The main problem with these things is initialization. Does it initialize? You need to wait ungodly amounts of time before it starts talking.
The first time I tried this, though, I had some problems, so I built a little breakpoint routine that would wait for button presses before proceeding. With that, a listing, and a multimeter, it was easy to figure out what was going wrong. If you do this, make sure you debounce the button.
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Regards,
Bob Monsen
If a little knowledge is dangerous, where is the man who has
so much as to be out of danger?
Thomas Henry Huxley, 1877
I've googled for a 4bit LCD PIC program and I've come up with several. I'm not really sure what I'm looking for though. I've been using a pic16f873a uC, and every bit of assembly code I've tried to run for my LCD doesn't work. I've checked the obvious, like contrast and physical hookups. My LCD is a 24X2 character unit from crystalfontz.com. It has an industry standard driver. Maybe someone here could point me in the right direction on where to find simple, easy to use code to work my LCD in 4 bit mode. Short of something that I can cut-n-paste, maybe someone could show me a good article on LCD assembly programming for a PIC. I'm not afraid to research on this, just would like your opinion on what code to use. Thanks...
HD44100 is the expansion chip, the one he wants is the HD44780.
As far as I can tell, the clones (Samsung?) behave close enough to the same as the original and 2nd generation Hitachi parts.
You'll probably find it easier and more satisfying to just write the firmware from scratch rather than trying to debug all the random errors you'll find in the stuff you can download. Some of it will probably break or will be unreliable if you go, say, from 4MHz to
20MHz even if you fix the delays (because of setup and hold times).In particular, make sure your delay routines are really generating the required delays. I've seen gross errors, even in delay routines distributed with expensive compilers. You can easily use the stopwatch function in MPLAB to verify the delays.
Get the hd44100 datasheet or the one for the chip on your module, turn to the page with the timings for each command, now check your initialization routine, are you waiting ~5ms on one of the steps? you should...
Best Regards
-- Steve Sousa
I do have the datasheets on my parts, but wasn't paying close enough attention to the code. The timing could be the problem. I haven't verified this, but I'm sure that the code was running at 4MHz and I have a 20MHz xtal. I'll rewrite the delays, and give it a try. Thanks...
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