status-led

no_std monochrome status LED abstraction for the embassy ecosystem.

• Polarity — ActiveHigh / ActiveLow chosen at construction time via [PolarityMode].
• Reads hardware directly — no internal state cache; is_on() reads the ODR register and applies polarity conversion.
• Optional PWM — CIE L* perceptual brightness via PwmLed with a compact 32-byte lookup table + shift-add interpolation (zero multiply/divide). Supports 8-bit (0–255) and 12-bit (0–4095, via arbitrary_int::u12) brightness resolution.
• Optional breathing — Sinusoidal brightness animation via Breath (CORDIC algorithm — zero float/mul/large tables) and BreathLed wrapper, also respecting the selected brightness bit-depth.
• Zero mandatory dependencies — only embedded-hal 1.0.

Usage

use embassy_stm32::gpio::{Output, Level, Speed};
use status_led::{Led, PolarityMode};

let pin = Output::new(p.PA5, Level::High, Speed::Low);
let mut led = Led::from_pin(pin, PolarityMode::ActiveLow);

led.on().unwrap();
led.off().unwrap();

PWM with gamma correction

Enable the pwm feature:

status-led = { version = "0.7", features = ["pwm"] }

use status_led::pwm::{GammaCorrection, PwmLed};
use status_led::PolarityMode;

let mut led = PwmLed::new(ch, GammaCorrection::CieLStar, PolarityMode::ActiveLow).unwrap();
led.set_brightness(128).unwrap(); // ~50% perceived brightness

Breathing effect

Enable the breath feature:

status-led = { version = "0.7", features = ["breath"] }

Breath generates a stream of brightness values following a sinusoidal pattern — 0–255 by default, or 0–4095 with the brightness-12bit feature. Combine with BreathLed for a ready-to-use PWM LED wrapper:

use status_led::breath::{Breath, BreathLed};
use status_led::pwm::GammaCorrection;
use status_led::PolarityMode;

// Manual breath loop with Breath
let mut breath = Breath::new(Duration::from_millis(12_800), Duration::from_millis(50));
loop {
    led.set_brightness(breath.next()).unwrap();
    Timer::after_millis(50).await;
}

// Or use BreathLed for a single-call wrapper
let mut led = BreathLed::new(
    ch,
    GammaCorrection::CieLStar,
    PolarityMode::ActiveLow,
    Duration::from_millis(12_800),
    Duration::from_millis(50),
).unwrap();

loop {
    led.breathe().await.unwrap();
}

breathe() combines the brightness update with the sleep — no separate Timer call needed.

12-bit brightness

Enable the brightness-12bit feature for finer brightness control:

status-led = { version = "0.7", features = ["breath", "brightness-12bit"] }

This switches the brightness type from u8 (0–255) to arbitrary_int::u12 (0–4095), giving 16× finer resolution. The CIE L* gamma tables (still only 32 bytes) are reused with two-level interpolation — no extra flash cost.

use status_led::pwm::{GammaCorrection, PwmLed};
use status_led::PolarityMode;

let mut led = PwmLed::new(ch, GammaCorrection::CieLStar, PolarityMode::ActiveLow).unwrap();
led.set_brightness(2048.try_into().unwrap()).unwrap(); // ~50% perceived brightness

The u12 type guarantees values are always in the 0–4095 range at compile time — out-of-range values panic immediately.

Runtime polarity

When the polarity is read from configuration at runtime:

use status_led::{Led, PolarityMode};

let pol = if config.active_low {
    PolarityMode::ActiveLow
} else {
    PolarityMode::ActiveHigh
};
let mut led = Led::new(pin, pol).unwrap();
led.toggle().unwrap();

Features

License

Licensed under either of Apache License 2.0 or MIT license at your option.