Comments on: Arduino LCD Interfacing Part 1

By: Tweeks

Tweeks — Sun, 06 Jul 2008 04:26:32 +0000

I’m using the Arduino LCD4bit library with a HD44780 4×20 unit. I found that some of the init timing was not to spec (100uS instead of 160uS, etc). But the stock connections of 2(E),7(d4),8(d5),9(d6),10(d7),11(_R/W),12(_I/D) didn’t work. I had to tie _R/W to ground instead of 11, even though I hadn’t disabled it. But everything worked after that.

Tweeks

By: John

John — Mon, 01 Oct 2007 12:20:58 +0000

Yes your right those ads don’t do much anyway! and I removed that anoying external popup it’s now DHTML so can be ignored on home page!

Here’s a link to the ezine page to get access to the lcd-keypad project:
http://www.best-microcontroller-projects.com/ezine

The LCD keypad should be applicable to any microcontroller.

By: dfowler

dfowler — Sat, 01 Sep 2007 04:12:39 +0000

John,

Can you provide a link to the article that describes LCD interfacing? I tried the link you provided. The site is so full of ads and popups that I cant find anything.

By: John Main

John Main — Fri, 31 Aug 2007 06:32:11 +0000

You can interface a standard 12 button keypad and an LCD in 4 bit mode on a single 8 bit port without any extra interfacing circuits or components.

Check out the ezine page at http://www.best-microcontroller-projects.com

By: JohnS

JohnS — Thu, 26 Jul 2007 14:36:27 +0000

Hi Dave, great article, and you probably saved me hours by talking about commenting out the lines in the LCD library! Once I got that fixed, it took me quite a while to write to the second line of my display. I eventually figured out that the library does not default to a two line display so moving to the second line or writing there was impossible.

There must be some magic to editing the library (probably some compile step I don’t know yet) so I couldn’t get changes to take there. I finally pulled the whole init routine out of the library and put it into my main program and all worked well.

Now that the LCD is working well (in full 8-bit mode), I’m putting together a panel with 3 LEDs, 5 push buttons, and a beeper.

Thanks again for pointing me toward this mini Arduino board. It’s awsome.

John

By: xSmurf

xSmurf — Tue, 17 Jul 2007 02:28:10 +0000

@dfowler #12: Fair enough! Work is keeping me a little busy, but I guess there’s this time when you’ve gotta give back ^-^ As I said most of my stuff is still packed away, but it’s a good enough reason to unpack them. I’ll look into it It’s too bad I messed around the breadboard (3 wide), I pretty much had everything set. Ok enough talking…
*reaches for them boxes*

By: Axeman

Axeman — Tue, 10 Jul 2007 07:22:32 +0000

@dfowler

Yes, the library contains some form of 4 bit initialization, and if I remember correctly, that init sequence is the one shown on the old Hitachi 44780 datasheet. Unfortunately, it doesn’t work on every version of 44780 (or equivalent LCD controller). Also, timing is critical in the early init phase is if the busy flag can’t be read (and you can’t read busy flag with R/W tied to ground). I’ve used delays in MILLIseconds range in the init…

On the “new” datasheet http://web.mit.edu/6.115/www/datasheets/44780.pdf there is an updated init sequence for 4 bit operations (page 42) that “should” work nearly anywhere.

Anyway I’ll be able to recover my original PIC source code and post it here in a few days…

By: dfowler

dfowler — Mon, 09 Jul 2007 23:06:14 +0000

xSmurf,

This is the kind of article that I would like to have at uC Hobby. Pack your text, some links and some pictures into a short How-To for uCHobby and receive an Ardunio kit.

By: dfowler

dfowler — Mon, 09 Jul 2007 23:04:07 +0000

Axeman,

I assumed that the Arduino 4-Bit LCD library would do the initalization.

http://www.arduino.cc/playground/Code/LCD4BitLibrary

The instructions indicate that I should only need to tie the R/W to ground to make it work. So far my LCD just sits there when I try to use this Library.

I have tried leaving the extra data bits open, grounded and tied to VCC. Any help would be aperceiated. I guess I will have to dig into the library code to figure this out.

By: Axeman

Axeman — Mon, 09 Jul 2007 20:59:49 +0000

@dfowler: The 4 bit mode requires a special initialization, ’cause LCD starts up in 8 bit mode, so you must send a “fake” set of 8 bit commands using only the 4 bits connected. The first time I used 4 bit mode, I had to find the tricky sequence (and the right timing!!!) by trials and errors.

I have the resulting function and timings that SURELY works on my server, but it’s still boxed in the basement after I’ve moved in the new house.