usart.c

I want to use the DMA for receiving data over USART. I have configured the DMA as a circular Buffer. To detect the end of the USART package I use the receiver time out.

My Problem is, that when the receiver time out interrupt is triggered, not all Bytes are copied from the USART to the DMA Buffer. A few random Bytes remain the same as before. I know, that the DMA still increment the address, because I send an image and the rest of the image is not shifted.

Does anybody know what problem this could be?

I use a STM32f MCU and I have generated the basic DMA and USART configuration with the CubeMX software.

My interrupt handler

void USART3_IRQHandler(void)
{
 /* USER CODE BEGIN USART3_IRQn 0 */
	/* check for receive timeout interrupt */
	if( huart3.Instance->ISR & USART_ISR_RTOF ) {
		/* clear interrupt */
		__HAL_UART_CLEAR_FLAG(&huart3, USART_ICR_RTOCF);
		ToF_Rx_Timeout_Callback( );
	}
 /* USER CODE END USART3_IRQn 0 */
 HAL_UART_IRQHandler(&huart3);
}

/* UART rx callback */
void ToF_Rx_Timeout_Callback( void ) {
	static size_t old_pos;
	size_t pos;
	BaseType_t xHigherPriorityTaskWoken = pdFALSE; /* Initialised to pdFALSE. */
	pos = sizeof(ucDmaRxBuffer) - huart3.hdmarx->Instance->NDTR;
	if(pos != old_pos)
	{
		if(pos > old_pos)
		{
			uint16_t xBytesSent = xMessageBufferSendFromISR( 	xRxMessageBuffer,(void*) &ucDmaRxBuffer[old_pos],	pos-old_pos, &xHigherPriorityTaskWoken );
		}
		else
		{
			memcpy(&ucMsgRxTemp[0],&ucDmaRxBuffer[old_pos],sizeof(ucDmaRxBuffer)-old_pos);
			memcpy(&ucMsgRxTemp[sizeof(ucDmaRxBuffer)-old_pos],&ucDmaRxBuffer[0],pos);
			uint16_t xBytesSent = xMessageBufferSendFromISR( 	xRxMessageBuffer,(void*) ucMsgRxTemp, pos+sizeof(ucDmaRxBuffer)-old_pos, &xHigherPriorityTaskWoken );
		}
	}
	old_pos = pos;
	if(old_pos == sizeof(ucDmaRxBuffer))
	{
		old_pos = 0;
	}
	/* switch context if higher priority task is waiting on data */
	portYIELD_FROM_ISR( xHigherPriorityTaskWoken );	
}

Attached is the USART initialization.