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Arduino I2C display

danyboy

Hello:

I'm a hobbist electronics student and I have been experimenting with arduino for a while. I have worked with character and graphic LCD without any serious problems. I wanted to save wires, so I bought an I2C LCD 20x4 module from ebay. However I have not been able to get it working. I have downloaded the most recent I2C library and I have followed all the instructions but my LCD simply won't work. Instead it lights up like this. The supplier told me that the address of my display is 0x27, but when I use this address nothing happens. After trying different addresses, I dicovered that if I use 0x20 as an address some characters blink randomly with the example code running. the chip on the board is the pcf8574 from Phillips.

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  • 0

     

     

    #include <Wire.h>

     

    #include <LiquidCrystal_I2C.h>

     

    LiquidCrystal_I2C lcd2 = LiquidCrystal_I2C(0x27,20,4);  // Set the LCD address, # columns and # rows

     

    // Create 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]));

       lcd2.backlight();               // Switch on the backlight

       // lcd2.begin(20,4);               // initialize the lcd

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

       {

         lcd2.createChar ( i, (uint8_t *)charBitmap[i] );

       }

     

      lcd2.home ();                   // go home

      lcd2.print("Hello, ARDUINO ");

      lcd2.setCursor ( 0, 1 );        // go to the next line

      lcd2.print (" FORUM - fm   ");

      delay ( 1000 );

    }

     

    void loop()

    {

       lcd2.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++ )

          {

             lcd2.print (char(random(7)));

          }

          lcd2.setCursor ( 0, 1 );

       }

       delay (200);

    }


    This compiles clean:

    Got a clean compile with this sketch.  image

     

    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.


Reply
  • 0

     

     

    #include <Wire.h>

     

    #include <LiquidCrystal_I2C.h>

     

    LiquidCrystal_I2C lcd2 = LiquidCrystal_I2C(0x27,20,4);  // Set the LCD address, # columns and # rows

     

    // Create 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]));

       lcd2.backlight();               // Switch on the backlight

       // lcd2.begin(20,4);               // initialize the lcd

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

       {

         lcd2.createChar ( i, (uint8_t *)charBitmap[i] );

       }

     

      lcd2.home ();                   // go home

      lcd2.print("Hello, ARDUINO ");

      lcd2.setCursor ( 0, 1 );        // go to the next line

      lcd2.print (" FORUM - fm   ");

      delay ( 1000 );

    }

     

    void loop()

    {

       lcd2.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++ )

          {

             lcd2.print (char(random(7)));

          }

          lcd2.setCursor ( 0, 1 );

       }

       delay (200);

    }


    This compiles clean:

    Got a clean compile with this sketch.  image

     

    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.


Children
  • 0 in reply to billabott

    I should have read all the original post.

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

     

    Cheers

    mark

  • 0 in reply to billabott

    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

  • 0 in reply to danyboy

    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();

  • 0 in reply to danyboy

    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.

    image