GPIO

micro/gpio provides digital I/O pin control.

use micro/gpio
use std/time

fn main() -> never {
    let mut led = gpio.pin(25).into_output()
    defer led.low()

    loop {
        led.high()
        time.sleep_ms(250)
        led.low()
        time.sleep_ms(250)
    }
}

Getting a Pin

let pin = gpio.pin(25)      // get pin handle by number

Configuring Direction

let mut out = gpio.pin(25).into_output()     // digital output
let inp = gpio.pin(14).into_input()          // digital input (floating)
let inp = gpio.pin(14).into_input_pullup()   // input with pull-up
let inp = gpio.pin(14).into_input_pulldown() // input with pull-down

Output Operations

led.high()       // drive high
led.low()        // drive low
led.toggle()     // flip current state

These are infallible. GPIO state changes always succeed once the pin is configured.

Input Operations

let state = button.read()    // true = high, false = low

if button.read() {
    handle_press()
}

Common Patterns

LED toggle with defer for safe cleanup:

let mut led = gpio.pin(25).into_output()
defer led.low()    // ensure LED off on any exit

loop {
    led.toggle()
    time.sleep_ms(500)
}

Button polling:

use micro/gpio
use std/time

fn main() -> never {
    let mut led = gpio.pin(25).into_output()
    let button = gpio.pin(14).into_input_pullup()

    loop {
        if not button.read() {    // active low (pulled up)
            led.high()
        } else {
            led.low()
        }
        time.sleep_ms(10)
    }
}

Board package pin names:

When using a board package, you can use named pins instead of numbers:

use board/pico
use micro/gpio

fn main() -> never {
    let mut led = gpio.pin(pico.pin.led).into_output()
    loop {
        led.toggle()
        time.sleep_ms(1000)
    }
}

Do and Don’t

// Do: use defer to ensure cleanup
let mut pin = gpio.pin(25).into_output()
defer pin.low()

// Do: call toggle() instead of tracking state manually
led.toggle()

// Avoid: reading pin state immediately after write without delay
// (hardware may need settling time depending on load)

// Avoid: configuring direction multiple times; configure once at startup