gate.hpp

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// sbl/components/cv/gate.hpp — Gate input with Schmitt trigger hysteresis
//
// GateInput takes raw ADC values (uint16_t) and applies a Schmitt trigger
// threshold to produce a clean digital gate signal. Hysteresis prevents
// chatter near the threshold. One-shot edge detection for triggers.
//
// Usage:
//   sbl::components::cv::GateInput gate;
//   gate.update(adc_value);           // Feed raw ADC each tick
//   if (gate.rising()) { ... }        // One-shot rising edge (auto-resets)
//   if (gate.gate()) { ... }          // Current state
 
#pragma once
 
#include <cstdint>
 
namespace sbl::components::cv {
 
struct GateConfig {
    uint16_t threshold_high = 40000;  ///< ADC value to trigger gate ON (~2V for 3.3V/16-bit)
    uint16_t threshold_low  = 20000;  ///< ADC value to trigger gate OFF (hysteresis band)
};
 
/**
 * @brief Gate input with Schmitt trigger hysteresis and edge detection
 *
 * @note All public methods are ISR-safe — pure state machine with no hardware I/O.
 */
class GateInput {
public:
    explicit GateInput(const GateConfig& config = {})
        : thresh_high_(config.threshold_high),
          thresh_low_(config.threshold_low),
          state_(false), rising_(false), falling_(false) {}
 
    /**
     * @brief Feed a new raw ADC sample
     *
     * Schmitt trigger: gate turns ON when value >= threshold_high,
     * turns OFF when value < threshold_low. The hysteresis band
     * between the two thresholds prevents chatter.
     */
    void update(uint16_t raw) {
        bool was = state_;
 
        if (!state_ && raw >= thresh_high_) {
            state_ = true;
        } else if (state_ && raw < thresh_low_) {
            state_ = false;
        }
 
        if (state_ && !was) {
            rising_ = true;
        } else if (!state_ && was) {
            falling_ = true;
        }
    }
 
    /** @brief Current gate state (true = high) */
    bool gate() const { return state_; }
 
    /**
     * @brief True if gate just went high (rising edge)
     *
     * Consuming read — resets after first read. Call once per update cycle.
     */
    bool rising() {
        bool e = rising_;
        rising_ = false;
        return e;
    }
 
    /**
     * @brief True if gate just went low (falling edge)
     *
     * Consuming read — resets after first read. Call once per update cycle.
     */
    bool falling() {
        bool e = falling_;
        falling_ = false;
        return e;
    }
 
    /** @brief Reset all state */
    void reset() {
        state_ = false;
        rising_ = false;
        falling_ = false;
    }
 
private:
    uint16_t thresh_high_;
    uint16_t thresh_low_;
    bool state_;
    bool rising_;
    bool falling_;
};
 
} // namespace sbl::components::cv