clamp v0.1.0

Limit how far one output step may move from the previous output.

Application scenarios

• An ADC channel jumps because of a bad sample, but the physical signal is continuous.
• A UI or protocol sets a target, and the actuator must move at a bounded rate.
• A sensor is removed or reconnected and the first sample is far from the last good value.

Contract

void clamp_filter_init(clamp_filter_t *filter, int32_t initial, uint16_t max_delta);
int32_t clamp_filter_step(clamp_filter_t *filter, int32_t sample);
void clamp_filter_reset(clamp_filter_t *filter, int32_t value);

• max_delta is the largest allowed change per step.
• A larger delta is clamped, not rejected.
• State is one int32_t plus the limit; no allocation.

Parameters

• initial: the last known good value.
• max_delta: the largest physically plausible change in one sample period.
• Too small: a real step is delayed. Too large: spikes pass.

Memory and timing

• 8 bytes of state; O(1) per sample.

Integration

clamp_filter_t filter;
clamp_filter_init(&filter, 0, 10);
int32_t value = clamp_filter_step(&filter, adc_read());

When not to use

• A real step must pass immediately.
• Impulses must be removed: use median or trimmed-mean.
• The signal needs smoothing: combine with moving-average or ema.

Verification

make test covers steps, saturation, reset, zero delta, and negative values.

Behavior reference: Padauk Soft_Filter/AD_filter_01; this implementation is original.

int32_t value;
uint16_t max_delta;