ndless-async

Ndless-specific integration with async/await for the TI-Nspire

This crate provides an executor, reactor, and utilities to use Rust's async capabilities with the TI Nspire's timer and keypad. Note that normally async functions are used for I/O. However, as far as I'm aware, the TI-Nspire's OS has no support for asynchronous I/O of any sort. However, this still provides helpful utilities for doing multiple things at once, such as waiting for a key with a timeout.

You'll first need to create an instance of AsyncListeners with AsyncListeners::default(). This allows you to receive events from the Nspire's timer. From there, you can pass it into task::block_on, along with a Future of your choice.

Helpful resources

Check out the Rust Async Book. This has useful instructions about asynchronous programming. Although it is mostly written for usage with a full operating system, everything applies here except chapters 1.4, 6.3, 8, and 10.

futures_util has many useful utility functions. Add it to your project by adding the following to your Cargo.toml:

futures-util = { version = "0.3.5", default-features = false, features = ["alloc", "async-await-macro"] }

You may find its FuturesUnordered to be of help for scheduling multiple tasks. Although macros like join and first can be helpful, they aren't as efficient and flexible as it.

The macros join, select, try_join, and traits FutureExt & StreamExt are re-exported from it, so if that's all you need, you don't need to depend on it directly.

Example

use futures_util::future;
use ndless_async::task::{block_on, AsyncListeners};
use ndless_async::{first, StreamExt};
use ndless_async::keypad::KeypadListener;
use ndless::input::Key;

fn main() {
    let listeners = AsyncListeners::new();
    let keypad = KeypadListener::new(&listeners.timer());
    block_on(&listeners, async {
        let _ = listeners.timer().timeout_ms(5000, do_stuff(&keypad)).await;
        listeners.timer().sleep_ms(2000).await;
        first!(do_other_stuff(&listeners), wait_for_esc(&keypad));
    });
}

async fn wait_for_esc(keypad: &KeypadListener<'_>) {
    keypad
        .stream()
        .filter(|key| future::ready(key.key == Key::Esc))
        .next()
        .await;
}

async fn do_other_stuff(listeners: &AsyncListeners) {
    loop {
        listeners.timer().sleep_ms(1000).await;
        println!("1s!");
    }
}

async fn do_stuff(listeners: &KeypadListener<'_>) {
    use ndless_async::keypad::KeyState::*;
    let mut keypad = listeners.stream();
    while let Some(event) = keypad.next().await {
        println!(
            "Key {:?} was {}",
            event.key,
            if event.state == Released {
                "released"
            } else {
                "pressed"
            }
        );
        print!("Keys currently pressed: ");
        listeners
            .list_keys()
            .iter()
            .for_each(|key| print!("{:?} ", key));
        println!();
        if event.key == Key::Esc { break; }
    }
}

Check out ndless in addition to this crate.