> Example : I work with interrupt where i put this declaration
> HAL_UART_Receive_IT(&huart1, rx, 4);
I would suggest to check the implementation of this function, and see what it does.
I don't use Cube/HAL, for good reasons.
Besides of others, the handling of interrupts is obscure and overinflated for almost all purposes.
> In the end where i can find information about UART and register i need the check and clear ?
The first source would be the reference manual of the MCU, i.e. the UART/USART section.
Polling is the least recommendable method, wasting performance and prone to overflow errors.
DMA is fine for sending, but tricky for reception, especially when your protocol consists of periodical "burst" transmissions of unknown length.
And it complicates error handling. Especially with external devices, receive errors are not so rare.
Your code must be able to deal with receive errors, and be able to re-synchronize.
I used to go with interrupt handling for reception.
You usually want to enable the RXNE and error interrupts.
In the handler, you retrieve the received character, and do basic protocol checks (buffer handling, buffer size check, termination character etc.)
Check for error interrupt conditions as well (and clear them), or else reception will be blocked.
I used to pass complete messages from the handler to the main loop - whatever that is in the context of your protocol.
