extending library functionality

Using Arduino Programming Questions
1

I have an LED display module, well supported by a library. There are 8 LEDs on the module that I use as indicators for various parts of my program. However, it has a function setLEDs() which does not allow me to set/reset an LED without affecting the others. So I have written some functions to do that.

However, I'm not satisfied with my solution, but it does work now. I have instantiated a module object, imaginatively called "module". I then wrote three wrapper functions to work the LEDs. I have two main issues. One is practical, the other more concerning lack of elegance, I guess. The practical problem, is that I want to add a second module, and the code I have won't support that (because it has hard coded the module). The library and hardware already supports multiple display devices. I would hate to have three more functions that only differ in which module they call. The other issue is that I would prefer to leave the 20th century, and finally begin to respect OO more.

Here is my existing, working code:

#include <TM1638.h>
TM1638 module(TM1638dataPin, TM1638clockPin, TM1638strobePin, true, TM1638intensity);

//... my code here
const byte utcLED =    0b00000011;
const byte blinkLED =  0b10000000;

LEDon(blinkLED);
LEDtoggle(utcLED);

//... LED wrapper functions
//
byte LEDstatus = 0;

void LEDon( byte data)
{
  module.setLEDs(LEDstatus |= data);
}

void LEDoff( byte data)
{
  module.setLEDs(LEDstatus &= ~data);
}

void LEDtoggle( byte data)
{
  module.setLEDs(LEDstatus ^= data);
}

What I would really like, is to have something like the following, but I'm not sure of the approach to take. I have looked at some C++ tutorials and I did learn some a few years ago, but it's kind of locked up in my mind somewhere.

// now there are two display modules...
#include <TM1638.h>
TM1638 module(TM1638dataPin, TM1638clockPin, TM1638strobePin, true, TM1638intensity);
TM1638 module_B(TM1638dataPin_B, TM1638clockPin_B, TM1638strobePin_B, true, TM1638intensity);

//...in my code:
const byte utcLED =    0b00000011;
const byte blinkLED =  0b10000000;

module.LEDon(blinkLED);
module_B.LEDtoggle(utcLED);
//...
//etc. etc.

// mystery code to implement this goes somewhere

Is it possible?
Also, I don't want to change the library at all.

2

You can create a subclass of class tm1638.
You can add custom methods to your subclass and you don't even need to touch the original tm1638 class. the subclass will inherit everything from the parent.

3

But how do I access the methods of the superclass from within the class?

class sevenSegment : public TM1638
{
  public:
    void LEDon( byte data);
    void LEDoff( byte data);
    void LEDtoggle( byte data);
  private:
    byte LEDstatus = 0;
};

void sevenSegment::LEDon( byte data)
{
  ?????????.setLEDs(LEDstatus |= data);
}

void sevenSegment::LEDoff( byte data)
{
  ????????.setLEDs(LEDstatus &= ~data);
}

void sevenSegment::LEDtoggle( byte data)
{
  ???????.setLEDs(LEDstatus ^= data);
}

Where ????? represents a function that I need from the super class. setLEDs() is a superclass method. I hope you know what I mean.

4

Well, it was a bit of a struggle but I got it. This is really going to change how I do things!

class sevenSegment : public TM1638
{
  public:
    sevenSegment(byte dataPin, byte clockPin, byte strobePin, boolean activateDisplay, byte intensity);
    void LEDon( byte data);
    void LEDoff( byte data);
    void LEDtoggle( byte data);
  private:
    byte LEDstatus = 0;
};

// constructor:
sevenSegment::sevenSegment(byte dataPin, byte clockPin, byte strobePin, boolean activateDisplay = true, byte intensity = 7)
  : TM1638(dataPin, clockPin, strobePin, activateDisplay, intensity) {}

// routines to allow sharing display LEDs between different requesters.
//

void sevenSegment::LEDon( byte data)
{
  TM1638::setLEDs(LEDstatus |= data);
}

void sevenSegment::LEDoff( byte data)
{
  TM1638::setLEDs(LEDstatus &= ~data);
}

void sevenSegment::LEDtoggle( byte data)
{
  TM1638::setLEDs(LEDstatus ^= data);
}
5

If you want to call a function inherited from the superclass, simply

void sevenSegment::LEDon( byte data)
{
   setLEDs(LEDstatus |= data);
}