Why this code definition LCD this way?

Using Arduino Programming Questions
1

Hi,
One code has a way to definite LCD like:

//LCD Output
 #ifdef LCD_PRINT
#include <LiquidCrystal.h>
LiquidCrystal lcd(7, 6, 5, 4, 3, 2);           //RS,E,D4,D5,D6,D7
 #endif

any specialities and advantages?
Thanks
Adam

2

Compared to what?

What other way(s) have you seen it definited?

a7

1 Like
3

HI @shanren

For this library (<LiquidCrystal.h>) this is the default format.

RV mineirin

class LiquidCrystal : public Print {
public:
  LiquidCrystal(uint8_t rs, uint8_t enable,
		uint8_t d0, uint8_t d1, uint8_t d2, uint8_t d3,
		uint8_t d4, uint8_t d5, uint8_t d6, uint8_t d7);
  LiquidCrystal(uint8_t rs, uint8_t rw, uint8_t enable,
		uint8_t d0, uint8_t d1, uint8_t d2, uint8_t d3,
		uint8_t d4, uint8_t d5, uint8_t d6, uint8_t d7);
  LiquidCrystal(uint8_t rs, uint8_t rw, uint8_t enable,
		uint8_t d0, uint8_t d1, uint8_t d2, uint8_t d3);
  LiquidCrystal(uint8_t rs, uint8_t enable,
		uint8_t d0, uint8_t d1, uint8_t d2, uint8_t d3);
1 Like
4

Thanks.
I used to do this way, and that works.

#include <LiquidCrystal.h>
/////  const int rs = 8, en = 9, d4 = 10, d5 = 11, d6 = 12, d7 = 13;
const int rs = 7, en = 6, d4 = 5, d5 = 4, d6 = 3, d7 = 2;
LiquidCrystal lcd(7, 6, 5, 4, 3, 2);           //RS,E,D4,D5,D6,D7
5

Explain better.

1 Like
6

Thanks.
Attached a code below, that doesn't make my LCD work. if comment out all #ifdef LCD_PRINT and #endif , my LCD works.


/*
#include <LiquidCrystal.h>
/////  const int rs = 8, en = 9, d4 = 10, d5 = 11, d6 = 12, d7 = 13;
const int rs = 7, en = 6, d4 = 5, d5 = 4, d6 = 3, d7 = 2;
LiquidCrystal lcd(rs, en, d4, d5, d6, d7);
*/

//LCD Output
 #ifdef LCD_PRINT
#include <LiquidCrystal.h>
/////  const int rs = 8, en = 9, d4 = 10, d5 = 11, d6 = 12, d7 = 13;
const int rs = 7, en = 6, d4 = 5, d5 = 4, d6 = 3, d7 = 2;
LiquidCrystal lcd(7, 6, 5, 4, 3, 2);           //RS,E,D4,D5,D6,D7
 #endif


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

  
   #ifdef LCD_PRINT
  lcd.begin(16, 2);
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("ADAMDIY-ADMM");
  delay(1000);
  
 
  lcd.clear();
  lcd.setCursor(0, 1);
  lcd.print("hello, world!");
  delay(1000);
  #endif
}

void loop() {
  // put your main code here, to run repeatedly:
}
7

Go learn about

# define

# ifdef

    and

# endif

You don’t

# define LCD_PRINT

anywhere, so you code gets skipped. Not included.

a7

1 Like
8

Hi @shanren

There is no definition of LCD_PRINT

try this sketch:

/*
  #include <LiquidCrystal.h>
  /////  const int rs = 8, en = 9, d4 = 10, d5 = 11, d6 = 12, d7 = 13;
  const int rs = 7, en = 6, d4 = 5, d5 = 4, d6 = 3, d7 = 2;
  LiquidCrystal lcd(rs, en, d4, d5, d6, d7);
*/
#define LCD_PRINT
//LCD Output
#ifdef LCD_PRINT
#include <LiquidCrystal.h>
/////  const int rs = 8, en = 9, d4 = 10, d5 = 11, d6 = 12, d7 = 13;
//const int rs = 7, en = 6, d4 = 5, d5 = 4, d6 = 3, d7 = 2;
LiquidCrystal lcd(7, 6, 5, 4, 3, 2);           //RS,E,D4,D5,D6,D7
#endif


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

#ifdef LCD_PRINT
  lcd.begin(16, 2);
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("ADAMDIY-ADMM");
  delay(1000);


  lcd.clear();
  lcd.setCursor(0, 1);
  lcd.print("hello, world!");
  delay(1000);
#endif
}

void loop() {
  // put your main code here, to run repeatedly:
}
1 Like
9

Thanks.

10

Thanks.
The sketch works well.
Is this mean every time if I like to display some thing, I always need use this pattern?

#ifdef LCD_PRINT
  lcd.begin(16, 2);
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("xxxx");
  delay(1000);


  lcd.clear();
  lcd.setCursor(0, 1);
  lcd.print("yyyy");
  delay(1000);
#endif

and how about the post #3, that just need one time right?
Thanks.

11

In post #3 I just showed how it is written inside the library "LiquidCrystal".

RV mineirin

1 Like
12

Thank you.

13

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