HAL_UART_Transmit_DMA() trigger reset

[QE-Nicholas]

Hi guys, I was trying to implement HAL_UART_Transmit_DMA() since I am using freeRTOS. It auto trigger a reset for my stm32f427.

Tried HAL_UART_Transmit(), everything works well. Only HAL_UART_Transmit_DMA() causing the reset, Did I missed anything?

			  for (uint8_t j=1; j!=CPH_MAX_N_PORTS; ++j)													// can change to +1 after disabling drone troubleshoot port
			  {
				  if(byte_1 == j)
				  {
						if ((ports_handle[j-1])->hdmatx == NULL)
						{
						  USER_LOG_ERROR("TX DMA not linked for UART!");
						}
						HAL_UART_DMAStop(ports_handle[j-1]);  												// Stop RX DMA before TX
					    ports_handle[j-1]->gState = HAL_UART_STATE_READY;
					    __HAL_DMA_ENABLE_IT(ports_handle[j-1]->hdmatx, DMA_IT_TC);  						// TX Complete Interrupt
					    __HAL_DMA_ENABLE_IT(ports_handle[j-1]->hdmatx, DMA_IT_TE);  						// TX Error Interrupt
					    if (ports_handle[j-1]->hdmatx == NULL) {
					        USER_LOG_ERROR("TX DMA not linked for UART!");
					    }

					    if (ports_handle[j-1]->gState != HAL_UART_STATE_READY) {
					        USER_LOG_ERROR("UART TX is busy (State: %d)", ports_handle[j-1]->gState);
					    }

					    if (!(ports_handle[j-1]->hdmatx->Instance->CR & DMA_SxCR_TCIE)) {
					        USER_LOG_WARN("TX DMA Interrupts not enabled! Enabling now...");
					        __HAL_DMA_ENABLE_IT(ports_handle[j-1]->hdmatx, DMA_IT_TC);
					        __HAL_DMA_ENABLE_IT(ports_handle[j-1]->hdmatx, DMA_IT_TE);
					    }
					    USER_LOG_INFO("UART TX State: %d", HAL_UART_GetState(ports_handle[j-1]));
						if (HAL_UART_GetState(ports_handle[j-1]) == HAL_UART_STATE_READY)
						{
							  if(HAL_UART_Transmit(ports_handle[j-1], USB_recv_buf+cur_msg_pos+MSD_HEADER, totalBufLen-MSD_HEADER,10) != HAL_OK) // forward the buffer
							  {
								  USER_LOG_ERROR("UART transmission failed for port %d!", j); 				
							  }
						}
						else
						{
							USER_LOG_ERROR("UART transmission busy for port %d!", j);
							USER_LOG_ERROR("UART state -> %d!", HAL_UART_GetState(ports_handle[j-1]));
						}
						HAL_UARTEx_ReceiveToIdle_DMA(ports_handle[j-1], DMARxBuf[j], BUFFER_SIZE);			// restart the DMA
						__HAL_DMA_DISABLE_IT(DMAs_handle[j-1],DMA_IT_HT);									// disable the interrupt as we don’t need the Half Transfer interrupt
						valid_port_found = true;
						break;
				  }
			  }

* none of the error log was triggered. Initially, I tried without the non-essential code as below and I got the state value of 0x22 which is HAL_UART_STATE_BUSY_RX and that is why I am adding those extra lines of code.

						if (HAL_UART_GetState(ports_handle[j-1]) == HAL_UART_STATE_READY)
						{
							  if(HAL_UART_Transmit(ports_handle[j-1], USB_recv_buf+cur_msg_pos+MSD_HEADER, totalBufLen-MSD_HEADER,10) != HAL_OK) // forward the buffer
							  {
								  USER_LOG_ERROR("UART transmission failed for port %d!", j); 				
							  }
						}
						else
						{
							USER_LOG_ERROR("UART transmission busy for port %d!", j);
							USER_LOG_ERROR("UART state -> %d!", HAL_UART_GetState(ports_handle[j-1]));
						}

From my perspective, DMA for RX works fine, which I do receive what I want. Only calling the following will cause the HAL_UART_Transmit_DMA() reset:

HAL_UART_DMAStop(ports_handle[j-1]); 

The line of code when calling HAL_UART_Transmit_DMA:

if(HAL_UART_Transmit_DMA(ports_handle[j-1], USB_recv_buf+cur_msg_pos+MSD_HEADER, totalBufLen-MSD_HEADER) != HAL_OK)

OR should I ask what is the correct way to do this if we detect HAL_UART_STATE_BUSY_RX.

[Saket_Om]

Hello @QE-Nicholas 

>> Hi guys, I was trying to implement HAL_UART_Transmit_DMA() since I am using freeRTOS. It auto trigger a reset for my stm32f427.

1. What do you mean by "reset"? Is it a system reset?
2. Did you try to run the UART transfer without FreeRTOS, please?

>> OR should I ask what is the correct way to do this if we detect HAL_UART_STATE_BUSY_RX.

1. You should investigate if the bus is really busy (A transfer is ongoing).
2. Also, you need to be sure that the process before calling HAL_UART_Transmit_DMA is done correctly and the state is reset to ready.

[Karl Yamashita]

Did you enable the DMA for Transmit? I know I've forgotten to enable it for transmit. Though I vaguely remember it hard faulting, not resetting the STM32.  

[QE-Nicholas · Accepted solution]

Thanks everyone for the help, I think I have found the issue>

HAL_UART_Transmit_DMA(ports_handle[j-1], USB_recv_buf+cur_msg_pos+MSD_HEADER, totalBufLen-MSD_HEADER)

is reading on the buffer and I am continuing parsing the buffer in the loop.

My hypothesis, 
since it is not a blocking function, and the cur_msg_pos is continuously incrementing while I parsing the message, the system might read random memory causing overflow and reset.

Solution:
Make a copy for everything AND place a flag within HAL_UART_TxCpltCallback()
Then check for the flag before sending stuff.