MCUFriend TFT2.4 UNO Shield touch calibration

Hi Everyone.

The MCUFriend library work fine with all the examples , identifies the TFT Screen as ILI9341.

Arduino ide 1.8.15 and UNO R3.

When I run the Calibrate sketch with UNO and TFT Shield connected to my pc (Power from pc USB Voltage is 4.2V) calibrate ok.

When I remove the UNO from the pc and supply 12V to the UNO dc jack socket the calibration is out with around

I had some internet connection problems so my post was saved to Draft.

Later when I send the Draft I saw the botom lines is missing .

Should read ..calibration is out with around 5 pixels.

and

Thanks for any advice.

Why would anyone want to use 12V ?

The current Mcufriend pcb is badly designed. The backlight is powered by the wimpy Uno 3.3V pin.

I suspect that the working voltages are different between using USB and external jack. Simple enough to check with a DMM. e.g. measure the 5V pin and measure the 3.3V pin. Compare with the voltages obtained via USB.

Anyway, it is simple enough to tweak the Calibration values.

David.