UART DMA error - What is the proper way to restart the DMA?

[TSosi.1]

Hi,

I am injecting a UART DMA error by using DTCM memory and DMA2. For example:

// Induce a DMA error by using DTCM RAM for DMA2 which is inaccessible
if ( HAL_UART_Transmit_DMA( huart, transmit_buffer_dtcm_memory, num_bytes_to_transmit ) != HAL_OK )

{

// Log error

}

What happens is the frame error, parity error, and noise error interrupts are disabled after the DMA error on transmit. This I can see by the EIE bit in CR3.  HAL function UART_EndRxTransfer is called and clears EIE.

I have a streams connected to the TX and RX lines:

TX is connected to DMA2 Stream 5 - High priorty

RX is connected to DMA2 Stream 4 - High priority

When I try to restart the UART receiving:

if ( HAL_UART_Receive_DMA( uart_handle, receive_buffer, RX_BUF_SIZE ) != HAL_OK )
{
// Log error
}

There is a check in sub function HAL_DMA_Start_IT that returns an error because the DMA stream is busy.

So what is the correct way to recover/restart after a DMA and set the interrupt flags for frame, noise, and parity?\

Thanks!

[TDK · Accepted solution]

Did you call HAL_UART_Abort? That should set the state machine ready again.

[Karl Yamashita]

If HAL status returns HAL_BUSY, then you wait a little bit and try again.

Other functions to call for status or errors, HAL_UART_GetState, HAL_UART_GetError, 

[TSosi.1]

No, but I was looking at that function. It was a long day debugging the issue and was frustrated.  I'll try it.

[TSosi.1]

I tried.  The DMA stays busy. 

HAL_UART_GetError doesn't seem to return DMA error in all cases.  I noticed with a different UART that when the DMA error occurred, transfer complete was called and ErrorCode member of the UART handle was zero.

[TSosi.1]

Calling HAL_UART_Abort enables the frame, parity and noise error interrupts. Thank you!