Interrupt-driven keypad scanning method and apparatus

Details Interrupt-driven keypad scanning method and apparatus Interrupt-driven keypad scanning method and apparatus

1996-11-20

1998-06-02

Horabik, Michael

Coded data generation or conversion

Bodily actuated code generator

Including keyboard or keypad

341 22, 34082579, H03M 1100

Patent

active

057607141

ABSTRACT:
The interrupt-driven keypad scanning method and apparatus accurately interprets keypresses in single-keypress applications. Initially, interrupts (16, 26, 36, 46) associated with each column line (10, 20, 30, 40) of a keypad matrix (70) are set to trigger when a key is pressed. Once an interrupt triggers, a microcontroller (99) polls the row lines (15, 25, 35, 45, 55, 65) to determine which key, if any, was validly pressed. If exactly one keypress is detected, the keypress is valid. Next, the interrupt for the valid key's column line is enabled while the other column line interrupts are disabled. When a next interrupt is received, the keypad returns to the row-scan state for determination of which keys are depressed. If no keys are depressed, which occurs when the validly-pressed key has been released, the keypad returns to the keypress-detect state. The method also interprets pathological keypresses such as key rollover, multiple keypresses, and key mis-hits.

REFERENCES:
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patent: 5450080 (1995-09-01), Irwin
patent: 5486824 (1996-01-01), Kiwerk
patent: 5512893 (1996-04-01), Gulick

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