Arduino I2C display

Are you using this sketch?

Came for supplier's ad for similar device.  It may be that the library only supports 2x20 on that 4x20 device for now.  I don't know.

Hi billabot:

Thank you for responding so quickly. Im am using the sketch provided as an example that comes with the library:

#include <Wire.h>

#include <LiquidCrystal_I2C.h>

#define BACKLIGHT_PIN     13

LiquidCrystal_I2C lcd(0x20);  // Set the LCD I2C address

//LiquidCrystal_I2C lcd(0x38, BACKLIGHT_PIN, POSITIVE);  // Set the LCD I2C address

// Creat a set of new characters

const uint8_t charBitmap[][8] = {

   { 0xc, 0x12, 0x12, 0xc, 0, 0, 0, 0 },

   { 0x6, 0x9, 0x9, 0x6, 0, 0, 0, 0 },

   { 0x0, 0x6, 0x9, 0x9, 0x6, 0, 0, 0x0 },

   { 0x0, 0xc, 0x12, 0x12, 0xc, 0, 0, 0x0 },

   { 0x0, 0x0, 0xc, 0x12, 0x12, 0xc, 0, 0x0 },

   { 0x0, 0x0, 0x6, 0x9, 0x9, 0x6, 0, 0x0 },

   { 0x0, 0x0, 0x0, 0x6, 0x9, 0x9, 0x6, 0x0 },

   { 0x0, 0x0, 0x0, 0xc, 0x12, 0x12, 0xc, 0x0 }

};

void setup()

{

   int charBitmapSize = (sizeof(charBitmap ) / sizeof (charBitmap[0]));

  // Switch on the backlight

  pinMode ( BACKLIGHT_PIN, OUTPUT );

  digitalWrite ( BACKLIGHT_PIN, HIGH );

  lcd.begin(20,4);               // initialize the lcd

   for ( int i = 0; i < charBitmapSize; i++ )

   {

      lcd.createChar ( i, (uint8_t *)charBitmap[i] );

   }

  lcd.home ();                   // go home

  lcd.print("Hello, ARDUINO "); 

  lcd.setCursor ( 0, 1 );        // go to the next line

  lcd.print (" FORUM - fm   ");

  delay ( 1000 );

}

void loop()

{

   lcd.home ();

   // Do a little animation by writing to the same location

   for ( int i = 0; i < 2; i++ )

   {

      for ( int j = 0; j < 16; j++ )

      {

         lcd.print (char(random(7)));

      }

      lcd.setCursor ( 0, 1 );

   }

   delay (200);

}

By the way, I tried the sketch that you said, and my library doesn´t support most of the command. Still thank you

Daniel

Daniel

You might need to clarify some items here.

1.     Your sketch allocates the backlight on D13, but your display is a I2C version and the backlight pins are LCD 16 and 15 (as shown on top left of your first image)

2.     The address settings appear to have been soldered or unsoldered and the datasheet for the chip shows that the address should be 0x27.

3.     Your example does not seem to be for this library, as it is incomplete.

4.     The line lcd.begin(20,4) shows this is for a 20x4 LCD, and not an I2C version LCD

5.     Please confirm what pin on the lcd goes to what pin at the Arduino, to verify the connections.

Please try the code below, and advise if you get anything.

*** You may need to wind down the contrast until the top line of blocks is just visible. ***

#include <Wire.h>

#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27,16,2);  // set the LCD address to 0x27 for a 16 chars and 2 line display

LiquidCrystal_I2C lcd(0x27,20,4);  // set the LCD address to 0x27 for a 20 chars and 4 line display

void setup()

{

  lcd.init();                      // initialize the lcd

  // Print a message to the LCD.

  lcd.backlight();

  lcd.print("Hello, world!");

}

void loop()

{

}

Thanks

Mark

edit

oops, should have read all the original post

Is the library from the vendor's web site?  Which is where exactly?  provide link.

The source I found for the library is here: http://hmario.home.xs4all.nl/arduino/LiquidCrystal_I2C/LiquidCrystal_I2C.zip

All players should be familiar with: http://playground.arduino.cc/Code/LCDAPI

I have a feeling that the LC_I2C library demands the latest version of Arduino IDE.

Latest? info seems to be here: http://wentztech.com/radio/arduino/files/LCDI2C.html    -Happy Trails

-= End Of Line =-

Given

LiquidCrystal_I2C lcd = LiquidCrystal_I2C(0x27,20,4);//  (address of the display, cols, rows)   *

The underlined portion is a function call containing the parameters that define the LCD interface/capabilities.

It compiles for me.  I don't understand how your versions are compiling.   (See Postscript.)

It returns a value into lcd which might be seen by the sketch as a handle;  so that the other library functions can be accessed correctly with the proper parameters.  What if there were two or more LCDs listening on the same I2C wire with different addresses?   Hmmmm?  M'kay!

for example:

lcd.print("Hello W.A.T. Bottger");

This is hard stuff, y'all.

Postscript:  Now that the IDE has indexed the existance and location of the library, the original notation also works, but I don't like it as much as the syntactically understandable one on line two of this posting.  Yeah, I know it is a constructor instantiating an object. M'kay.  But who cares?

-=SyntaxMatters=-

This compiles clean:

Got a clean compile with this sketch. 

and this one:

#include <Wire.h>

#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd=LiquidCrystal_I2C(0x27,20,4); //set the LCD address to 0x27 for a 16 chars and 2 line display

void setup()

{

lcd.init();

lcd.backlight();

lcd.setCursor(0, 0);

lcd.print("b2cqshop");

lcd.setCursor(0, 1);

lcd.print("Voltage: ");

lcd.setCursor(13, 1);

lcd.print("V");

}

void loop()

{

int val;

float temp;

val=analogRead(0);

temp=val/4.092;

val=(int)temp;//

lcd.setCursor(9, 1);

lcd.print(0x30);

lcd.print(0x30+(val%100)/10);

lcd.print('.');

lcd.print(0x30+val%10);

delay(100);

}

So please report back if it actually works with the I2C LCD.  thanks.  And give me my points.  I earned them tonight.

I should have read all the original post.

I've edited the initialisation line to reflect the 20x4 display.

Cheers

mark

Hi billabot:

First of all thank you so much for all your help.

I double checked all my connections, I'm using an arduino mega 1280, the vcc is connected to +5v, gnd is connected to ground, SCL is connected to pin 21 (it is marked SCL), and SDA is connected to pin 20(It is marked SDA).

The address setting jumpers were already like that when I got may LCD, they are just tined, none is making contact.

I just downloaded the most reacent arduino ide, and I also downloaded the library you sugested. But this time there is a new problem, the compiller sends the following error mesage:

Users/dany/Documents/Arduino/libraries/LiquidCrystal_I2C/LiquidCrystal_I2C.cpp: In member function 'void LiquidCrystal_I2C::expanderWrite(uint8_t)':

Users/dany/Documents/Arduino/libraries/LiquidCrystal_I2C/LiquidCrystal_I2C.cpp:243: error: 'class TwoWire' has no member named 'write'

I supose that there is something incompatible with the wire library and the LCD I2C library, but I'm not sure.

Thanks again for your patience and support.

PS:

This is the first time I use element 14, so I don't know you to give you points. As soon as I find out how to do it, I will immediately give you points

Daniel

As MarkB said : The backlight is not controlled by pin 13 in this situation. 

Take out the 3 lines pertaining to pin 13 and backlight control.

They are only optionally used with a plain old 2x16 LCD using the parallel interface.  The I2C interface is 4 wires, right?  Ground, Vcc, clk, and serial data.  The one I looked at on eBay.com had a tiny round dial potentiometer to adjust the backlight brightness.  After that you can only programmatically turn it ON or OFF.

The LC_i2c library includes:

// flags for backlight control

#define LCD_BACKLIGHT 0x00

#define LCD_NOBACKLIGHT 0x80

and functions that would appear in sketch as:

lcd.backlight();

or

lcd.noBacklight();

You should see some boxes at the bottom of each posted response.  Choose ONE posted answer for the Best Answer and other posted answers for helpful answers if you wish to do so.