Abstract:
A multimedia interface cable for achieving complete interoperability between different types of multimedia display interfaces. The cable comprises a first multimedia connector including a plurality of contact pins of at least high-speed multimedia signals and control signals; a second multimedia connector including a plurality of contact pins of least high-speed multimedia signals and control signals; a plurality of un-crossing conducting wires for coupling the plurality of contact pins of the high-speed multimedia signals in the first multimedia connector to the plurality of contact pins of the high-speed multimedia signals in the second multimedia connector; and a plurality of conducting wires for coupling the plurality of contact pins of the control signals in the first multimedia connector to the plurality of contact pins of the control signals in the second multimedia connector.

Description:
TECHNICAL FIELD 
     This invention generally relates to the connectivity of electronic display devices. 
     BACKGROUND OF THE INVENTION 
     The high-definition multimedia interface (HDMI) is a compact audio/video connector interface for transmitting uncompressed digital streams. The HDMI connects a digital multimedia (or audio/video) source (e.g., a set-top box, a DVD player, a personal computer, a video game console, etc.) to a compatible digital sink, such as a digital television. The HDMI is fully described in the HDMI Specification version 1.4 published on Jun. 5, 2009, incorporated herein by reference in its entirety merely for the useful understanding of the background of the invention. 
     A HDMI cable is a transport medium including three transition minimized differential signaling (TMDS®) channels utilized to transfer video, audio, and auxiliary data encapsulated in TDMS characters and the transmission is synchronized using a high-frequency clock signal running over a clock channel. The TDMS and clock channels are differential pairs. A HDMI cable also includes the following channels: a display data channel (DDC_SCL and DDC_SDA), a consumer electronics control (CEC), and a hot-plug detect (HPD) signal which originates at the sink. The HDMI interface is implemented using a HDMI cable and connectors, each of which includes 19 pins. A source and sink connectors have the same configuration. Table 1 lists the pins in a type A HDMI connector (either a source or sink). 
     
       
         
               
               
             
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 Pin Number 
                 HDMI Signal 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 1. 
                 TMDS_Data2+ 
               
               
                 2. 
                 Shield 
               
               
                 3. 
                 TMDS_Data2− 
               
               
                 4. 
                 TMDS_Data1+ 
               
               
                 5. 
                 Shield 
               
               
                 6. 
                 TMDS_Data1− 
               
               
                 7. 
                 TMDS_Data0+ 
               
               
                 8. 
                 Shield 
               
               
                 9. 
                 TMDS_Data0− 
               
               
                 10. 
                 TMDS_Clk+ 
               
               
                 11. 
                 Shield 
               
               
                 12. 
                 TMDS_Clk− 
               
               
                 13. 
                 CEC 
               
               
                 14. 
                 Utility 
               
               
                 15. 
                 SCL 
               
               
                 16. 
                 SDA 
               
               
                 17. 
                 DDC/CEC/Ground 
               
               
                 18. 
                 +5 V 
               
               
                 19. 
                 HPD 
               
               
                   
               
             
          
         
       
     
     DisplayPort™ is a standard that defines a digital display interface of a new digital audio/video interconnect. The DisplayPort is intended to be used primarily between a computer and its display monitor, or a computer and a home-theater system. The DisplayPort standard is fully described in the DisplayPort Specification Version 1.1a published in Jan. 11, 2008, by the video electronics standards association (VESA), incorporated herein by reference in its entirety merely for the useful understanding of the background of the invention. 
     Transport channels of a DisplayPort interface include a main link, an auxiliary (AUX), and a hot plug detect (HPD). The main link is a unidirectional channel that allows data transfers over up to 4 lanes that carry clock signals in addition to the video/audio streams. Each lane is an AC-coupled differential pair. The auxiliary channel is a bi-directional half-duplex channel that carries control and management information and the HPD channel is used by a sink device to interrupt a source device when a plug is connected or disconnected. The DisplayPort interface is facilitated using a proprietary cable and connectors, each of which includes 20 pins. The DisplayPort cable is a cross cable, i.e., a source and sink connector has a different configuration. Table 2 lists the pins and their signals of source and sink DisplayPort connectors. 
     
       
         
               
               
               
             
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                   
                 DisplayPort 
                 DisplayPort 
               
               
                 Pin Number 
                 Sink 
                 source 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 1. 
                 ML_lane0P 
                 ML_lane3N 
               
               
                 2. 
                 GND 
                 GND 
               
               
                 3. 
                 ML_lane0N 
                 ML_lane3P 
               
               
                 4. 
                 ML_lane1P 
                 ML_lane2N 
               
               
                 5. 
                 GND 
                 GND 
               
               
                 6. 
                 ML_lane1N 
                 ML_lane2P 
               
               
                 7. 
                 ML_lane2P 
                 ML_lane1N 
               
               
                 8. 
                 GND 
                 GND 
               
               
                 9. 
                 ML_lane2N 
                 ML_lane1P 
               
               
                 10. 
                 ML_lane3P 
                 ML_lane0N 
               
               
                 11. 
                 GND 
                 GND 
               
               
                 12. 
                 ML_lane3N 
                 ML_lane0P 
               
               
                 13. 
                 Config1 
                 Config1 
               
               
                 14. 
                 Config2 
                 Config2 
               
               
                 15. 
                 AUX_CHP 
                 AUX_CHP 
               
               
                 16. 
                 GND 
                 GND 
               
               
                 17. 
                 AUX_CHN 
                 AUX_CHN 
               
               
                 18. 
                 HPD 
                 HPD 
               
               
                 19. 
                 Return 
                 Return 
               
               
                 20. 
                 AUX_PWR 
                 AUX_PWR 
               
               
                   
               
             
          
         
       
     
     Multimedia interfaces that allow connectivity of both the HDMI and DisplayPort (will be referred hereinafter as a “dual mode connectivity interface”) have been recently developed. Specifically, such interfaces can process data compliant with the HDMI and DisplayPort. However, even if a source or sink device has dual-mode connectivity capabilities, the connection is either through a HDMI or a DisplayPort connector. In the related art there is no physical medium (e.g., a cable), other than HDMI or DisplayPort cables, to connect source and sink devices having different connector types. 
     Interoperability between HDMI and DisplayPort is defined in the VESA DisplayPort Interoperability Guideline Version 1.1a published on Feb. 5, 2009, which requires a dedicated adapter and a HDMI cable. As illustrated in  FIG. 1A , a source device  110  including a dual mode connectivity interface and a DisplayPort connector  160  is connected using an adapter  130  and a HDMI cable  120  to a sink device  140  having a HDMI connector  150 . Similar configuration, shown in  FIG. 1B , is applied when the sink device  140  includes a dual mode connectivity interface and is connected through the DP connector  160  and an adapter  170  to the source device  110  having a HDMI connector  150 . This is the only available interoperability configuration that allows a reliable connection between a HDMI compliant source/sink to a DisplayPort dual mode connectivity sink/source. For example, there is no solution for connecting a dual mode connectivity sink/source device having a HDMI connector to a source/sink device with a DisplayPort connector. That is, currently there is no known technique to support complete interoperability at least between HDMI and DisplayPort multimedia interfaces. 
     SUMMARY OF THE INVENTION 
     Certain embodiments of the invention include multimedia interface cable. The multimedia comprises a first multimedia connector including a plurality of contact pins of at least high-speed multimedia signals and control signals; a second multimedia connector including a plurality of contact pins of least high-speed multimedia signals and control signals; a plurality of un-crossing conducting wires for coupling the plurality of contact pins of the high-speed multimedia signals in the first multimedia connector to the plurality of contact pins of the high-speed multimedia signals in the second multimedia connector; and a plurality of conducting wires for coupling the plurality of contact pins of the control signals in the first multimedia connector to the plurality of contact pins of the control signals in the second multimedia connector. 
     Certain embodiments of the invention further include an apparatus for enabling interoperability between multimedia display interfaces, the apparatus is operable in a source multimedia device. The apparatus comprises an input coupled to a multimedia connector; and a comparator for determining a type of the multimedia display interface of a sink multimedia device connected to the source multimedia device based on at least a voltage level of a clock signal received through the multimedia connector. 
     Certain embodiments of the invention also include an apparatus for enabling interoperability between multimedia display interfaces, the apparatus is operable in a sink multimedia device. The apparatus comprises an input interface coupled to a multimedia connector; and a detector for determining a type of the multimedia display interface of a source multimedia device connected to the sink multimedia device based on at least one control signal received through the multimedia connector. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The subject matter that is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other objects, features and advantages of the invention will be apparent from the following detailed description taken in conjunction with the accompanying drawings. 
         FIGS. 1A and 1B  are diagrams illustrating the connection between a HDMI device and a DisplayPort device using an adapter. 
         FIGS. 2A and 2B  are schematic diagrams illustrating the connection between a HDMI device and a DisplayPort device using a cable designed in accordance with the principles of the invention. 
         FIG. 3  is a schematic diagram of a multimedia interface cable constructed in accordance with an embodiment of the invention. 
         FIG. 4  is a schematic diagram of a source dual mode connectivity interface adapted to perform sink recognition in accordance with an embodiment of the invention. 
         FIG. 5  is a schematic diagram of a sink dual mode connectivity interface adapted to perform source recognition in accordance with an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     It is important to note that the embodiments disclosed by the invention are only examples of the many advantageous uses of the innovative teachings herein. In general, statements made in the specification of the present application do not necessarily limit any of the various claimed inventions. Moreover, some statements may apply to some inventive features but not to others. In general, unless otherwise indicated, singular elements may be in plural and vice versa with no loss of generality. In the drawings, like numerals refer to like parts through several views. 
     One embodiment of the invention, illustrated in  FIG. 2A , includes a multimedia interface cable  200  that enables a proper connection between a DisplayPort compliant source device  210  and a HDMI compliant sink device  220  that includes a dual mode connectivity interface  222 . The devices  210  and  220  respectively include a DisplayPort and HDMI connector  215  and  225 . As shown in  FIG. 2B , the cable  200  can be also utilized to connect a DisplayPort compliant sink device  230  to a HDMI compliant source device  240  that includes a dual mode connectivity interface  242 . The devices  230  and  240  respectively include a DisplayPort and HDMI connector  235  and  245 . 
     In accordance with an embodiment of the invention both dual mode connectivity interfaces  222  and  242  implement an automatic recognition technique for determining the type of the multimedia interface (e.g., a HDMI or DisplayPort) connected at the other end of the cable  200 , and configuring the respective device accordingly. For example, if the source device  210  also supports a HDMI, the dual mode connectivity interface  222  recognizes that HDMI data is transmitted by the source device  210 , and sets the sink device  220  to process such type of data. As will be described in detail below, each of the dual mode connectivity interfaces implement a different automatic recognition technique. 
       FIG. 3  is an exemplary diagram of the multimedia interface cable  200  wired according to an embodiment of the invention. The cable  200  provides a transport medium between two different types of multimedia interfaces. In one embodiment the multimedia interfaces include, but are not limited to, the HDMI and DisplayPort. Without departing from the scope of the invention the structure of the cable will be described hereinafter with a reference to this embodiment. 
     The multimedia interface cable  200  comprises a HDMI connector  310  including 19 pins and a DisplayPort connector  320  with 20 pins. The wiring between the connectors  310  and  320  is depicted in  FIG. 3 . It is important to note that in order to ensure good performance no transport data channels (e.g., TDMS and main lane channels) are crossed. As listed in Table 2 above, the wires between a source DisplayPort connector and a sink DisplayPort connector are crossed. For example, pin  1  on a source DisplayPort connector is main Lane  3 , while on the sink connector this pin is main Lane  0 . This does not affect the wiring of the cable  200 , however, the signals are swapped by, for example, the dual mode connectivity interface to ensure proper connection. In accordance with an exemplary embodiment of the invention, the switching of the signals is performed as described in U.S. patent application Ser. No. 12/260,419 to Bar-Niv, assigned to the common assignee, and incorporated herein by reference. 
     To allow proper connection, such as the configuration illustrated in  FIG. 2A , DisplayPort Lane  0  (e.g., pins  1  and  3  on connector  320 ) is connected to TDMS channel  2  (e.g., pins  1  and  3  on connector  310 ); Lane  1  (e.g., pins  4  and  6  on connector  320 ) to TDMS channel  1  (e.g., pins  4  and  6  connector  310 ); Lane  2  (e.g., pins  7  and  9  on connector  320 ) is connected to TDMS channel  0  (e.g., pins  7  and  9  on connector  310 ); and Lane  3  (e.g., pins  10  and  12  on connector  320 ) is connected to the clock channel (e.g., pins  10  and  12  on connector  310 ). 
     To allow a proper connection between a source HDMI (dual mode) and a sink DisplayPort, such as the configuration illustrated in  FIG. 2B , DisplayPort Lane  3  (e.g., pins  1  and  3  on connector  320 ) is connected to TDMS channel  2  (e.g., pins  1  and  3  on connector  310 ); Lane  2  (e.g., pins  4  and  6  on connector  320 ) to TDMS channel  1  (e.g., pins  4  and  6  connector  310 ); Lane  1  (e.g., pins  7  and  9  on the connector  320 ) is connected to TDMS channel  0  (e.g., pins  7  and  9  on connector  310 ); and Lane  0  (e.g., pins  10  and  12  on connector  320 ) is connected to the clock channel (e.g., pins  10  and  12  on connector  310 ). In addition, a polarity inverter is utilized on each of the TDMS and clock channels. 
     Control signals (in the configurations depicted both in  FIGS. 2A and 2B ) are wired as described in the VESA standard referenced above. Specifically, as illustrated in  FIG. 3  the following pins are wired together: Config 1  (e.g., pin  13  on connector  320 ) and Utility (e.g., pin  14  on connector  310 ); Config 2  (e.g., pin  14  on connector  320 ) and CEC (e.g., pin  13  on connector  310 ); AUX_CHP (e.g., pin  15  on connector  320 ) and SCL (e.g., pin  15  on connector  310 ); AUX_CHN (e.g., pin  17  on connector  320 ) and SDA (e.g., pin  16  on connector  310 ); HPD (e.g., pin  18  on connector  320 ) and HDP (e.g., pin  19  on connector  310 ); Return (e.g., pin  19  on connector  320 ) and DDC (e.g., pin  17  on connector  310 ); and AUX_PWR (e.g., pin  20  on connector  320 ) and +5V (e.g., pin  18  on connector  310 ). The indicated pin numbers are only examples used for ease of understanding. One of ordinary skill in the art recognizes that the pin assignments may be designed to be in any location based on design expediency. 
       FIG. 4  shows an exemplary diagram of a source dual mode connectivity interface  242  adapted to automatically recognize a type of a sink multimedia interface connected to the interface  242 . The sink recognition technique is performed by a voltage comparator  410  that compares the voltage level on the TMDS clock channel (e.g., pins  10  and  11  on connector  310 ) to a predefined threshold (TH). Specifically, if the voltage level of the TDMS clock (Vtdms_clk) signal is above 3 volts (V) the sink device is of a HDMI type; if the value of Vtdms_clk&#39;s values is between 1.6V and 2V, the sink is of a DisplayPort type; and when the Vtdms_clk is below 1.6V a sink device is off or not connected. It should be noted that the sink recognition can be performed when a HDP signal is inactive, when no data is transferred on the HDMI channels, or when a +5V/DP_PWR signal (e.g., pin  18  on connector  310 ) is too low. The indicated voltage values of the predefined threshold are only examples used for ease of understanding. One of ordinary skill in the art recognizes that the value may be designed to be any value based on design expediency. 
     Upon recognition of the type of the sink, the source dual mode connectivity interface  242  is set to be compliant with the multimedia interface type of the sink device. This includes, for example, setting analog circuits of an analog front-end (not shown) of the interface  242  to a mode of operation compliant with the type of the sink, setting the power level of the interface  242  and adapting passive components of control signals by, for example, disabling the AC component of AUX channel and enabling a CEC signal when setting the interface  242  to operate in a HDMI mode. 
       FIG. 5  shows an exemplary diagram of a sink dual mode connectivity interface  222  adapted to automatically recognize a type of a source multimedia interface connected to the interface  222 . The source recognition technique is performed by a detector  510 , which may detect the type of the source based on at least one of the following techniques: sensing of an auxiliary channel, sensing of a CEC signal, or by comparing the voltage level of an auxiliary power (AUX_PWR) signal to a predefined threshold. 
     The detector  510  implements the sensing of an auxiliary channel using a logic circuit (not shown) that generates a decision regarding the type of a source device based on the logic values of the signals AUX_CHP and AUX_CHN (e.g., pins  15  and  16  on connector  310 ). Specifically, if a logic value of both signals AUX_CHP and AUX_CHN is ‘0’, the source device is a DisplayPort device not being powered; if the value of AUX_CHP is ‘0’ and the value of the AUX_CHN is ‘1’ the source is a DisplayPort device; if the logic values of AUX_CHP and AUX_CHN are ‘1’ and ‘0’ respectively, no device is connected at the other end of the cable; and if a logic value of both AUX_CHP and AUX_CHN is ‘1’, the source is a HDMI device. 
     In another embodiment the detector  510  senses the CEC and AUX_PWR signals using a logic circuit (not shown) to determine the type of a source device according to logic values of the CEC signal (e.g., pin  13  on connector  310 ) and the AUX_PWR signal (e.g., pin  18  on connector  310 ). Specifically, if logic values of both CEC and AUX_PWR signals are ‘1’, the source is a HDMI device not being powered; if the logic values of AUX_PWR and CEC signals are ‘1’ and ‘0’ respectively, the source is a DisplayPort device; and if the value of AUX_PWR is ‘0’, no device is connected at the other end of the cable. 
     Yet in another embodiment the detector  510  includes a comparator (not shown) that compares the voltage level on an AUX_PWR signal (e.g., pin  18  on connector  310 ) to a predefined threshold. Specifically, if the voltage level of the AUX_PWR is below 0.8V, no device is connected at the source; if the voltage level of the AUX_PWR signal is between 3V and 4V, the source is a DisplayPort device; and when the amplitude of AUX_PWR is above 4.5V the source is a HDMI device. It should be noted that the logic values ‘1’ and ‘0’ may also be referred to as high and low values respectively. Furthermore, the indicated logic values of ‘1’ and ‘0’ and voltage values of the predefined threshold are only examples used for ease of understanding. One of ordinary skill in the art recognizes that the value may be designed to be any value based on design expediency. 
     Upon recognition of the type of a source device, the sink dual mode connectivity interface  222  is set to be compliant with the multimedia interface type of the source device. This includes, for example, setting analog circuits of an analog front-end of the interface  222  to a mode of operation compliant with the source device. 
     It should be appreciated that the multimedia interface cable  200  together with the automatic sensing techniques implemented between the dual mode connectivity interfaces  222  and  242  provide complete interoperability of at least HDMI and DisplayPort. Specifically, the teachings of the invention disclosed herein can be utilized to connect a DisplayPort compliant source device to a HDMI compliant sink device and a HDMI compliant source device to a DisplayPort compliant sink device using either the cable  200  or a standard HDMI cable without using any dedicated adapter, such as described in the VESA standard referenced above or any other type of an active adapter. 
     Furthermore, connections such as those illustrated in  FIGS. 2A and 2B  may be achieved using a standard HDMI or DisplayPort cable and a passive adapter connected at one end of the standard cable. The passive adapter is merely a connector compatible with the connector type at the end device. For example, the connection between the sink device  230  and the source device  240  can be achieved using a DisplayPort cable with a passive adapter connected to the HDMI connector  245 . The passive adapter does not alert the signals, but rather ensures that a connector of the DisplayPort cable can be mechanically connected to the HDMI connector  245 . As another example, the connection between the sink device  220  and the source device  210  can be achieved using a HDMI cable with a passive adapter connected to the DisplayPort connector  215 . The passive adapter does not alert the signals, but rather ensures that a connector of the HDMI cable can be mechanically connected to the DisplayPort connector  215 . In both configurations the respective dual mode connectivity interface recognizes the type of the device connected at the other end of the cable and processes the multimedia and control signals according to the recognized type of device. 
     While the present invention has been described at some length and with some particularity with respect to the several described embodiments, it is not intended that it should be limited to any such particulars or embodiments or any particular embodiment, but it is to be construed with references to the appended claims so as to provide the broadest possible interpretation of such claims in view of the prior art and, therefore, to effectively encompass the intended scope of the invention. Furthermore, the foregoing describes the invention in terms of embodiments foreseen by the inventor for which an enabling description was available, notwithstanding that insubstantial modifications of the invention, not presently foreseen, may nonetheless represent equivalents thereto. All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the principles of the invention and the concepts contributed by the inventors to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions.