rppal async interrupt test (slightly modified from: https://users.rust-lang.org/t/good-gpio-crate-for-raspberry-pi-with-example-reading-code/104744/7)

main.rs

use std::error::Error;
use std::io;

use rppal::gpio::{Gpio, Trigger}; // 0.16.1

pub const BTN1: u8 = 13;
pub const BTN2: u8 = 4;

fn main() -> Result<(), Box<dyn Error>> {
    let mut btns = [
        Gpio::new()?.get(BTN1)?.into_input_pullup(),
        Gpio::new()?.get(BTN2)?.into_input_pullup(),
    ];
    for (i, btn) in btns.iter_mut().enumerate() {
        btn.set_reset_on_drop(false);
        btn.set_async_interrupt(Trigger::Both, move |lvl| eprintln!("btn {i} is now {lvl}"))?;
    }

    eprintln!("Play with the buttons, and hit Enter when done to terminate.");
    let mut s = String::new();
    io::stdin().read_line(&mut s)?;

    Ok(())
}