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I have 6 identical set-ups with a raspberry pi's (PI 3), and each of them has a 22 inch Dell touchscreen (HDMI / USB). The raspberry pi's are running latest stable Jessie with a kiosk browser (chromium) which is displaying a webpage (html and javascript), sourced from a local server (cable connection). No other heavy processes and no other devices attached to the PI.

The 6 PI's all run from the same SDcard (cloned); only the IP address is different...

The issue is that 3 out of the 6 set-ups respond very slowly to touch activities on the touch screen. To be more precise: when touching the display, the mouse cursor does not respond immediately, but it could take 1 - 2 secs before it responds (and after that, it works fluently). This is extremely annoying.

Things I've considered so far: - slow PI performance due to heavy webpages: considered this, but then all 6 PI's (and thus touchscreens) should behave in the same way since they all run exactly the same webpages, so I don't think this is an issue (more-over, I don't see heavy CPU or memory usage of Chromium) - bad USB cable Pi - Screen: I did try to replace the USB cable with thicker ones, and tried to switch the USB cables between the "good" and the "bad" set-ups, but again no noticeable difference - bad power-supply for the PI's. The Pi's get powered from a 5VDC stabilized power supply; 10A for 3 PI's (and the "good" and "bad" set-ups are split over those 2 power supplies), thus definitely enough available current. I did get the flash symbol occasionally, so I increased voltage slightly to get to 5.1 VDC and thicker wires, but this did not really help, though I had the impression it got slightly better. - when I close Chromium, the touchmouse on the "bad" PI's work as you would expect, so it does seem to be an issue related to Chromium (maybe the Javascript??), though it is still strange that some (identical!) set-ups do work, other don't - when I attach a normal USB mouse to the "bad" PI's, they work instantly, so the issue is really coming from the touchmouse

I really got out of ideas for solving this issue. I searched around, but couldn't find any tips that might help solving this.

Any thoughts? Anything I would need to check further...?

Thanks - Pieter

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  • Can you supply some more details about the touch technology being used... Is it resistive? capacitive? that could lead to some clues. A capacitive screen could potentially work in an unexpected way if it is dirty. When cleaning it should be cleaned all the way to the bezel. Are the screens raw parts or do they come in some kind of enclosure from the factory. If they are OEM parts it could potentially not be grounded correctly resulting in inconsistent behavior. Also, you should try swapping parts (screens, pi's and power supplies) to isolate the offending components (even SD cards)
    – Inflexionist
    Dec 21, 2017 at 22:38
  • Welcome to the Raspberry Pi flavoured corner of the Stack Exchange network - you may like to take the tour at some point which may give you some insight into how this place operates. This actually sounds like an interesting setup - do you have any pictures - not necessarily to show the touch-screens and the issues (though it could help) but so we can gawp and point others at them (once this issue has been sorted) 8-)
    – SlySven
    Dec 22, 2017 at 5:12
  • What are the details of the touch screens - do they have any "power-saving" modes that puts them to sleep after a period of inactivity...
    – SlySven
    Dec 22, 2017 at 5:19
  • Update: 1) the touchscreens are 22 inch DELL S2240T (Capacitive). Simply connected with HDMI and USB to the PI, no power-saving mode (only black screen after period of inactivity, but this is managed by the PI) 2) screens are not dirty, no stains, nothing.. each of them approx only 2 months old 3) in the mean time, I use KWeb as kiosk browser (instead of Chromium), and the situation improved a lot, yet the "bad setups" have an occasional slow response (let's say once every 10 minutes). The good setups worked (and still work) well.
    – pieterdp
    Jan 9, 2018 at 19:23

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