HC165ExpanderAdapter.h

#ifndef HC165ExpanderAdapter_h
#define HC165ExpanderAdapter_h
 
#include "Arduino.h"
#include "GpioExpanderAdapter/GpioExpanderAdapter.h"
#include "PinAdapter/PinAdapter.h"
 
class HC165ExpanderAdapter : public GpioExpanderAdapter {
    static const int cascadeDefaultLength = 1; // single 74HC164 is default
    static const int cascadeMaxLength = 4;     // max number of 74HC164 supported by this implementation
    static const int piPinCount = 8;           // number of parallel input pins
  public:
 
    HC165ExpanderAdapter(byte dataPin, byte clockPin, byte shldPin, byte cascadeLength = cascadeDefaultLength)
        : dataPin(dataPin), 
          clockPin(clockPin), 
          shldPin(shldPin), 
          cascadeLength(cascadeLength)
        {
            cascadeLength = cascadeLength > cascadeMaxLength ? cascadeMaxLength : cascadeLength;
        }
 
    void begin() override {
        pinMode(dataPin, INPUT);
        pinMode(clockPin, OUTPUT);
        pinMode(shldPin, OUTPUT);
    }
 
    void update() override {
        // Step 1: Sample
        digitalWrite(shldPin, LOW);
        digitalWrite(shldPin, HIGH);
 
        // Step 2: Read & Shift
        for (int i = 0; i < cascadeLength * piPinCount; i++) {
            int pin = digitalRead(dataPin);
            if (pin == HIGH)
                bitSet(pins, i);
            else
                bitClear(pins, i);
 
            // Shift out the next bit
            digitalWrite(clockPin, HIGH);
            digitalWrite(clockPin, LOW);
        }
    }
 
    bool read(byte pin) override {
        return bitRead(pins, pin);
    }
 
    void attachPin(byte pin, int mode = INPUT_PULLUP) override {}
 
    ~HC165ExpanderAdapter() {}
 
  private:
    byte dataPin;
    byte clockPin;
    byte shldPin;
    int cascadeLength;
    uint32_t pins = 0;
};
 
#endif