(12> Ulllted States Patent
`Burrus, IV
`
`(10) Patent N0.:
`(45) Date of Patent:
`
`US 6,934,561 B2
`Aug. 23, 2005
`
`US006934561B2
`
`(54) CABLE OR MODULE IDENTIFICATION
`APPARATUS AND METHOD
`
`(75) Inventor: Philip H_ Burrus, IV, Lilburn, GA
`(Us)
`
`_
`(73) Ass1gnee: Motorola, Inc., Schaumburg, IL (US)
`
`( * ) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 539 days.
`
`(21) Appl- NO? 09/ 961,049
`(22) Filed
`SEP‘ 2 4 2001
`'
`’
`Prior Publication Data
`
`(65)
`
`Us 2003/0060243 A1 Mar‘ 27’ 2003
`Int. Cl.7 .......................... .. H04M 1 00- H04B 1 38
`51
`/
`,
`/
`(
`)
`(52) us. Cl. ...................... .. 455/559; 320/106; 307/125
`(58) Field Of Search ............................... .. 455/418 420
`455/5501 559 572_573. 307/112 125.
`3’20/166_110 11,2 125. 3’24/66’
`’
`’
`’
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`2/1977 Bogut
`4,006,396 A
`5,184,059 A * 2/1993 Patino et al. ............. .. 320/125
`
`5,818,197 A * 10/1998 Miller et a1. .............. .. 320/107
`5,822,427 A 10/1998 Braitberg et al.
`6,337,557 B1 * 1/2002 Kates et al. .............. .. 320/112
`6,509,659 B1 * 1/2003 Carroll et al. ...... ..
`307/125
`6,661,805 B1 * 12/2003 Romano et al. .......... .. 370/450
`
`* cited by examiner
`Primary Examiner—George Eng
`(74) Attorney, Agent, or Firm—Philip H. Burrus, IV
`
`ABSTRACT
`(57)
`This invention includes a universal base unit having a
`plurality of cables, each corresponding to a unique electronic
`host device. The cable includes a capacitor having a value
`corresponding to a particular electronic host device. The
`capacitor is coupled in series With a resistor to ground in the
`universal base unit. The cable further includes a unique
`mating connector for coupling to the electronic host device.
`The universal base unit identi?es the cable b actuatin a
`y
`g
`Step fuherioh aeross the eapaeiter-resister network, causing
`an exponentially decaying WoVoforrrr- A microprocessor in
`the host device then measures the Width of the Waveform to
`determine the identity of the cable or host device. The
`system alloWs a user to carry a single poWer supply or
`universal base unit With multiple cables as opposed to
`having to transport a different accessory for each electronic
`device_
`
`9 Claims, 6 Drawing Sheets
`
`UNIVERSAL
`BASE UNIT
`
`V50;
`
`~Je2
`
`31%
`
`HOST
`T
`BA TERY_
`\
`
`3 "
`
`H305
`.506
`(
`
`504
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`u 305
`
`r307 /31
`
`XI. v' *1
`T /\
`508/
`
`Apple 1015 - Page 1
`
`

`
`U.S. Patent
`
`Aug. 23,2005
`
`Sheet 1 6f 6
`
`US 6,934,561 B2
`
`FIG.
`-PRIOR ARI
`
`4
`
`F OUT
`
`22
`
`6.2 vous I0 BATTERY PAcx'
`REMOTE SENSE
`CPU T0 LOCAL PORT
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`GROUND
`CPU CLOCK
`LOCAL-CPU PORI
`,
`59~>—-— GROUND
`k40~|>----~Aun1o INPUI
`L, 4 1
`
`Apple 1015 - Page 2
`
`

`
`U.S. Patent
`
`Aug. 23,2005
`
`Sheet 2 6f 6
`
`US 6,934,561 B2
`
`Apple 1015 - Page 3
`
`

`
`U.S. Patent
`
`Aug. 23,2005
`
`Sheet 3 6f 6
`
`US 6,934,561 B2
`
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`#99
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`1
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`
`Apple 1015 - Page 4
`
`

`
`Apple 1015 - Page 5
`
`

`
`Apple 1015 - Page 6
`
`

`
`U.S. Patent
`
`Aug. 23,2005
`
`Sheet 6 6f 6
`
`US 6,934,561 B2
`
`209w
`
`204 XUNIVERSAL?
`
`206
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`mcrzopaocasson 2,3
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`
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`an
`
`Apple 1015 - Page 7
`
`

`
`US 6,934,561 B2
`
`1
`CABLE OR MODULE IDENTIFICATION
`APPARATUS AND METHOD
`
`BACKGROUND
`
`1. Technical Field
`This invention relates generally to interfacing systems for
`portable electronic devices, and more particularly to an
`apparatus for providing a poWer and communications inter
`face betWeen a portable electronic device, selected from a
`variety of such devices, to a common base unit.
`2. Background Art
`Electronic devices are being developed today at a diZZy
`ing rate. EveryWhere you look, people are carrying cellular
`phones, compact disc (CD) players, personal digital assis
`tants (PDAs), pagers, radios, MP3 players, and laptop com
`puters. This proliferation of electronic devices is especially
`true in the case of cellular telephones. According to the
`Cellular Telecommunications Industry Association (CTIA),
`cellular telephone usage in the United States increased 27%
`betWeen 1999 and 2000. As of December 2000, there Were
`over 109 million cellular subscribers in the United States
`alone.
`There are tWo problems With this proliferation of elec
`tronic devices, hoWever: First, they seem to all use different
`poWer supplies With different connectors. Nothing is more
`frustrating than packing for a trip and having to leave your
`sWimming suit at home because your suitcase is full With
`four different poWer supplies for your computer, PDA,
`phone and CD player.
`There is a reason for the various poWer supplies and
`connectors. Each host device has different poWer require
`ments. For example, a laptop computer consumes much
`more energy than does a cellular phone. The extra poWer is
`needed to run motors like disk drives and CD-ROM players
`that the phone does not have. Additionally, the laptop may
`have to illuminate a 120 square inch screen continuously,
`While the cellular phone need only light a 4 square inch
`screen occasionally.
`Another reason for the differing poWer supplies are the
`batteries associated With each device. Different rechargeable
`batteries have differing charging requirements. For example,
`a nickel-metal hydride battery may charge to a termination
`of 6 volts, While a single-cell Lithium-Ion battery can only
`be charged to 4.2 volts. If the lithium battery Were charged
`With a nickel charger, the lithium battery could become
`“overcharged” When the voltage exceeded 4.2 volts. Under
`these conditions, the reliability of lithium cells can be
`compromised.
`The second problem is that as the sophistication of
`electronic devices increases, data ports to and from the
`electronic devices are required to transmit data for remote
`antenna connections, voice and data communications, and
`most importantly, What is knoWn as “hands free” operation.
`These functions generally require a physical connection
`betWeen the phone unit and parts or devices found in a
`vehicle or accessory. These data ports are typically seem to
`be manufacturer speci?c—each manufacturer has it’s oWn
`unique connector.
`The tWo problems are essentially the same: every portable
`device has a unique connector for poWer and data. Designing
`a “universal” device to Work With a plurality of devices is
`thus problematic.
`One solution to the “multiple-device, multiple-accessory”
`problem is the multi-connector. Referring to FIG. 1, illus
`
`15
`
`25
`
`35
`
`40
`
`45
`
`55
`
`65
`
`2
`trated therein is a multi-prong adaptor 5 commonly available
`at electronics stores. Such an adapter 5 generally has several
`different prongs 1,2,3 coupled in parallel to a poWer cord 4.
`The poWer cord 4 may thus be connected to three different
`types of connectors. The problem With such a device is that
`the poWer delivered by the supply is the same no matter What
`connection you are using. If the poWer supply is a 6-volt
`supply, you still cannot charge a single-cell lithium battery
`With this connector (even if it does ?t) because the battery
`performance may be compromised. Additionally, these con
`nectors generally have no provisions for data communica
`tion.
`Another possible solution made speci?cally for cellular
`phones is the car kit. Cellular phone manufacturers have
`made available car kits to provide both charging and data
`communication, as Well as hands-free operation. These kits
`include physical hardWare to retain the phone in the vehicle
`including an attachment for establishing an electrical con
`nection to the phone and various types of remote speakers,
`microphones, poWer supplies and antenna connections.
`These kits also include complex electronics modules to
`provide battery charging, audio ampli?cation and digital
`communication interface to the phone unit.
`The problem With these car kits is that they are device
`speci?c. In other Words, you cannot use a Nokia accessory
`With a Motorola phone. As a result, car kits do not provide
`any form of universal connection and are neither physically
`nor electrically interchangeable. Additionally, device spe
`ci?c car kits can be expensive, With costs of the accessory
`rivaling the cost of the phone itself.
`This situation has caused a hardship on cellular telephone
`users and affected the marketplace for neW equipment. Fleet
`users, for example, cannot provide a universal car kit
`connection for the variety of phones they may acquire. Users
`are forced to abandon their investment in the car kit When
`purchasing neW models of telephones. These limitations
`have prevented businesses such as car rental agencies from
`providing users With means to use their car phones in rented
`vehicles. Further, the high cost of these car kits has caused
`many users to operate hand-held units While driving, an
`unsafe condition Which is subject to increasing governmen
`tal concern and regulation.
`There is thus a need for an improved interface system
`capable of coupling to and identifying a plurality of portable
`electronic devices.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 is a prior art multiple-terminal connector.
`FIG. 2 shoWs a contemporary cellular telephone and its
`interconnection port.
`FIGS. 3A—3F shoW examples of a variety of hand-held
`cellular telephone input/output physical interfaces.
`FIG. 4 is a tabulation of the electrical functions associated
`With a typical input/output connector for a contemporary
`cellular telephone.
`FIG. 5 is a tabulation of an exemplary connection assign
`ment discipline associated With a typical input/output con
`nector for a contemporary cellular telephone.
`FIG. 6 is a block diagram of a typical hand-held cellular
`phone unit.
`FIG. 7 is a cable assembly for coupling accessories to
`electronic devices.
`FIGS. 8A—8D illustrate a prior art method of embodying
`a coded adapter cable connector.
`FIG. 9 is a prior art block diagram of a battery charac
`teristic detector.
`
`Apple 1015 - Page 8
`
`

`
`US 6,934,561 B2
`
`3
`FIG. 10 is a prior art block diagram of an intelligent
`battery charging system.
`FIG. 11 is a voltage stabilization curve associated With the
`prior art system of FIG. 10.
`FIG. 12 is a schematic block diagram of an intelligent
`accessory system in accordance With the invention.
`FIG. 13 is one preferred embodiment of an identi?cation
`apparatus in accordance With the invention.
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`
`10
`
`15
`
`25
`
`4
`levels and signal coding schemes. Referring noW to FIG. 4,
`a typical example of the functions assigned to the pins of a
`conventional phone input/output connector 22 containing
`connector contacts or pins 31—40 is shoWn. Note that con
`nector 22 might or might not represent the speci?c pin
`function assignments for connector 22 shoWn in FIG. 2.
`While there is a certain amount of commonality of functions
`associated With many cellular phones, the particular function
`assigned to a given pin often varies, as does the number of
`functions, the number of pins and their physical con?gura
`tions.
`Connector 22 is shoWn With a coaxial connector 25 to
`provide for direct connection to the RF output. Pin 31 is used
`for battery charging from the remote adapter, While pin 32
`is used to detect the presence of the remote adapter and pin
`33 is used for digital communication to the remote adapter.
`Pin 34 is used to signal the remote adapter that phone poWer
`is on. Pin 35 has the loW level audio output signal to drive
`a remote speaker ampli?er. Pins 36 and 39 provide internal
`ground connections. Pin 37 provides the CPU clock signal,
`pin 38 is the local to CPU communications port, and pin 40
`is used to receive the signal from the remote microphone.
`The internal architecture of a typical phone unit is shoWn
`in block diagram form in FIG. 6 Where further details of the
`interconnections With the internal block functions of the
`phone With the input/output connector 22 described above
`are presented. The peripheral elements of FIG. 6 correspond
`to their counterparts of FIG. 2. Note that the speaker 15A is
`separate from the microphone 15B but both are housed at
`that end of unit 10. This is to prevent production of the
`ringing sound directly into the ear of the user. Radio board
`42 contains the radio frequency signal handling components
`Whereas a computer including a conventional CPU With its
`input/output interfaces is contained in board 44. The CPU of
`board 44 handles all the host functions associated With the
`components shoWn.
`It is possible to create a custom tailored adapter cable
`con?gured internally to transpose connections betWeen the
`various interconnection disciplines along the lines of those
`shoWn in FIG. 3. It has long been knoWn in the art that cables
`may be manufactured With connectors of different types as
`illustrated in FIG. 7. Referring noW to FIG. 7, illustrated
`therein is a cable 46 With different connectors 45,48 on each
`end. Auniversal connector 45 or plug is arranged in accor
`dance With a predetermined assignment of pin functions. On
`the opposite end of cable 46 is a connector or plug 48
`con?gured to attach to a particular electronic device. That is,
`connector 48 is different for each differently con?gured
`connector on a cellular phone. The conductors Within cable
`46 are connected Within plugs 45 and 48 so that the pin
`functions are matched.
`The problem With such a cable 46 linking a speci?c
`electronic device and a universal base unit is that the
`universal base unit must be able to identify just What speci?c
`device is attached at the other end. One object of this
`invention is an apparatus and method for identifying an
`electronic device via a cable having a universal connector on
`one end and a device speci?c connector on the other. This
`invention has numerous advantages over the prior art,
`including simpler implementation With control units and
`microprocessors, reduced cost, increased breadth, and
`expanded ?exibility. These advantages Will be discussed in
`more detail beloW. First it is Well to examine the prior art.
`One solution to the “identi?cation issue” is taught by US.
`Pat. No. 5,822,427, issued to Braitberg et al. Referring noW
`to FIGS. 8A—8D, illustrated therein is the Braitberg et al.
`
`Apreferred embodiment of the invention is noW described
`in detail. Referring to the draWings, like numbers indicate
`like parts throughout the vieWs. As used in the description
`herein and throughout the claims, the folloWing terms take
`the meanings explicitly associated herein, unless the context
`clearly dictates otherWise: the meaning of “a,” “an,” and
`“the” includes plural reference, the meaning of “in” includes
`“in” and “on.”
`Referring noW to FIG. 2, illustrated therein is one embodi
`ment of a conventional hand held cellular telephone 10.
`Such telephones 10 employ a Wide variety of physical
`interfaces. There are a large number of models of cellular
`telephones in existence and each physical interconnection
`and electrical interface is unique to a manufacturers speci?c
`model.
`Cellular phone 10 includes a typical array of features for
`such devices. Keypad 12 alloWs dialing and other data
`processing/generating functions. An earphone 14 is posi
`tioned at one end While a microphone/speaker 15 is located
`at the other end. Liquid crystal display (LCD) 16 provides
`a compact presentation of limited information to the user
`While sWitch 18 is for on/off control. Antenna 19, Which may
`be either internal or external, communicates With the toWer
`infrastructure When the phone 10 is in transmission. A
`battery pack 20 is attached to the phone 10 and requires
`periodic recharging When phone 10 is coupled to a charger
`or poWer supply. Some phones 10 include a release button
`21 for decoupling from accessories.
`Accessories are connected to the phone 10 by a plug 22
`at one end of the phone 10. The particular connector of FIG.
`2 is a male connection With a center extension 24 having
`arrays of electrical contacts on the upper and loWer surfaces
`thereof. Additionally, an RF coaxial type element 25 is
`included as a portion of plug 22. Note that not every cellular
`telephone has an RF connector even though one is included
`in the example shoWn as element 25. In conventional use,
`the phone 10 may be stored in a desktop charger so as to
`couple plug 22 With a complementary connector in the
`charger.
`FIGS. 3A through 3F shoW a series of examples of
`physical interconnections for cellular telephones. That is,
`FIGS. 3A to 3F present typical examples of cylindrical,
`rectangular, spring contact and pad type connections used in
`common cellular phone units, usually in the base plate
`thereof. From this, it is apparent the Wide range of con?gu
`rations and physical siZes prohibits a common interconnec
`tion to a base unit or the like. Cellular phones are expected
`to use even smaller connectors as the units are further
`miniaturiZed in the future.
`Electrical interfaces to the various phone units present
`still more problems. For instance, as stated, there are a Wide
`variety of battery types and voltages used in the rechargeable
`battery packs incorporated into the phone units. Further, the
`electrical phone signals exist in a Wide variety of voltage
`
`40
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`Apple 1015 - Page 9
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`

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`US 6,934,561 B2
`
`5
`solution for determining the make and model of an elec
`tronic device coupled at the end of a cable. This solution
`utiliZes the cable adapter to identify itself to a universal base
`unit. This is accomplished by a number of pins reserved at
`the processor or common end of the cable connector for use
`as a programming device. An electrically conductive struc
`ture 50 containing a plurality of physically and electrically
`interconnected pins 51—55 is inserted into and retained by
`connector body 58 as seen in FIG. 8B. A short connecting
`link 56 extends above ridge or shoulder 57 above the
`connector body 58 When connector 50 is inserted therein.
`These links are preferably clipped in a binary pattern to
`produce the identi?cation data for the processor 154 so that
`it can determine the type of cellular phone attached to the
`other end of the cable.
`For example, if link 54 is clipped as shoWn as gap 59 in
`FIG. 8C, the resulting circuit to pin 54 is opened. Thus
`electrical current sensing of the pins 51—55 in FIG. 8D Will
`re?ect the open circuit status of pin 54. The connector body
`58 includes conventional, Well-knoWn means (not shoWn)
`for retaining the end of the clipped contact in place so as to
`prevent it from falling out or sliding back into the connector
`body When the connectors are coupled.
`The problem With this solution is that many pins must be
`used for nothing other than identi?cation. For example, to
`identify nine different phones, four extra pins must be
`dedicated to the universal connector solely for the identi?
`cation function. These excess pins make the connector large,
`unWieldy and expensive to manufacture.
`Braitberg et al. teaches other solutions, including a
`memory device being stored in the cable, as is taught in
`copending application Ser. No. 09/730,691, ?led Dec. 6,
`2000, assigned to Motorola, Inc. Again, this solution can be
`expensive and dif?cult to manufacture. Semiconductor
`devices are quite costly and dif?cult to assemble in connec
`tor housings and cables. Such manufacture typically requires
`hand soldering, Which increases labor costs as Well as
`material costs.
`Braitberg et al. teaches yet another solution, as illustrated
`in FIG. 9. In this embodiment, analog to digital (A/D)
`converter 80 provides a reference voltage (Vref) to line 81
`that is presented to the mating connector pins 82 and 83. The
`voltage produces a current through the circuit consisting of
`resistor 84 (Rprog) and resistor 85 (R?xed) in a half-bridge
`con?guration providing a voltage at pin 87 Which is con
`nected to the signal input of A/D converter 80. A 6 bit A/D
`converter can provide 64 possible binary codes to logic 86.
`The value for each Rprog resistor 84 is calculated from the
`equation: Vout*R?xed/(Vref-Vout).
`This particular solution is a extremely similar on a
`resistor-based identi?cation scheme ?rst disclosed by Bogut
`in US. Pat. No. 4,006,396, issued in 1977, entitled “Uni
`versal Battery Charging Apparatus”, assigned to Motorola,
`Inc. The problem With the solution of Braitberg et al. is that
`it can also be costly and cumbersome. The Braitberg et al.
`solution requires a dedicated analog to digital (A/D)
`converter, dedicated voltage reference and tWo resistors.
`These components can be as expensive as microprocessors.
`Additionally, to accommodate a Wide variety of phones,
`both the voltage reference and the resistors must be preci
`sion components, Which further adds to the cost. Another
`issue is that resistors are dif?cult to incorporate into semi
`conductor devices. Thus, if one desired to incorporate the
`resistors into an integrated circuit chip, the cost Would soar
`as the resistors Would most likely need to be laser trimmed.
`Another prior art solution is taught in commonly assigned
`US. Pat. No. 5,184,059, issued to Patino et al., entitled
`
`15
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`6
`“Expanded Battery Capacity Identi?cation Scheme and
`Apparatus”. Referring noW to FIG. 10, illustrated therein is
`this solution. The microprocessor 1038 is either connected to
`or includes conventional analog-to-digital (A/D) converter
`functions or the like. As is knoWn, the microprocessor 1038
`is programmed to periodically measure the value of voltage
`connected to the A/D input. To form a charging algorithm
`sensing circuit, the resistor R18 is connected to the negative
`charger contact 1026 so that a predetermined external
`impedance (or voltage source) may be connected to com
`plete a voltage divider With a pull-up resistor R62. In this
`manner, predetermined values of voltage at the negative
`charger contact 1026 can be calculated to provide one factor
`relating to the battery capacity. It is appreciated that the
`measured voltage Vm is directly related to the resistance of
`the connected resistor R18 in accordance With the usual
`voltage divider relationship:
`
`Where
`Vm equals the measured voltage at the negative battery
`charger contact 1026 or the A/D input(line);
`B.sup.+=the supply voltage (i.e. as may have also just
`previously been measured With the aid of the A/D
`converter) at the A/D input;
`R62 equals the knoWn pull-up resistance internal to the
`charging circuit 1030a;
`R18 equals the unknoWn resistance, not necessarily asso
`ciated uniquely With a particular capacity. After solving
`for the resistance of R18, one factor relating to the
`battery capacity can thus be determined.
`The Patino et al. solution utiliZes a capacitor to expand the
`present capability of battery capacity sensing and to alloW
`for radio family type differentiation. This is accomplished by
`utiliZing the non-ideal presently coded resistor implemen
`tation and a coded capacitor C72 Within the charger pocket
`1030b. The coded capacitor C72 is connected in parallel
`With the coded resistor R18 When the battery 1012 is inserted
`into the pocket 1030b. The coded capacitor C72 is uniquely
`coded for each radio family type, Wherein a 47 uF may
`denote a type Aradio, 27 uF may denote a type B radio, and
`68 uF may denote a type C radio.
`Referring noW to FIG. 11, a time constant
`T1=R18.times.C72 developed by the coded resistor R18 and
`capacitor C72 has to elapse before the voltage Vm is
`stabiliZed enough for the resistance of the coded resistor R18
`to be measured. This time constant provides a second factor
`Which is also related to the battery capacity, aside from
`relating to the radio family type. From determining the time
`constant alone or in combination With the resistance value of
`the coded resistor R18, the battery capacity and the family
`type of the associated radio can be identi?ed by the micro
`processor 1038 accessing its look-up table stored in memory.
`The problem With the Patino et al. solution is that it
`requires a connection betWeen the identifying capacitor and
`the resistor embedded in the battery. Additionally, this
`particular solution is only amenable to electronic devices
`and batteries having coding resistors stored therein. As
`coding resistors Were patented until the expiration of the
`Bogut patent, only the patent holder and licensees Were able
`to include such resistors in their products. Consequently,
`some user’s phones Would not Work With this particular
`solution.
`One object of the present invention is to provide an
`adapter cable With a universal interface as a common con
`nector at one end but With that cable provided With a suitable
`
`Apple 1015 - Page 10
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`US 6,934,561 B2
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`7
`connector at the other end to attach to a particular connector
`con?gured to another type of mating connector. The present
`invention further contemplates the creation of a plurality of
`pocket adapter devices, each pocket adapter device being
`adapted to establish a physical and electrical interconnection
`betWeen a particular model of cellular telephone and a
`common base unit.
`One object of the present invention is to provide a method
`of identifying a cable having a universal connector on one
`end and a device speci?c connector on the other end. The
`method has advantages over the prior art in that it is loWer
`cost, offers a broader spectrum of identi?cation and is easily
`incorporated into semiconductor devices. The invention
`includes a universal base unit that has a universal connector.
`Multiple cables may be provided, each having a universal
`connector (for mating to the universal unit) and an electronic
`device-speci?c connector for mating to an electronic device.
`Referring noW to FIG. 12, illustrated therein is a sche
`matic block diagram in accordance With the present inven
`tion. The circuit 200 includes a capacitor 201 in the cable
`203. The capacitor 201 has a value that corresponds to a
`speci?c electronic device (not shoWn). The capacitor 201 is
`coupled in series With a resistor 201 to ground. While the
`capacitor 201 is disposed in the cable 203, the resistor 201
`is disposed in the universal device 204. When the cable 203
`is attached to the universal device 204, the microprocessor
`209 of the universal device 204 takes the capacitor connec
`tion 205 and applies a step function 210 by toggling an
`output 206 from loW to high. When this occurs, an expo
`nentially decaying, or “shark-?n”, function 211 is created
`across the resistor 202.
`The shark-?n function 211 is then coupled back into the
`microprocessor 209. An optional comparator 212 provides
`clean transitions that are easily readable by an input 213 of
`the microprocessor 209. A Schottky-type latch may also be
`added to ensure clean transitions. Pull-up resistors may be
`added to both the output 206 and input 213 of the micro
`processor 209. The microprocessor 209 is then able to detect
`the Width of the shark-?n 211 by comparing the high to loW
`transition seen the input 213 to the internal clock. The Width
`of the shark-?n 211 corresponds to the identity of the
`electronic device coupled at the end of the cable 203.
`In one preferred embodiment, the output line 205 and the
`input line 214 may be sWitched With optional transistors
`215,216. In this manner, the identi?cation lines 205,214 are
`coupled to the microprocessor 209 only until the identi?ca
`tion has been made. They may then be sWitched to other
`functions. This fact that dedicated lines are not required
`alloWs additional functionality for the user from the same
`microprocessor.
`To recap, the microprocessor 209 senses cable 203 attach
`ment by conventional means, including pull-up resistors,
`?oating inputs becoming non-?oating, etc. Once the cable
`203 connection is sensed, the microprocessor 209 sWitches
`the output 206 from loW to high. This step function 210 is
`applied to the capacitor 201—resistor 202 combination. The
`microprocessor 209 then Waits for the corresponding input
`213 to go loW. When this occurs, the microprocessor 209
`calculates the time betWeen output trigger (output transi
`tioning from loW to high) and input trigger (input transi
`tioning from high to loW). This time corresponds to a
`particular electronic device or cable.
`Suitable microprocessors for the invention include those
`like the uPD78F0034 series manufactured by NEC. This
`processor includes an on-board voltage reference (shoWn as
`element 217 in FIG. 12) in the event that a comparator is
`used for cleaner sWitching. A typical clock frequency that
`
`10
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`15
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`25
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`35
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`40
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`45
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`55
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`65
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`8
`this microprocessor operates comfortably in is 4 MHZ. At
`this frequency, the microprocessor is able to differentiate
`sWitching edges With an on-board interrupt at a resolution of
`2 microseconds. Alternatively, a polling subroutine (a rou
`tine that constantly polls the input until a transition is seen)
`is able to differentiate sWitching edges With a resolution of
`5 microseconds. It Will be clear to those in the art that
`numerous microprocessors, including much more poWerful
`units running at higher frequencies may be used for better
`resolution.
`In the exemplary embodiment described in the preceding
`paragraph, a ?rst cellular phone may correspond to a 5
`microsecond delay, While a second cellular phone may
`correspond to a 10 microsecond delay, and so on. Assuming
`a 10 k resistor to ground, the ?rst phone Would need a 1 nF
`capacitor, While the second phone Would need a 2 nF
`capacitor, and so on.
`The invention takes advantage of the Well-knoWn expo
`nential decay associated With resistor-capacitor netWorks.
`The voltage decays exponentially according to Vi*(1—
`e.sup.—t/RC), Where Vi is the initial voltage, R is the resistor
`value and C is the capacitor value. The “e” represents the
`exponential function. Assuming that one desires to measure
`the time it takes to reach 50% of it’s initial value (to trigger
`a comparator With a reference equal to half the supply), the
`math progresses as folloWs:
`
`We Want:
`
`V0=Vi/2
`
`Thus:
`
`1/2=1—e—t/RC
`
`e—t/RC=1/2
`
`—t/RC=ln(1/2)
`
`[equation 3]
`
`[equation 5]
`
`[equation 6]
`
`[equation 7]
`
`Thus for t=5 microseconds, R=10 k, C=0.72 nF. Rounding
`this off to 1 nF, a 10 microsecond delay Would require a 2
`nF cap, and so on.
`The invention provides several advantages over the prior
`art. To begin, precision resistors and voltage references are
`not required. Neither are bulky connectors With large num
`bers of pins. The invention provides a loW-cost, easily
`manufacturable means of identifying a universal cable, in
`that a simple capacitor is the only identifying component in
`the cable. Additionally, it is Well knoWn in the art that
`capacitors are relatively simple to construct on semiconduc
`tor Wafers using technologies such as complimentary metal
`oxide semiconductor (CMOS) fabrication techniques. As
`this is the case, this invention is easily combinable With
`memory devices, microprocessors, programmable logic
`devices, and other application speci?c integrated circuits
`(ASICs) that may be disposed in the cable. In the event that
`circuitry is coupled from the electronic device through the
`cable to the universal device, the identifying capacitor may
`be disposed in the electronic device as Well.
`Referring noW to FIG. 13, illustrated therein is an intel
`ligent accessory system 300 in accordance With the inven
`tion. Auniversal device 301 is provided having an accessory
`circuit (not shoWn) disposed Within. The poWer conversion
`circuit could be any number of Well knoWn circuits, includ
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`US 6,934,561 B2
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`9
`ing a hands-free circuit, answering machine, infrared
`communications, computer modems, facsimile machines,
`scanners, bar code readers, digital information processors,
`?y back regulator, a step-doWn, o