Keyboard apparatus

Details Keyboard apparatus Keyboard apparatus

1987-12-07

1988-09-20

Brigance, Gerald L.

Communications: electrical

Audible indication

Percussion-type sound producer

340365C, 340365E, G08B 706

Patent

active

047728744

ABSTRACT:
A capacitive keyboard apparatus including a plurality of keys and a matrix of capacitive switches arranged in columns and rows and connected to the keys, respectively, wherein first and second drive signals sweep the columns of switches and first and second matrix output signals are generated from the rows of switches as the result of first and second drive signal supplied, provided that any key has been depressed during the sweeping. The first and second matrix output signals are convertred to first and second logic signals, respectively, each of which has a pulse width proportional to how deeply the key has been depressed. When the first logic signal has a pulse width broader than a first predetermined width, the second drive signal sweeps the columns of switches. It is determined that the key has been depressed and a key-code corresponding to the depressed key is output, when the second logic signal has a pulse width broader than a second predetermined width and when the second keys during the sweeping by the first and second drive signals are identical.

REFERENCES:
patent: 3757322 (1973-09-01), Barkan et al.
patent: 3918051 (1975-11-01), Bernin et al.
patent: 4106011 (1978-08-01), Melanson et al.
patent: 4263582 (1981-04-01), Dumbovic
patent: 4302011 (1981-11-01), Pepper, Jr.
patent: 4502039 (1985-02-01), Vercesi et al.
patent: 4520906 (1985-01-01), Deforeit
J. T. Rowe, Jr.--"Dynamic Updating of Key-Sensing Thresholds"--vol. 27, No. 4A, Sep. 1984--pp. 2012-2018.

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