XPT2046_Touchscreen is a library for the XPT2046 resistive touchscreen controllers used on many low cost TFT displays.
The XPT2046 chip has an interrupt output, which is typically labeled T_IRQ on many low cost TFT displays. No special software support is needed in this library. The interrupt pin always outputs a digital signal related to the touch controller signals, which is LOW when the display is touched. It also is driven low while software reads the touch position.
The interrupt can be used as a wakeup signal, if you put your microcontroller into a deep sleep mode. Normally, you would stop reading the touch data, then enable the interrupt pin with attachInterrupt(), and then configure your processor to wake when the interrupt occurs, before enter a deep sleep mode. Upon waking, you would normally disable the interrupt before reading the display, to prevent false interrupts caused by the process of reading touch positions.
Touchscreen Arduino Library for XPT2046 Touch Controller Chip – [Link]