Browse Prior Art Database

Method of Detecting and Debouncing Keyboard Switch Changes

IP.com Disclosure Number: IPCOM000041687D
Original Publication Date: 1984-Mar-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 2 page(s) / 67K

Publishing Venue

IBM

Related People

Fitch, DG: AUTHOR [+2]

Abstract

A separate microprocessor controller is utilized to scan a keyboard array for a switch change. This switch scanning is done so that periods between controller activity (awaiting for a command from a host processor) are used to scan the key switches. This allows the controller to detect switch changes, debounce those changes, and determine if they should be reported to the hose processor. The controller then sends the new switch status to the hose, which can process the data as required. The controller storage is utilized to compare the current switch state with the previous switch state. When a difference is detected between the two switch states, the switch debounce process starts.

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Method of Detecting and Debouncing Keyboard Switch Changes

A separate microprocessor controller is utilized to scan a keyboard array for a switch change. This switch scanning is done so that periods between controller activity (awaiting for a command from a host processor) are used to scan the key switches. This allows the controller to detect switch changes, debounce those changes, and determine if they should be reported to the hose processor. The controller then sends the new switch status to the hose, which can process the data as required. The controller storage is utilized to compare the current switch state with the previous switch state. When a difference is detected between the two switch states, the switch debounce process starts. If the new switch state does not change after being checked a specified number of times, the switch state is compared with the last state sent to the host. If the switch state has changed, it is reported to the host. For system flexibility, the number of times the switches have to remain unchanged is programmed into the controller by the hose rather than being hard coded in the controller. This permits the debounce time to be adjusted to suit a particular situation or application. Additionally, a controller command is provided which allows the hose processor to selectively enable or disable switch scanning. The keyboard is effectively shut off as an input device when switch scanning is disabled.

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