USART in interrupt mode

[PNaph.2]

Hi, I want to use USART in interrupt mode in stm32f429 evaluation board.

I saw the demo example UART_Hyperterminal_IT, but I didn't understood why they are calling HAL_UART_Receive_IT() function if we are using USART in interrupt mode not in polling mode ?

Calling this function, look like we are polling for coming message on USART.

Please correct me if I am wrong ?

And please tell how can I use USART in interrupt mode?

Thanks

Pratik

[waclawek.jan]

The Cube/HAL functions are relatively inflexible, as they expect a fixed number of data to arrive. Especially if you are experienced with programming on other mcus, you may be better off avoiding them and using direct register access.

JW

[KnarfB]

No, HAL_UART_Receive_IT is just preparing the receive and non-blocking. Once the buffer is filled, the HAL_UART_RxCpltCallback will be called which you have to implement. A typical implementation will call HAL_UART_Receive_IT inside to enable further eceives. Like

char ch;
 
void main()
{
	...
	HAL_UART_Receive_IT(&huart1, &ch, 1); // kick-off receive
	...
}
 
void HAL_UART_RxCpltCallback(UART_HandleTypeDef *huart)
{
	if(huart == &huart1) {
		// process the byte received
		HAL_UART_Receive_IT(&huart1, &ch, 1); // kick-off next receive
	}
}

The easiest use is with single char buffers unless you know the expected packet size precisely. Even then, you have to care about errors. See Tilen Majele's code http://stm32f4-discovery.net/2017/07/stm32-tutorial-efficiently-receive-uart-data-using-dma/