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Intermittent Touch Fault
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Intermittent Touch Fault

by pharmacare on Wed Apr 21, 2021 8:50 am

Recently I purchased a 7.0" 40-pin TFT Display - 800x480 with Touchscreen together with an RA8875 Driver Board for 40-pin TFT Touch Displays. I built a PCB and I am controlling the display using an Arduino Nano (refer to attached image). It noticed however that at very random intervals (sometimes it takes hours), the touch screen stops functioning correctly.

When I connect it to the Arduino serial monitor (during the fault) I noticed that the co-ordinates value differ from the usual values and this is very odd. I reset the board and the issue disappears immediately. Note that I am driving the RA8875 through an external 5V power supply (SCWN03B-5) not the 5V of the Arduino (obviously I connected both grounds together). The reason is that when connecting the 5V from the Arduino the fault is escalated even more.

By any chance do you happen to know the reason why this touchscreen issue is occurring pls?
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pharmacare
 
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Joined: Fri May 26, 2017 8:52 am

Re: Intermittent Touch Fault

by pharmacare on Thu Apr 22, 2021 5:47 am

Further to my previous post I did some more debugging. I noticed that when the fault occurs not all the of the screen remains sensitive to a touch. he picture below describes roughly where it remains effective. Also, when the fault occurs I noticed that some colors on the display change (refer also to the attached image and the image in my previous post for comparison). To obtain the touch co-ordinates I am using the X+, X-, Y+, Y- pins not the INT. It looks like this particular issue is related to the RA8875 driver board but I don't know what else I am going to do.

Could it be a voltage noise on supply issue? Or a cooling issue?
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pharmacare
 
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