[timehat]

While using a screen tester app on my wife's Nexus 7, I found that one of the test patterns made her digitizer freak out. I looked online and the app creator even made another app specifically to show the issue (though many people claimed it was a fake). I'm wondering if this webpage with the checkered black/white background (appears gray) causes anyone else's digitizer to stop responding. (Don't worry, the background auto-clears after 10 seconds so you can keep using your device.)

2013 Nexus 7 Digitizer Disabler

[NoraMelua]

No problem with the browser controls or the system keys when using Chrome. But each time I open the page in Firefox, the app minimizes itself.

What's the name of the screen tester app? I'd like to try it out myself.

[ErnstMach]

Wow. That actually screwed with my digitiser quite a bit in chrome. It would register touches all over the place, pulling up new tabs or even opening Google Now. As soon as the timer runs down and the pattern disappears, I get full functionality back. This is very weird... I wonder what's causing it

UPDATE: trying it in portrait mode is even worse... I didn't even touch the screen and things were going crazy. It was registering touches all over the screen, pulling down notification shades, closing the tab, scrolling all over the place, and again opening Google now. All this without even touching the screen

Posted via Android Central App

[timehat]

The app is called Nexus 7 II Tester

https://forums.androidcentral.com/e?...token=5uKUw4BN

While checkerboard patterns like this aren't found most of the time in general use, I wonder if some of the crashes people have when using the keyboard/general usage could be a result of this behavior expressed differently. The theory here is that the electronic noise the individual pixels create (one on and the adjacent one off) might be picked up by the digitizer (which I believe is integrated into the LCD panel in this new model) in the same way a finger causes some sort of electrical bridge or however it works.

For example, the keyboard has a gradient background. I'm not completely sure, but it looks like the LCD display is actually only 24 bits, so it may use some dithering to achieve a perceptual equivalent of a 32 bit depth. Perhaps some of the dithering artifacts could trigger this behavior as random touches on the keyboard.

When I've used the screen tester app by the same author of the app linked above, I saw that app crash when the digitizer freaked out. Perhaps something about the coding of the app not anticipating/handling the thousands of random "touches" all over the place.

[NoraMelua]

Thanks for the link, timehat!

The app registered about 20 to 30 random touch points without me actually touching the screen! Thankfully I haven't encountered any problems with the keyboard during regular usage, so I'm not overly worried. But I still wonder if this is a problem that can be corrected with a software update at all.