Hysteresis.hpp

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#pragma once
 
#include <AH/Settings/NamespaceSettings.hpp>
 
#include <stdint.h>
 
BEGIN_AH_NAMESPACE


template <uint8_t Bits, class T_in = uint16_t, class T_out = uint8_t>
class Hysteresis {
  public:
    bool update(T_in inputLevel) {
        T_in prevLevelFull = (T_in(prevLevel) << Bits) | offset;
        T_in lowerbound = prevLevel > 0 ? prevLevelFull - margin : 0;
        T_in upperbound = prevLevel < max_out ? prevLevelFull + margin : max_in;
        if (inputLevel < lowerbound || inputLevel > upperbound) {
            setValue(inputLevel);
            return true;
        }
        return false;
    }

    T_out getValue() const { return prevLevel; }

    void setValue(T_in inputLevel) { prevLevel = inputLevel >> Bits; }
 
  private:
    T_out prevLevel = 0;
    constexpr static T_in margin = (1ul << Bits) - 1ul;
    constexpr static T_in offset = Bits >= 1 ? 1ul << (Bits - 1) : 0;
    constexpr static T_in max_in = static_cast<T_in>(-1);
    constexpr static T_out max_out = static_cast<T_out>(max_in >> Bits);
    static_assert(max_in > 0, "Error: only unsigned types are supported");
};
 
template <class T_in, class T_out>
class Hysteresis<0, T_in, T_out> {
  public:
    bool update(T_in inputLevel) {
        bool changed = inputLevel != prevLevel;
        prevLevel = inputLevel;
        return changed;
    }
 
    T_out getValue() const { return prevLevel; }
    void setValue(T_in inputLevel) { prevLevel = inputLevel; }
 
  private:
    T_in prevLevel = 0;
};

 
END_AH_NAMESPACE