user question to developers - digitizing screen spikes

[fireflyrsmr]

my newton used to create random spikes as i wrote on the screen. i've noticed that my iPAQ 3670 does the same thing. It does not happen all the time but seems to happen more with some software and not at all with others. i'm sure there is all kinds of magic (tuning) that you guys must do to get the signals from the screen to pixels. My question is how do i know when the screen is dying? I'd consider a new screen (or machine) if i could avoid these spikes but i suspect they happen to everyone with a paint program (for instance).

I'm expecting someone is going to tell me that this is an issue you all have to work around and you do it with some kind of buffer. Calligrapher 6.5 never seems to spike. When i'm drawing with Pocket Artist i occasionally get some which is a pain. :x I'm really just looking to understand this aspect of the machine better. Thanks.

[PPCdev]

Not being argumentitive, but Im not entirly sure what you mean by "spikes". Are the random dots that appear on the screen in areas other than which you are writing, or in screen areas your pen is dragging at the time?

I only have a Maestro, never had any artifact on the screen what so ever using Transcriber or any other writing software, nor have I while using any paint software.

I suspect what my possibly be happening is, the digitizer is sending erroneous information along with legitimate information to the OS, and the OS is responding with placing pixles where it was "told".

The top most layer of the "screen" (actually screen assembly) is the digitizer, below that is the LCD dispaly that shines -through- the digitizer.

It is possible the digitizer is defective and the screen is perfectly fine. It could also be that the screen is defective and throwing pixels where they are not supposed to be.

If, while you are writing or tapping, dots appear where they are not supposed to, but are erased when you switch to another screen, etc.. etc.., Id suspect its the digitizer.

If while your writing, dots appear that stay there until its powered off, I would suspect its the LCD screen.

These are my thoughts, though they may be incorrect, I still hold them as mine. :-)

Good luck

[Janak Parekh]

PPCdev, you don't know because you've never seen it, most likely. Close guesses though. :)

fireflyrsmr, I hate to tell you this but it's the digitizer. It's particularly a known issue on the 3600 series -- as the digitizer "wears out", it tends to spike. For what it's worth, HP released a ROM update that reduced the sensitivity of the digitizer somewhat, so the spiking effect is reduced. If you already have that ROM and are experiencing problems, then you're SOL. :(

The fact you're experiencing it with some software and not with others would indicate to me more that certain software use certain worn-out areas of the screen more than others. Most heavy 3600 users would find the spiking to be worst in the lower-middle of the screen, where most of the text input was done and as a result where the digitizer wore away the most.

--janak

[PPCdev]

Janak Parekh, Hey man, I got close! Is that good for a star or a brownie or anything? HEHE!

[fireflyrsmr]

ok - i understand, kind of. and yes i would guess that compaq would consider me a heavy user. 7 days a week several hours. thanks for the information. I'm not aware of it happening in particular areas of the screen. as i said i use calligrapher and write everywhere all the time with no spikes. i'll watch of it though until i get it fixed or change machines.

I knew that the screen was a layered construction but i don't really understand what makes up the digitizer part. is it a real fine grid of - something like wires - and your telling me that the grid is breaking down? again i'm just curious. i'm surprised to be the first one asking about this. 8O I did a search in the forum and couldn't find any information about it. i thought maybe it meant that my machine was busted and PPCdev's response seems to indicate it is more rare than common. next stop ppc tech.

PPCdev how about a big lick from my beagle? :wink:

[Janak Parekh]

I knew that the screen was a layered construction but i don't really understand what makes up the digitizer part. is it a real fine grid of - something like wires - and your telling me that the grid is breaking down? again i'm just curious. i'm surprised to be the first one asking about this. 8O
It's thin glass layer on top of the LCD, if I remember correctly. If you hold your PDA under a light at the right angle, you'll see it - it does look like a "grid". Take a look at this link at PPCTechs (http://www.pocketpctechs.com/ppc_faq/ipaqTSrepair.asp) for some more info -- even though they particularly focus on the cracked problems, that's not the only time the touchscreen needs replacement.

Oh, and BTW, you're not the first to ask. :) This used to be a very common question when the 36xx units were dominant. Check the Brighthand forums, for example (PPCT didn't have forums back then...). It's died down a bit now as newer units seem not to be prone to this problem.

--janak