Potentiometer Question

[Brady]

I recently purchased a custom CFAG from CrystalFontz, with the T6963 controller. I have run into one problem, and I'm not sure what the root of the problem may be.

We initialize all of our home addresses, modes, etc, but we still don't see anything on the screen, even if we write something to it.

We think it may be one of two things, or both:

#1)
We purchased this LCD no potentiometer on it, so we had Vee and Vo sitting as open. We figured we'd need these for contrast adjusement, so we purchased a 10k pot, hooked the wiper into Vo, and hooked the other two pins on the pot between Vee and 5V (Vee is called '-20 V, Negative Voltage, and Vo is called 'Power Supply For LCD Driver', with no value given). Is it possible that the contrast is still too dim and we're just not seeing the data?

#2)
The microcontroller we're using operates at 40Mhz. We're sure we've accounted for the delays with rise and fall time of certain bits (C/D, RD, etc), but we're still stuck.

Any suggestions anyone?

Thanks,
Shawn

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[cosmicvoid]

Have you checked that Vee is actually present? What is the range of Vo that you can set with the pot?

Do you have a link to the controller data sheet?

Also, see my answer to your duplicate post in the LCD Industry Forum.

 

[Brady]

Figured it out...

Ok, I figured it out.... it's not exactly good news. Turns out the model has no negative voltage out... essentially, Vee is 0. Can anyone recommend a regulator, or circuit that may do the trick for me?

Thanks for all the help!

 

[cosmicvoid]

I seem to recall a similar thread in the past year. Someone had a CFAG display but the footprint where the voltage inverter was to be located was empty... unstuffed.

I think that the inverter is a 7660 or equivalent, in a SOT package, but maybe CFTech would remember better.

Anyway, you could try a 9 volt battery as a negative voltage source, just to see if it makes the display visible.

 

[CF Tech]

The only difference between a "-V" and a "-N" is whether the parts for the negative voltage are loaded. I think cosmic is right, it is a 7660. The 9v is good idea for initial bring-up.