Duemilanove Confusion
 

I cant get my MPGuino to work. It will power up but the screen displays random symbols and letters or nothing at all. The backlight does turn on though.

Arduino Duemilanove Atmega 328 (works for blink example code)
16x2 LCD HD44780 compliant.

I've checked and rechecked my wiring and it all looks good.

I've tried every version of code that I can find. cpp,pde,wtf

I've tried Arduino 21 and 13

My guess is that I have the wrong code still...

Please help, Im totally lost and frustrated

Thanks

Whenever that's happened to me, it was a solder problem between the guino & LCD. In those cases, i could sometimes get it working by bending the wires a certain way, until they were resoldered. Note that if the display gets corrupted or out-of-sync, you will have to reset the mpguino to get it going again.

I cant see any solder problems and bending wires isnt changing anything for me. Will it hurt anything to take a multi meter to it? Check for continuity.

Also does anybody know exactly which version of code I should be using?

By all means, do check it with a multimeter.

Code version shouldn't hurt/help your LCD problem. You should probably start out with the pde, then work up to the cpp once you can see on the LCD that it's wired up correctly.

Well, all the wiring checked good with the multimeter. Im starting to think that I might have a dud LCD or Arduino.

I was looking through some wiring diagrams for the LCDs and it looks like the backlight is a separate circuit. Which leads me to believe that the Arduino is crapped because the backlight does not dim when I press the middle button (I think thats the dim button). Maybe Im uploading code wrong?

I was going to try the "hello world" example but I dont have a 10k pot. Is there any other way to test the LCD?

You dont need a pot to test LCD - it is for contrast.
Just make that pin "Analog out" and send there some value - example 100 (it is 0..255 so 100 should show something)

Meelis

cool. Thanks. I will try that right now.

Another thing. My LCD says it is HD44780. But pins number one and two are labeled different in the data sheets. The official ones that most people use are labeled VDD and Vo. Mine are Vcc and VEE. I would think it is the same thing by a different name but Im not sure of anything anymore.

Update: The Confusion Grows

I hooked it up for the "Hello World" example. I needed a small jumper for the wire going to the Analog out contrast (the one that should go to a pot). I grabbed a diode because I had one laying on the table and the wire ends are the right size to fit into the arduino headers. Everything worked great.

Then I grabbed a piece of wire to replace the diode, just for a slightly better setup. The letters then went crazy again.

I have tried it many times in both setups, it will always work with the diode and never with the wire.

The diode is properly oriented. And once the display is working jumpering across the diode with wire does not make it go crazy. It just gets slightly brighter.

I guess my next step is to wireit up mpguino style with the diode on the contrast pin and see what happens.

Any other ideas?

Are you sure that you dont mix (in schematic or in text here) brightness pin and contrast pin?
Contrast pin should not make screen brighter.

Umm. I mean that the text stands out little more. The backlight does not come on at all in "Hello World" configuration.

I did wire it up in MPGuino mode with the diode on the ?contrast? pin. It almost worked it powered up and said "ontrast 3000" or "$ontrast2" kinda stuff. After I press random buttons and get outof that screen it said " 350 0"
" 350 0" or someting like that.

Also I found out that the backlight does cycle through brightness settings. I had a bum button.

Im gonna guess that my screen is stupid and order a new one.