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TIME DOMAIN ACCESSORY RECOGNITION SCHEME UTILIZING OPTICAL INTERCONNECT

IP.com Disclosure Number: IPCOM000006654D
Original Publication Date: 1992-Dec-01
Included in the Prior Art Database: 2002-Jan-21
Document File: 1 page(s) / 61K

Publishing Venue

Motorola

Related People

Joseph Patino: AUTHOR [+2]

Abstract

Presently, accessory recognition is accomplished via the interconnection of an electrical lime or lines. This scheme allows the radio to recognize an accessory and select an external option class (external speaker, exter- nal microphone, external RE .) by sensing the frequency that a light source, such as an LED, is being strobed at by a multivibrator contained in the accessory. Thus, the accessory recognition is achieved via an optical inter- connect and not an electrical interconnect.

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MOTOROLA INC. Technical Developments Volume 17 December 1992

TIME DOMAIN ACCESSORY RECOGNITION SCHEME UTILIZING OPTICAL INTERCONNECT

by Joseph Patiiio and Daniel Michael Nigro

  Presently, accessory recognition is accomplished via the interconnection of an electrical lime or lines. This scheme allows the radio to recognize an accessory and select an external option class (external speaker, exter- nal microphone, external RE .) by sensing the frequency that a light source, such as an LED, is being strobed at by a multivibrator contained in the accessory. Thus, the accessory recognition is achieved via an optical inter- connect and not an electrical interconnect.

  The attached block diagram shows an Astable 555 timer configuration which allows the accessory when connected to the radio to trigger itself and run as a multivibrator. The external capacitor "Cl" charges through Ra + Rb, and discharges through Rb. The duty cycle can be controlled by the ratio of these two resis- tors. The rate that the LED is strobed at is controlled by capacitor Cl and the selection of Ra and Rb. This strobe rate is sensed by the pp through an optical interconnect. This can be achieved by using the existing 'Ik LED indi- cator on the radio to access a light pipe and photo detec- tor in the radio. The pp can then determine the rate by

either counting rising or falling edges from the photo detector output. The particular frequency of the con- nected accessory detines its particular configura...