emWin and touchscreen example

Hi, I'm trying to understand how the touch screen works on the Embedded Artist's LPC1788 developer's kit with the 7" LCD board.
I've loaded on the board the example obtained from segger's website, with the LCD_Conf.c patch from EA's website. I've noticed a problem with the coordinates of the touch screen: when I press a point, the cursor is displayed elsewere.
Also with the "Industrial demo" example I have great problems with the coordinates. In this second example, it is very hard to move the sliders control.
If I use the TOUCH_Calibrate.c example in the sample/tutorial directory of the NXP's emWin 5.14 BSP file, I cannot touch the two points used for the calibration: the touch screen appears unable to detect the pressure of the fingers.
I want to use one of this example as the basis for a "virtual keyboard" application. Have you any suggestion? Any help is greatly appreciated.