I need to gat digital data on the "RX" and "read" it every 3 sec,
Why? It should read continuously, shouldn't it?
I need to send a 5V to an external buzzer from leg "TX"
Do you want to use RX and TX for serial communication or for the buzzer? Both is the wrong answer. So is yes.
Hope you can answer me fast.
Of course. But, probably not the answers you wanted.