Abstract:
An apparatus and a method are provided. The apparatus includes a connector to connect with an electronic device external to the apparatus, and a processor configured to identify a connection with the electronic device via the connector, receive, using a first communication scheme, a message from the electronic device based at least in part on the identifying, determine, based at least in part on the message, whether the electronic device supports a second communication scheme, and establish a communication link corresponding to the second communication scheme with the electronic device based at least in part on a determination that the electronic device supports the second communication scheme.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is a continuation application of prior application Ser. No. 14/254,425, filed on Apr. 16, 2014, which claimed the benefit under 35 U.S.C. §119(a) of a Korean patent application filed on May 21, 2013 in the Korean Intellectual Property Office and assigned Serial No. 10-2013-0057279, the entire disclosure of which is hereby incorporated by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a communication system. More particularly, the present disclosure relates to an apparatus and method of recognizing an external device in a communication system. 
     BACKGROUND 
     Portable terminals, such as smartphones and tablets, provide a variety of useful functions to users through a lot of applications. Therefore, the portable terminals are evolving toward devices that provide various types of information, in addition to voice call information, via various functions. Such a portable terminal is connected to an external device and outputs data to the external device or receives data from the external device by a data Input/Output (I/O) function. 
     To provide the data I/O function, the portable terminal and the external device should be connected in a specific connection scheme, such as Universal Serial Bus (USB) connectivity and Mobile High-Definition Link (MHL) connectivity. If the external device supports MHL connectivity and USB connectivity, the portable terminal recognizes a USB device of the external device based on a resistance of a USB IDentifier (ID) pin. 
     However, since USB ID pins are limited resources, ACcessory Detection (ACD) values corresponding to the resistance values of the USB ID pins cannot be defined for all supported accessories. As a consequence, a portable terminal recognizes only a limited number of external devices, and may not recognize all external devices supporting USB connectivity. 
       FIG. 1  illustrates a configuration of a communication system according to the related art. 
     Referring to  FIG. 1 , the communication system includes a portable terminal  101  and an external device  103 . When the external device  103  is connected to the portable terminal  101  via a Universal Serial Bus (USB) cable  105 , the external device  103  provides its specific function to the portable terminal  101 . The external device  103  is called an accessory and may be any of a TeleVision (TV), a monitor, a beam projector, a keyboard, a touch screen, a Personal Computer (PC), an audio player, an auxiliary battery, and any other similar and/or suitable electronic device. For example, if the external device  103  is a TV, then the external device  103  may provide a multimedia play function of receiving multimedia data from the portable terminal  101  and displaying the received multimedia data. 
     When the portable terminal  101  is connected to the external device  103  via the USB cable  105 , the portable terminal  101  measures a resistance of a pin corresponding to a USB IDentifier (ID), from among a plurality of pins included in a connector of the portable terminal  101 . The portable terminal  101  determines the external device  103  based on the measured resistance, referring to a table tabulating ACcessory Detection (ADC) values with respect to predetermined resistance values of USB IDs. Then the portable terminal  101  recognizes the external device  103  by performing a USB host function. 
     The USB host function refers to a function that enables operation between portable terminals such as a Personal Digital Assistant (PDA), an MP3 player, and a portable phone, without intervention of a main computer. For example, the USB host function may include a data exchange function between the portable terminal  101  and the external device  103 , and a battery charging function of the portable terminal  101 , when the external device  103  is an auxiliary battery. 
       FIG. 2  is a table that tabulates ADC values versus the resistance values of USB ID pins according to the related art. 
     Referring to  FIG. 2 , a table  201  that tabulates ADC values versus the resistance values of USB ID pins includes ADC values  203  allocated to a plurality of accessories. For example, if a USB ID resistance is 28.7KΩ, the portable terminal  101  may detect an ADC value of 0x0E mapped to the USB ID resistance 28.7KΩ. If determining that the external device  103  corresponds to Accessory  1  mapped to the ADC value 0x0E, then the portable terminal  101  may recognize the external device  103  by performing the USB host function. 
     However, since USB ID pins are limited resources, ADC values corresponding to the resistance values of USB ID pins cannot be defined for all supported accessories. Consequently, the portable terminal  101  may recognize a limited number of accessories, because not all accessories support USB connectivity. For example, the portable terminal  101  may recognize only five types of accessories  203  preset in the table  201  listing ADC values versus the resistance values of USB ID pins, and thus, may not recognize other types of accessories. 
     The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure. 
     SUMMARY 
     Aspects of the present disclosure are to address at least the above-mentioned problems and/or disadvantages and to provide at least the advantages described below. Accordingly, an aspect of the present disclosure is to provide an apparatus and method of recognizing all external devices supporting Universal Serial Bus (USB) connectivity in a communication system. 
     Another aspect of the present disclosure is to provide an apparatus and method of recognizing all external devices supporting USB connectivity using Mobile High-Definition Link (MHL) connectivity in a communication system. 
     Another aspect of the present disclosure is to provide an apparatus and method of recognizing all external devices supporting USB connectivity using a Control BUS (CBUS) line, from among MHL lines, in a communication system. 
     In accordance with an aspect of the present disclosure, an apparatus is provided. The apparatus includes a connecter to connect with an electronic device external to the apparatus, and a processor configured to identify a connection with the electronic device via the connector, receive, using a first communication scheme, a message from the electronic device based at least in part on the identifying, determine, based at least in part on the message, whether the electronic device supports a second communication scheme, and establish a communication link corresponding to the second communication scheme with the electronic device based at least in part on a determination that the electronic device supports the second communication scheme. 
     In accordance with another aspect of the present disclosure, a method is provided. The method includes identifying, at the electronic device, a connection with an external electronic device via a connector, receiving, using a first communication scheme, a message from the external electronic device based at least in part on the identifying, determining, based at least in part on the message, whether the external electronic device supports a second communication scheme, and establishing a communication link corresponding to the second communication scheme with the external electronic device based at least in part on a determination that the external electronic device supports the second communication scheme. 
     In accordance with another aspect of the present disclosure, a non-transitory machine-readable storage device storing instructions that, when executed by one or more processors, cause the one or more processors to perform operations is provided. The operations include identifying, at the electronic device, a connection with an external electronic device via a connector, receiving, using a first communication scheme, a message from the external electronic device based at least in part on the identifying, determining, based at least in part on the message, whether the external electronic device supports a second communication scheme, and establishing a communication link corresponding to the second communication scheme with the external electronic device based at least in part on a determination that the external electronic device supports the second communication scheme. 
     Other aspects, advantages, and salient features of the disclosure will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses various embodiments of the disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features, and advantages of certain embodiments of the present disclosure will be more apparent from the following description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  illustrates a configuration of a communication system according to the related art; 
         FIG. 2  is a table that tabulates Accessory Detection (ADC) values versus the resistance values of Universal Serial Bus (USB) IDentifier (ID) pins according to the related art; 
         FIG. 3  illustrates a configuration of a communication system according to an embodiment of the present disclosure; 
         FIG. 4  illustrates lines between a portable terminal and an external device in a communication system according to an embodiment of the present disclosure; 
         FIG. 5  is a block diagram of a portable terminal according to an embodiment of the present disclosure; 
         FIG. 6  is a block diagram of an external device according to an embodiment of the present disclosure; 
         FIG. 7  is a flowchart illustrating an operation of recognizing an external device in a communication system according to an embodiment of the present disclosure; 
         FIG. 8  is a flowchart illustrating an operation of recognizing an external device in a portable terminal according to an embodiment of the present disclosure; 
         FIG. 9  is a flowchart illustrating an operation of transmitting a USB connection response message in an external device according to an embodiment of the present disclosure; 
         FIG. 10  illustrates a configuration of a communication system according to another embodiment of the present disclosure; 
         FIG. 11  illustrates lines between a portable terminal and an external device in a communication system according to another embodiment of the present disclosure; 
         FIG. 12  is a block diagram of a portable terminal according to another embodiment of the present disclosure; 
         FIG. 13  is a block diagram of an external device according to another embodiment of the present disclosure; 
         FIG. 14  is a flowchart illustrating an operation of recognizing an external device in a communication system according to another embodiment of the present disclosure; and 
         FIG. 15  is a flowchart illustrating an operation of recognizing an external device in a portable terminal according to another embodiment of the present disclosure. 
     
    
    
     Throughout the drawings, like reference numerals will be understood to refer to like parts, components, and structures. 
     DETAILED DESCRIPTION 
     The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of various embodiments of the present disclosure as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the various embodiments described herein can be made without departing from the scope and spirit of the present disclosure. In addition, descriptions of well-known functions and constructions may be omitted for clarity and conciseness. 
     The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the present disclosure. Accordingly, it should be apparent to those skilled in the art that the following description of various embodiments of the present disclosure is provided for illustration purpose only and not for the purpose of limiting the present disclosure as defined by the appended claims and their equivalents. 
     It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a component surface” includes reference to one or more of such surfaces. 
     By the term “substantially” it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide. 
     Various embodiments of the present disclosure will be provided to achieve the above-described technical aspects of the present disclosure. In an implementation, defined entities may have the same names, to which the present disclosure is not limited. Thus, various embodiments of the present disclosure can be implemented with same or ready modifications in a system having a similar technical background. 
     In various embodiments of the present disclosure, the term “portable terminal” refers to a portable, mobile electronic device, covering a variety of terminals including a video phone, a portable phone, a smart phone, a Wideband Code Division Multiple Access (WCDMA) phone, a Universal Mobile Telecommunication System (UMTS) terminal, a Personal Digital Assistant (PDA), a Portable Multimedia Player (PMP), a Digital Multimedia Broadcasting (DMB) terminal, an e-book reader, a portable computer, e.g., a laptop and a tablet, a digital camera, a Motion Picture Experts Group (MPEG) Audio Layer 3 (MP3) player, and any other similar and/or suitable electronic device. 
       FIG. 3  illustrates a configuration of a communication system according to an embodiment of the present disclosure. 
     Referring to  FIG. 3 , the communication system includes a portable terminal  301  and an external device  303 . 
     The external device  303  supports Universal Serial Bus (USB) connectivity and Mobile High-Definition Link (MHL) connectivity. When the external device  303  is connected to the portable terminal  301  via a cable  305 , the external device  303  provides its specific function to the portable terminal  301 . MHL is a technique of decreasing 13 High Definition Multimedia Interface (HDMI) lines to 3 lines, especially for transmission of multimedia data between the portable terminal  301  and the external device  303 . 
     The external device  303  is also referred to as an accessory and may be any of a TeleVision (TV), a monitor, a beam projector, a touch screen, and the like. For example, if the external device  303  is a TV, then the external device  303  may provide a multimedia play function of receiving multimedia data from the portable terminal  301  and displaying the received multimedia data. 
     Particularly, when the external device  303  is connected to the portable terminal  301  via the cable  305 , the external device  303  determines whether a USB connection message has been received from the portable terminal  301  via a MHL Link Control BUS (CBUS) line of the cable  305 . The USB connection message is transmitted to determine whether the external device  303  supports USB connectivity. The CBUS line is a single cable bus that transmits auxiliary data between an MHL source device and an MHL sink device. As shown in  FIG. 3 , the portable terminal  301  may serve as an MHL source device and the external device  303  may serve as an MHL sink device. 
     Upon receipt of the USB connection message, the external device  303  determines whether the external device  303  supports USB connectivity. Then the external device  303  generates a USB connection response message based on the determination result and transmits the USB connection response message to the portable terminal  301  via the CBUS line. The USB connection response message is a response to the USB connection message that indicates whether the external device  303  supports USB connectivity. The portable terminal  301  determines whether the external device  303  has been connected to the portable terminal  301  via the cable  305 . 
       FIG. 4  illustrates lines between a portable terminal and an external device in a communication system according to an embodiment of the present disclosure. 
     Referring to  FIG. 4 , the cable  305  between the portable terminal  301  and the external device  303  includes a CBUS line  401 , an MHL Data Minus (DM) line  403 , an MHL Data Positive (DP) line  405 , a USB DM line  407 , and a USP DP line  409  to support both USB connectivity and MHL connectivity. Specifically, the CBUS line  401 , the MHL DM line  403 , and the MHL DP line  405  are lines for MHL connectivity and the USB DM line  407  and the USP DP line  409  are lines for USB connectivity. 
     If the external device  303  has been connected to the portable terminal  301 , then the portable terminal  301  determines whether the external device  303  supports MHL connectivity. If the external device  303  supports MHL connectivity, then the portable terminal  301  is connected to the external device  303  by MHL connectivity. Then the portable terminal  301  generates a USB connection message and transmits the USB connection message to the external device  303  via the CBUS line  401 . 
     The portable terminal  301  receives a USB connection response message as a response to the USB connection message from the external device  303  via the CBUS line  401  and determines, from the USB connection response message, whether the external device  303  supports USB connectivity. If the external device  303  supports USB connectivity, then the portable terminal  301  recognizes the external device  303  by executing a USB host function. 
     The USB host function may refer to a function that enables operation between portable terminals, such as a PDA, an MP3 player, a portable phone, and other similar and/or suitable portable electronic devices, without intervention of a main computer. For example, the USB host function may include a data exchange function between the portable terminal  301  and the external device  303 , and a battery charging function of the portable terminal  301 , when the external device  303  is an auxiliary battery. 
       FIG. 5  is a block diagram of a portable terminal according to an embodiment of the present disclosure. 
     Referring to  FIG. 5 , the portable terminal  301  includes a first controller  501 , a first memory unit  503 , a first MHL unit  505 , a first USB unit  507 , and a first connector  509 . The first MHL unit  505  supports HDMI, to which MHL is applied. HDMI is one type of uncompressed digital video/audio interface standards. HDMI interfaces between a multimedia source, such as an HDMI-enabled set-top box, an HDMI-enabled Digital Versatile Disk (DVD) player, and the like, and a device, such as an Audio/Visual (AV) device, a monitor, a digital TV, and the like. MHL is a technique of enabling output of multimedia data from the portable terminal  301  to the external device  303 . Multimedia data includes video data, game data, and any other similar and/or suitable type of data, information, and/or content. 
     The first USB unit  507  supports USB connectivity. USB is a port standard developed for the connection of Personal Computer (PC) peripherals to computers including Intel, Compaq, IBM, DEC, Microsoft, NEC, and Northern Telecom. USB is widely been used and supports a plug-and-play interface that connects a portable terminal directly to a peripheral such as a joystick, a keyboard, a phone, a scanner, a printer, or the like. 
     The first memory unit  503  includes a program memory (not shown) and a data memory (not shown). The program memory stores a booting program and an Operating System (OS) to control overall operations of the portable terminal  301  and the data memory stores data generated during operations of the portable terminal  301 . Especially, the first memory unit  503  stores an MHL driver for MHL connectivity and a USB driver for USB connectivity. 
     The first connector  509  connects the portable terminal  301  to the external device  303  via the cable  305 . For example, if the first connector  509  is an 11-pin connector, the first connector  509  may include a plurality of pins listed in Table 1. 
     
       
         
               
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 Pin 
                 1 
                 2 
                 3 
                 4 
                 5 
                 6 
                 7 
                 8 
                 9 
                 10 
                 11 
               
               
                   
               
             
             
               
                 Function 
                 VBUS 
                 USB 
                 USB 
                 Power 
                 Power 
                 MHL 
                 MHL 
                 MHL ID 
                 GND 
                 USB 
                 GND 
               
               
                   
                   
                 DM 
                 DP 
                   
                   
                 DM 
                 DP 
                 (CBUS) 
                   
                 ID 
               
               
                   
               
             
          
         
       
     
     In order to support both USB connectivity and MHL connectivity, the first connector  509  includes a CBUS pin  511 , i.e. Pin 8, an MHL DM pin, i.e. Pin 6, an MHL DP pin, i.e. Pin 7, a USB DM pin, i.e. Pin 2, a USB DP pin, i.e. Pin 3, and a USB ID pin, i.e. Pin 10. Specifically, the CBUS pin  511 , i.e. Pin 8, the MHL DM pin, i.e. Pin 6, and the MHL DP pin, i.e. Pin 7 are pins for MHL connectivity, whereas the USB DM pin, i.e. Pin 2, the USB DP pin, i.e. Pin 3, and the USB ID pin, i.e. Pin 10, are pins for USB connectivity. 
     The first controller  501  provides overall control to the portable terminal  301 . Particularly, the first controller  501  determines, based on a USB connection response message, whether the external device  303  includes a USB device and recognizes the USB device of the external device by executing a USB host function according to the determination result. 
     More specifically, the first controller  501  determines whether the portable terminal  301  has been connected to the external device  303  via the cable  305 . If the portable terminal  301  has been connected to the external device  303 , then the first controller  501  determines whether the external device  303  supports MHL connectivity. The first controller  501  measures a resistance of a USB ID pin, from among a plurality of pins included in the first connector  509 , and compares the measured resistance with a predetermined resistance. If the measured resistance is equal to the predetermined resistance, then the first controller  501  determines that the external device  303  supports MHL connectivity. 
     For example, referring to  FIG. 2 , if the measured resistance of the USB ID pin is 1KΩ, then the first controller  501  may determine that the first connector  509  is connected to an MHL cable and that the external device  303  supports MHL connectivity. If determining that the external device  303  supports MHL connectivity, the first controller  501  activates the first MHL unit  505  and connects the portable terminal  301  to the external device  303  via MHL connectivity. Then the first controller  501  generates a USB connection message and transmits the USB connection message to the external device  303  via the CBUS pin  511  of the first connector  509 . The USB connection message is generated in a CBUS command format and transmitted to determine whether the external device  303  supports USB connectivity. 
     The first controller  501  receives a USB connection response message from the external device  303 , via the CBUS pin  511  of the first connector  509 , as a response to the USB connection message. The USB connection response message is generated in a CBUS command format, indicating whether the external device  303  supports USB connectivity. 
     The first controller  501  determines, based on the USB connection response message, whether the external device  303  supports USB connectivity. To be more specific, if the first controller  501  determines that the USB connection response message is a first USB connection response message by analyzing the USB connection response message, then the first controller  501  determines that the external device  303  supports USB connectivity. If the USB connection response message is a second USB connection response message, then the first controller  501  determines that the external device  303  does not support USB connectivity. The first USB connection response message is a message indicating support of USB connectivity in the external device  303  and the second USB connection response message is a message indicating non-support of USB connectivity in the external device  303 . 
     If the external device  303  supports USB connectivity, then the first controller  501  activates the first USB unit  507 , activates a USB host driver through the first USB unit  507 , and executes a USB host function, thereby recognizing the external device  303 . For example, if the external device  303  is a Human Interface Device (HID), such as a USB touch screen, then the first controller  501  may recognize all accessories supported by the USB host driver by activating the USB host driver, and thus may recognize the external device  303  being a touch screen. 
       FIG. 6  is a block diagram of an external device according to an embodiment of the present disclosure. 
     Referring to  FIG. 6 , the external device  303  is an HDMI-enabled display device that supports both USB connectivity and MHL connectivity. The external device  303  includes a second controller  601 , a display unit  603 , an input unit  605 , a second memory unit  607 , a second MHL unit  609 , a second USB unit  611 , and a second connector  613 . 
     The input unit  605  includes alphanumerical keys used to enter numbers and characters and function keys used to set functions. The display unit  603  displays an image signal on a screen and displays data requested by the second controller  601 . The display unit  603  may be configured with a Liquid Crystal Display (LCD). In this case, the display unit  603  may include an LCD controller, a memory that stores image data, and an LCD display device. If the LCD is configured into a touch screen, the display unit  603  may act as the input unit  605  and thus display the same keys as in the input unit  605 . However, the present disclosure is not limited thereto, and the display unit  603  may be any type of suitable display device, such as a Light Emitting Diode (LED) display, an Organic LED (OLED) display, a Thin-Film Transistor (TFT) display, or any other similar and/or suitable type of display. 
     The second memory unit  607  includes a program memory (not shown) and a data memory (not shown). The program memory stores a booting program and an OS to control overall operations of the external device  303  and the data memory stores data generated during operations of the external device  303 . 
     The second MHL unit  609  supports HDMI, to which MHL is applied. The second USB unit  611  supports USB connectivity. The second connector  613  connects the external device  303  to the portable terminal  301  via the cable  305 . For example, if the second connector  613  is an 11-pin connector, then the second connector  613  may include the plurality of pins listed in Table 1. 
     The second controller  601  provides overall control to the external device  303 . Particularly, upon receipt of a USB connection message from the portable terminal  301 , the second controller  601  generates a USB connection response message and transmits the USB response message to the portable terminal  301 . 
     More specifically, if the external device  303  is connected to the portable terminal  301  via the cable  305 , then the second controller  601  activates the second MHL unit  609  and connects the external device  303  to the portable terminal  301  by MHL connectivity. Then the second controller  601  determines whether a USB connection message has been received via a CBUS pin  615  of the second connector  613 . The USB connection message is transmitted to determine whether the external device  303  supports USB connectivity. 
     Upon receipt of the USB connection message, the second controller  601  determines whether the external device  303  supports USB connectivity. The second controller  601  generates a USB connection response message based on the determination result and transmits the USB connection response message to the portable terminal  301  via the CBUS pin  615  of the second connector  613 . The USB connection response message is a response to the USB connection message, indicating whether the external device  303  supports USB connectivity. 
     To be more specific, if the external device  303  supports USB connectivity, then the second controller  601  generates a first USB connection response message indicating support of USB connectivity in the external device  303  and transmits the first USB connection response message to the portable terminal  301 . If the external device  303  does not support USB connectivity, then the second controller  601  generates a second USB connection response message indicating non-support of USB connectivity in the external device  303  and transmits the second USB connection response message to the portable terminal  301 . 
       FIG. 7  is a flowchart illustrating an operation of recognizing an external device in a communication system according to an embodiment of the present disclosure. 
     Referring to  FIG. 7 , the portable terminal  301  is connected to the external device  303  via the cable  305  such that there is a connection between the portable terminal  301  and the external device  303  in operation  701 . The portable terminal  301  determines whether the external device  303  supports MHL connectivity in operation  703 . If the external device  303  supports MHL connectivity, then the portable terminal  301  goes to operation  705  and otherwise, the portable terminal  301  terminates the operation of recognizing the external device  303 . 
     The portable terminal  301  connects to the external device  303  by MHL connectivity such that there is an MHL connection in operation  705  and generates a USB connection message in operation  707 . The USB connection message is generated to determine whether the external device  303  supports USB connectivity. 
     In operation  709 , the portable terminal  301  transmits the USB connection message, to the external device  303 , via the CBUS line  401 . The CBUS line  401  is a single cable bus through which auxiliary data is transmitted from an MHL source device and an MHL sink device. As shown in  FIG. 7 , the portable terminal  301  may serve as an MHL source device, whereas the external device  303  may serve as an MHL sink device. 
     In operation  711 , the external device  303  receives the USB connection message, determines whether the external device  303  supports USB connectivity, and generates a USB connection response message based on the determination result. The USB connection response message is a response to the USB connection message and indicates whether the external device  303  supports USB connectivity. The external device  303  transmits the USB connection response message to the portable terminal  301  via the CBUS line  401  in operation  713 . 
     In operation  715 , the portable terminal  301  receives the USB connection response message as a response to the USB connection message and determines, based on the USB connection response message, whether the external device  303  supports USB connectivity. If the external device  303  supports USB connectivity, then the portable terminal  301  goes to operation  717  and otherwise, the portable terminal  301  terminates the operation of recognizing the external device  303 . 
     The portable terminal  301  recognizes a USB device of the external device  303  by executing a USB host function in operation  717 . The USB host function refers to a function that enables operation between portable terminals, such as a PDA, an MP3 player, and a portable phone, without intervention of a main computer. For example, the USB host function may include a data exchange function between the portable terminal  301  and the external device  303 , and a battery charging function of the portable terminal  301 , when the external device  303  is an auxiliary battery. 
       FIG. 8  is a flowchart illustrating an operation of recognizing an external device in a portable terminal according to an embodiment of the present disclosure. 
     Referring to  FIG. 8 , the first controller  501  of the portable terminal  301  connects the portable terminal  301  to the external device  303  via the first connector  509  in operation  801  and determines whether the external device  303  supports MHL connectivity in operation  803 . 
     In order to determine whether the external device  303  supports MHL connectivity, the first controller  501  measures the resistance of a USB ID pin, from among a plurality of pins included in the first connector  509 , and compares the measured resistance with a predetermined resistance. If the measured resistance is equal to the predetermined resistance, then the first controller  501  determines that the external device  303  supports MHL connectivity. For example, referring to  FIG. 2 , if the measured resistance of the USB ID pin is 1KΩ, then the first controller  501  may determine that the first connector  509  is connected to an MHL cable and that the external device  303  supports MHL connectivity. 
     If the first controller  501  determines that the external device  303  supports MHL connectivity, then the first controller  501  goes to operation  805  and otherwise, the first controller  501  terminates the operation of recognizing the external device  303 . 
     In operation  805 , the first controller  501  activates the first MHL unit  505  and connects the portable terminal  301  to the external device  303  by establishing an MHL connection. Then the first controller  501  generates a USB connection message in operation  807  and transmits the USB connection message to the external device  303  via the CBUS line of the first connector  509  in operation  809 . The USB connection message is generated in a CBUS command format and transmitted to determine whether the external device  303  supports USB connectivity. 
     In operation  811 , the first controller  501  determines whether a USB connection response message from the external device  303  is received via the CBUS line of the first connector  509 , as a response to the USB connection message. The USB connection response message is generated in a CBUS command format, indicating whether the external device  303  supports USB connectivity. 
     If the USB connection response message is received, then the first controller  501  goes to operation  813  and otherwise, the first controller  501  repeats operation  811 . 
     In operation  813 , the first controller  501  determines, based on the USB connection response message, whether the external device  303  supports USB connectivity. If the external device  303  supports USB connectivity, then the first controller  501  goes to operation  815  and otherwise, the first controller  501  terminates the operation of recognizing the external device  303 . 
     To be more specific, if the first controller  501  determines that the USB connection response message is a first USB connection response message by analyzing the USB connection response message, then the first controller  501  determines that the external device  303  supports USB connectivity. If the USB connection response message is a second USB connection response message, then the first controller  501  determines that the external device  303  does not support USB connectivity. The first USB connection response message is a message indicating support of USB connectivity in the external device  303  and the second USB connection response message is a message indicating non-support of USB connectivity in the external device  303 . 
     In operation  815 , the first controller  501  activates the first USB unit  507 , activates a USB host driver through the first USB unit  507 , and executes a USB host function, thereby recognizing a USB device of the external device  303 . For example, if the external device  303  is an HID, such as a USB touch screen, then the first controller  501  may recognize all accessories supported by the USB host driver by activating the USB host driver and thus may recognize the external device  303  being a touch screen. 
       FIG. 9  is a flowchart illustrating an operation of transmitting a USB connection response message in an external device according to an embodiment of the present disclosure. 
     Referring to  FIG. 9 , the second controller  601  of the external device  303  connects the external device  303  to the portable terminal  301  via the cable  305  in operation  901 . In operation  903 , the second controller  601  activates the second MHL unit  609 , connects the external device  303  to the portable terminal  301  by MHL connectivity, and determines whether a USB connection message has been received via the CBUS line of the second connector  613  in operation  903 . The USB connection message is transmitted to determine whether the external device  303  supports USB connectivity. Upon receipt of the USB connection message, the second controller  601  goes to operation  905  and otherwise, the second controller  601  repeats operation  903 . 
     In operation  905 , the second controller  601  determines whether the external device  303  supports USB connectivity. If the external device  303  supports USB connectivity, then the second controller  601  goes to operation  907  and otherwise, the second controller  601  goes to operation  909 . 
     In operation  907 , the second controller  601  generates a first USB connection response message indicating support of USB connectivity in the external device  303  and goes to operation  911 . On the other hand, the second controller  601  generates a second USB connection response message indicating non-support of USB connectivity in the external device  303  in operation  909  and goes to operation  911 . The second controller  601  transmits the first USB connection response message or the second USB connection response message, via the CBUS line, to the portable terminal  301  in operation  911 . 
       FIG. 10  illustrates a configuration of a communication system according to another embodiment of the present disclosure. 
     Referring to  FIG. 10 , the communication system includes a portable terminal  1001 , a first external device  1003 , and a second external device  1007 . The second external device  1007  supports USB connectivity, is connected to the first external device  1003  via a USB cable  1009 , and provides a specific function to at least one of the first external device  1003  and the portable terminal  1001 . For example, if the second external device  1007  is a keyboard, the second external device  1007  is used as an input device. Thus, the second external device  1007  transmits data related to a user-selected key to at least one of the first external device  1003  and the portable terminal  1001  through the first external device  1003 . 
     The first external device  1003  supports USB connectivity and MHL connectivity. When the first external device  1003  is connected to the portable terminal  1001  via a cable  1005 , the first external device  1003  provides its specific function to the portable terminal  1001 . MHL is a technique of decreasing 13 HDMI lines to 3 lines, especially for transmission of multimedia data between the portable terminal  1001  and the external device  1003 . 
     The first and second external devices  1003  and  1007  are called accessories. The first external device  1003  may be a display device supporting MHL connectivity, such as a TV, a monitor, a beam projector, a touch screen, or the like. The second external device  1007  may be a device supporting USB connectivity, such as a USB memory, an auxiliary USB battery, a dongle, a USB mouse, or the like. 
     Particularly, when the first external device  1003  is connected to the portable terminal  1001  via the cable  1005 , the first external device  1003  determines whether a USB connection message has been received from the portable terminal  1001  via a CBUS line of the cable  1005 . The USB connection message is transmitted to determine whether the first external device  1003  supports USB connectivity. The CBUS is a single cable bus that transmits auxiliary data between an MHL source device and an MHL sink device. As shown in  FIG. 10 , the portable terminal  1001  may serve as an MHL source device and the first external device  1003  may serve as an MHL sink device. 
     Upon receipt of the USB connection message, the first external device  1003  determines whether the first external device  1003  supports USB connectivity. Then the first external device  1003  generates a USB connection response message based on the determination result and transmits the USB connection response message to the portable terminal  1001  via a CBUS line. The USB connection response message is a response to the USB connection message and indicates whether the first external device  1003  supports USB connectivity. The portable terminal  1001  determines whether the first external device  1003  has been connected to the portable terminal  301  via the cable  1005 . 
       FIG. 11  illustrates lines between a portable terminal and an external device in a communication system according to another embodiment of the present disclosure. 
     Referring to  FIG. 11 , the cable  1005  between the portable terminal  1001  and the first external device  1003  includes a CBUS line  1101 , an MHL DM line  1103 , an MHL DP line  1105 , a USB DM line  1107 , and a USP DP line  1109  to support both USB connectivity and MHL connectivity. Specifically, the CBUS line  1101 , the MHL DM line  1103 , and the MHL DP line  1105  are lines for MHL connectivity and the USB DM line  1107  and the USP DP line  1109  are lines for USB connectivity. 
     If the first external device  1003  has been connected to the portable terminal  1001 , then the portable terminal  1001  determines whether the first external device  1003  supports MHL connectivity. If the first external device  1003  supports MHL connectivity, then the portable terminal  1001  is connected to the first external device  1003  by MHL connectivity. Then the portable terminal  1001  generates a USB connection message and transmits the USB connection message to the first external device  1003  via the CBUS line  1101 . 
     The portable terminal  1001  receives a USB connection response message, as a response to the USB connection message, from the first external device  1003  via the CBUS line  1101  and determines, from the USB connection response message, whether the first external device  1003  supports USB connectivity. If the first external device  1003  supports USB connectivity, then the portable terminal  1101  recognizes USB devices of the first external device  1003  and the second external device  1007 , which is connected to the first external device  1003 , by executing a USB host function. For example, if the first external device  1003  includes USB devices, such as a USB hub and a USB touch screen, then the portable terminal  1001  may recognize the USB hub and the USB touch screen of the first external device  1003  via the USB host function. 
     The USB host function refers to a function that enables operation between portable terminals, such as a PDA, an MP3 player, and a portable phone, without intervention of a main computer. For example, the USB host function may include a data exchange function between the portable terminal  1001  and the first external device  1003 , and a battery charging function of the portable terminal  1001 , when the first external device  1003  is an auxiliary battery. 
     The portable terminal  1001  uses a specific function provided by the second external device  1007  connected directly to the first external device  1003  by a USB enumeration procedure. The USB enumeration procedure is known in the art and will not be described herein in detail. 
       FIG. 12  is a block diagram of a portable terminal according to another embodiment of the present disclosure. 
     Referring to  FIG. 12 , the portable terminal  1001  includes a third controller  1201 , a third memory unit  1203 , a third MHL unit  1205 , a third USB unit  1207 , and a third connector  1209  that includes a CBUS pin  1211 . The third MHL unit  1205  supports HDMI, to which MHL is applied. HDMI interfaces between a multimedia source, such as an HDMI-enabled set-top box, an HDMI-enabled Digital Versatile Disc (DVD) player, and the like, and a device such as an Audio Video (AV) device, a monitor, a digital TV, and the like. MHL is a technique of enabling output of multimedia data from the portable terminal  1001  to an external device. Multimedia data includes video data, game data, media content data, sound data, image data, and the like. The third USB unit  1207  supports USB connectivity. 
     The third memory unit  1203  includes a program memory and a data memory. The program memory stores a booting program and an Operating System (OS) to control overall operations of the portable terminal  1001  and the data memory stores data generated during operations of the portable terminal  1001 . Especially, the third memory unit  1003  stores an MHL driver for MHL connectivity and a USB driver for USB connectivity. 
     The third connector  1009  connects the portable terminal  1001  to the first external device  1003  via the cable  1005 . For example, if the third connector  1209  is an 11-pin connector, the third connector  1209  may include the plurality of pins listed in Table 1. 
     The third controller  1201  provides overall control to the portable terminal  1001 . Particularly, the third controller  1201  determines, based on a USB connection response message, whether an external device includes a USB device and recognizes the USB device of the external device by executing a USB host function according to the determination result. 
     More specifically, the third controller  1201  determines whether the portable terminal  1001  has been connected to the first external device  1003  via the cable  1005 . If the portable terminal  1001  has been connected to the first external device  1003 , then the third controller  1201  determines whether the first external device  1003  supports MHL connectivity. The third controller  1201  measures the resistance of a USB ID pin, from among a plurality of pins included in the third connector  1209 , and compares the measured resistance with a predetermined resistance. If the measured resistance is equal to the predetermined resistance, then the third controller  1201  determines that the first external device  1003  supports MHL connectivity. 
     For example, referring to  FIG. 2 , if the measured resistance of the USB ID pin is 1KΩ, then the third controller  1201  may determine that the third connector  1209  is connected to an MHL cable and that the first external device  1003  supports MHL connectivity. 
     If the third controller  1201  determines that the first external device  1003  supports MHL connectivity, then the third controller  1201  activates the third MHL unit  1205  and connects the portable terminal  1001  to the first external device  1003  by MHL connectivity. Then the third controller  1201  generates a USB connection message and transmits the USB connection message via the CBUS pin of the third connector  1209 . The USB connection message is generated in a CBUS command format and transmitted to determine whether the first external device  1003  supports USB connectivity. 
     The third controller  1201  receives a USB connection response message from the first external device  1003  via the CBUS pin of the third connector  1209 , as a response to the USB connection message. The USB connection response message is generated in a CBUS command format and indicates whether the first external device  1003  supports USB connectivity. 
     The third controller  1201  determines, based on the USB connection response message, whether the first external device  1003  supports USB connectivity. To be more specific, if the third controller  1201  determines that the USB connection response message is a first USB connection response message by analyzing the USB connection response message, then the third controller  1201  determines that the first external device  1003  supports USB connectivity. If the USB connection response message is a second USB connection response message, then the third controller  1201  determines that the first external device  1003  does not support USB connectivity. The first USB connection response message is a message indicating support of USB connectivity in the first external device  1003  and the second USB connection response message is a message indicating non-support of USB connectivity in the first external device  1003 . 
     If the first external device  1003  supports USB connectivity, then the third controller  1201  activates the third USB unit  1207 , activates a USB host driver through the third USB unit  1207 , and executes a USB host function, thereby recognizing USB devices of the first external device  1003 . 
     For example, if the first external device  1003  includes USB devices such as a USB hub and a USB touch screen, then the portable terminal  1001  may recognize all accessories supported by a USB host driver by activating the USB host driver and thus may recognize the USB hub and the USB touch screen of the first external device  1003 . As the third controller  1201  recognizes the USB hub of the first external device  1003 , the third controller  1201  may recognize a USB device of the second external device  1007 . 
     The portable terminal  1001  uses a specific function provided by the second external device  1007  connected directly to the first external device  1003  by a USB enumeration procedure. 
       FIG. 13  is a block diagram of an external device according to another embodiment of the present disclosure. 
     Referring to  FIG. 13 , the first external device  1003  is an HDMI-enabled display device that supports both USB connectivity and MHL connectivity. The first external device  1003  includes a fourth controller  1301 , a display unit  1303 , an input unit  1305 , a fourth memory unit  1307 , a fourth MHL unit  1309 , a fourth USB unit  1311 , a USB hub  1313 , and a fourth connector  1315  that includes a CBUS pin  1317 . 
     The input unit  1305  includes alphanumerical keys used to enter numbers and characters and function keys used to set functions. The display unit  1303  displays an image signal on a screen and displays data requested by the fourth controller  1301 . The display unit  1303  may be configured with an LCD or any other similar and/or suitable display device type. In this case, the display unit  1303  may include an LCD controller, a memory that stores image data, and an LCD display device. If the LCD is configured to be a touch screen, then the display unit  1303  may act as the input unit  1305  and thus display the same keys, similar keys, and/or other keys, as in the input unit  1305 . 
     The fourth MHL unit  1309  supports HDMI to which MHL is applied. The fourth USB unit  1311  supports USB connectivity. The fourth memory unit  1307  includes a program memory and a data memory. The program memory stores a booting program and an OS to control overall operations of the first external device  1003  and the data memory stores data generated during operations of the first external device  1003 . 
     The fourth connector  1315  connects the first external device  1003  to the portable terminal  1001  via the cable  1005 . For example, if the fourth connector  1315  is an 11-pin connector, then the fourth connector  1315  may include the plurality of pins listed in Table 1. The USB hub  1313  includes at least one USB port and connects the first external device  1003  to the second external device  1007  via the USB cable  1009  connected to a USB port. 
     The fourth controller  1301  provides overall control to the first external device  1003 . Particularly, upon receipt of a USB connection message from the portable terminal  1001 , the fourth controller  1301  generates a USB connection response message and transmits the USB response message to the portable terminal  1001 . 
     More specifically, if the first external device  1003  is connected to the portable terminal  1001  via the cable  1005 , then the fourth controller  1301  activates the fourth MHL unit  1309  and connects the first external device  1003  to the portable terminal  1001  by MHL connectivity. Then the fourth controller  1301  determines whether a USB connection message has been received via the CBUS pin  1317  of the fourth connector  1315 . The USB connection message is transmitted to determine whether the first external device  1003  supports USB connectivity. 
     Upon receipt of the USB connection message, the fourth controller  1301  determines whether the first external device  1003  supports USB connectivity. The fourth controller  1301  generates a USB connection response message based on the determination result and transmits the USB connection response message to the portable terminal  1001  via the CBUS pin  1317  of the fourth connector  1315 . The USB connection response message is a response to the USB connection message and indicates whether the first external device  1003  supports USB connectivity. 
     To be more specific, if the first external device  1003  supports USB connectivity, then the fourth controller  1301  generates a first USB connection response message indicating support of USB connectivity in the first external device  1003  and transmits the first USB connection response message to the portable terminal  1001 . If the first external device  1003  does not support USB connectivity, then the fourth controller  1301  generates a second USB connection response message indicating non-support of USB connectivity in the first external device  1003  and transmits the second USB connection response message to the portable terminal  1001 . 
       FIG. 14  is a flowchart illustrating an operation of recognizing an external device in a communication system according to another embodiment of the present disclosure. 
     Referring to  FIG. 14 , the portable terminal  1001  is connected to the first external device  1003  via the cable  1005  in operation  1401 . The portable terminal  1001  determines whether the first external device  1003  supports MHL connectivity in operation  1403 . If the first external device  1003  supports MHL connectivity, then the portable terminal  1001  goes to operation  1405  and otherwise, the portable terminal  1001  terminates the operation of recognizing the first external device  1003 . 
     The portable terminal  1001  connects to the first external device  1003  by MHL connectivity such that there is an MHL connection in operation  1405  and generates a USB connection message in operation  1407 . The USB connection message is generated to determine whether the first external device  1003  supports USB connectivity. 
     In operation  1409 , the portable terminal  1001  transmits the USB connection message to the first external device  1003  via the CBUS line  1101 . The CBUS is a single cable bus through which auxiliary data is transmitted from an MHL source device and an MHL sink device. As shown in  FIG. 14 , the portable terminal  1001  may serve as an MHL source device, whereas the first external device  1003  may serve as an MHL sink device. 
     In operation  1411 , the first external device  1003  receives the USB connection message, determines whether the first external device  1003  supports USB connectivity, and generates a USB connection response message based on the determination result. The USB connection response message is a response to the USB connection message and indicates whether the first external device  1003  supports USB connectivity. The first external device  1003  transmits the USB connection response message to the portable terminal  1001  via the CBUS line in operation  1413 . 
     In operation  1415 , the portable terminal  1001  receives the USB connection response message as a response to the USB connection message and determines, based on the USB connection response message, whether the first external device  1003  supports USB connectivity. If the first external device  1003  supports USB connectivity, then the portable terminal  1001  goes to operation  1417  and otherwise, the portable terminal  1001  terminates the operation of recognizing the first external device  1003 . The portable terminal  1001  recognizes at least one USB device of the first external device  1003  and a USB device of the second external device  1007  by executing a USB host function in operation  1417 . The USB host function refers to a function that enables operation between portable terminals, such as a PDA, an MP3 player, and a portable phone, without intervention of a main computer. 
     For example, if the first external device  1003  includes USB devices, such as a USB hub and a USB touch screen, then the portable terminal  1001  may recognize all accessories supported by a USB host driver by activating the USB host driver, and thus may recognize the USB hub and the USB touch screen of the first external device  1003 . As the third controller  1201  recognizes the USB hub of the first external device  1003 , the third controller  1201  may recognize a USB device of the second external device  1007 . 
     The portable terminal  1001  uses a specific function provided by the second external device  1007  connected directly to the first external device  1003  by a USB enumeration procedure. 
       FIG. 15  is a flowchart illustrating an operation of recognizing an external device in a portable terminal according to another embodiment of the present disclosure. 
     Referring to  FIG. 15 , the third controller  1201  of the portable terminal  1001  connects the portable terminal  1001  to the first external device  1003  via the third connector  1209  in operation  1501  and determines whether the first external device  1003  supports MHL connectivity in operation  1503 . 
     The third controller  1201  measures the resistance of a USB ID pin, from among a plurality of pins included in the third connector  1209 , and compares the measured resistance with a predetermined resistance. If the measured resistance is equal to the predetermined resistance, then the third controller  1201  determines that the first external device  1003  supports MHL connectivity. For example, referring to  FIG. 2 , if the measured resistance of the USB ID pin is 1KΩ, then the third controller  1201  may determine that the third connector  1209  is connected to an MHL cable and that the first external device  1003  supports MHL connectivity. 
     If the first external device  1003  supports MHL connectivity, then the third controller  1201  goes to operation  1505  and otherwise, the third controller  1201  terminates the operation of recognizing the first external device  1003 . 
     In operation  1505 , the third controller  1201  activates the third MHL unit  1205  and connects the portable terminal  1001  to the first external device  1003  by establishing an MHL connection. Then the third controller  1201  generates a USB connection message in operation  1507  and transmits the USB connection message to the first external device  1003  via the CBUS line of the third connector  1209  in operation  1509 . The USB connection message is generated in a CBUS command format and transmitted to determine whether the first external device  1003  supports USB connectivity. 
     In operation  1511 , the third controller  1201  determines whether a USB connection response message is received from the first external device  1003  via the CBUS line of the third connector  1209 , as a response to the USB connection message. The USB connection response message is generated in a CBUS command format and indicates whether the first external device  1003  supports USB connectivity. 
     If it is determined, in operation  1511 , that the USB connection response message has been received, then the third controller  1201  goes to operation  1513  and otherwise, the third controller  1201  repeats operation  1511 . 
     In operation  1513 , the third controller  1201  determines, based on the USB connection response message, whether the first external device  1003  supports USB connectivity. If the first external device  1003  supports USB connectivity, then the third controller  1201  goes to operation  1515  and otherwise, the third controller  1201  terminates the operation of recognizing the first external device  1003 . 
     To be more specific, if the third controller  1201  determines that the USB connection response message is a first USB connection response message by analyzing the USB connection response message, then the third controller  1201  determines that the first external device  1003  supports USB connectivity. If the USB connection response message is determined to be a second USB connection response message, then the third controller  1201  determines that the first external device  1003  does not support USB connectivity. The first USB connection response message is a message indicating support of USB connectivity in the first external device  1003  and the second USB connection response message is a message indicating non-support of USB connectivity in the first external device  1003 . 
     In operation  1515 , the third controller  1201  activates the third USB unit  1207 , activates a USB host driver through the third USB unit  1207 , and executes a USB host function, thereby recognizing at least one USB device of the first external device  1003  and the second external device  1007  connected directly to the first external device  1003 . 
     For example, if the first external device  1003  includes USB devices, such as a USB hub and a USB touch screen, then the third controller  1021  may recognize all accessories supported by a USB host driver by activating the USB host driver, and thus may recognize the USB hub and the USB touch screen of the first external device  1003 . As the third controller  1201  recognizes the USB hub of the first external device  1003 , the third controller  1201  may recognize a USB device of the second external device  1007 . 
     The third controller  1201  uses a specific function provided by the second external device  1007  connected directly to the first external device  1003  by a USB enumeration procedure. An operation of transmitting a USB connection response message in an external device according to another embodiment of the present disclosure is same as the operation illustrated in  FIG. 9  and thus an operation of transmitting a USB connection response message in the first external device  1003  will not be described herein. 
     As is apparent from the above description of the present disclosure, all external devices supporting USB connectivity may be recognized in a communication system. All external devices supporting USB connectivity may be recognized by MSB connectivity in a communication system. All external devices supporting USB connectivity may be recognized using a CBUS line among MHL lines in a communication system. 
     At this point it should be noted that the various embodiments of the present disclosure as described above typically involve the processing of input data and the generation of output data to some extent. This input data processing and output data generation may be implemented in hardware or software in combination with hardware. For example, specific electronic components may be employed in a mobile device or similar or related circuitry for implementing the functions associated with the various embodiments of the present disclosure as described above. Alternatively, one or more processors, such as an Integrated Circuit (IC), an Application Specific IC (ASIC), an Erasable Programmable Read Only Memory (EPROM), or any other similar and/or suitable hardware device that performs information processing, operating in accordance with stored instructions may implement the functions associated with the various embodiments of the present disclosure as described above. If such is the case, it is within the scope of the present disclosure that such instructions may be stored on one or more processor and/or computer readable mediums. Examples of the processor and/or computer readable mediums include a Read-Only Memory (ROM), a Random-Access Memory (RAM), a Compact Disc (CD)-ROMs, magnetic tapes, floppy disks, and optical data storage devices. The processor and/or computer readable mediums may be non-volatile, and may also be distributed over network coupled computer systems so that the instructions are stored and executed in a distributed fashion. Also, functional computer programs, instructions, and instruction segments for accomplishing the present disclosure can be easily construed by programmers skilled in the art to which the present disclosure pertains. 
     While it has been described that a connector is an 11-pin connector in the present disclosure, the connector is not limited to the specific number of pins. Thus the connector may be an 18-pin, 22-pin, or any suitable number of pins connector. In another example, while it has been described that a portable terminal recognizes a first external device supporting MHL connectivity and USB connectivity, the first external device is not limited to the specific connection schemes. Thus the first external device may support a connection scheme other than MHL connectivity and USB connectivity. Further, it has been described in the present disclosure that the portable terminal receives a USB connection message via a CBUS line being a cable line from the external device. However, communication between the portable terminal and the external device is not limited to wired communication. Thus, the portable terminal may transmit a USB connection message or receive a USB connection response message in a radio frequency. 
     While the present disclosure has been shown and described with reference to various embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present disclosure as defined by the appended claims and their equivalents.