clamp-average v0.1.0

Limit each step, then smooth with a moving average.

Application scenarios

• A noisy actuator feedback can jump, but the physical value moves slowly.
• Battery voltage has load spikes and the gauge needs a smooth value.
• A remote setpoint changes quickly, but the local output must ramp.

Contract

void clamp_average_init(clamp_average_t *filter, uint16_t initial, uint16_t max_delta, uint16_t *window, uint8_t size);
uint16_t clamp_average_step(clamp_average_t *filter, uint16_t sample);

• max_delta caps the change from the previous clamped value.
• The clamped value enters a moving-average window.
• The caller owns window; size must be 1..255.
• No allocation.

Parameters

• max_delta: largest plausible change per sample.
• size: smoothing after the clamp; larger is smoother but slower.
• The clamp runs before the average, so a spike is both limited and diluted.

Memory and timing

• State is 20 bytes plus the caller's 2*size bytes.
• O(1) per sample.

Integration

uint16_t window[4];
clamp_average_t filter;
clamp_average_init(&filter, 0, 20, window, 4);
uint16_t value = clamp_average_step(&filter, adc_read());

When not to use

• A real step must pass immediately; the clamp delays it.
• Only one of the two behaviors is needed; use clamp or moving-average.

Verification

make test covers unclamped averaging, clamping, size 1, and size 0.

Behavior reference: Padauk Soft_Filter/AD_filter_06.

uint16_t value;
uint16_t max_delta;
uint16_t *window;
uint8_t size;
uint8_t count;
uint8_t index;
uint32_t sum;