4 wire resistive EDT 7" display faulty touch detection

Hi, I am using the EDT 7" 800x480 display. Sometimes after pressing and releasing the button, it appears to be stuck and falsely detected as pressed by the touch screen. The button “checkable” property(Qt) is disabled. The button is released when some other part of screen is touched or mouse is moved. This faulty touch happens to any button present on the GUI

Any help is greatly appreciated

I don’t think that the source of this issue is on hardware or driver level. To verify this, please try to click any OS buttons (e.g. the START button or the virtual keyboard). If my guess is correct, this should still work fine.

Maybe the Qt framework or your application does not handle special situations properly. For example, what happens if you “drag-and-drop” a button - press on the button, keep the touch pressed while moving your finger away, then release the finger outside the button, or on another button. In this operation, the faulty button might receive the “press” event, but miss the “release” event?

I tried the “pressing and dragging” of button, but it seems to work well.
Please note that the false detection does not happen all the time but once in 12-15 chances

Dear @Eshwar
The drag-and-drop was just one possible idea.
Please try to find out whether the issue is OS, Hardware or Qt related (or which combination). Some ideas:

  1. Can you reproduce it using a mouse?
  2. How about OS buttons (they are working perfectly fine here)?

Herein i have attached a video of the issue.
As you can see in the video, when we clicked on a folder in explorer using a stylus, it got selected. As we released it and moved the mouse, the folder was moving along as if we are have clicked the folder and are dragging it. This was happening without our application running
HW issue video

I see that you have some additional film between the screen and the stylus and that is has some bubbles. Can you try to remove this? It may be that this film stitches to the screen when you click the stylus and may prevent the underlying touch screen from detecting its detachment.

Can you also try to change the parameter:




If this fixes the issue you can try to reduce the value to 4 or 3 and keep the lowest value that is not generating problem.

I have checked the registry settings and for me the STMPE811_Settling key does not exist under [HKLM\HARDWARE\DEVICEMAP\TOUCH].

So, I have created it.

FYI, the keys under my [HKLM\HARDWARE\DEVICEMAP\TOUCH] are now:

(Default) REG_SZ (Value not set)

CalibrationData REG_SZ 513,498 796,789 804,203 218,203 215,786

DriverName REG_SZ colibri_touch.dll

STMPE811_Settling REG_DWORD 5

The issue seems to have stopped, I will confirm after running more tests

Can you give a short explanation of what this setting is doing?

Yes, the default value (2) is used if the key is not there, so it’s ok to add it to override that setting.

Dear @Eshwar
Resistive touch screens require analog measurements - voltages are applied to particular pins and the analog voltages are read back on other pins. After applying a voltage it takes some time for the resulting voltages to settle. The required time is longer for larger screens and longer cables (due to larger capacitance). This settling time is configured with the STMPE811_Settling parameter.
If you have an oscilloscope around, you can hook it up to the 4 touch signals TSMX, TSPX, TSMY and TSPY to see the difference.
Regards, Andy

Dear @Eshwar

Can you please send us some oscilloscope pictures of the 4 analog touch signals. This will give us an understanding how to optimize the settings for your case. Please have a look at the pictures below as a reference how the measurements could look like. I took them on my Evaluation Board which was equipped with a Colibri iMX6DL (default settings) and a 7" resistive touch screen.

Keep touching the screen

short click onto the screen

Regards, Andy

alt text

Dear sir, as desired by you I have attached the oscilloscope screen shot for pressed button and clicked button.

@andy.tx cuadra has uploaded the required images. Please have a look and give us the solution for the touch screen issue

Dear @Eshwar
The signals look fine, so we can say it’s most probably not related to your hardware.

Meanwhile I was also able to reproduce the issue here and already got some insights what could happen.

We have to do more investigations to identify the root cause of the problem and find a fix. We will keep you informed.

Regards, Andy

Dear @Eshwar
Our analysis proved that we can solve the problem, but it will take some time. We planned to implement a fix in the June/July time frame. Is that suitable for you?
Regards, Andy

Dear@andy.tx, already we have finished the project and we are entering in production phase. If you are going to solve the problem in June/July it will be too late and we have to stop entering in to production activity. We request you to give the solution till the end of May 2018.

Dear @cuadra
Thank you for the feedback about your schedule. I’ll get back to you after our weekly metting on Thursday.
Regards, Andy

Dear @cuadra
We will prioritize this issue and get back to you with a solution (or at least a workaround) in the second half of May 2018.
Regards, Andy

Dear @andy.tx , I hope you must have found solution to our touch screen problem. As we are unable to launch the product due to this problem , request you to update me on this issue.
You assured to solve this problem in second half of May 2018.