how compute a parameter for a function that is globally declared?

Projects Programming
1

I have two projects that have the same source code. Both projects have a I2C display, that is initialized like

Liquidcrystal_I2C mylcd(0x3F,2,1... etc.

where 0x3F is the address of the display. However: the two displays have two different addresses. It is easy to let the program find the address, but that takes a few lines of code in setup(). If I initialize the LCD inside the setup() function, it is invisible to loop() and other functions.

Of course I can use #ifdef, but I would rather do it automagically.

This got me stymied.

2

paai:
I have two projects that have the same source code. Both projects have a I2C display, that is initialized like

Liquidcrystal_I2C mylcd(0x3F,2,1... etc.

where 0x3F is the address of the display. However: the two displays have two different addresses. It is easy to let the program find the address, but that takes a few lines of code in setup(). If I initialize the LCD inside the setup() function, it is invisible to loop() and other functions.

Of course I can use #ifdef, but I would rather do it automagically.

This got me stymied.

Instantiated, not initialized.

3

create a global pointer to a LiquidCrystal_I2C object, create the instance in setup() and copy the global pointer to the 'new' lcd object...

something like this (just an example I had handy...)

class Shapes{
  
  public:
    Shapes() {};
    int area() {return _length * _width;};
    void setLength(int length){ _length = length;};
    void setWidth(int width){_width = width;};
  
  private:
    int _width, _length;
};

Shapes* myPtr;  //<< global pointer

int myValue = 10;

void setup() 
{
  Serial.begin(9600);
  Shapes* myBox = new Shapes();  // create a new instance of Shapes pointed to by myBox
  myPtr = myBox;  //<< copy the pointer to the new object
  myBox->setLength(10);
  (*myBox).setWidth(5);
  Serial.println(myBox->area());
}

void loop() 
{
  myPtr->setLength(myValue+=5);  // I can now manipulate the object
  Serial.println(myPtr->area());       // and reference it globally
  delay(1000);
}

So like this:

liquidCrystal_I2C* lcd;

void setup()
{
  // find your I2C device
  // Create an I2C object:
  liquidCrystal_I2C* myLcd = new liquidCrystal_I2C();
  etc...
  // copy th pointer
  lcd = myLcd;
  // etc...
  lcd->print("hey, this works");
4

@BulldogLowel: Hey, this works!:slight_smile: Thanks.

Paai