LCDInfo.com

Hi all,
just tried to connect a GDM12864A(KS0108) to a parallel port(64128A_ver2.pdf), but nothing works. The display is (was?!) brand new.
I was wondering if (despite all the other things that may go wrong), the display, once powered should show something with the contrast pot turned either counterclockwise and/or clockwise.
I say that because I can't exclude a wiring problem, but I was thinking that I should be able to see the pixel pattern(very lightly), but actually the display is perfectly "blank". This is little scaring me...

I tried to check with a logic probe the signals and they toggle while using the test program, I even tried to leave one CS connected and tie the other to the ground. I also changed the computer and the results are the same.
What else should I try?

TIA,

Giuseppe Marullo

The display should turn black (or some other color) when turning the contrast potentiometer. This should happen even if there's no pins connected to the parallel port cable.

You should try measuring the contrast voltage to see if it's ok.

This is your display ?
http://perso.wanadoo.fr/rs-rey/electron ... 12864a.pdf

Henri,
thank you for your answer. Yes, this is my display, purchased thru www.elettroshop.it

I have just checked this schematic( http://www.elettroshop.it/download/vari ... 16F876.pdf )

where the potentiometer is tied to Vdd, Vee and V0.
On the schematic I used(www.skippari.net) this was tied to Vss. I hope I have not screwed it.

This should explain why it remains blank. I will try this evening, finger crossed.

Thanks again, I will report results here...

It shouldn't have done anything bad there. There just probably wasn't enough contrast voltage.

If Vee is -5v for example
then Vss <-> Vee = 5v
and Vdd <-> Vee = 10v

Henri,
thanks for your help. It works! I had to rewire the potentiometer to Vdd and voila, I am testing it now.
It turned out that the central lead of the micro potentiometer was not were it was supposed to be. Ouch. Luckly the magic smoke didn't come out.

I am using the included vcl, impout32.dll driver under w2ksp4 and the test program works fine.

I had to install LINX driver to let LCDInfo work, and the clock digits seems a little too big to fit, other things are perfect.


Do you know where could I take a look at some simple Delphi examples that drives the display? I have to translate them to use the LCD on my robots also!

For KS0108 I'm not aware of Delphi examples.

Here you can get some Delphi source for T6963C that might be of some help in the process: http://www.skippari.net/lcd/t6963c_prog.html