Crate ph_curves 

no_std, zero-allocation curve lookup tables and tickless scheduling for embedded Rust.

ph-curves stores pre-computed forward (and optionally inverse) lookup tables as static arrays so that curve evaluation reduces to a single array index. Combined with the tickless scheduler, interrupt-driven firmware can sleep between value transitions instead of polling at a fixed tick rate.

Quick start

Use the companion CLI (ph-curves-gen) to generate static LUTs from a TOML definition file, then include! the output in your crate:

use ph_curves::{Curve, MonotonicCurve, Tickless, Rounding};

include!("curves.rs");

// Forward evaluation — a single table lookup.
let brightness: u8 = GAMMA_22.eval(input);

// Inverse lookup (monotonic curves only).
let input: u8 = GAMMA_22.inv(brightness);

// Tickless scheduling — sleep until the next quantized value change.
let schedule = EASE_IN_QUAD.tickless_schedule(
    0,     // t0_ms
    1000,  // duration_ms
    0,     // start_val
    255,   // end_val
    10,    // step (quantization)
    Rounding::Nearest,
    0,     // min_dt_ms
);

for deadline in schedule.iter(0) {
    set_timer(deadline.deadline_ms);
    set_output(deadline.current_val);
}

Key types

Everything is re-exported at the crate root.

• Curves — Curve / MonotonicCurve traits and the LUT-backed CurveLut / MonotonicCurveLut types.
• Tickless scheduling — Tickless extension trait, TicklessSchedule, and the TicklessIter iterator.
• Math helpers — UnitValue trait, lerp_u8, lerp_u16, map_u8_to_u16, quantize, and next_target_value.

Structs

CurveLut

A curve backed by an N-entry forward and optional M-entry inverse LUT.

MonotonicCurveLut

A monotonic curve backed by an N-entry forward and M-entry inverse LUT.

TicklessDeadline

A single output produced by the tickless scheduler.

TicklessIter

Iterator over successive TicklessDeadline values produced by a TicklessSchedule.

TicklessSchedule

A tickless schedule bound to a monotonic curve and segment parameters.

Enums

RepeatMode

Repeat behaviour for a tickless schedule.

Rounding

Rounding policy used by quantize and the tickless scheduler.

Traits

Curve

Curve evaluation trait.

MonotonicCurve

Trait for monotonic curves that can be inverted.

Tickless

Extension trait that adds tickless scheduling to any MonotonicCurve<T, T> where T: UnitValue.

UnitValue

A normalized value type usable as a curve domain / range.

Functions

lerp_u8

Linearly interpolate between a and b with a u8 blend weight.

lerp_u16

Linearly interpolate between two u16 values with a u8 blend weight.

map_u8_to_u16

Scale a normalized u8 value (0..=255) into a u16 range 0..=max.

next_target_value

Return the next quantized target value one step closer to end.

quantize

Snap value to the nearest multiple of step according to rounding.

Type Aliases

CurveLut256

A 256-entry curve lookup table (u8 domain and range).

CurveLut65536

A 65536-entry curve lookup table (u16 domain and range).

MonotonicCurveLut256

A 256-entry monotonic curve lookup table (u8 domain and range).

MonotonicCurveLut65536

A 65536-entry monotonic curve lookup table (u16 domain and range).