Our first task will be to send a single byte from the microcontroller to the computer over the serial connection.

This time, I'm going to provide you with an already initialized USART peripheral. You'll only have to work with the registers that are in charge of sending and receiving data.

Go into the 11-usart directory and let's run the starter code therein. Make sure that you have minicom/PuTTY open.

#![deny(unsafe_code)]
#![no_main]
#![no_std]

#[allow(unused_imports)]
use aux11::{entry, iprint, iprintln};

#[entry]
fn main() -> ! {
    let (usart1, mono_timer, itm) = aux11::init();

    // Send a single character
    usart1.tdr.write(|w| w.tdr().bits(u16::from(b'X')));

    loop {}
}

This program writes to the TDR register. This causes the USART peripheral to send one byte of information through the serial interface.

On the receiving end, your computer, you should see show the character X appear on minicom/PuTTY's terminal.