Attotime

Ultra-compact C library for working with timings. Framework-agnostic and overflow-safe.

Setup

The library requires a clock source — a function that returns current time in milliseconds as uint32_t. Call atto_init once at startup:

#include <attotime.h>

// Arduino
void setup() {
    atto_init(millis);
}

// Or any custom clock
uint32_t my_clock(void) { /* ... */ }
atto_init(my_clock);

Usage

Timer

A simple countdown timer that reports whether a given interval has passed.

atto_timer_t timer = ATTO_TIMER_INIT;

void setup() {
    atto_init(millis);
    atto_timer_start(&timer, 1000);
}

void loop() {
    if (atto_timer_finished(&timer)) {
        // 1 second has passed
    }
}

Stopwatch

Measures how much time has passed since it was started.

atto_stopwatch_t sw = ATTO_STOPWATCH_INIT;

void setup() {
    atto_init(millis);
    atto_stopwatch_start(&sw);
}

void loop() {
    uint32_t elapsed = atto_stopwatch_split(&sw);
}

Progress

Reports the completion of a time interval as a uint8_t value (0–255 by default). Convenient for programming animations.

atto_progress_t progress = ATTO_PROGRESS_INIT;

void setup() {
    atto_init(millis);
    // Ramp from 0 to 255 over 2 seconds
    atto_progress_start(&progress, 2000);
}

void loop() {
    uint8_t brightness = atto_progress_get(&progress);
    // use brightness to drive LEDs, etc.
}

Overflow safety

All time comparisons use elapsed-time arithmetic (now - start >= duration) which handles uint32_t wrap-around correctly. Timers, stopwatches and progress instances keep working across the ~49.7-day millis() overflow boundary.

Development

Available Makefile targets:

• test — Run the unit tests (native).
• format — Format C source code.