Well I have finally finished the update to the original LCD4Bit library I have been hacking to bits. I’ve changed the code so that it now supports the 4×40 LCD with a NXP 74HC595N shift register. I had a hell of a time getting it all to work together and ended up having to setup the shift register with LEDs to determine what pins were doing what.

Anyway, after I got the LEDs working right I was able to send data to the first two lines of the LCD and then managed to get the code changed to allow the second Enable IC pin to work. So now I got it all up and running as it was before with the v0.1 library. The best part, I’m only using 3 pins now on the Arduino which is great for my project with everything I plan on hooking up.

Here are a few pics of the setup. Sorry for the messy wires.

 Arduino + Purdy LCD + 74HC595N Shift Register

 Arduino + Purdy LCD + 74HC595N Shift Register

You can get the modified library here.

Schematics are here.

Change Log
v0.2 – 25/Apr/2008
* Modded code to enable a 4×40 parallel LCD screen to work through a shift register.
* Cleaned up the code a lot

v0.1 – 13/Apr/2008
* Cleaned up the code
* Enabled programmer to pass pin and other variable settings through the constructor.
* Tested with a Purdy AND791GST-LED 4×40 LCD screen
* Added rightScroll function
* Added number printing functions

I believe I will go update the LCD driver now in the RFID sketch.

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7 Responses to “Arduino + Purdy LCD + 74HC595N Shift Register”

  1. on 21 Oct 2008 at 3:24 pm FaTMollY

    At me such question
    I can not change the menu in Windows, it looks on new why that….
    Help to adjust… At me of a Window 98

  2. on 03 Mar 2009 at 7:04 pm TheKidd

    I’m sorry…what?

  3. on 05 May 2009 at 1:47 am Cyrille

    That interest me!
    I can’t wait getting my LCD and 595s! ;)
    Will the library work with any HD44780 LCD like the original LCD4Bit does? I want to do that with a 40×2…


  4. on 05 May 2009 at 1:41 pm Cyrille

    (I meant 20×4)

  5. on 14 May 2009 at 1:39 pm TheKidd

    Hey Cyrille, glad you enjoyed. The code should work great with a 20×4 and does have most of the functionality of the LCD4Bit and will work with any compatible HD44780 controller.

    One note on the shift register. The main reason I incorporated that is because my Purdy LCD screen had two LCD controllers on it. Therefore the shit register allows me to shift between top two rows and bottom two rows.

    This should work great with your 20×4 row screen.

  6. on 26 Jun 2010 at 6:38 pm Collin


    Very nice project! Is it possible to add 3 more shift registers? Right now im contolling 3, 7segment displays with 3 595`s. The 595lcd has to go in front of them.



  7. on 02 Jul 2010 at 2:04 pm TheKidd

    I don’t see why not. I believe i saw a post on linked off of arudino.cc which was using the 74HC595N to do just that. I will see if I can locate it. I do know you can also control multiple shift registers with a shift register also.

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