Patent Publication Number: US-6334793-B1

Title: Enhanced universal serial bus

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This is a divisional of U.S. patent application Ser. No. 08/807,493 filed Feb. 27, 1997 U.S. Pat. No. 6,086,430. 
     This application for patent is related to co-pending U.S. patent application Ser. No. 08/842,695, which is hereby incorporated by reference herein. 
    
    
     TECHNICAL FIELD 
     The present invention relates to supplying various voltages and power levels via a standard bus interface. More particularly, it relates to an apparatus for supplying multiple voltages via a Universal Serial Bus compatible interface. 
     BACKGROUND INFORMATION 
     Recently, personal computers (“PCs”) used a variety of techniques for providing input and output. These included a serial port, usually an RS232, a parallel port and several ISA expansion slots included on the mother board. Connecting the PCs to anything more complicated than a mouse, modem or printer, required the lid to be removed and dip switches to be set and software configured. SCSI (small computer systems interface) permitted access to external storage devices, but required a large cable connector with the need to manually set ID numbers and have a terminator. 
     Referring to FIG. 1, Universal Serial Bus (“USB”) is specified to be an industry standard extension to the PC architecture with a focus on computer telephony interface, consumer and productivity applications. The USB architecture provides for ease of use of peripheral expansion, transfer rates up to 12 megabits per second, protocol flexibility for mixed modes, isochronous data transfers and asynchronous massaging. USB is a cable bus supporting data transfer between the host PC and a range of simultaneously testable peripherals. One host controller can support up to 127 physical devices using a tiered topology. The hub is at the center of each star with each wire segment creating a point-to-point connection of up to 5 meters. The 5 meter limitation may be between a host and a hub or a hub function or a hub connected to another hub or function. 
     Alternatively, a number of peripherals can be daisy-chained together via the 4-wire USB cable. One of the 4 wires referred to as VBUS provides a DC voltage of +5 volts and another wire provides a ground signal. The USB cable provides power to the devices along the chain. Signaling takes place over two wires between two end points. The signals of each end point are driven differentially over a 90 ohm impedance with each receiver featuring input sensitivity of at least 200 millivolts. A non-return to zero invert (NRZI) with bit stuffing to insure adequate transitions is used to carry the bus clock down the chain. A sync field precedes each data package to allow the receivers to synchronize their bit recovery clocks. The serial interface provides a maximum bandwidth of 12 megabits per second and can connect as many as 127 devices to a host system. 
     Physically, USB devices ranging from a mouse, joystick to telephones connect to a host via layers of multiport hubs. The requisite hub called “the root hub” is located in the host and can include multiple ports. Hubs linked to USB devices via point-to-point connections. The host views all USB devices as if they connect in a true star arrangement. USB supports both the standard devices that operate a full 12 megabit rate and low end devices that use only a 1.5 megabit sub channel. Hubs must always support 12 megabit operations and must insure that 12 megabit transmissions do not go to 1.5 megabit devices. 
     USB cables that carry 12 megabit traffic require a shielded twisted pair construction on the signal pair and can be no longer than 5 meters. Low speed cables can be no longer than 3 meters and require no shielding or twisting of the signaling pair. The host uses a master slave protocol to control the bidirectional communications with USB devices. The interface employs a 1 KHZ bus clock that instigates bussing a new frame every 1 millisecond. The interface handles multiple transactions including time critical isochronous transactions within each frame in 1 millisecond period and 12 megabit per second bandwidth limit type of isochronous data streams that the interface can successfully carry. 
     One problem with the universal serial bus is that it provides only one voltage. Devices that operate at different voltages or have high power requirements are required to supply their own voltage sources and power sources. In some environments, for instance, the retail point-of-sale environment, this additional cabling for power creates a non-aesthetic appearance at the store front. 
     The co-pending U.S. patent application Ser. No. 08/842,695 cross-referenced above, discloses an enhanced USB interface cable, which provides auxiliary power levels other than the standard USB power levels described previously. A problem with providing such an enhanced USB signaling is that an end-user may attempt to couple a standard USB plug into the enhanced USB receptacle. 
     SUMMARY OF THE INVENTION 
     The foregoing problem is addressed by the present invention which provides a unique keying pattern stamped into the system unit enclosure containing the enhanced and standard USB receptacles, which is only matable with a unique cut-out pattern in the shield of the molded plug of the enhanced USB connector. As a result, a standard USB plug is prevented from coupling with an enhanced USB receptacle. 
     In an alternative embodiment of the present invention, the keying pattern stamped into the system unit enclosure, or chassis, may be configured to permit only a polarized connection to be made with the enhanced USB connector portion. 
     The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which: 
     FIG. 1 illustrates an example bus topology for the USB; 
     FIG. 2 illustrates hubs in a desktop computer environment using USB interconnections; 
     FIG. 3 illustrates a standard USB cable plug; 
     FIG. 4 illustrates exemplary signaling provided within an enhanced USB connection; 
     FIGS. 5-7 illustrate various views of a USB interface; 
     FIG. 8 illustrates an interconnection of an enhanced USB interface; 
     FIGS. 9-12 illustrate various keying configurations in accordance with the various embodiments of the present invention; and 
     FIG. 13 illustrates an enhanced USB cable plug in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION 
     In the following description, numerous specific details are set forth to provide a thorough understanding of the present invention. However, it will be obvious to those skilled in the art that the present invention may be practiced without such specific details. In other instances, well-known circuits have been shown in block diagram form in order not to obscure the present invention in unnecessary detail. For the most part, details concerning timing considerations and the like have been omitted inasmuch as such details are not necessary to obtain a complete understanding of the present invention and are within the skills of persons of ordinary skill in the relevant art. 
     Refer now to the drawings wherein depicted elements are not necessarily shown to scale and wherein like or similar elements are designated by the same reference numeral through the several views. 
     Within the following description, a standard Universal Serial Bus (“USB”) connector, receptacle, plug, and signaling all refer to the USB architecture described within the  Universal Serial Bus Specification , 1.0 Final Draft Revision, Copyright Nov. 13, 1995, which is hereby incorporated by reference herein. USB is a cable bus that supports data exchange between a host computer and a wide range of simultaneously accessible peripherals. The attached peripherals share USB bandwidth through a host scheduled token based protocol. The bus allows peripherals to be attached, configured, used, and detached while the host and other peripherals are in operation. This is referred to as dynamic (or hot) attachment and removal. 
     FIG. 1 illustrates the topology of the USB. The USB connects USB devices with the USB host. The USB physical interconnect is a tiered star topology. A hub is at the center of each star. Each wire segment is a point-to-point connection between the host and a hub or function, or a hub connected to another hub or function. 
     There is generally only one host on any USB system. The USB interface to the host computer system is referred to as the host controller. The host controller may be implemented in a combination of hardware, firmware, or software. A root hub is integrated within the host system to provide one or more attachment points. 
     USB devices include: 
     hubs, which provide additional attachment points to the USB; 
     functions, which provide capabilities to the system; for example, an ISDN connection, a digital joy stick, or speakers. USB devices present a standard USB interface in terms of their: 
     comprehension of the USB protocol; 
     response to standard USB operations such as configuration and reset; 
     standard capability descriptive information. 
     Referring next to FIG. 2, there is illustrated a diagram of how hubs provide connectivity in a desktop computer environment. The data processing system shown in FIG. 2 includes computer (PC)  201 , monitor  202 , and keyboard  203 . Coupled to PC  201  are phone  208  and another hub  209 . Coupled to monitor  202  are speaker  206  and microphone (MIC)  207 . Coupled to keyboard  203  are pen  204  and mouse  205 . PC  201  is coupled to monitor  202 , which is coupled to keyboard  203 . All of the previously noted and shown coupling is via USB buses  302  with USB plug connectors  301 . 
     A function is a USB device that is able to transmit or receive data or control information over the bus. A function is typically implemented as a separate peripheral device with a cable that plugs into a port on a hub. However, a physical package may implement multiple functions and an embedded hub with a single USB cable. This is known as a compound device. A compound device appears to the host as a hub with one or more permanently attached USB devices. 
     Each function contains configuration information that describes its capabilities and resource requirements. Before a function can be used, it must be configured by the host. This configuration includes allocating USB bandwidth and selecting function specific configuration options. 
     Referring next to FIG. 3, there is illustrated standard USB cable plug  301  having bus  302  coupled thereto. Plug  301  includes a standard USB shielded plug housing  303 , which conforms to the standard USB architecture described in the Universal Serial Bus specification referenced above. Standard USB shielded plug housing  303  operates to communicate differentially driven data signals D+ and D−, a 5-volt signal, and a ground signal. 
     Referring next to FIGS. 5 and 6, there are illustrated two views of standard shielded plug housing  303 , which is encased within plug overmold  304 . Standard USB signaling is communicated by contacts  503 - 506 . 
     Referring next to FIG. 7, there is illustrated a cross-sectional view of a mating of shielded plug housing  303  with receptacle  701 , whereby contact  703  is shown making physical and electrical connection with contact  504  when shielded housing  303  is fully engaged into receptacle  701  at position  702 . 
     Referring to FIG. 13, plug  1301  further includes a non-standard USB portion  1304 , which may communicate non-standard USB signaling, such as auxiliary voltage signals and corresponding ground signals. Plug  1301  has overmold  1306  corresponding to overmold  304 , standard USB portion (plug housing)  1303  corresponding to shielded standard portion (plug housing)  303 , and bus  1302  corresponding to bus  302 , except that additional hardware and parts have been added to implement non-standard USB portion  1304  As will be described below in further detail, housing  1304  includes a housing having cut-out portion  1305 , which enables housing  1304  to mate with a standard USB receptacle through specifically designed chassis cut-outs (see FIGS.  8 - 12 ). 
     Also as further noted herein, portions  1303  and  1304  may be swapped in their relative position to each other on plug  1301 . 
     Please note that enhanced plug portion  1304  may be configured in a manner similar to portion  303  illustrated in FIGS. 5 and 6, except that cut-out portion  1305  may also be implemented on housing  1304 . 
     Referring next to FIG. 8, there is illustrated a USB interface whereby plug  1301  having portions  1303  and  1304  is mated with USB receptacle  802 , which is coupled to circuit card  803 , which may be implemented within any of the devices shown in FIG.  2 . Receptacle  802  and circuit card  803  are enclosed within chassis  801 . 
     In order that portions  1303  and  1304  may mate with receptacle  802 , cut-out portions, or holes, are required within chassis  801 . This is further illustrated in FIGS. 9-12 in various embodiments. 
     In FIG. 9, chassis  801  has holes  901  and  902  stamped therein. Hole  902  has a key  903  so that only portion  1304  of plug  1301  may be coupled through hole  902  into receptacle  802 , since portion  1304  includes cut-out  1305 . Hole  901  is adaptable for receiving plug portion  1303 . 
     FIG. 10 illustrates an alternative embodiment of the present invention whereby hole  1001  within chassis  801  is adaptable for receiving standard USB plug portion  1303  while hole  1002  has an off-set key  1003 , so that the enhanced portion  1304  may only mate through hole  1002  in a particular manner, which may be implemented for insuring that a polarized connection is properly coupled. The required cut-out in portion  1304  is not shown but could be implemented by one skilled in the art viewing the illustration in FIG.  10 . 
     Likewise, FIG. 11 shows a left polarizing key tab cut-out  1103  in hole  1102 . 
     FIG. 12 shows another alternative embodiment of the present invention whereby hole  1201  has key  1202 . Hole  1201  is thus adaptable for receiving plug  1301  where portions  1303  and  1304  have been swapped (see FIG.  4 ). 
     Referring next to FIG. 4, there is illustrated a possible embodiment for connector  802  whereby connector section  406  is operable for receiving standard USB portion  1303 , while connector section  405  is operable for receiving enhanced USB portion  1304 . Note, the configuration shown in FIG. 4 may correspond to a plug configuration whereby portions  1303  and  1304  have been swapped, as described above with respect to FIG.  12 . 
     Connector section  406  operates to communicate the differential data signals D+ and D− and the 5-volt and ground signaling. Connector section  405  operates to communicate ground signaling and alternative voltage signals, which are switched into place by voltage switches  401 - 403  as in the example shown in FIG.  4 . Decoder  404 , which is selectable by the voltage select signal (under control of the hub) operates to control voltage switches  401 - 403 . 
     Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.