GLCD and TouchScreen trouble

[Ron Marcus]

Where does the frame ground go? (pin 18)

[mister_e]

Silly questions:
1. What happen if you remove ALL ferrite beads?
2. what happen if you leave all unused i/o to input when you do ADC reading instead of setting them to LOW or HIGH
3. do you have any 10uF-47uF tantalum capacitor close to the GLCD Vdd rails
4. What happen if you use lower voltage for ADC convertion.
5. what happen if you tie VEE to GND with a 10k resistor
6. what happen if you load WAIT pin to GND or VDD with a resistor?
7. What happen if you slow down the ADCs readings?
8. How far the GLCD is away of the PIC?
9. What happen if you use some resistor in serie to the adc pins + 0.1 uF to GND?

[SteveB]

Skimask:
Is the bezel of the touchscreen or the GLCD painted? Maybe that's why it isn't getting a good ground?(pin 18)
The GLCD is painted black

Ron:
Where does the frame ground go? (pin 18)
I've got it tied to the GND rail on the breadboard

Steve:
1. What happen if you remove ALL ferrite beads?
No Change, thats what I started with.
2. What happen if you leave all unused i/o to input when you do ADC reading instead of setting them to LOW or HIGH?
I assume you mean the i/o connected to the TS. If this is the case, any pins connected to the TS that don't need to be driven a specific direction are made inputs so the pin floats. Typical, you drive one direction (X+ to X-) then read the opposite neg (Y-), and leave the other pin (Y+) floating. The exception are the pins used for ADC (A0 and A1), those are stuck with being analog inputs (at least A0 is).
3. do you have any 10uF-47uF tantalum capacitor close to the GLCD Vdd rails
Nope, good idea, and I imagine it can't hurt.
4. What happen if you use lower voltage for ADC convertion.
haven't tried it yet, I could drive it with 3v, probably using some MOSFETs I guess. I will put this in the hopper to try if/when I can
5. what happen if you tie VEE to GND with a 10k resistor
Don't know yet, into the hopper
6. what happen if you load WAIT pin to GND or VDD with a resistor?
Don't know yet, into the hopper
7. What happen if you slow down the ADCs readings?
By slow down, do you mean the frequency of readings or the actual ADC aquasition time?
8. How far the GLCD is away of the PIC?
They are at least 6 inches apart, at times as much as 8 or 9. I've use an old floppy drive cable to plug into the GLCD and break out to the breadboard.
9. What happen if you use some resistor in serie to the adc pins + 0.1 uF to GND?
I'll try this with the caps on the GLCD rails. Quick and easy to implement. Got a suggestion for the resistors, I'm thinking 330, or maybe even lower.

I'll start with the decouple caps first (and the suggestions from above posts, like Ron's poly bag for trouble shooting purposes), as they should be there anyway, then work through the list as I get time. Busy week at work. (I've written the last two posts on lunch/dinner breaks).

Thanks to all for the helping hand,
Steve

[SteveB]

More Info after some playing:
- Static sheild products had no discernable effect. Except that the "foil" loking bag (I tried a plastic product as well) actually caused the same phenomona just on it's own on e time, but I could not repeat it.

- Caps and Resistors, both and seperately, did not help, and caused problems with the TS Scanning. Decoupling Caps don't help either.

- I slowed the frequency of the scans, but no change. Increase the ADC time. No change.

I did have succus with a "frame" made of 18gauge bare copper wire between the GLCD and the TS. But, If I only put the wire on two or three sides, it wouldn't consistantly solve the problem. I might try to find some copper sheet and cut out a frame to see what that does. I may also try connecting it to GND.

I think that leaves working with the Vee pin, Wait pin, and driving with a lower voltage.

SteveB

[Ron Marcus]

Have you tried disconnecting the frame ground altogether? With audio work, I know ground loops can be induced with multiple connections to the same point. Try moving it around on the board and see if this has any effect.
Ron

[mister_e]

mmm, it's one of those thread i wish i could have the same hardware on hand...mmm

One thing is sure, the 0.1+10-47uF have to be mounted on the GLCD board. Now i don't know how good this will be if you use a dedicated voltage regulator ONLY for the glcd...

I'm thinking the Vee and Vo pin should be connected to a Trim pot as per the datasheet, unless some noise may go directly to the Column/row driver and produce some kind of problem... sure it's something like that. Kind of floating MCLR... sort of.

keep thinking...

EDIT: yeah ground loop could be something like that as well.