Touchpad pen-input controller

Abstract

Systems and methods for the detection of motions of a pointed object upon a writing surface such as a touchpad is disclosed. The motions will be detected and converted in a multiplexing analog-to-digital converter to digital codes representing the location of the pointed object and the pressure of the pointed object upon the touchpad. The location and the pressure will be translated into a pen detect signal indicating the presence of the pointed object upon the touchpad. The digital codes will be averaged to minimize noise created by vibrations and variations in the motions of the pointed object held by the human hand and formed into an absolute coordinate digital code. The absolute coordinate digital code, the pressure digital code, and the pen detect signal will be converted to a touchpad-computer interface protocol for transmission to a computer system for further processing. The pen detect signal will be sense to determine if the pointed object has not been in contact with the touchpad for a long period of time and remove power from the circuitry controlling the touchpad. For battery power operations, a battery sense line will be connected to the multiplexing analog-to-digital converter to create a battery power set of digital codes which are manipulated in a battery gauge circuit to create a battery condition set of digital codes which are transmitted to the computer system.