P2714T, touch screen ignores quick taps

Question

SN: CN-03K257-74445-37T-008S, bought 20 November 2014 (yesterday)

rev. num. A00

Computer - Desktop (motherboard ASUS M5A78L-M, processor AMD FX-6200)

OS: Windows 8.1

Radeon HD 7700

Monitor is connected via HDMI + USB(for touch)

The cables came with the monitor

resolution 1920*1080, 60Hz

The issue is that the touchscreen ignores the first quick tap after not being touched for about 6 seconds. That often prevents me to invoke Windows Charms menu, as well as simply ignoring taps. If I do a prolonged tap (about 1/4 of a second), the touch is recognized. Further taps are recognized very well unless I let the touchscreen alone for more than 6 seconds.

I have tried downloading the software fro the monitor's support page, in hope it will update the firmware or otherwise fix the problem, but it didn't help. I've also run the built-in diagnostic with no problems (it looks like it only tests the display, but not touchscreen)

I've done a quick test by placing oscilloscope probe near the touchscreen. I observed that after 6 seconds of rest, the continuous train of pulses transforms into bursts of pulses. This transition seems to coincide with the onset of the problem.

Is there any chance to fix the problem... It's quite annoying.

DELL-Chris M · Accepted Answer

We could not replicate this issue on multiple P2714T. Contact Dell Technical Support for your country to have them setup a monitor exchange.

DeepSOIC · Accepted Answer

It looks like I have solved the problem.

The solution:

Open device manager. Find the USB hub devices that are inside the monitor (I saw two). Go to properties -> power management and disallow powering off the device for energy saving.

I've done the same to a bunch of HID devices too, and the problem is finally gone. I haven't figured out yet what exact devices need to be kept awake... And I haven't yet got it to work on the stationary PC - only for the notebook so far.

Excuse me for imprecise names of the UI items - I have a Russian version of windows :emotion-4:.

As for the replacement - I've asked for it, but I was told that no new monitor was available, and I can send it for repair. I decided not to, and I've taken the monitor apart to see if I can do anything myself. And after a bit of investigation it turned out I didn't have to take it apart Oops!

DeepSOIC · Answer

A quick update: I've connected the monitor to my notebook (Sony Vaio Duo 11, Windows 8.1) and I'm still getting the same problem, so it's not the computer at fault.

DELL-Chris M · Answer

Unplug and re-plug the power cable from the power adapter to allow auto-recalibration of the touch module. Open Control Panel, open Hardware and Sound, and then open Tablet PC Settings. Select Calibrate. The User's Guide states that touch response time is < 10ms. Are you saying that your testing is showing a 250ms touch response time after no touching for six seconds?

DELL-Chris M · Answer

I will email the Displays team to get their thoughts. I should get a response Tuesday or Wednesday.

DeepSOIC · Answer

Thanks for your answers!

The User's Guide states that touch response time is < 10ms. Are you saying that your testing is showing a 250ms touch response time after no touching for six seconds?

Well, I've done the measurements by recording a few videos, and the touch response time after no touching for >6 s is somewhere between 75 and 120 ms. I.e. if the touch lasts for less than 75 milliseconds, it is ignored. if it lasts more than 120 ms, it is detected. What happens between those figures - I don't know, I cant force my touch to last for some exact time.

Unplug and re-plug the power cable from the power adapter to allow auto-recalibration of the touch module.

Done. No chages.

Open Control Panel, open Hardware and Sound, and then open Tablet PC Settings. Select Calibrate.

Done. The calibration went without problems. But it didn't help.

DeepSOIC · Answer

Anther small update: I've run windows update (something that I haven't done for more than a year). It was a lot, including two updates mentioning DELL. But the symptoms remain.

DeepSOIC · Answer

Hi again! No news so far? I've just got an update for Dell Display Manager. I've installed it. Unfortunately, the problem is not resolved.

DELL-Chris M · Answer

This will be a long investigation.

DeepSOIC · Answer

Chris, thank you very much for support! I'll try.

Monitors

P2714T, touch screen ignores quick taps

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