A simple example in BBC Basic to:

open UART port

send/receive UART data

close UART port

Run the basic program. Typing keys will send that ascii out the serial uart. Hit SPACE to chage to receive data mode. Hit S to go to send data mode

Hit ENTER to exit

I am aware that this code is in no way optimised. It is just a working prototype.

In this example, I use the UART of Agon attached to a serial USB device plugged into my computer

Agon PC

Tx <-> Rx

Rx <-> Tx

Gnd <-> Gnd