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CFAG320240CX-TFH-T-TS Touch Screen Problem

swright

New member
I am working with a CFAG320240CX-TFH-T-TS connected to a PIC and programmed with Swordfish Basic. The display is working fine and I can reliably draw on the display and write text. However, I am now trying to get the touch screen working but have come across problems. The driver circuit consists of 4 transistors to pull the X and Y elements high and low and the analogue ports of the PIC are used to read the output. The circuit works fine for a while and gives consistent ouputs. However, after a random length of time that can vary from a fraction of a second up to many seconds, the screen clears and then nothing else is written. Blue edges then start appearing around the edge of the screen, as if the panel has turned off and not reset. If writing to the display is disabled, the problem goes away. Disconnecting the touch scree also removes the problem. It only occurs when the touch screen is connected and the display is written to.

One suggestion that has been made is that there is capacitive coupling between the touch screen and the display. If so, what could I do to eliminate the problems caused by this?

Thanks in advance for any help.

Regards,

Steven W
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swright

New member
The FG is floating, but I've also tried it grounded with no benefit. The touch screen controller circuit is attached.

Thanks for any help.

Steven
 

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swright

New member
I'm still having trouble with the display resetting at random intervals due to the touchscreen. I have added a R-C filter circuit to each of the touchscreen connections to try and remove any noise from fast transients on the switched touchscreen electrodes, but this has made very little difference. Any further ideas would be most welcome.

Many thanks,

Steven W
 
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