From: Bob Blick <bobblick@outlook.com>
To: Microcontroller discussion list - Public. <piclist@mit.edu>
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Date: Thu, 30 Jul 2020 15:52:36 -0700
Subject: Re: [PIC] Simple GCC question
Thread-Topic: [PIC] Simple GCC question
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Here's a copy of an email Wouter sent directly. I will need to read up on a=
 singleton. So much to learn!

> I'm using a nice little HD44780 LCD library in an STM32 project, it works=
 great but I'm stuck with a variable scope problem that I can only seem to =
make worse because GCC is a bit stricter than I want it to be at this point=
.. Sorry if the code example doesn't wordwrap properly.

You could switch to C++, which allows globals to be initialized at
run-time ..... (but that comes with its own can of worms, so I never use
that feature).

I think your problem is solved by having a global pointer to your LCD
object, which you assign its value after you created the LCD thingy in
main. Just take care that nobody uses it before that time.

If you want to look clever, you could make a singleton: a function that
returns the lcd pointer. The first time it is executed, it creates the
LCD thingy. Maybe the ports and pins must be static too, depending on
whether the lcd thingy uses them after its creation.

   Lcd_HandleTypeDef * Lcd(){
      static Lcd_HandleTypeDef * p =3D NULL;
      static lcd_thingy;
      if( p =3D=3D NULL ){
         Lcd_PortType ports[] =3D {LCD_D4_GPIO_Port, LCD_D5_GPIO_Port, LCD_=
D6_GPIO_Port, LCD_D7_GPIO_Port};
         Lcd_PinType pins[] =3D {LCD_D4_Pin, LCD_D5_Pin, LCD_D6_Pin, LCD_D7=
_Pin};
         lcd_thingy =3D Lcd_create(ports, pins, LCD_RS_GPIO_Port, LCD_RS_Pi=
n, LCD_EN_GPIO_Port, LCD_EN_Pin, LCD_4_BIT_MODE);
         p =3D & lcd_thingy;
       }
       return p;
    }

--=20
Wouter "Objects? No Thanks!" van Ooijen
--=20
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