Patent Publication Number: US-2011060850-A1

Title: Mobile device of supporting uart and usb communication using same connector and operating method there-of

Description:
TECHNICAL FIELD 
     The present invention relates to a mobile device, and more particularly, to a circuit for supporting universal asynchronous receiver/transmitter (UART) and universal serial bus (USB) communication using a single connector and a mobile device including the same. 
     BACKGROUND ART 
     Mobile devices usually include one or more connectors for interface with external devices and support communication using those connectors. Serial communication, universal asynchronous receiver/transmitter (UART) communication, and universal serial bus (USB) communication are usually used for interface between mobile devices and external devices. 
     When the more communication modes are supported by mobile devices, additional connectors suitable for the communication modes need to be provided, resulting in the increase in size and cost of mobile devices. Therefore, a technique for supporting different communication modes using a single connector is desired to prevent the size and the cost of mobile devices from increasing. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Technical Goal of the Invention 
     The present invention provides a mobile device for supporting universal asynchronous receiver/transmitter (UART) communication and universal serial bus (USB) communication using a single connector. 
     The present invention also provides a mobile device for identifying a USB device coupled to a connector and automatically switching the path of the connector. 
     Effect of the Invention 
     According to the present invention, a mobile device can be coupled and communicate with both a USB device and a UART device through a single USB connector. Accordingly, the mobile device does not need to include separate connectors for different communication modes supported by the mobile device, so that the size and the cost of the mobile device are reduced. 
     In addition, since whether an external device coupled to the USB connector is a USB device is detected and data lines of the connector are automatically switched to either an internal USB module or an internal UART module, user convenience is increased. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The brief description of the drawing is provided for sufficient understanding of the attached drawings referred to in the detailed description of the present invention: 
         FIG. 1  is a block diagram of a mobile device according to some embodiments of the present invention; 
         FIG. 2  is a diagram of the structure of a switching unit illustrated in  FIG. 1 ; 
         FIG. 3  is a diagram of the structure of a universal serial bus (USB) signal detector illustrated in  FIG. 1 ; and 
         FIG. 4  is a flowchart of a method of automatically switching the path of a universal serial bus (USB) connector of a mobile device according to some embodiments of the present invention. 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     According to an aspect of the present invention, there is provided a mobile device including a universal serial bus (USB) connector, a USB module selectively connected with the connector to communicate with an external USB device, at least one internal universal asynchronous receiver/transmitter (UART) device selectively connected with the connector to communicate with an external UART device, a determiner configured to determine whether the connector has been coupled to the external USB device or the external UART device based on a signal applied to at least one of pins of the connector, a switching unit configured to selectively connect data lines of the connector to one among the USB module and the at least one internal UART module based on a determination result of the determiner, and a central processing unit (CPU) configured to control the switching unit. 
     The connector includes a power supply voltage pin, a first data pin and a second data pin for data transmission, and a ground pin, and the data lines of the connector are respectively connected with the first data pin and the second data pin. 
     The determiner determines that the connector has been coupled to the external USB device when the second data pin is a predetermined logic level and a voltage applied to the power supply voltage pin is at least a predetermined level. 
     According to another aspect of the present invention, there is provided a method of operating a mobile device. The method includes driving data line of a USB connector to a high-impedance state in a system disable state; detecting a signal applied to the USB connector and determining whether a device coupled to the connector is a USB device; and selectively connecting the data lines of the connector to one module among an internal USB module and at least one internal UART module, which are included in the mobile device, based on the determination result in a system enable state. 
     The connector includes a power supply voltage pin, a first data pin and a second data pin for data transmission, and a ground pin, and the determining whether the device is the USB device comprises determining that the connector has been coupled to the USB device when the second data pin is a predetermined logic level and a voltage applied to the power supply voltage pin is at least a predetermined level. 
     EMBODIMENTS 
     The attached drawings for illustrating preferred embodiments of the present invention are referred to in order to gain a sufficient understanding of the present invention, the merits thereof, and the objectives accomplished by the implementation of the present invention. Hereinafter, the present invention will be described in detail by explaining preferred embodiments of the invention with reference to the attached drawings. Like reference numerals in the drawings denote like elements. 
       FIG. 1  is a block diagram of a mobile device  100  according to some embodiments of the present invention.  FIG. 2  is a diagram of the structure of a switching unit  130  illustrated in  FIG. 1 .  FIG. 3  is a diagram of the structure of a universal serial bus (USB) signal detector  140  illustrated in  FIG. 1 . 
     Referring to  FIGS. 1 through 3 , the mobile device  100  includes a central processing unit (CPU)  110 , a connector  120 , the switching unit  130 , a determiner ( 140  and  150 ), a USB module  111 , and a universal asynchronous receiver/transmitter (UART) unit  160 . Although not shown, the mobile device  100  may also include a display module, a speaker and microphone module, a memory, a Bluetooth module, a battery module, and an antenna. 
     The CPU  110  executes a program and/or firmware for the operation of the mobile device  100  and generates a control signal for controlling the operation of each module or element included within the mobile device  100 . In the current embodiments of the present invention, the USB module  111  is provided within the CPU  110 , but the present invention is not restricted to the current embodiments. 
     The connector  120  is used to couple the mobile device  100  to an external device (e.g., a personal computer (PC) or an adaptor) through a cable (not shown) and includes at least four pins. One end of the cable is coupled to the connector  120  and another end of the cable is coupled to a connector of the external device. Of the four pins of the connector  120 , one may be for a power supply voltage VBUS, two others may be for transmission of data D+ and D−, and the other may be for a ground GND. When the connector  120  includes at least five pins, all but four pins may not be used in a no connect (NC) state. For instance, the connector  120  may be a 5- or 9-pin USB connector. The switching unit  130  selectively connects the data lines DL 1  and DL 2  of the connector  120  to the USB module  111  or at least one of elements included in the UART unit  160 . For instance, the switching unit  130  may controlled by the CPU  110  to automatically switch the path of the connector  120 . 
     Referring to  FIG. 2 , the switching unit  130  includes a first switch  131  and a second switch  132 . 
     The first switch  131  connects the data lines DL 1  and DL 2  of the connector  120  to the second switch  132  or drives the data lines DL 1  and DL 2  to a high-impedance state Hi-Z in response to a first switch control signal CSW 1  generated by the CPU  110 . For instance, when the first switch control signal CSW 1  is set to a first logic level (e.g., “1”), the first switch  131  connects the data lines DL 1  and DL 2  to the second switch  132 . When the first switch control signal CSW 1  is set to a second logic level (e.g., “0”), the first switch  131  drives the data lines DL 1  and DL 2  to the high-impedance state Hi-Z. 
     The first switch control signal CSW 1  may be set differently according to the state of the CPU  110  or the mobile device  100 . For instance, the first switch control signal CSW 1  may be set to logic “1” while the mobile device  100  is powered on with a battery installed and to logic “0” while the battery is removed from the mobile device  100  or the power of the mobile device  100  is turned off. In another instance, the first switch control signal CSW 1  may be set to logic “1” while the CPU  110  is in a wake-up, standby or sleep state and to logic “0” while the CPU  110  is in a deep-sleep state. 
     The system states in which the first switch control signal CSW 1  is set to logic “1” may be defined as system enable states and the system states in which the first switch control signal CSW 1  is set to logic “0” may be defined as system disable state. A system enable signal may be output from the CPU  110  to indicate a system enable or disable state. The system enable signal is set to, for example, a first logic level “1” in a system enable state. Accordingly, the first switch control signal CSW 1  may be set to logic “1” when the system enable signal is at logic “1” and to logic “0” when the system enable signal is at logic “0”. 
     In a system disable state, the USB operation of the CPU  110  is unstable, which may cause errors. The first switch  131  drives the data lines DL 1  and DL 2  to the high-impedance state Hi-Z when the CPU  110  is in a predetermined state (e.g., a deep-sleep state), thereby preventing errors that may occur when the connector  120  is connected to USB terminals D+ and D− of the CPU  110  in the system disable state. 
     The second switch  132  connects data lines DL 1 ′ and DL 2 ′ of the first switch  131  to the USB terminals D+ and D− of the CPU  110  or to a complex programmable logic device (CPLD)  150  in response to a second switch control signal CSW 2  generated by the CPU  110 . For instance, when the second switch control signal CSW 2  is set to a first logic level (e.g., “1”), the second switch  132  connects the data lines DL 1 ′ and DL 2 ′ to the USB terminals D+ and D− of the CPU  110 . When the second switch control signal CSW 2  is set to a second logic level (e.g., “0”), the second switch  132  connects the data lines DL 1 ′ and DL 2 ′ to UART terminals UART_TXD and UART_RXD of the CPLD  150 . 
     The determiner ( 140  and  150 ) determines whether an external device coupled to the connector  120  is a USB device or a UART device based on a signal VBUS, D+, D−, or GND applied to at least one of the pins of the connector  120 . For this operation, the determiner includes the USB signal detector  140  and the CPLD  150 . 
     The USB signal detector  140  detects whether an external device coupled to the connector  120  is a USB device based on the level of the power supply voltage VBUS applied to a power supply voltage pin of the connector  120  and the signal D− applied to a second data pin of the connector  120  and generates a USB detection signal USB_INT. 
     An example of the structure of the USB signal detector  140  is illustrated in  FIG. 3 . Referring to  FIG. 3 , the USB signal detector  140  includes a low-dropout (LDO) regulator  141 , a voltage detector  142 , and a flip-flop  143 . 
     The LDO regulator  141  is connected with the power supply voltage pin of the connector  120  and generates a predetermined output voltage BYP when a voltage within a predetermined range is applied to the power supply voltage pin of the connector  120 . For instance, the LDO regulator  141  includes an input terminal connected with the power supply voltage pin of the connector  120  and an output terminal outputting the output voltage BYP. When the voltage VBUS applied to the input terminal is at least a predetermined voltage (e.g., 3 V), the LDO regulator  141  may output the predetermined output voltage BYP (e.g., 3 V). In other words, the LDO regulator  141  may output the output voltage BYP of 3 V when the power supply voltage VBUS is at least 3 V. 
     The LDO regulator  141  may be implemented separately outside a charge integrated circuit (IC) (not shown) or may be implemented within the charge IC. The charge IC is a circuit for charging a battery of a mobile device and supplying system power to an internal system of the mobile device. 
     The voltage detector  142  includes an internal delay circuit and delays and outputs the output voltage BYP of the LDO regulator  141 . Since a cable for the connection of an external device may not be properly coupled to the connector  120  at once when a user try to couple the cable to the connector  120 , delay time is set in the voltage detector  142  to provide a temporal margin until the cable is satisfactorily stably coupled to the connector  120 . 
     An output signal VBUS_CLK of the voltage detector  142  is input to a clock terminal CLK of the flip-flop  143  and the signal D− of the second data pin of the connector  120  is input to an input terminal D of the flip-flop  143 . The flip-flop  143  may be a D-Q flip-flop. 
     The flip-flop  143  latches the signal D− input to the input terminal D at a rising edge of the output signal VBUS_CLK of the voltage detector  142  to output the USB detection signal USB_INT. 
     When an external USB device is coupled to the connector  120 , the power supply voltage VBUS has a predetermined voltage level (e.g., 5 V) and the signal D− of the second data pin is maintained at a predetermined logic level (e.g., a logic low) for a predetermined period of time and then changes to be complementary to the signal D+ of a first data pin of the connector  120  according to transmitted data. 
     Accordingly, when an external USB device is coupled to the connector  120 , the signal D− of the second data pin is at the logic low at a rising edge of the output signal VBUS_CLK of the voltage detector  142 . Therefore, the USB detection signal USB_INT output from the flip-flop  143  is also at a logic low. 
     When a different external device other than USB devices is coupled to the connector  120 , an operation is performed so that a signal input to the input terminal D of the flip-flop  143  is at a logic high at a rising edge of the output signal VBUS_CLK of the voltage detector  142 . For this operation, although not shown in  FIG. 3 , the output terminal of the LDO regulator  141  may be connected via a resistor (not shown) to the input terminal D of the flip-flop  143 . In other words, the input terminal D of the flip-flop  143  may be connected with both the output terminal of the LDO regulator  141  via the resistor and the second data pin of the connector  120 . 
     Accordingly, when an external USB device is coupled to the connector  120 , the USB detection signal USB_INT is output at the logic low by the signal D− of the second data pin. When a UART device other than USB devices is coupled to the connector  120 , the USB detection signal USB_INT is output at the logic high. 
     The CPLD  150  generates and outputs an alarm signal to the CPU  110  based on the USB detection signal USB_INT and the system enable signal generated by the CPU  110 . The USB detection signal USB_INT may also input to the CPU  110 . The CPU  110  may generate the second switch control signal CSW 2  based on the system enable signal, the USB detection signal USB_INT, and the alarm signal from the CPLD  150 . For instance, when the USB detection signal USB_INT is at the logic low, the CPU  110  may determine that a device coupled to the connector  120  is a USB device and thus set the second switch control signal CSW 2  so that the second switch  132  connects the data lines DL 1 ′ and DL 2 ′ to the USB module  111 . 
     Contrarily, when the USB detection signal USB_INT is at the logic high, the CPU  110  determines that a device coupled to the connector  120  is a UART device and thus set the second switch control signal CSW 2  so that the second switch  132  connects the data lines DL 1 ′ and DL 2 ′ to the CPLD  150 . 
     The CPLD  150  selectively connects a data line to one of a plurality of modules using UART communication in compliance with the CPU  110 . In the current embodiments of the present invention, the CPLD  150  is controlled by the CPU  110  to selectively connect the data line to one module among a UART IC  163 , a global positioning system (GPS) module  161 , and a communication modem  162 . Which one of the UART IC  163 , the GPS module  161 , and the communication modem  162  is connected to the data line may be controlled by the CPU  110  according to setting by a user. 
     The communication modem  162  may support code division multiple access (CDMA) communication and/or global system for mobile communications (GSM) communication. The communication modem  162  may be connected with an external UART device using UART communication to download firmware. 
       FIG. 4  is a flowchart of a method of operating the mobile device  100  according to some embodiments of the present invention. Referring to  FIGS. 1 through 4 , it is determined whether the mobile device  100  is in a system enable state in operation S 41 . When the mobile device  100  is not in the system enable state, that is, the mobile device  100  is in a system disable state, the data pins of the connector  120  are driven to the high-impedance state Hi-Z in operation S 42  to prevent the occurrence of errors. 
     When the mobile device  100  is in the system enable state, a signal applied to the connector  120  is detected to determine whether a device coupled to the connector  120  is a USB device in operation S 43 . In detail, when a signal at the D− pin of the connector  120  is at a predetermined logic level (e.g., “0”) and a voltage at the VBUS pin of the connector  120  is at least a predetermined level, it is determined that the device coupled to the connector  120  is a USB device in operation S 43 . When the device coupled to the connector  120  is determined to be a USB device, the data pins of the connector  120  are connected to the USB module  111  in operation S 44 . When the device coupled to the connector  120  is determined not to be a USB device, the data pins of the connector  120  are connected to one of the UART modules  161 ,  162 , and  163  in operation S 45 . 
     As described above, according to the present invention, a mobile device can be coupled and communicate with both a USB device and a UART device through a single USB connector. Accordingly, the mobile device does not need to include separate connectors for different communication modes supported by the mobile device. In addition, since whether an external device coupled to the USB connector is a USB device is detected and data lines of the connector are automatically switched to either an internal USB module or an internal UART module, different types of external devices are conveniently coupled to the single USB connector and used when necessary. 
     While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in forms and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims. 
     INDUSTRIAL APPLICABILITY 
     The present invention can be applied to mobile devices and reduce the size and the manufacturing cost of the mobile devices.