support for 40x4 (dual enable line) LCD

Issue #44 new
Former user created an issue

Is there any chance to add support for dual HD44780 40x4 LCD to a 4bit I2C code ? Such LCD have two enable lines for controlling rows.

Comments (10)

  1. Francisco Malpartida repo owner

    Perhaps, but it will take some time before I can get round to continue to enhance this library.

    Sorry for the inconvenience.

  2. Hjalmar Skovholm Hansen

    HI just use 2 instances of this VERY fine library

    LiquidCrystal lcd(31, 29, 28, 27, 26, 32, 33); LiquidCrystal lcd2(31, 29, 30, 27, 26, 32, 33);

    lcd.begin(40, 2); lcd2.begin(40, 2);

    lcd.setCursor(2, 1); lcd.print("min tur til at lege");

    lcd2.setCursor(0, 0); lcd2.print(" den 3 linje som man kan");

    it works fine on a chipkit ;o)


  3. Cobus


    Thank you Hjalmar for your bright idea of using two instances of this library ! But, as the original poster, I would like to use I2C to drive a (not yet bought) 40x4 LCD.

    I successfully drive a 20x4 LCD with an I2C backpack with the following instance :

    //                                   addr,en,rw,rs,d4,d5,d6,d7,LED,polarity
    LiquidCrystal_I2C lcd_2004_all_lines(0x27, 2, 1, 0, 4, 5, 6, 7, 3, POSITIVE);

    As far as I know, there is no I2C backpack for 40x4 displays. I plan to use a 20x4 I2C backpack. Following Hjalmar's idea, should I sacrifice the LED management and use the following instances with I2C ?

    //                                   addr,en,rw,rs,d4,d5,d6,d7      
    LiquidCrystal_I2C lcd_4004_lines_0_1(0x27, 2, 1, 0, 4, 5, 6, 7);
    LiquidCrystal_I2C lcd_4004_lines_2_3(0x27, 3, 1, 0, 4, 5, 6, 7);

    Side note : I can use an I2C DAC (digital to analog converter) to manage backlight. It seems, your library does not handle dimming, though.

    Any other way to use I2C to drive a 40x4 LCD ?

    I found 40x4 displays driven by S6A0069 or KS0066 or SPLC780D or twin ST7066U. Should all of them work or are there known incompatibilities ?

    Have a nice day !


  4. Francisco Malpartida repo owner

    I haven't tried it out. You just need to control the current to the backlights they are just leds.

  5. Francisco Malpartida repo owner

    One thing I forgot to mention, you can use a simple PWM to control the back light intensity. That's how I use it.

  6. Francisco Malpartida repo owner

    I missed my ne of the question :-). I use two instances for these displays. It works very well.

  7. Cobus


    Do you ever put the R/W pin in the read state, or is it always in the write state ? I want to connect R/W to ground (always in the write state) to save a pin of the PCF8574 for E2.

  8. Yves De Saedeleer

    Hi community,

    Any furhter news on this topic? Want to use the library with a ESP32...

    I am a newbie on LCD's



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