One of the most useful debugging tools available to you is the serial terminal, which allows you to view live data from a VEX brain on your computer as your program runs.

print and println

The easiest way to send some data to the terminal is through the print family of macros. You might recall println from our “Hello World” example:

use vexide::prelude::*;#[vexide::main]async fn main(peripherals: Peripherals) {    println!("Hello World!");}

That will send Hello World! followed by a newline to your computer over a USB or bluetooth connection. This is useful in cases where you need to quickly view or debug a value on the brain, or send some logs over for future use.

We also have a print macro, which is the same as println except it won’t end your message in a newline.

{...}
use vexide::prelude::*;
#[vexide::main]async fn main(peripherals: Peripherals) {    print!("Hello");    print!("Hello");}

That will send the data HelloHello to your computer.

Reading the Terminal

That’s cool and all but… where am I supposed to be seeing all this?

Simply running all of this code with no connection to a computer won’t visibly do anything, so let’s change that.

Terminal data can be read over a USB connection to a V5 brain or controller using cargo-v5 (one of the prerequisites that you should already have installed). To open a terminal connection with the brain, we’ll simply run the following command:

cargo v5 terminal

When you run your program, you should be greeted by vexide’s startup banner along with the output of print/println.

Disabling the vexide Banner

In the video above, vexide printed a startup banner along with your Hello world! message. If you don’t want this banner to be printed, you can disable this in your program:

{...}
use vexide::prelude::*;
#[vexide::main(banner(enabled = false))]async fn main(_peripherals: Peripherals) {    println!("Look ma! No banners!");}

Advanced Logging Solutions

If you need a more advanced logging solution, crates in the rust ecosystem such as log may be of interest to you.