C++ Hardware Abstraction Layers

Same application, different chip.

An abstraction layer hides chip-specific details behind a common interface. Application code calls led.on() and does not care which register makes it happen.

Moving to a new chip then means rewriting only the driver classes. An abstract base class gives a fixed interface, though virtual calls add a small cost; templates can remove it.

Keep the interface small and honest about what the hardware cannot do.

class Pin {
  public:
    virtual void high() = 0;
    virtual void low()  = 0;
};

class LedDriver {
  public:
    explicit LedDriver(Pin &p) : pin(p) {}
    void on()  { pin.high(); }
    void off() { pin.low(); }
  private:
    Pin &pin;
};