Capacitive touch screens are very sensitive to power noise. Ripple voltage/current from the power adapter can cause the LCD ripples, as well as the malfunction of the capacitive touch. If you use the APK Multi-Touch under Android to test it, you can find the touchpoint float. You can solve this problem by using
- a high-quality power adapter.
- a battery to provide the power, like a cell phone or tablet PC
If the power adapter isn’t good enough, make sure Pin 3 is connected to the Ground. This can eliminate the problem totally. You can test it by touching the Ground of the product with one hand, and the capacitive touch screen with the other hand.