Capacitance sensors that respond to charge, current, or voltage can be used to detect position or proximity (or motion or presence or any similar information), and are commonly used as input devices for computers, personal digital assistants (PDAs), media players, video game players, consumer electronics, cellular phones, payphones, point-of-sale terminals, automatic teller machines, kiosks and the like. Capacitive sensing techniques are used in user input buttons, slide controls, scroll rings, scroll strips and other types of sensors. One type of capacitance sensor used in such applications is the button-type sensor, which can be used to provide information about the existence or presence of an input. Another type of capacitance sensor used in such applications is the touchpad-type sensor, which can be used to provide information about an input such as the position, motion, and/or similar information along one axis (1-D sensor), two axes (2-D sensor), or more axes. Both the button-type and touchpad-type sensors can also optionally be configured to provide additional information such as some indication of the force, duration, or amount of capacitive coupling associated with the input. One example of a 2-D touchpad-type sensor that is based on capacitive sensing technologies is described in U.S. Pat. No. 5,880,411, which issued to Gillespie et al. on Mar. 9, 1999. Such sensors can be readily found, for example, in input devices of electronic systems including handheld and notebook-type computers.
A user generally operates a capacitive input device by placing or moving one or more fingers, styli, and/or objects, near a sensing region of one or more sensors located on or in the input device. This creates a capacitive effect upon a carrier signal applied to the sensing region that can be detected and correlated to positional information (such as the position(s) or proximity or motion or presences or similar information) of the stimulus/stimuli with respect to the sensing region. This positional information can in turn be used to select, move, scroll, or manipulate any combination of text, graphics, cursors and highlighters, and/or any other indicator on a display screen. This positional information can also be used to enable the user to interact with an interface, such as to control volume, to adjust brightness, or to achieve any other purpose.
Although capacitance sensors have been widely adopted for several years, sensor designers continue to look for ways to improve the sensors' functionality and effectiveness. In particular, engineers continually strive to simplify the design and implementation of position sensors without increasing costs. Moreover, as such sensors become increasingly in demand in various types of electronic devices, a need for a highly-flexible yet low cost and easy to implement sensor design arises. In particular, a need exists for a sensor design scheme that is flexible enough for a variety of implementations and powerful enough to provide accurate capacitance sensing while remaining cost effective.
Accordingly, it is desirable to provide systems and methods for quickly, effectively and efficiently detecting a measurable capacitance. Moreover, it is desirable to create a design scheme that can be readily implemented using readily available components, such as standard ICs, microcontrollers, and discrete components. Other desirable features and characteristics will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.