Browse Prior Art Database

WAVEFORM RECOGNITION INPUT SENSING METHOD

IP.com Disclosure Number: IPCOM000009858D
Original Publication Date: 2000-May-01
Included in the Prior Art Database: 2002-Sep-24
Document File: 2 page(s) / 78K

Publishing Venue

Motorola

Related People

Chin Wee Wong: AUTHOR [+2]

Abstract

In embedded system design using a microprocessor, one of the problems encountered by the designer is the limited number of input ports. This limitation restricts the number of input keys that can be implemented in a product. These papers describe an alternative solution to sense a number of input keys by using the input capture function of a microprocessor.

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MOTOROLA

Technical Developments

WAVEFORM RECOGNITION INPUT SENSING METHOD

by Chin Wee Wong and Suet Hwa Lee

INTRODUCTION

In embedded system design using a microprocessor, one of the problems encountered by the designer is the limited number of input ports. This limitation restricts the number of input keys that can be implemented in a product. These papers describe an alternative solution to sense a number of input keys by using the input capture function of a microprocessor.

INPUT CAPTURE CONCEPT

Input capture functions, used to record the time at which some external event occurred, are accomplished by latching the contents of the free-running counter when a selected edge is detected at the related timer input pin. The time at which the event occurred is saved in the input capture register; therefore, although it may take an undetermined variable amount of time to respond to the event, software can tell exactly when the event occurred. By recoriling the times for successive edges on an incoming signal, software can determine the period of the signal.

IMPLEMENTATION

The concept of using the input capture function to detect the input key pressed is to use the software of the microprocessor to determine the period of the input signal generated by the key pressed action.

Each input key, when pressed, will generate a signal that has a unique period. The input signal is

Motorola, Inc. 2000

connected to the input pin of the microprocessor that can perform input capture function. When the input key is pressed, the microp...