Browse Prior Art Database

ROTATING KEYPAD BASED ON VOLTAGE DIVIDER FUNDAMENTAL

IP.com Disclosure Number: IPCOM000033036D
Original Publication Date: 2004-Nov-22
Included in the Prior Art Database: 2004-Nov-22
Document File: 5 page(s) / 238K

Publishing Venue

Motorola

Related People

Kenny Teoh Ken Kuan: AUTHOR [+3]

Abstract

A new user interface using different voltage levels provides a distinctive communications device’s user input interface. The interface has also been integrated into the keypad to change the conventional keypad shape to round shape for providing various keypad choices.

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ROTATING KEYPAD BASED ON VOLTAGE DIVIDER FUNDAMENTAL

By Ashburn Chan Kok Yong, Kenny Teoh Ken Kuan, Chiam Heng Cheng

ABSTRACT

A new user interface using different voltage levels provides a distinctive communications device’s user input interface. The interface has also been integrated into the keypad to change the conventional keypad shape to round shape for providing various keypad choices.

INTRODUCTION

Conventional keypads have multiple data lines that feed to the digital IC in order to process input data. The new interface only needs a data line to achieve this task and provides a distinctive appearance to the communications device.

CONVENTIONAL METHOD

Conventional keypads process a dialed number by routing input pins from the microprocessor directly to the keypad buttons as shown in Figure 1.

In Figure 1, there are 25 buttons with 10 data lines for the keypad button combinations. This data lines greatly increased the size of communications device because of a separated keypad board and added spaces in flex design or additional connectors’ pin out.

VOLTAGE DIVIDER METHOD

The new interface of implementing a voltage divider has the following advantages:

1.      Reduce radio thickness

2.      Less PCB cost (no keypad board required)

3.      Less input/output microprocessor pins

4.      Less connectors – reduced pin out.

The concept is based on Kirchoff’s law.

Figure 2:  Block diagram of Rotating Keypad Concept

Figure 2 illustrates the rotating keypad concept block diagram with a rotating contact point, resistance value fixed at rotating button, VCC block, A/D and micro processor. When the contact is made, a signal will be sent to the A/D to convert the analog signal to a serialized digital signal to be processed by the microprocessor.

Figure 1: Conventional circuits

Figure 3: Detail of rotating keypad contact point and the rotation top view

Figure 3 exhibits a detail illustration of the rotating keypad contact point with the corresponding circuitry in the rotational button. Any contact point will trigger a different signal level hence interpreting to a desired selected number or alphabet character.

Figure 4 shows the schematic of the rotating keypad circuitry with each digit or alphabet being defined. Each LED will be turned ON to indicate a close circuit or a contact which had been made.

DESIGN CONCEPT

Voltage Divider Fundamentals

A simple voltage divider concept is used to indicate every number and alphabet character by varying resistor values on the rotating keypad. Different voltage levels represent the specified number, alphabet and character on the keypad indicator.

DSP (Digital Signal Processing)

Digitization process of serial data processing will be performed by the...