Moving code to a library but can't get the imported LCD library to work [solved]

Projects Programming
1

I'm trying to clean up my sketch by putting related code chunks into libraries, but I'm having trouble with the display code; specifically, I can't seem to get the hd44780 library to work from a cpp file rather than a sketch.

This works fine in a sketch:

#include <hd44780.h>
#include <hd44780ioClass/hd44780_pinIO.h>


const int rs = 8, en = 9, db4 = 4, db5 = 5, db6 = 6, db7 = 7;
hd44780_pinIO lcd(rs, en, db4, db5, db6, db7);


const int LCD_COLS = 20;
const int LCD_ROWS = 4;


void setup() {
  lcd.begin(LCD_COLS, LCD_ROWS);
  lcd.setCursor(0, 0);          // col 1, row 1
  lcd.print("***              ***");
}

void loop() {
  

}

Where do I put each part of that in c++ class files?

I've tried every which way that I could think of, but here's one:

sketch:

#include "UIv2.h"

UI ui();

void setup() {

}

void loop() {
  

}

UIv2.h:

#ifndef UIV2_H_
#define UIV2_H_

#include <hd44780.h>
#include <hd44780ioClass/hd44780_pinIO.h>

class UI {
public:

	UI();
	virtual ~UI();

};

#endif /* UIV2_H_ */

UIv2.cpp

#include "UIv2.h"

const int rs = 8, en = 9, db4 = 4, db5 = 5, db6 = 6, db7 = 7;
hd44780_pinIO lcd(rs, en, db4, db5, db6, db7);

const int LCD_COLS = 20;
const int LCD_ROWS = 4;

UI::UI() {
	lcd.begin(LCD_COLS, LCD_ROWS);
	lcd.setCursor(0, 0);          // col 1, row 1
	lcd.print("***              ***");
}



UI::~UI() {
	// TODO Auto-generated destructor stub
}

I swear I had this working a few days ago, but I botched it somehow and now I can't figure out what I had done. Thank you for any help!

2

The cpp file should NOT declare any variables. The header file should. If you REALLY need to have your library create the LCD object, and I would argue that you should NOT do that, you need to create the instance at the same time as you create your instance:

UI::UI() : lcd(rs, en, db4, db5, db6, db7)
{
}

The arguments to the lcd constructor should be passed to your constructor.

3

I think part of the problem might be:

UI ui();

I think you wanted to create an instance of the UI class named 'ui'. What I think you did is declare a function named 'ui' which returns an object of class UI and takes no arguments. I think what you want is:

UI ui;
4

The constructor of your global UI instance will run before the platform is initialized, so it's not recommended to use lcd methods. I'd recommend adding a "begin" method where you do your initialization, instead of doing it in the constructor.

Pieter

5

PaulS, johnwasser, and PieterP, thank you for your replies.

PaulS, you say I should not have my library create the LCD object. I'm listening. Create it in the sketch and pass it by pointer? I was considering that, but then won't it be local to setup() and thus vanish at the end of setup? Creating it in loop doesn't sound right, either. I feel like I'm not understanding what you meant.

johnwasser, I had a V8 moment reading your reply. Facepalm. Yes, you're absolutely right. That might have been the problem all along. I come over from the Microchip-C crowd and my old habits bit me in the butt.

PieterP, that sounds like a good solution.

I'll work on it this eve and hopefully post my fixed and working code. Thank you all for your guidance.

6

I can't believe I did this. Long story short, the files that I was saving in Eclipse were not the files that the Arduino IDE were using in its builds. So of course, absolutely nothing I did worked, because none of it was ever used by the compiler.

Sigh.

If only using Eclipse for Arduino development was easier. I messed around for DAYS trying to switch over to Eclipse only, but could never get it to work. In the major mess from that, I ended up with two sets of files.

I'm going back to the simpler Geany where I could get things done.

Tomorrow I will face it anew.

7

Incorporating my new knowledge, I have moved the LCD set up code to the sketch and I am trying to pass the object by reference. This seems to work fine for the receiving function, but if I want to hold on to that for future use by the class, I don't know how to store it as a reference. What I mean is, if I tell the class here's a declaration for later, it tries to construct the object instead of waiting to receive the object later:

.h

class UI {
public:
 UI();
 void go(hd44780_pinIO & _lcd);
 virtual ~UI();

private:
 hd44780_pinIO lcd;
//protected:
};

.cpp

UI::UI() {
}

void UI::go(hd44780_pinIO & _lcd) {
 lcd = _lcd;
 lcd.setCursor(0, 0);          // col 1, row 1
 lcd.print("***              ***");
}

At compile I get what I would expect:

/Users/ncd/Documents/Arduino/libraries/UIv2/UIv2.cpp: In constructor 'UI::UI()':
/Users/ncd/Documents/Arduino/libraries/UIv2/UIv2.cpp:9:8: error: no matching function for call to 'hd44780_pinIO::hd44780_pinIO()'
 UI::UI() {
        ^
In file included from /Users/ncd/Documents/Arduino/libraries/UIv2/UIv2.h:9:0,
                 from /Users/ncd/Documents/Arduino/libraries/UIv2/UIv2.cpp:3:
/Users/ncd/Documents/Arduino/libraries/hd44780/hd44780ioClass/hd44780_pinIO.h:113:1: note: candidate: hd44780_pinIO::hd44780_pinIO(uint8_t, uint8_t, uint8_t, uint8_t, uint8_t, uint8_t, uint8_t, uint8_t, uint8_t)
 hd44780_pinIO(uint8_t rs,  uint8_t rw, uint8_t en,
 ^
/Users/ncd/Documents/Arduino/libraries/hd44780/hd44780ioClass/hd44780_pinIO.h:113:1: note:   candidate expects 9 arguments, 0 provided
/Users/ncd/Documents/Arduino/libraries/hd44780/hd44780ioClass/hd44780_pinIO.h:98:1: note: candidate: hd44780_pinIO::hd44780_pinIO(uint8_t, uint8_t, uint8_t, uint8_t, uint8_t, uint8_t, uint8_t)
 hd44780_pinIO(uint8_t rs,  uint8_t rw, uint8_t en,
 ^
/Users/ncd/Documents/Arduino/libraries/hd44780/hd44780ioClass/hd44780_pinIO.h:98:1: note:   candidate expects 7 arguments, 0 provided
/Users/ncd/Documents/Arduino/libraries/hd44780/hd44780ioClass/hd44780_pinIO.h:81:1: note: candidate: hd44780_pinIO::hd44780_pinIO(uint8_t, uint8_t, uint8_t, uint8_t, uint8_t, uint8_t, uint8_t, uint8_t)
 hd44780_pinIO(uint8_t rs,  uint8_t en,
 ^
/Users/ncd/Documents/Arduino/libraries/hd44780/hd44780ioClass/hd44780_pinIO.h:81:1: note:   candidate expects 8 arguments, 0 provided
/Users/ncd/Documents/Arduino/libraries/hd44780/hd44780ioClass/hd44780_pinIO.h:66:1: note: candidate: hd44780_pinIO::hd44780_pinIO(uint8_t, uint8_t, uint8_t, uint8_t, uint8_t, uint8_t)
 hd44780_pinIO(uint8_t rs,  uint8_t en,
 ^
/Users/ncd/Documents/Arduino/libraries/hd44780/hd44780ioClass/hd44780_pinIO.h:66:1: note:   candidate expects 6 arguments, 0 provided
/Users/ncd/Documents/Arduino/libraries/hd44780/hd44780ioClass/hd44780_pinIO.h:58:7: note: candidate: constexpr hd44780_pinIO::hd44780_pinIO(const hd44780_pinIO&)
 class hd44780_pinIO : public hd44780
       ^
/Users/ncd/Documents/Arduino/libraries/hd44780/hd44780ioClass/hd44780_pinIO.h:58:7: note:   candidate expects 1 argument, 0 provided
/Users/ncd/Documents/Arduino/libraries/hd44780/hd44780ioClass/hd44780_pinIO.h:58:7: note: candidate: constexpr hd44780_pinIO::hd44780_pinIO(hd44780_pinIO&&)
/Users/ncd/Documents/Arduino/libraries/hd44780/hd44780ioClass/hd44780_pinIO.h:58:7: note:   candidate expects 1 argument, 0 provided
Using library UIv2 in folder: /Users/ncd/Documents/Arduino/libraries/UIv2 (legacy)
Using library hd44780 at version 1.0.1 in folder: /Users/ncd/Documents/Arduino/libraries/hd44780 
exit status 1
Error compiling for board Arduino Nano.

... and maybe it's my imagination, but it seems slower going through the class rather than in the original sketch.

8

You can pass it in by reference, but save and use it as a pointer. Note, I don't have that library installed so I can't compile this. But, you should get the idea. Also, don't forget the #include guards in your .h file.

class UI {
  public:
    UI(hd44780_pinIO & _lcd) : lcd(& _lcd) {};
    void go();
    virtual ~UI();

  private:
    hd44780_pinIO *lcd;
};

void UI::go() {
 lcd->setCursor(0, 0);          // col 1, row 1
 lcd->print("***              ***");
}

void setup() {
  // put your setup code here, to run once:

}

void loop() {
  // put your main code here, to run repeatedly:

}
9

gfvalvo:
You can pass it in by reference, but save and use it as a pointer.

Why would you save it as a pointer? Just save the reference.

10

PieterP:
Why would you save it as a pointer? Just save the reference.

True, I was originally thinking that the "passing in" might happen in a begin() method rather than the class's constructor. In that case, you can pass in a reference, but you can't assign it to a class data member that's a reference. I think that can only be done in an Initializer List. That's why it would need to be a pointer. Correct?

11

gfvalvo:
True, I was originally thinking that the "passing in" might happen in a begin() method rather than the class's constructor. In that case, you can pass in a reference, but you can't assign it to a class data member that's a reference. I think that can only be done in an Initializer List. That's why it would need to be a pointer. Correct?

Correct!

12

I think passing it in in the begin method could give rise to lifetime problems:

UI ui;

void setup() {
    hd44780_pinIO lcd;
    ui.begin(lcd);
}

void loop() {
    ui.go();  // Oops! lcd no longer exists
}

If you pass it in the constructor, the user can still make the same mistake, but it's much harder to do so.

13

OK... This compiles without errors. I don't have that LCD so I can't test it.

MainSketch.ino:

#include <UIv2.h>


UI ui;


void setup()
{
  ui.begin();
}


void loop()
{
}

UIv2.h:

#ifndef UIV2_H_
#define UIV2_H_

#include <hd44780.h>
#include <hd44780ioClass/hd44780_pinIO.h>

class UI
{
  public:
    void begin();  // Complete the initialization

  private:
    // Class private member. Shared by all instances.
    static hd44780_pinIO lcd;
};

#endif /* UIV2_H_ */

UIv2.cpp:

#include "UIv2.h"

static const int rs = 8, en = 9, db4 = 4, db5 = 5, db6 = 6, db7 = 7;

// Constructing the class member object
hd44780_pinIO UI::lcd(rs, en, db4, db5, db6, db7);

const int LCD_COLS = 20;
const int LCD_ROWS = 4;

void UI::begin() 
{
  UI::lcd.begin(LCD_COLS, LCD_ROWS);
  UI::lcd.setCursor(0, 0);          // col 1, row 1
  UI::lcd.print("***              ***");
}
14

@johnwasser, that was brilliant. It works, exactly as I wanted, and it's so clean! Thank you so much for your help. I need to study it (and c++ more) to understand better why everything is the way it is. Do you recommend any particular online or paper resource for c++, particularly for transitioning from c? If not, I'm sure I can find something; I just thought you might already be familiar. Thanks again.

15

johnwasser:
OK... This compiles without errors. I don't have that LCD so I can't test it.

Don't know why you want the private hd44780_pinIO object to be static to the class. Theoretically, there's no reason you couldn't have multiple UI objects each controlling their own hd44780_pinIO object.

I've come around to @PieterP's point of view. Pass a reference in to the constructor and use it to set a private internal reference member via the initializer list.

16

gfvalvo:
I've come around to @PieterP's point of view.

Well, mostly. If you really want the UI object to contain a hd44780_pinIO object, you could do this without losing the flexibility of letting the calling code decide how the hd44780_pinIO is connected:

#include <hd44780.h>
#include <hd44780ioClass/hd44780_pinIO.h>

class UI
{
  public:
    UI(uint8_t rs, uint8_t en, uint8_t db4, uint8_t db5, uint8_t db6, uint8_t db7) : lcd(rs, en, db4, db5, db6, db7) {}
    void begin() {
      const uint8_t LCD_COLS = 20;
      const uint8_t LCD_ROWS = 4;

      lcd.begin(LCD_COLS, LCD_ROWS);
      lcd.setCursor(0, 0);
      lcd.print("***              ***");
    }

  private:
    hd44780_pinIO lcd;
};

UI ui(8, 9, 4, 5, 6, 7);

void setup() {
  ui.begin();
}

void loop() {}

Or, you might decide that the UI class is a type of hd44780_pinIO class:

#include <hd44780.h>
#include <hd44780ioClass/hd44780_pinIO.h>

class UI : public hd44780_pinIO
{
  public:
    UI(uint8_t rs, uint8_t en, uint8_t db4, uint8_t db5, uint8_t db6, uint8_t db7) : hd44780_pinIO(rs, en, db4, db5, db6, db7){}
    void begin() {
      const uint8_t LCD_COLS = 20;
      const uint8_t LCD_ROWS = 4;

      hd44780_pinIO::begin(LCD_COLS, LCD_ROWS);
      hd44780_pinIO::setCursor(0, 0);
      hd44780_pinIO::print("***              ***");
    }
};

UI ui(8, 9, 4, 5, 6, 7);

void setup() {
  ui.begin();
}

void loop() {}

Lots of ways this cat can be skinned.