Is it possible to combine USART2 Rx in autonomous DMA mode with IDLE mode?

[ledi7]

Hi,

i am using STM32WBA55CG and i want:

1. wake-up from STOP mode to receive bytes over USART2 Rx 

2. Handle data with half-complete and complete callback

3. Use the IDLE interrupt to detect the end of transmission

Each works perfectly on its own. However, when I try to combine both variants, the CPU hangs.

Since I cannot expect a specific byte length (1 byte could also be transferred as 100kB), I would like to process the data via a 1kB ring buffer. I can use half complete and complete callback for this. To recognize the end of the data transfer, I want to use the IDLE interrupt.

[TDK]

> Is it possible to combine USART2 Rx in autonomous DMA mode with IDLE mode?

Yes. The HAL_UARTEx_ReceiveToIdle with DMA in circular mode should do this.

> CPU hangs.

Debug, diagnose and fix.

[ledi7]

I tried different variants, but could not use the DMA in autonomous mode together with IDLE mode.

 

HAL_UART_Receive_DMA(&huart2, dma_rx_buffer, 1024); // start UART2 Rx DMA
__HAL_UART_ENABLE_IT(&huart2, UART_IT_IDLE); //enable IDLE Interrupt

 As shown in the graphic, I want to receive data of unknown length in the dma_rx_buffer. The buffer has a size of 1024 bytes and I start with HAL_UART_Receive_DMA.

After half of the data has been received, the CPU wakes up with a half complete callback. When 1024 bytes have been received, the complete callback is triggered and the DMA buffer is overwritten with the next byte at position [0]. If the data transfer is terminated after a total of 1124 bytes, the IDLE interrupt should be triggered here.

I start in UART Receive DMA mode and enable the IDLE interrupt, but the CPU hangs as soon i insert __HAL_UART_ENABLE_IT(&huart2, UART_IT_IDLE); function.

 

[TDK]

If you want to use HAL, you need to adhere to its rules for usage. Use HAL_UARTEx_ReceiveToIdle to receive data with an idle indicator. HAL_UART_Receive_DMA will not get you there.

[Pavel A.]

Please see these examples: https://github.com/MaJerle/stm32-usart-uart-dma-rx-tx