Cube's authors.

I don't Cube/CubeMX.

JW

[Werner Dähn]

Okay. Is there any side effect when using DMA on four UARTs (2 RX+TX, 1 TX and 1 RX)? I have the feeling that I experience packet loss when these errors happen. At least I cannot get some parts working, currently trying to figure out if the problem is my code or the interaction with the remote device.

I expect DMA for UARTs, especially if the use 38400 and 115200 baud is essentially side effect free. Correct or wrong?

[Tesla DeLorean]

Race conditions

Reentrant behaviour

Failures in exit paths, and response to error conditions

[Werner Dähn]

:face_screaming_in_fear:

I hate micro controllers. ;)