Computer graphics processing and selective visual display system – Display peripheral interface input device
Reexamination Certificate
1998-12-29
2001-05-15
Hjerpe, Richard (Department: 2674)
Computer graphics processing and selective visual display system
Display peripheral interface input device
C345S157000, C345S158000, C345S159000, C345S161000, C345S162000, C345S163000, C345S164000
Reexamination Certificate
active
06232958
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to input devices for computer systems. In particular, the present invention relates to multi-switch input devices.
In computer systems, hand-held input devices such as mice and trackballs, are provided to allow the user to control different functions of the computer system. Most of these input devices include at least one button, which activates a switch inside the input device. The button allows the user to select items on the screen and allows the user to perform drag-and-drop functions.
To detect the closure of a switch, input devices typically include an Application Specific Integrated Circuit (ASIC) that has one input for every switch on the device. When conventional microprocessors are used for this task, an individual I/O port pin is allocated for each switch input. Thus, in a two-button mouse the detection circuit has at least two inputs and for a three-button mouse the detection circuit has at least three inputs.
To take advantage of economies of scale, some detection circuits have been designed to be used in input devices that are of the same general type but that have different numbers of switches. For example, the same detection circuit may be used in a two-button mouse and in a three-button mouse. To achieve this flexibility, these detection circuits must have as many inputs as the maximum number of switches that will be connected to the detection circuit. Thus, if a detection circuit is designed to be used in three-button mice and two-button mice it must have at least three inputs.
To reduce costs, detection circuits typically do not include excess inputs. Thus, if the maximum number of switches that will be connected to the detection circuit is three, the detection circuit typically will not have four inputs. Unfortunately, as the number of buttons on an input device increases, this strategy means that the detection circuit must be redesigned to include additional inputs. This involves costly redesign time and does not take advantage of the economies of scale available with current detection circuits.
SUMMARY OF THE INVENTION
An input device for a computer system includes a detection circuit with first and second inputs capable of carrying first and second input signals. A user depressible switch adapted to allow a user to interact with the computer system is placed in series with a rectification device between the two inputs. The rectification device being adapted to limit electrical current in a first direction between the first input and the second input.
In some embodiments of the present invention, the detection circuit has three inputs with a diode and a switch connected in series between two of the inputs. In other embodiments, there are five diode-and-switch pairs connected between various inputs pair combinations of the three inputs. This allows a five button input device to be realized using a three input detection circuit. In general, under embodiments of the invention, a detection circuit with N inputs supports up to N×(N−1) buttons.
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Hjerpe Richard
Jean Lesperance
Magee Theodore M.
Microsoft Corporation
Westman Champlin & Kelly P.A.
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