Method and circuit for reading a potentiometer

Details Method and circuit for reading a potentiometer Method and circuit for reading a potentiometer

2002-08-30

2004-05-18

Le, N. (Department: 2858)

Electricity: measuring and testing

Impedance, admittance or other quantities representative of...

Lumped type parameters

C324S535000, C324S677000, C324S678000, C324S714000

Reexamination Certificate

active

06737877

ABSTRACT:

TECHNICAL FIELD OF THE INVENTION
This disclosure relates to reading a potentiometer, and more particularly, to digitally reading an analog potentiometer without the need for an ADC (Analog to Digital Converter).
BACKGROUND OF THE INVENTION
Traditionally, both PC (Personal Computer) and USB (Universal Serial Bus) gamepads have been simple “digital” devices, made of a set of buttons that are used for both directional control (e.g., arranged as a “thumb pad”) and for feature activation such as firing weapons in a game. More recently, Game Consoles such as the Sony® Playstation® and Microsoft® Xbox™ have been developed to support gamepads that provide various analog controls, including “thumb sticks” for directional control and “proportional triggers.” Providing such analog controls allows the game user to have a more “natural” gaming experience, which in turn increases his or her enjoyment in playing the games.
Analog position-sensing controls used by some gamepads and joysticks typically use potentiometers to generate a variable voltage based on the position of the control. This approach requires an expensive ADC to convert the analog signals into digital values that can be manipulated by a microprocessor. Additionally, the analog sensors are susceptible to various electrical conditions including center-point calibration, temperature drift, and noise.
Connected Xbox™ game peripherals communicate with their game console using a restricted implementation of the USB implementation. Typically, the peripherals incorporate both a USB peripheral manager to manage the game controller functions and a USB hub to provide an interface for “add-in” modules, such as memory cards, which may be inserted into the peripheral. Common peripheral implementations use a USB hub microcontroller together with an external ADC (used to read the potentiometers), or use a standard USB hub IC together with a USB peripheral microcontroller having an integrated ADC.
Embodiments of the invention address the concerns discussed above.
SUMMARY OF THE INVENTION
Embodiments of the invention include a method that allows nearly any microcontroller to accurately read a potentiometer with minimal external components. Some embodiments include two capacitors connected to the respective ends of a potentiometer, which can be charged or discharged simultaneously by a current source or current sink attached to the wiper of the potentiometer. The time when the voltage of each capacitor charges or discharges to a predetermined level is recorded and subsequently used to determine the position of the wiper on the potentiometer. Some embodiments of the invention includes, for example, first and second charge storage devices coupled to a physical input device; and a circuit for determining a position of the physical input device by comparing charge or discharge time for the first and second charge storage devices.


REFERENCES:
patent: 3571764 (1971-03-01), Koenigk
patent: 4987372 (1991-01-01), Ofori-Tenkorang et al.
patent: 5563519 (1996-10-01), Honkanen
patent: 6472859 (2002-10-01), Tippy et al.
patent: 6577297 (2003-06-01), Wright
U.S. patent application Ser. No. 09/821,680, filed Mar. 29, 2001.

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