Can't find LL function to clear USART_ISR_RXNE_RXFNE

[yuanyuan]

Dear Mr. or Ms.

When I tried to clear IT flag of USART_ISR_RXNE_RXFNE, I can't find any fuction to do it.

In stm32g4xxx_ll_usart.h, I can find fuction named LL_USART_IsActiveFlag_RXNE_RXFNE() but there's no function like LL_USART_ClearFlag_RXNE_RXFNE() .

Do I need to clear corresponding IT flag ? Or it would be cleared automatically?

Thanks and Wishes

[Sarra.S]

Hello @yuanyuan, welcome to ST Community, 

According to RM: "RXFNE is cleared when the RXFIFO is empty. The RXFNE flag can also be cleared by writing 1 to the RXFRQ in the USART_RQR register"

So by writing 1 to USART_RQR_RXFRQ, you can clear the flag. 

You can use SET_BIT(USARTx->RQR, (uint16_t)USART_RQR_RXFRQ) in stm32g4xxx_ll_usart.h.

Hope that helps!

[yuanyuan]

Thank you for your prompt reply.

[TDK]

Typically, RXNE is cleared by reading the data in the FIFO.

[yuanyuan]

that's good design.

your kind reply helped me on my confusion.

thanks

[Pavel A.]

LL_USART_ReceiveData8 or LL_USART_ReceiveData9

To discard received data: LL_USART_RequestRxDataFlush

 

[yuanyuan]

thank you for your kind reply.