Patent Publication Number: US-2021173453-A1

Title: Electronic device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2019-221614, filed in Dec. 6, 2019, the entire contents of which are incorporated herein by reference. 
     FIELD 
     Embodiments described herein relate generally to an electronic device and a connection method. 
     BACKGROUND 
     In a POS terminal of a related art, a technology referred to as low voltage differential signaling (LVDS) is adopted for a graphic interface that processes a display signal. However, since LVDS will not be supported in the future, a change to a USB Type-C standard is considered. Specifications of the graphic interface are changed to the USB Type-C standard, whereby a general-purpose connector (a receptacle) and a general-purpose plug cable that comply with the standard can be used for a transmission unit of the display signal. 
     Meanwhile, a POS display device is provided with a touch panel as well as a display. A control signal of the touch panel passes through the general-purpose plug cable that connects a control unit main body of the POS terminal and the POS display device together with the display signal. Therefore, a terminal of the general-purpose connector that connects the general-purpose plug cable has a terminal configuration unique to the POS terminal, and is different from a standard terminal configuration of the USB Type-C standard. When a display device that uses the general-purpose plug cable and has the standard terminal configuration is connected to the general-purpose connector, there is a problem that a circuit may malfunction or may be short-circuited due to a difference in the terminal configuration. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an external perspective view illustrating an example of a commodity reading apparatus according to an embodiment; 
         FIG. 2  is a hardware block diagram of a motherboard; 
         FIG. 3  is a diagram illustrating an example of an external shape of a connector; 
         FIG. 4  is a comparison diagram of a terminal configuration of the connector and a terminal configuration of a general-purpose type; 
         FIG. 5  is a diagram illustrating a configuration example of a first switching control unit, a first switching unit, a second switching control unit, and a second switching unit; 
         FIG. 6  is a diagram illustrating a configuration example related to detection of a connection direction of a plug of the second switching control unit; and 
         FIG. 7  is a flowchart illustrating an example of an operation procedure of the commodity reading apparatus. 
     
    
    
     DETAILED DESCRIPTION 
     According to one embodiment, there is provided an electronic device capable of preventing electrical connection between devices of connection destinations when connecting the devices having different terminal configurations of connectors. 
     In general, according to one embodiment, an electronic device includes a connector, a first determination unit, and a first switching unit. The connector includes a plurality of terminals for being electrically connected to a peripheral device. The first determination unit determines whether or not a peripheral device compatible with an own device is connected to the connector, based upon an electrical state of a terminal that is not used in a terminal configuration of the own device among the plurality of terminals. The first switching unit is provided on a transmission line connecting the terminal of the connector and an electric circuit of the own device, electrically connects the transmission line when the first determination unit determines that the peripheral device compatible with the own device is connected, and electrically disconnects the transmission line when the first determination unit determines that a non-compatible peripheral device is connected. According to another embodiment, a connection method involves determining whether or not a peripheral device compatible with an electronic device is connected to a connector including a plurality of terminals for being electrically connected to the peripheral device, based upon an electrical state of a non-use terminal that is not used in a terminal configuration of the electronic device among the plurality of terminals; electrically connecting a transmission line connecting a terminal of the plurality of terminals of the connector and an electric circuit of the electronic device when determining that the peripheral device compatible with the electronic device is connected; and electrically disconnecting the transmission line when determining that a non-compatible peripheral device is connected. 
     Hereinafter, embodiments of an electronic device will be described in detail with reference to the accompanying drawings. In the embodiment described below, a peripheral device is used as a display device, and an application example of the electronic device and the display device to a point of sales (POS) device is shown. 
       FIG. 1  is an external perspective view illustrating an example of a commodity reading apparatus. A commodity reading apparatus  1  is an example of a POS device, and includes a POS display device  1 - 1  and a main body unit  1 - 2  as illustrated in  FIG. 1 . The main body unit  1 - 2  corresponds to the “electronic device”, and the commodity reading apparatus  1  corresponds to a “display apparatus”. The POS display device  1 - 1  corresponds to a “peripheral device” or a “corresponding device” as one of the peripheral device and a “dedicated display device”. 
     The POS display device  1 - 1  includes a display  10 , a touch panel  11 , a speaker, and the like. The POS display device  1 - 1  is electrically connected to the main body unit  1 - 2  by a general-purpose plug cable (not illustrated). An electric wire (a signal line) for transmitting various signals and an electric signal such as driving power is housed in the general-purpose plug cable. The POS display device  1 - 1  can be attached to and detached from the main body unit  1 - 2 , and can be replaced with another display by removing and inserting the general-purpose plug cable. 
     The display  10  is a display such as a liquid crystal display, and displays various screen data on a display screen such as a liquid crystal according to a display signal from a control unit of the main body unit  1 - 2 . For example, registration screen data in which a commodity selection button for registering a commodity by a touch input is disposed are displayed. For example, the touch panel  11  is a touch panel such as an electrostatic capacity system, and is provided on the display screen of the display  10 . For example, when an operator touches the commodity selection button on the display screen, the touch panel  11  detects the touch operation of the operator and outputs a signal indicating coordinates on the display screen to the control unit of the main body unit  1 - 2 . 
     The main body unit  1 - 2  includes a reading scanner  13  such as a laser scanner. The reading scanner  13  is a scanner for reading a barcode attached to a commodity. 
     A housing (a second housing)  12 - 2  of the main body unit  1 - 2  houses a motherboard  2  (refer to  FIG. 2 ) for controlling the whole commodity reading apparatus  1 . The motherboard  2  is mounted with the control unit and a controller for each unit, for example, a controller for the POS display device  1 - 1 . In the embodiment, a USB Type-C standard is adopted as an interface system for display signal processing. Therefore, a USB Type-C compliant connector is used for a connector  31  (refer to  FIG. 2 ) as a receptacle on the side of the motherboard  2  and a connector as a receptacle on the side of the display device  1 - 1 . A USB Type-C compliant general-purpose plug cable is used to connect a signal line between the connectors. 
     Next, a configuration of the motherboard  2  will be described.  FIG. 2  is a hardware block diagram of the motherboard  2 . The motherboard  2  illustrated in  FIG. 2  includes a CPU  20 , a BIOS-ROM  21 , a memory  22 , a chipset  23 , an external storage apparatus  24 , a scanner controller  25 , a communication I/F  26 , a first switching control unit  27 , a first switching unit  28 , a second switching control unit  29 , a second switching unit  30 , a connector  31 , and a power supply unit P. 
     The CPU  20  is a central processing unit and executes various programs to generate data and output a control signal. 
     The BIOS-ROM  21  is a read only memory (ROM) that stores a basic input and output system (BIOS). 
     The memory  22  is a random access memory (RAM) used as a work region of the CPU  20 . 
     The chipset  23  is an example of an electronic circuit. The chipset  23  includes a north bridge and a south bridge, and performs memory control and control of an I/O device. In the embodiment, a USB controller  230  and a VGA controller  231  are mounted on the chipset  23 . The USB controller  230  controls the touch panel  11  of a USB device (refer to  FIG. 1 ), and processes an input signal from the touch panel  11 . The VGA controller  231  generates display data, and outputs the display signal to the display  10  (refer to  FIG. 1 ). 
     The external storage apparatus  24  is an HDD and a flash ROM, and stores a control program, commodity information for inquiring a commodity name, and screen data. 
     The scanner controller  25  is connected to the reading scanner  13  (refer to  FIG. 1 ). The scanner controller  25  drives the reading scanner  13  to read barcode information. 
     The communication I/F  26  is a communication interface for transmitting the commodity information read by the commodity reading apparatus  1  to a POS register. 
     The first switching control unit  27  outputs a predetermined control signal to the first switching unit  28  in response to whether the display device connected to the connector  31  via the general-purpose plug cable is a non-compatible device of its own device or a compatible device thereof. For example, when the display device of the non-compatible device, which is not the POS display device  1 - 1  corresponding to the compatible device of its own device, is connected to the connector  31 , the first switching control unit  27  outputs a control signal for controlling the first switching unit  28  to be “disconnected”. When the POS display device  1 - 1  corresponding to the compatible device of its own device is connected to the connector  31 , the first switching control unit  27  outputs a control signal for controlling the first switching unit  28  to be “connected”. Hereinafter, a case where the display device of the non-compatible device is used as a USB Type-C compliant general-purpose display device is described as an example. 
     The first switching unit  28  electrically connects or disconnects a signal line between the motherboard and the display device of a connection destination by, for example, switching a switch circuit, based upon an input of the control signal from the first switching control unit  27 . 
     The second switching control unit  29  outputs a control signal for switching a terminal group of the connector  31  connected to the chipset  23  to the second switching unit  30  in response to a connection direction of a plug of the general-purpose plug cable connected to the connector  31 . As will be described later, since the USB Type-C compliant connector  31  does not distinguish between up and down, it is possible to connect the plug upside down. The second switching control unit  29  detects a direction of the plug connected to the connector  31 , and outputs a control signal for switching the terminal of the connector  31  connected to the chipset  23  to the second switching unit  30  in response to the detected connection direction of the plug. 
     The second switching unit  30  selectively connects one of the pair of connection terminal groups provided in the connector  31  to the chipset  23  based upon the input of the control signal from the second switching control unit  29 . The second switching unit  30  switches the connection terminal group to be connected to the chipset  23  by, for example, switching the switch circuit. 
     The connector  31  is a receptacle that complies with the USB Type-C standard and includes  24  terminals. A signal line such as a display signal, a touch panel control signal, and a power supply for a display device is connected to each terminal. 
     The power supply unit P appropriately performs voltage conversion on the electric power of a commercial power supply to supply the electric power to each unit. For example, the power supply unit P supplies the electric power for the display device to the POS display device  1 - 1  via the general-purpose plug cable. 
     Next, a terminal configuration of the connector  31 , that is, a terminal configuration of a POS type will be described with reference to  FIGS. 3 and 4 . 
       FIG. 3  is a diagram illustrating an example of an external shape of the connector  31  (including a shape of a terminal connection unit).  FIG. 3  is a schematic front view of the terminal connection unit of the connector  31 , and terminal numbers (Pin 1  to Pin 24 ) are added to positions of the respective terminals. The shape of the connector  31  illustrated in  FIG. 3  complies with the USB Type-C standard. Therefore, the general-purpose plug cable used in the general-purpose display device can be used for the connector  31 . 
       FIG. 4  is a comparison diagram of a terminal configuration of the connector  31  and a terminal configuration of a general-purpose type. In this example, as the terminal configuration of the general-purpose type, a terminal configuration of the general-purpose display device that complies with the USB Type-C standard is shown.  FIG. 4  shows a list of terminal numbers of the terminals provided in the connector  31 . A general-purpose type list showing an example of the terminal configuration of the general-purpose type and a POS type list showing an example of the terminal configuration of the POS type are shown in association with each terminal number of a terminal number list. 
     As illustrated in  FIG. 3 , the connector  31  of the USB Type-C standard includes a terminal group of “Pin 1 ” to “Pin 12 ” disposed at an upper stage and a terminal group of “Pin 13 ” to “Pin 24 ” disposed at a lower stage. Even though the upper and lower parts of the plug are switched and connected, these terminal groups are symmetrically disposed to be able to be connected to the same general-purpose type terminal. 
     Specifically, in the terminal configuration of the general-purpose type, “Pin 1 ” and “Pin 12 ” are terminals for ground (hereinafter abbreviated as GND). “Pin 1 ” and “Pin 12 ” correspond to “Pin 13 ” and “Pin 24 ”. “Pin 2 ” and “Pin 3 ” are terminals for a data path (TX). “Pin 2 ” and “Pin 3 ” correspond to “Pin 14 ” and “Pin 15 ”. “Pin  4 ” and “Pin  9 ” are terminals for bus power. “Pin  4 ” and “Pin  9 ” correspond to “Pin  16 ” and “Pin  21 ”. “Pin  5 ” is a terminal for detecting a plug configuration. “Pin  5 ” corresponds to “Pin  17 ”. “Pin 6 ” and “Pin 7 ” are terminals for a data path (USB 2.0). “Pin  6 ” and “Pin  7 ” correspond to “Pin  18 ” and “Pin  19 ”. “Pin  8 ” is a terminal for a sideband. “Pin  8 ” corresponds to “Pin  20 ”. “Pin  10 ” and “Pin  11 ” are terminals for a data path (RX). “Pin  10 ” and “Pin  11 ” correspond to “Pin  22 ” and “Pin  23 ”. 
     That is, in the connector  31  of the USB Type-C standard, the terminal group of “Pin 1 ” to “Pin 12 ” and the terminal group of “Pin 13 ” to “Pin 24 ” form a pair of terminal groups that can be connected even though the directions of the plug are switched. In the following, a state in which the plug is connected to the terminal group of “Pin 1 ” to “Pin 12 ” is also referred to as a “forward direction”, and a state in which the plug is connected to the terminal group of “Pin 13 ” to “Pin 24 ” is also referred to as a “reverse direction”. The terminal group of “Pin 1 ” to “Pin 12 ” is also referred to as a “forward direction side”, and the terminal group of “Pin 13 ” to “Pin 24 ” is also referred to as a “reverse direction side”. 
     On the other hand, in the terminal configuration of the POS type, “Pin 2 ” and “Pin 3 ”, or “Pin 14 ” and “Pin 15 ” are used for transmitting the display signal. In the terminal configuration of the POS type, “Pin 6 ” and “Pin 7 ”, or “Pin 18 ” and “Pin 19 ” are used for controlling the USB device (the touch panel  11  in this example (refer to  FIG. 1 )). In the terminal configuration of the POS type, “Pin  1 ” or “Pin  13 ” is used for GND, and “Pin  4 ” or “Pin  16 ” is used for power supply to the display device  1 - 1 . 
     In the terminal configuration of the POS type, “Pin 8 ” and “Pin 12 ” on the forward direction side or “Pin 20 ” and “Pin 24 ” on the reverse direction side are used for a connection direction detection for detecting whether the plug is connected to the forward direction side or the reverse direction side. A symbol “-” shown in a POS type list  32  indicates that Pin is not used in the POS type. 
     In this manner, in the terminal configuration of the POS type of the embodiment, “Pin 5 ”, “Pin 9 ” to “Pin 11 ”, “Pin 17 ”, “Pin 21 ” to “Pin 23 ” are not used for electrical connection with the display device  1 - 1 . Therefore, the main body unit  1 - 2  detects which one of the compatible device and the general-purpose display device that complies with the USB Type-C standard (the non-compatible device) is connected, based upon electrical states of the terminals of “Pin 5 ”, “Pin 9 ” to “Pin 11 ”, “Pin 17 ”, “Pin 21 ” to “Pin 23 ”. Hereinafter, the terminals of “Pin 5 ”, “Pin 9 ” to “Pin 11 ”, “Pin 17 ”, and “Pin 21 ” to “Pin 23 ” are also collectively referred to as “monitor terminals”. 
     Next, a configuration example of the first switching control unit  27 , the first switching unit  28 , the second switching control unit  29 , and the second switching unit  30  will be described.  FIG. 5  is a diagram illustrating a configuration example of the first switching control unit  27 , the first switching unit  28 , the second switching control unit  29 , and the second switching unit  30 . Here, the first switching control unit  27  is an example of a first determination unit. The first switching unit  28  is an example of a first switching unit. The second switching control unit  29  is an example of a second determination unit. The second switching unit  30  is an example of a second switching unit. In  FIG. 5 , a plurality of sets of electric wires relating to various types of transmission are shown by one line. 
     As illustrated in  FIG. 5 , the first switching unit  28  includes a forward direction side switch  281  and a reverse direction side switch  282 . The forward direction side switch  281  includes single-throw type switches SW 11  to SW 14  and is connected between the forward direction side terminal of the connector  31  and the second switching unit  30 . Specifically, one end side of the switch SW 11  is connected to “Pin 1 ” of the connector  31 , and the other end side of the switch SW 11  is connected to a line L 11  that connects the second switching unit  30  and the switch SW 11 . One end side of the switch SW 12  is connected to “Pin 2 ” and “Pin 3 ” of the connector  31 , and the other end side of the switch SW 12  is connected to a line L 21  that connects the second switching unit  30  and the switch SW 12 . One end side of the switch SW 13  is connected to “Pin 4 ” of the connector  31 , and the other end side of the switch SW 13  is connected to a line L 31  that connects the second switching unit  30  and the switch SW 13 . One end side of the switch SW 14  is connected to “Pin 6 ” and “Pin 7 ” of the connector  31 , and the other end side of the switch SW 13  is connected to a line L 41  that connects the second switching unit  30  and the switch SW 14 . 
     The reverse direction side switch  282  includes single-throw type switches SW 21  to SW 24 , and is connected between the reverse direction side terminal of the connector  31  and the second switching unit  30 . Specifically, one terminal of the switch SW 21  is connected to “Pin 13 ” of the connector  31 , and the other terminal is connected to a line L 12  that connects the second switching unit  30  and the switch SW 21 . One terminal of the switch SW 22  is connected to “Pin 14 ” and “Pin 15 ” of the connector  31 , and the other terminal is connected to a line L 22  that connects the second switching unit  30  and the switch SW 22 . One terminal of the switch SW 23  is connected to “Pin 16 ” of the connector  31 , and the other terminal is connected to a line L 32  that connects the second switching unit  30  and the switch SW 23 . One terminal of the switch SW 24  is connected to “Pin 18 ” and “Pin 19 ” of the connector  31 , and the other terminal is connected to the line L 42  that connects the second switching unit  30  and the switch SW 24 . 
     The forward direction side switch  281  and the reverse direction side switch  282  switch on or off each switch in response to a control signal Y 1  outputted from the first switching control unit  27 , whereby the connector  31  and the second switching unit  30  (the chipset  23 ) are electrically connected or disconnected. 
     The first switching control unit  27  is connected to the monitor terminal of the connector  31 . The first switching control unit  27  monitors a voltage value applied to the monitor terminal as an input signal X 1  as the electrical state of the monitor terminal. The first switching control unit  27  is connected to the first switching unit  28  (the forward direction side switch  281  and the reverse direction side switch  282 ), and outputs the control signal Y 1  for turning on or off all the switches of the first switching unit  28  in response to the input signal X 1 . 
     In the terminal configuration of the POS type used in the embodiment, as illustrated in  FIG. 4 , none of the monitor terminals is used. Therefore, when the POS display device  1 - 1  is connected to the connector  31 , the voltage value at the monitor terminal becomes zero or almost zero. On the other hand, when the general-purpose display device is connected to the connector  31 , a voltage value in response to a function of each terminal is applied to the monitor terminal as the input signal X 1 . 
     Next, the first switching control unit  27  determines whether or not the display device connected to the connector  31  is the POS display device  1 - 1  based upon the voltage value of the input signal X 1 , and outputs the control signal Y 1  in response to the determination result to the first switching unit  28 . Specifically, when the voltage value of the input signal X 1  is zero or almost zero, the first switching control unit  27  determines that the POS display device  1 - 1  is connected, and outputs the control signal Y 1  for turning on all the switches of the first switching unit  28 . When the voltage value of the input signal X 1  is equal to or greater than a threshold value which is greater than zero, the first switching control unit  27  determines that the general-purpose display device is connected, and outputs the control signal Y 1  for turning off all the switches of the first switching unit  28 . 
     Accordingly, when the general-purpose display device is connected to the connector  31 , the first switching control unit  27  can disconnect the chipset  23  and the connector  31  so that the chipset  23  and the connector  31  are not electrically connected to each other. When the POS display devicel- 1  is connected to the connector  31 , the first switching control unit  27  can electrically connect the chipset  23  and the connector  31 . 
     The first switching control unit  27  may be configured to monitor all of the monitor terminals, or may be configured to monitor some of the terminals. For example, the first switching control unit  27  may be configured to monitor Pin 5  and Pin 17  that are used for detecting the plug configuration with the general-purpose type among the monitor terminals. 
     The second switching unit  30  includes double-throw type switches SW 31  to SW 34 , and is connected between the first switching unit  28  and the chipset  23 . Specifically, two terminals on the switching side of the switch SW 31  are connected to the line L 11  of the switch SW 11  and the line L 12  of the switch SW 21 , and a remaining one terminal is connected to a line L 1  that connects the chipset  23  and the switch SW 31 . Two terminals on the switching side of the switch SW 32  are connected to the line L 21  of the switch SW 12  and the line L 22  of the switch SW 22 , and a remaining one terminal is connected to a line L 2  that connects the chipset  23  and the switch SW 32 . Two terminals on the switching side of the switch SW 33  are connected to the line L 31  of the switch SW 13  and the line L 32  of the switch SW 23 , and a remaining one terminal is connected to a line L 3  that connects the chipset  23  and the switch SW 33 . Two terminals on the switching side of the switch SW 34  are connected to the line L 41  of the switch SW 14  and the line L 42  of the switch SW 24 , and a remaining one terminal is connected to a line L 4  that connects the chipset  23  and the switch SW 34 . 
     The second switching unit  30  switches the connection destination to either one of the two terminals on the switching side in response to a control signal Y 2  outputted from the second switching control unit  29 , whereby the chipset  23  is electrically connected to the forward direction side or the reverse direction side of the connector  31 . 
     The second switching control unit  29  is connected to Pin 8  and Pin 12  of the connector  31 . The second switching control unit  29  detects (determines) the connection direction of the plug connected to the connector  31  based upon the electrical state of the Pin  12 . Specifically, the second switching control unit  29  outputs an output signal X 2  via Pin 8 , and receives an input of an input signal X 2 ′ corresponding to the output signal X 2  via Pin 12 . Next, the second switching control unit  29  determines the connection direction of the plug to the connector  31  based upon a reception result of the input signal X 2 ′, and the control signal Y 2  for switching all the switches of the second switching unit  30  to the forward direction side or the reverse direction side of the connector  31  is outputted in response to the connection direction. 
       FIG. 6  is a diagram illustrating a configuration example relating to the detection of the connection direction of the plug of the second switching control unit  29 . As described above, the second switching control unit  29  outputs the output signal X 2  via “Pin 8 ”. The output signal X 2  is inputted to a terminal T 1  connected by the terminal “Pin 8 ” and a signal line K 1 . 
     The POS display device  1 - 1  loops back the output signal X 2  inputted to the terminal T 1  to a terminal T 2  connected to the terminal “Pin 12 ” of the main body unit  1 - 2  by a signal line K 2  by a loopback unit  60 . The loopback unit  60  can be realized by, for example, connecting the terminal T 1  and the terminal T 2  of the POS display device  1 - 1  by a short-circuiting unit  61  such as a lead wire and pattern wiring. 
     According to the above-described configuration, when the plug is connected to the connector  31  in the forward direction, the output signal X 2  is inputted to the terminal “Pin 12 ” of the main body unit  1 - 2  as the input signal X 2 ′ by the above-described loopback unit  60 . On the other hand, when the plug is connected to the connector  31  in the reverse direction, the terminals T 1  and T 2  of the display device  1 - 1  are connected to the terminals “Pin 20 ” and “Pin 24 ” of the main body unit  1 - 2 , such that the output signal X 2  is not transmitted to the display device  1 - 1  and the input signal X 2 ′ is not also looped back. 
     The second switching control unit  29  detects the connection direction of the plug connected to the connector  31  based upon whether or not the input signal X 2 ′ is looped back, and outputs the control signal Y 2  in response to the detection result to the second switching unit  30 . Specifically, when the input signal X 2 ′ is looped back, the second switching control unit  29  determines that the plug is connected to the forward direction side, and outputs the control signal Y 2  for switching all the switches of the second switching unit  30  to the forward direction side of the connector  31 . When the input signal X 2 ′ is not looped back, the second switching control unit  29  determines that the plug is connected to the reverse direction side, and outputs the control signal Y 2  for switching all the switches of the second switching unit  30  to the reverse direction side of the connector  31 . 
     In this manner, when the POS display device  1 - 1  is connected to the connector  31 , the second switching control unit  29  switches the connection destination of the second switching unit  30  to the forward direction side or the reverse direction side in response to the connection direction of the plug. Accordingly, since the POS display device  1 - 1  and the chipset  23  are electrically connected to each other, it becomes possible to transmit an electric signal between the main body unit  1 - 2  and the POS display device  1 - 1 . 
     In the embodiment, the second switching control unit  29  detects (determines) the connection direction of the plug by using “Pin  8 ” and “Pin  12 ” on the forward direction side, and maybe configured to determine the connecting direction of the plug by using “Pin  20 ” and the “Pin  24 ” on the reverse direction side. The second switching control unit  29  outputs the output signal X 2  to “Pin  8 ” on the forward direction side and “Pin  20 ” on the reverse direction side, and may determine the connection direction of the plug in response to whether the terminal receiving the input signal X 2 ′ is “Pin  12 ” on the forward direction side or “Pin  24 ” on the reverse direction side. 
     Hereinafter, an operation procedure of the commodity reading apparatus  1  when the main body unit  1 - 2  and the display device are connected by the general-purpose plug cable will be described.  FIG. 7  is a flowchart illustrating an example of the operation procedure of the commodity reading apparatus  1 . 
     First, the first switching control unit  27  waits until the display device is connected via the connector  31  (ACT  11 : No). Here, the first switching control unit  27  outputs the control signal Y 1  for turning off all the switches of the first switching unit  28  during the standby in ACT  11 . 
     Next, when the display device is connected to the connector  31  of the main body unit  1 - 2  (ACT  11 : Yes), the first switching control unit  27  determines whether the display device of the connection destination is a POS type display device or a general-purpose display device (a non-compatible display device) based upon a voltage value (the input signal X 1 ) of the monitor terminal (ACT  12 ). 
     Here, when the display device of the connection destination is the general-purpose display device (ACT  13 ; No), the first switching control unit  27  outputs the control signal Y 1  for turning off all the switches of the first switching unit  28 . Accordingly, the first switching unit  28  electrically disconnects the general-purpose display device by turning off all the switches (ACT  14 ), and terminates this processing. 
     On the other hand, when the display device of the connection destination is the POS type display device (ACT  13 ; Yes), the first switching control unit  27  outputs the control signal Y 1  for turning on all the switches of the first switching unit  28 . Accordingly, the first switching unit  28  electrically connects the POS type display device by turning on all the switches (ACT  15 ). 
     Next, the second switching control unit  29  determines the connection direction of the plug connected to the connector  31  based upon the loopback (the input signal X 2 ′) of the output signal X 2  outputted to the display device via “Pin 8 ” (ACT  16 ). 
     Here, when the connection direction of the plug is the forward direction (ACT  17 ; Yes), the second switching control unit  29  connects all the switches of the second switching unit  30  to the forward direction side switch  281  of the first switching unit  28  (ACT  18 ), and terminates this processing. When the connection direction of the plug is the reverse direction (ACT  17 ; Yes), the second switching control unit  29  connects all the switches of the second switching unit  30  to the reverse direction side switch  282  of the first switching unit  28  (ACT  19 ), and terminates this processing. 
     As described above, in the main body unit  1 - 2 , the type of the display device connected to the connector  31  is determined based upon the electrical state of the monitor terminal of the connector  31 . When the POS type display device is connected to the connector  31 , the main body unit  1 - 2  electrically connects a transmission line between the chipset  23  and the connector  31 , and when the general-purpose display device is connected to the connector  31 , the main body unit  1 - 2  electrically cut off the transmission line between the chipset  23  and the connector  31 . Therefore, the main body unit  1 - 2  can prevent electrical connection with the device of the connection destination when connecting a device having a different terminal configuration of a connector. 
     When the POS type display device is connected to the connector  31  via the general-purpose plug cable, the main body unit  1 - 2  determines the connection direction of the plug connected to the connector  31  based upon the electrical state of a predetermined terminal (Pins  8  and  12  or Pins  20  and  24 ) provided in any one of the terminal groups among the pair of terminal groups provided in the connector  31 . Next, the main body unit  1 - 2  switches the connection destination of the chipset  23  to the forward direction side or the reverse direction side of the connector  31  in response to the determined connection direction of the plug. Accordingly, when the POS type display device is connected to the connector  31 , the main body unit  1 - 2  can electrically connect the chipset  23  and the POS type display device regardless of the direction of the plug. Therefore, it is possible to effectively utilize characteristics of the general-purpose plug cable that complies with the USB Type-C standard. 
     In the embodiment, as the terminal configuration of the POS type, a form using the terminal configuration illustrated in  FIG. 4  is described, but the terminal configuration is not limited thereto. For example, when a sound output is performed by using a speaker provided in the display device, a terminal for the sound output may be secured. 
     In the embodiment, the first switching unit  28  switches the connection and disconnection of the transmission lines relating to Pins  1  to  4 , Pins  6 , and  7  (Pins  13  to  16  and Pins  18  and  19 ), but the transmission line to be connected and disconnected is not limited thereto. For example, when there is no electrical impact on mutual devices, the transmission line may be excluded from a target of the switching control. For example, Pin 8  and Pin 12  (Pin 20  and Pin 24 ) used for detecting the connection direction of the plug may be included in the target of the switching control. 
     In the embodiment, the connection direction is determined by using the two terminals of Pins  8  and  12  (or Pins  20  and  24 ), but the embodiment is not limited thereto. The connection direction may be determined by using any one of the terminals. In this case, when the POS type display device  1 - 1  receives the output signal X 2  via a terminal set for the determination of the connection direction, the POS type display device  1 - 1  loops back and outputs the output signal X 2  (the input signal X 2 ′) by using the terminal. 
     In the embodiment, a form in which the second switching unit  30  is provided between the chipset  23  and the first switching unit  28  is described, but the second switching unit  30  may be provided between the first switching unit  28  and the second switching unit  30 . In this case, the second switching unit  30  connects the forward direction side of the connector  31  and the forward direction side switch  281  or the reverse direction side of the connector  31  and the reverse direction side switch  282  in response to the control signal Y 2  of the second switching control unit  29 . 
     In the embodiment, a form using the USB Type-C standard is described, but other standards may be used. For example, in the case of a Lightning (registered trademark) standard, in the same manner as that of the USB Type-C standard, since there is no distinction between the upper and lower parts of the connector portion and the upper and lower parts thereof can be connected upside down, the same configuration as that of the above-described embodiment can be applied. 
     In the embodiment, when the general-purpose display device is connected to the connector  31 , the general-purpose display device is not displayed, such that a user can recognize the connected display device is the general-purpose display device, and a notification unit for explicitly notifying that the connected display device is the general-purpose display device may be further provided. For example, the main body unit  1 - 2  may include a sound output apparatus that emits a beep sound or a buzzer sound as the notification unit. In this case, the notification unit is configured to emit the beep sound or the buzzer sound in association with the switch-off control signal Y 1  outputted from the first switching control unit  27  and the switch-off operation by the first switching unit  28 , whereby the user can be notified that the general-purpose display device is connected thereto. 
     In the embodiment, an application example to the main body unit and the display device of the commodity reading apparatus is shown as the electronic device and the display device, but the embodiment is not limited thereto. This may be applied to other POS devices. For example, the electronic device and the display device may be applied to a main body unit and a display device of a POS register. Further, the electronic device and the display device may be applied to a main body unit and a display device of a self-POS. When the display device is required to connect two display devices, one device for a store clerk and the other device for a customer, the electronic device and the display device may be respectively applied to the main body unit and the display device for the store clerk, and the main body unit and the display device for the customer. 
     In the embodiment, the configuration of the main body unit and the display device is described by taking the USB Type-C standard as a connection interface as an example. However, a device other than the display device may be connected to the main body unit as a peripheral device, and the device may be expanded to one that identifies the non-compatible device at the time of connection. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein maybe made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.