Communication system, communication system control method, program and storage medium

Abstract

To provide a technology capable of further appropriately detecting whether a connection failure of a certain line in a USB cable occurs or not.SOLUTION: A communication system includes a first machine and a second machine communicable with each other by a USB cable that includes a first communication line, a second communication line, and a third communication line. The first machine includes: determining means for determining whether such a machine is connected to the second machine by the first communication line or not; and first control means for outputting a first signal to the third communication line when the determining means determines that such a machine is connected to the second machine not by the first communication line. The second machine includes: detecting means for detecting the first signal when the first signal is output to the third communication line; and another detecting means for detecting that a connection failure of the first communication line is occurring when the detecting means detects the first signal.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a communication system, a control method for a communication system, a program, and a storage medium.

Background Art

[0002] Currently, various devices can communicate with a computer or the like by USB communication conforming to the USB (Universal Serial Bus) standard. Here, in USB Type-C, by using the CC line, it is possible to detect the connection of a physical cable (USB cable). On the other hand, when a connection failure (such as a contact failure or disconnection) occurs in the CC (Configuration Channel) line of USB Type-C, the connection detection and communication establishment of USB Type-C cannot be performed. The connection failure of the CC line is, for example, a contact failure caused by the adhesion of foreign matter to the electrode portion or the corrosion of the electrode portion. Further, the connection failure of the CC line is, for example, a connection failure caused by the disconnection of the cable, or the disconnection of components inside the cable plug or the device due to aging stress.

[0003] Patent Document 1 describes a technique for determining whether a short circuit has occurred between a charging terminal and a signal terminal by using the timing change of the voltage rise of the signal terminal.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In Patent Document 1, when a short - circuit fault is detected by using the timing change of the voltage rise of the signal terminal, the VBUS power supply is turned off and USB communication is disabled. On the other hand, it is impossible to detect a connection failure of the USB cable when no short - circuit occurs.

[0006] Therefore, an object of the present invention is to provide a technique capable of more appropriately detecting whether a connection failure has occurred in a specific line of the USB cable.

Means for Solving the Problems

[0007] One aspect of the present invention is A communication system having a first device and a second device that can communicate with each other, connected by a USB (Universal Serial Bus) cable having a first communication line, a second communication line, and a third communication line, When the first device and the second device are connected by the first communication line, USB communication is possible on the second communication line, The first device has Determination means for determining whether or not it is connected to the second device by the first communication line, First control means for controlling to output a first signal to the third communication line when it is not determined by the determination means that it is connected to the second device by the first communication line, And The second device has Detection means for detecting the first signal when the first signal is output to the third communication line, And Detection means for detecting that a connection failure has occurred in the first communication line when the detection means detects the first signal, And A communication system characterized by this.

[0008] One aspect of the present invention is A control method for a communication system having a first device and a second device that can communicate with each other by being connected by a USB (Universal Serial Bus) cable having a first communication line, a second communication line, and a third communication line, comprising: When the first device and the second device are connected by the first communication line, USB communication is possible on the second communication line, In the first device, a determination step of determining whether or not the first device is connected to the second device via the first communication line; In the first device, when it is not determined in the determination step that the first device is connected to the second device via the first communication line, an output step of outputting a first signal to the third communication line; In the second device, a detection step of detecting the first signal when the first signal is output to the third communication line; In the second device, when the first signal is detected in the detection step, a detection step of detecting that a connection failure has occurred in the first communication line; A control method for a communication system, characterized by comprising the above steps.

Advantages of the Invention

[0009] According to the present invention, it is possible to more appropriately detect whether or not a connection failure has occurred in a specific line of a USB cable.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5A

Figure 5B

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

[0011] In USB Type-C, seven-step configuration control using the CC line is added. The following (1) to (5) are defined in the USB Type-C standard, and (6) and (7) are defined in the USB PD (Power Delivery) standard. (1) Detection of physical cable connection (Attach). (2) Detection of the plug surface (front and back of the plug surface). (3) Establishment of the relationship between Source (USB host) - to - Sink (USB device). (4) Whether the USB Type-C compatible cable requires Vconn or not Detection. (5) Detection of the current value supplied from VBUS (5V / 3A, 5V / 1.5A, 5V / 500mA). (6) Power Negotiation (negotiation when using a VBUS voltage of 5V or higher). (7) Alternate Mode (negotiation when using an extended function other than USB communication such as DisplayPort).

[0012] <Embodiment 1> FIG. 1 is a configuration diagram of a communication system 100 according to Embodiment 1. The communication system 100 includes a source device 101 having a USB Type-C host port and a sink device 151 having a USB Type-C device port. In FIG. 1, only the configuration related to the connection (communication) control of USB Type-C is shown limitedly among the configurations of the communication system 100.

[0013] The source device 101 includes a first CPU 102, a host controller 103, a first control unit 104, a first multiplexer 105, a connection notification detection unit 106, a first port 107, and a user notification unit 108.

[0014] The sink device 151 includes a second CPU 152, a device controller 153, a second control unit 154, a second multiplexer 155, a connection notification unit 156, and a second port 157.

[0015] The first port 107 and the second port 157 are each a USB Type-C port. The first port 107 and the second port 157 are connected by a cable 121.

[0016] The first CPU 102 is a control unit that performs system control of the source device 101. The first CPU 102 acquires the connection state of the CC line (USB Type-C) by communicating with the first control unit 104.

[0017] The second CPU 152 is a control unit that performs system control of the sink device 151. The second CPU 152 acquires the connection state of the CC line (USB Type-C) by communicating with the second control unit 154. Usually, if the source device 101 and the sink device 151 are connected by the cable 121, the first CPU 102 and the second CPU 152 perform USB communication (USB data communication) with each other via the host controller 103 and the device controller 153. Note that USB communication is data communication according to the USB standard.

[0018] The user notification unit 108 notifies the user of the occurrence of a connection error when an error occurs in the connection of the CC line (USB Type-C). For example, the user notification unit 108 displays matters related to the error on the liquid crystal display unit included in the source device 101. When the source device 101 receives remote control from an external device via a network, the user notification unit 108 may send an error notification to the external device via the network. Then, the external device may display matters related to the error on its own display unit using an OSD (On-Screen Display).

[0019] The host controller 103 is a controller that performs USB communication as a host (USB host) in the host device relationship when the USB communication function is enabled. When the first CPU 102 detects the connection of the CC line (USB Type-C) through communication with the first control unit 104, the USB communication function of the host controller 103 is enabled.

[0020] The device controller 153 is a controller that performs USB communication as a device (USB device) in the host device relationship when the USB communication function is enabled. When the second CPU 152 detects the connection of the CC line (USB Type-C) through communication with the second control unit 154, the USB communication function of the device controller 153 is enabled.

[0021] When USB communication between the host controller 103 and the device controller 153 transitions to the link-up state, the first CPU 102 and the second CPU 152 can perform USB communication. The host controller 103 and the device controller 153 support USB communication compliant with the USB3.2 standard and the USB3.1 standard (hereinafter referred to as "USB3.2 communication") and USB communication compliant with the USB2.0 standard (hereinafter referred to as "USB2.0 communication"). USB3.2 communication is performed using the TX / RX ports of the respective controllers. USB2.0 communication is performed using the D+ / D- ports of the respective controllers.

[0022] The first control unit 104 and the second control unit 154 comply with the USB Type-C standard. The first control unit 104 and the second control unit 154 each transmit and receive a CC1 signal from and to the CC1 terminal, and transmit and receive a CC2 signal from and to the CC2 terminal. Based on the voltage of the CC1 terminal and the voltage of the CC2 terminal (hereinafter, the voltages of these two terminals are collectively referred to as the "CC1 / CC2 terminal voltage"), the first control unit 104 and the second control unit 154 integrally perform connection detection and plug surface detection of the cable 121.

[0023] Pull-up resistors Rp are respectively connected to the CC1 terminal and the CC2 terminal of the first control unit 104. Pull-down resistors Rd are respectively connected to the CC1 terminal and the CC2 terminal of the second control unit 154. When the cable 121 is not connected, a pull-up voltage VDD (usually 5V or 3.3V) is generated at the CC1 terminal and the CC2 terminal in the first control unit 104. When the cable 121 is not connected, a voltage at the GND level around 0V is generated at the CC1 terminal and the CC2 terminal in the second control unit 154. When the cable 121 is connected to the first port 107 and the second port 157, the pull-up voltage VDD changes to vRd (about 0.25 to 2.6V). In response to this voltage change, the connection (electrical connection) between the source device 101 and the sink device 151 by the cable 121 (CC line) is detected.

[0024] Cable 121 is a USB cable compatible with USB Type-C. Cable 121 has at least three communication lines: a CC line, an RX / TX line, and a D line. There is only one CC line in Cable 121. Therefore, Cable 121 is electrically connected to only one of the CC1 terminal and the CC2 terminal in the first control unit 104, and is also electrically connected to only one of the CC1 terminal and the CC2 terminal in the second control unit 154. The first control unit 104 determines the terminal whose voltage has changed between the CC1 terminal and the CC2 terminal, and determines the orientation (plug face) in which the plug of Cable 121 is inserted into the first port 107. Similarly, the second control unit 154 determines the terminal whose voltage has changed between the CC1 terminal and the CC2 terminal, and determines the orientation (plug face) in which the plug of Cable 121 is inserted into the second port 157. In Embodiment 1, each control unit determines that the plug is inserted in the front orientation if the voltage of the CC1 terminal changes, and determines that the plug is inserted in the back orientation if the voltage of the CC2 terminal changes.

[0025] Therefore, when the plug of Cable 121 is connected to the first port 107 in the front orientation, the first control unit 104 generates a plug face signal indicating "0", and when the plug is connected to the first port 107 in the back orientation, it generates a plug face signal indicating "1". Similarly the second control unit 154 generates a plug face signal indicating "0" when the plug of Cable 121 is connected to the second port 157 in the front orientation, and generates a plug face signal indicating "1" when the plug is connected to the second port 157 in the back orientation. The first control unit 104 outputs the generated plug face signal to the first multiplexer 105 as the result of the plug face determination. The second control unit 154 outputs the generated plug face signal to the second multiplexer 155 as the result of the plug face determination.

[0026] In addition, based on the result of detecting the connection of cable 121 based on the CC1 / CC2 terminal voltage and the presence or absence of a notification of the detection of the connection of cable 121 from the connection notification detection unit 106, the first control unit 104 determines whether the sink device 151 is electrically connected. When it is determined that the sink device 151 is electrically connected, the first control unit 104 notifies the first CPU 102 that the sink device 151 is connected. And in this case, the first control unit 104 enables VBUS power supply (power supply from VBUS) by turning on the VBUS switch.

[0027] Also, when the connection of the sink device 151 is not detected by the CC1 / CC2 terminal voltage, the first control unit 104 enables the connection detection function of the connection notification detection unit 106. When receiving a connection notification from the connection notification detection unit 106, the first control unit 104 notifies the first CPU 102 of a connection error on the CC line (USB Type-C) after determining that a connection failure has occurred on the CC line of the cable 121.

[0028] Based on the result of detecting the connection of the cable based on the CC1 / CC2 terminal voltage and the detection result of VBUS power supply using the VBUS DET pin, the second control unit 154 determines whether the source device 101 is electrically connected to the sink device 151. When the second control unit 154 determines that the source device 101 is electrically connected to the sink device 151, the second control unit 154 notifies the second CPU 152 that the source device 101 is electrically connected to the sink device 151. Also, when the electrical connection of the source device 101 is not detected by the CC1 / CC2 terminal voltage and VBUS power supply is not detected, the second control unit 154 enables the connection notification function of the connection notification unit 156.

[0029] The first multiplexer 105 is a USB SS (Super Speed) multiplexer. The first multiplexer 105 switches the port used for USB3.2 communication according to the plug surface signal received from the first control unit 104. Specifically, when the plug surface signal indicates "0", the first multiplexer 105 connects the TX / RX port and the Tx1 / Rx1 port, so as to control the host controller 103 to perform USB3.2 communication through the Tx1 / Rx1 port. On the other hand, when the plug surface signal indicates "1", the first multiplexer 105 connects the TX / RX port and the TX2 / RX2 port, so as to control the host controller 103 to perform USB3.2 communication through the Tx2 / Rx2 port.

[0030] The second multiplexer 155 is a USB SS multiplexer that operates in the same manner as the first multiplexer 105 according to the plug surface signal received from the second control unit 154.

[0031] The connection notification unit 156 includes a pull-up resistor Rdet connected to 3.3V and a switch. The connection notification unit 156 detects the electrical connection by the cable 121 between the source device 101 and the sink device 151 according to the voltage change of the D+ line between the second port 157 and the device controller 153.

[0032] As described above, for a device compliant with the USB Type-C standard, USB3.2 communication can be achieved regardless of whether the plug (cable plug) of the cable 121 is connected to the port in either the front or back orientation.

[0033] By the way, if a connection failure occurs in the CC line of the cable 121, the connection detection and communication establishment of USB Type-C cannot be performed. In this case, although the cable 121 is connected to each device, the sink device 151 cannot receive USB VBUS power supply and the USB communication link-up has not been achieved. Therefore, the user cannot grasp the cause why the connection detection and communication establishment of USB Type-C cannot be performed. Thus, while the connection notification function is enabled by the second control unit 154, the connection notification unit 156 turns on the switch of the connection notification unit 156 to control the voltage of the D+ signal of USB2.0 communication to the pull-up voltage 3.3V, thereby generating a connection notification signal.

[0034] The connection notification detection unit 106 monitors whether the voltage of the D+ signal of USB2.0 communication changes to the pull-up voltage 3.3V while the connection detection function is enabled by the first control unit 104. The connection notification detection unit 106 detects the connection between the source device 101 and the sink device 151 based on the change in the voltage of the D+ signal. When the connection notification detection unit 106 detects a connection, it sends a connection notification to the first control unit 104. Thereby, the communication system 100 enables alternative connection detection using the D line which is a USB2.0 communication line. Note that a power supply independent of VBUS power supply is used for the power supply of the pull-up voltage. That is, a device operating with USB bus power is not used as the sink device 151 of the present embodiment.

[0035] Note that the pull-up switching circuit for transfer speed detection in the device controller 153 may realize the function of the connection notification unit 156.

[0036] The operation of the source device 101 which is a USB host according to Embodiment 1 will be described using the flowchart of FIG. 2A.

[0037] In step S201, the first control unit 104 attempts to detect the connection of cable 121 (CC1 / CC2 connection detection) based on the CC1 / CC2 terminal voltage. If it is detected that the cable 121 is connected (i.e., the electrical connection between the source device 101 and the sink device 151 by the cable 121), the process proceeds to step S204. If it is not detected that the cable 121 is connected, the process proceeds to step S202.

[0038] In step S202, the first control unit 104 enables the connection detection function of the connection notification detection unit 106. The connection notification detection unit 106 attempts to detect the connection notification signal using the voltage change of the aforementioned D+ signal while the connection detection function is enabled by the first control unit 104. If the connection notification signal is not detected, the process returns to step S201. If the connection notification signal is detected, after the connection notification detection unit 106 notifies the first control unit 104 of the connection notification, the process proceeds to step S203. At this time, if the sink device 151 does not support alternative connection detection using the USB2.0 communication line, the process does not proceed to step S203. In this case, the processes of steps S201 and S202 are repeated at a certain interval until the connection of the cable 121 is detected in step S201.

[0039] In step S203, the first control unit 104 acquires the connection notification from the connection notification detection unit 106 in a state where the connection of the cable 121 based on the CC1 / CC2 terminal voltage is not detected. Therefore, the first control unit 104 determines that a connection failure has occurred in the CC line and notifies the first CPU 102 of the USB Type-C connection error. Then, the first CPU 102 uses the user notification unit 108 to notify the user of the occurrence of the connection error (connection failure in the CC line) and prompts the user to check the USB Type-C connection status.

[0040] In step S204, the first control unit 104 determines that there is no connection failure in the CC line, and shifts to the normal operation according to the USB Type-C standard. That is, using at least one of the RX1 / TX1 line and the RX2 / TX2 line, the source device 101 and the sink device 151 perform USB3.2 communication.

[0041] Using the flowchart of FIG. 2B, the operation of the sink device 151 which is a USB device according to Embodiment 1 will be described.

[0042] In step S251, the second control unit 154 attempts to detect the connection of the cable 121 (electrical connection between the source device 101 and the sink device 151 by the cable 121) (CC1 / CC2 connection detection) based on the CC1 / CC2 terminal voltage. If it is detected that the cable 121 is connected, the process proceeds to step S253. If it is not detected that the cable 121 is connected, the process proceeds to step S252.

[0043] In step S252, the second control unit 154 enables the connection notification function of the connection notification unit 156 while the connection of the source device 101 is not detected based on the CC1 / CC2 terminal voltage and VBUS power supply is not detected. In a state where the connection notification function of the connection notification unit 156 is enabled, the switch of the connection notification unit 156 is turned on and a connection notification signal is output.

[0044] In step S253, the second control unit 154 disables the connection notification function of the connection notification unit 156. In a state where the connection notification function of the connection notification unit 156 is disabled, the switch of the connection notification unit 156 is turned off and the output of the connection notification signal is stopped.

[0045] In step S254, the second control unit 154 determines that there is no connection failure in the CC line, and shifts to the normal operation. That is, using at least one of the RX1 / TX1 line and the RX2 / TX2 line, the source device 101 and the sink device 151 perform USB3.2 communication.

[0046] In Embodiment 1, the sink device 151 has a connection notification unit 156 for outputting a connection notification signal to the USB 2.0 communication line, and the source device 101 has a connection notification detection unit 106 for detecting the connection notification signal in the USB 2.0 communication line. While the connection due to the voltage change of the CC line is not detected, the sink device 151 outputs a connection notification signal to the USB 2.0 communication line, and the source device 101 detects the connection notification signal. Thereby, when the connection by the CC line is not detected, the communication system 100 can detect the connection of the cable 121 by performing alternative detection by the USB 2.0 communication line. And the communication system 100 can notify the user of the connection failure of the CC line.

[0047] <Embodiment 2> Hereinafter, the process for realizing USB 2.0 communication even when a connection failure occurs in the CC line of USB Type-C according to Embodiment 2 will be described. Note that the system configuration of Embodiment 2 is the same as that of the communication system 100 of Embodiment 1, and the configuration description will be omitted.

[0048] Using the flowcharts of FIGS. 3A and 3B, the process until the start of USB 2.0 communication according to Embodiment 2 will be described. Hereinafter, regarding FIGS. 3A and 3B, mainly the differences from the processes of the flowcharts of FIGS. 2A and 2B will be described.

[0049] First, referring to the flowchart of FIG. 3A, the process of the source device 101 according to Embodiment 2 will be described. The processes of steps S301 and S308 are the same as the processes of steps S201 and S204 of Embodiment 1.

[0050] In step S302, similar to step S202 of Embodiment 1, the connection notification detection unit 106 attempts to detect a connection notification signal using the voltage change of the D+ signal. If the connection notification signal is not detected, the process returns to step S301. If the connection notification signal is detected, after the connection notification detection unit 106 notifies the first control unit 104 of the connection notification, the process proceeds to step S303.

[0051] In step S303, since the first control unit 104 receives a connection notification from the connection notification detection unit 106 in a state where the connection of the cable 121 based on the CC1 / CC2 terminal voltage is not detected, it is determined that a connection failure has occurred in the CC line. In Embodiment 1, in such a case, a notification of the occurrence of a connection error is made. In Embodiment 2, such a notification of the occurrence of an error is made, and further, the communication system 100 can operate in a recovery mode that realizes at least USB2.0 communication. Therefore, the first CPU 102 notifies the user of "the occurrence of a connection error and the operation of the communication system 100 in the recovery mode". Note that the first CPU 102 may request permission to operate in the recovery mode instead of notifying the operation in the recovery mode, and proceed to step S304 when permission is received.

[0052] In step S304, the first control unit 104 turns on the VBUS switch and starts VBUS power supply (power supply on the VBUS line).

[0053] In step S305, after starting the VBUS power supply in step S304, the connection notification detection unit 106 monitors whether the connection notification signal transitions to the off state within a certain period (whether the connection notification signal changes to a state where it is not detected within a certain period). If the connection notification signal transitions to the off state within a certain period, the process proceeds to step S306. If the connection notification signal does not transition to the off state within a certain period, the process proceeds to step S307.

[0054] In step S306, the first CPU 102 enables the USB communication function of the host controller 103 to operate in the recovery mode. As a result, a USB communication link-up becomes possible between the host controller 103 and the device controller 153. Therefore, at least USB 2.0 communication becomes possible between the source device 101 and the sink device 151. Further, when the port switching relationship between the first multiplexer 105 and the second multiplexer 155 is appropriate (that is, when communication is possible via the Tx1 / Rx1 port or the Tx2 / Rx2 port), USB 3.2 communication also becomes possible.

[0055] In step S307, since the connection notification signal does not transition to the off state even though the VBUS power supply is turned on in the recovery mode, the connection notification detection unit 106 determines that the sink device 151 does not support the recovery mode. Then, the first CPU 102 notifies the user of the occurrence of a recovery error using the user notification unit 108 and terminates the VBUS power supply.

[0056] Note that when a connection failure occurs in the CC line, the supplyable current of the source device 101 using the CC line cannot be detected. For this reason, the source device 101 operates as a rated power supply that supplies 5V / 500mA power to the sink device 151 for USB 2.0, 5V / 900mA power for USB 3.1, and 5V / 1.5A power for USB 3.2.

[0057] Subsequently, referring to the flowchart of FIG. 3B, the processing of the sink device 151 according to Embodiment 2 will be described. The processing in step S351 is the same as the processing in step S251 of Embodiment 1. The processing in step S352 is the same as the processing in step S251 of Embodiment 1.

[0058] In step S352, the second control unit 154 attempts to detect VBUS power supply although the connection of the cable 121 based on the CC1 / CC2 terminal voltage has not been detected. If VBUS power supply is detected, the process proceeds to step S357. If VBUS power supply is not detected, the process proceeds to step S353.

[0059] In step S353, the second control unit 154 enables the connection notification function of the connection notification unit 156 in the same manner as step S252 of Embodiment 1.

[0060] In step S354, the second control unit 154 attempts to detect VBUS power supply for a certain period after the process of step S353 (a time sufficient until VBUS power supply starts in step S304). If VBUS power supply is not detected, it is determined that the source device 101 does not support recovery mode operation, and the process returns to step S351. If VBUS power supply is detected, the process proceeds to step S355.

[0061] In step S355, the second control unit 154 disables the connection notification function of the connection notification unit 156.

[0062] In step S356, after a certain time has elapsed after the second control unit 154 disables the connection notification function of the connection notification unit 156, in order to operate in recovery mode, the second control unit 154 enables the USB communication function of the device controller 153. As a result, USB communication link-up between the host controller 103 and the device controller 153 becomes possible. Therefore, at least USB2.0 communication becomes possible between the source device 101 and the sink device 151. Further, when the port switching relationship of the first multiplexer 105 and the second multiplexer 155 is appropriate (when communication is possible at the Tx1 / Rx1 port or the Tx2 / Rx2 port), USB3.2 communication also becomes possible.

[0063] In step S357, the second control unit 154 determines that there is a connection abnormality. This is because when the connection of the cable 121 is not detected based on the CC1 / CC2 terminal voltage, normally VBUS power supply is not received. Therefore, without shifting to the normal operation, the connection notification signal is not output, and the USB communication function remains disabled, and the processing of this flowchart ends. In this case, afterwards, when the cable 121 is unplugged from the sink device 151 and the VBUS power reception is turned off, the processing of this flowchart starts again.

[0064] The processes of step S358 and step S359 are the same as the processes of step S253 and step S254.

[0065] As described above, in the second embodiment, when the connection by the CC line is not detected and the VBUS power supply is not performed, the sink device 151 outputs a connection notification signal to the USB2.0 communication line. Then, when the source device 101 detects the connection notification signal, it enables the VBUS power supply. After that, when the sink device 151 receives the VBUS power supply, it stops outputting the connection notification signal and enables the USB communication function. When the connection notification signal is no longer detected by the source device 101, it enables the USB communication function.

[0066] Thereby, when the connection of the cable 121 is not detected by the CC line, by using the USB2.0 communication line for alternative detection, it becomes possible to detect the connection of the cable 121. For this reason, it becomes possible to detect a connection failure of the CC line and to notify the user of the connection failure. Furthermore, at least USB2.0 communication becomes possible.

[0067] <Embodiment 3> In the first and second embodiments, the communication system performs alternative detection of the connection of the cable 121, but in the third embodiment, it further performs alternative detection of the plug surface. Note that the description of the common parts between the third embodiment and the first and second embodiments is omitted.

[0068] FIG. 4 is a configuration diagram of a communication system 400. The communication system 400 includes a source device 401 having a USB Type-C host port and a sink device 451 having a USB Type-C device port.

[0069] The source device 401 includes a first CPU 102, a host controller 103, a first control unit 104, and a first multiplexer 105. The source device 401 further includes a connection notification detection unit 402, a connection response unit 403, a first USB 2.0 multiplexer 404, a first port 107, and a user notification unit 108. The connection response unit 403 includes switches SWh1+, SWh1-, SWh2+, and SWh2-.

[0070] The sink device 451 includes a second CPU 152, a device controller 153, a second control unit 154, a second multiplexer 155, a connection notification unit 452, a plug surface detection unit 453, a second USB 2.0 multiplexer 454, and a second port 157. The connection notification unit 452 includes pull-up resistors Rdet1 and Rdet2 each connected to a voltage of 3.3V, and switches SWd+ and SWd-.

[0071] Similar to Embodiment 1, the first port 107 and the second port 157 are connected by a cable 121. Note that the solid line of the cable 121 in FIG. 4 represents the case where the plug of the cable 121 is connected face-up to both the first port 107 and the second port 157. The dashed line indicates the case where the plug is connected face-up to the first port 107 and the plug is connected face-down to the second port 157.

[0072] Regarding the configuration differences between FIG. 1 and FIG. 4, the first USB2.0 multiplexer 404 selects the signal connected to cable 121 among the D1+ signal, D1- signal, D2+ signal, and D2- signal. The first USB2.0 multiplexer 404 connects the selected signal to the signals (D+ signal and D- signal) in the device controller 153. For this purpose, the first USB2.0 multiplexer 404 switches the port used for USB2.0 communication according to the plug surface signal received from the first control unit 104. Specifically, when the plug surface signal indicates "0", the first USB2.0 multiplexer 404 connects the D1+ / D1- port to the D+ / D- port. Thus, the first USB2.0 multiplexer 404 controls so that the host controller 103 can execute USB2.0 communication through the D1+ / D1- port. On the other hand, when the plug surface signal indicates "1", the first USB2.0 multiplexer 404 connects the D2+ / D2- port to the D+ / D- port. Thus, the first USB2.0 multiplexer 404 controls so that the host controller 103 can execute USB2.0 communication through the D2+ / D2- port.

[0073] While the connection notification function of the connection notification unit 452 is enabled by the second control unit 154, the connection notification unit 452 turns on the switch SWd+ and the switch SWd- of the connection notification unit 452. Thus, the connection notification unit 452 generates a connection notification signal by controlling the voltages of the D1+ signal and the D2- signal in USB2.0 communication to the pull-up voltage 3.3V.

[0074] The connection notification detection unit 402 has the connection detection function enabled by the first control unit 104 During this period, it is monitored whether the voltages of the D1+ signal, D1- signal, D2+ signal, and D2- signal in USB2.0 communication have changed to the pull-up voltage of 3.3V. Since there is only one set of USB2.0 communication lines in cable 121, the connection notification detection unit 402 detects a voltage change in the signal of any one of the lines. By detecting the connection notification signal due to the voltage change, it is possible to detect the connection of cable 121 and the plug surface of cable 121 at the first port 107.

[0075] When a connection notification signal is detected, the switches SWh1+, SWh1-, SWh2+, and SWh2- of the connection response unit 403 are turned on, and the source device 401 converts the voltage of the connection notification signal from the sink device 451 to the GND voltage. As a result, the connection response unit 403 returns a connection detection response to the sink device 451 side.

[0076] The plug surface detection unit 453 of the sink device 451 is an orientation detection unit that detects whether cable 121 is connected to each device with the front or back facing (detects the plug surface). First, while the connection notification function is enabled, the plug surface detection unit 453 determines whether the D1+ signal or D2- signal in USB2.0 communication has changed from the state of the pull-up voltage of 3.3V to Low. If either the D1+ signal or the D2- signal has changed to Low, the connection of cable 121 is detected in the source device 401. When the D1+ signal changes to Low, the plug surface detection unit 453 can determine that the plug surface of cable 121 at the second port 157 is the front surface. On the other hand, when the D2- signal changes to Low, the plug surface detection unit 453 can determine that the plug surface of cable 121 at the second port 157 is the back surface.

[0077] The processing of alternative connection detection and plug surface detection using the USB2.0 communication line according to Embodiment 3 will be described with reference to the flowcharts of FIGS. 5A and 5B.

[0078] In FIG. 5A, the processes of steps S501 to S503 are the same as the processes of steps S301 to S303. Note that in step S502, different from step S303, the connection notification detection unit 402 attempts to detect a connection notification signal by using the voltage changes of the D1+ signal, D1− signal, D2+ signal, and D2− signal as described above.

[0079] In step S504, the connection notification detection unit 402 detects the plug surface on the first port 107 side. FIG. 6 shows the connection relationship of USB2.0 signals in the connection between the source device 401 and the sink device 451. In FIG. 6, the white areas indicate the connection relationship. The signals (signal lines) indicated by “◯” are signals controlled to a pull-up voltage of 3.3V by the connection notification unit 452.

[0080] For example, when the plug of the cable 121 is connected to the first port 107 on the surface (front side) and the plug of the cable 121 is connected to the second port 157 on the back side, on the source device 401 side, the D1− signal is controlled to the pull-up voltage of 3.3V. Since different signals are controlled to the pull-up voltage of 3.3V for each connection relationship, the source device 401 can detect the plug surfaces for both the first port 107 and the second port 157. The connection notification detection unit 402 notifies the first control unit 104 of the detection result of the plug surface.

[0081] In step S505, the first control unit 104 generates a plug surface signal based on the detection result of the plug surface of the first port 107 in step S504. Specifically, the first control unit 104 generates a plug surface signal indicating “0” when the plug is connected in the front side. On the other hand, when the plug is connected in the back side, the first control unit 104 generates a plug surface signal indicating “1”. The first control unit 104 outputs the plug surface signal to the first multiplexer 105 and the first USB2.0 multiplexer 404. The first m The multiplexer 105 switches the USB 3.2 communication port according to the plug surface signal. The first USB 2.0 multiplexer 404 switches the USB 2.0 communication port according to the plug surface signal.

[0082] In step S506, the connection notification detection unit 402 returns a connection detection response to the sink device 451 side by turning on the switches SWh1+, SWh1-, SWh2+ and SWh2- of the connection response unit 403.

[0083] In step S507, the first control unit 104 turns on the VBUS switch and starts VBUS power supply.

[0084] In step S508, after the VBUS power supply is turned on in step S507, the connection notification detection unit 402 monitors whether the connection notification signal transitions to the off state within a certain period. If the connection notification signal transitions to the off state within a certain period, the process proceeds to step S509. If the connection notification signal does not transition to the off state within a certain period, the process proceeds to step S510.

[0085] In step S509, the first CPU 102 enables the USB communication function of the host controller 103 to operate in the recovery mode.

[0086] The processes of steps S510 and S511 are the same as the processes of steps S307 and S308.

[0087] In FIG. 5B, the processes of steps S551 to S553 and S559 to S561 are the same as the processes of steps S351 to 353 and S357 to S359. In step S553, the second control unit 154 turns on both the switch SWd+ and the switch SWd- in the connection notification unit 452 simultaneously.

[0088] In step S554, the second control unit 154 attempts to detect VBUS power supply for a certain period after the process of step S553 (a time sufficient until VBUS power supply starts in step S507). If VBUS power supply is not detected, the process returns to step S551. If VBUS power supply is detected, the process proceeds to step S555.

[0089] In step S555, the plug surface detection unit 453 attempts to detect that the voltage of the D1+ signal or D2- signal in USB2.0 communication has changed from the pull-up voltage of 3.3V to Low. For example, when the plug of the cable 121 is connected to the first port 107 on the front surface and the plug of the cable 121 is connected to the second port 157 on the back surface, on the source device 401 side, the voltage of the D1- signal is controlled to the pull-up voltage of 3.3V. Then, as a result of the process in step S506, on the sink device 451 side, the voltage of the D2- signal changes from the pull-up voltage of 3.3V to Low. Due to this voltage change, the plug surface detection unit 453 can detect the plug surface at the second port 157 of the cable 121. The plug surface detection unit 453 notifies the second control unit 154 of the detection result of the plug surface.

[0090] In step S556, the second control unit 154 generates a plug surface signal based on the detection result of the plug surface of the second port 157 in step S555. Specifically, when the plug is connected facing forward, the second control unit 154 generates a plug surface signal indicating "0". When the plug is connected facing backward, the second control unit 154 generates a plug surface signal indicating "1". The second control unit 154 outputs the plug surface signal to the second multiplexer 155 and the second USB2.0 multiplexer 454. The second multiplexer 155 switches the communication port of USB3.2 according to the plug surface signal. The second USB2.0 multiplexer 454 switches the USB2.0 communication port according to the plug surface signal.

[0091] In step S557, the second control unit 154 disables the connection notification function of the connection notification unit 452.

[0092] In step S558, after a certain period of time has elapsed since the second CPU 152 disabled the connection notification function of the connection notification unit 452, in order to operate in the recovery mode, the second CPU 152 enables the USB communication function of the device controller 153.

[0093] By the above processing, the connections of the communication ports of the first multiplexer 105 and the first USB2.0 multiplexer of the source device 401 are correctly switched. Further, the connections of the communication ports of the second multiplexer 155 and the second USB2.0 multiplexer of the sink device 451 are correctly switched. For this reason, link-up of USB3.2 Gen1×1 or Gen2×1 communication and USB2.0 communication becomes possible between the host controller 103 and the device controller 153.

[0094] As described above, in Embodiment 3, while the connection of the cable 121 by the CC line is not detected and the VBUS power supply is not performed, the sink device 451 outputs a connection notification signal to the USB2.0 communication line. When the source device 401 detects the connection notification signal, it determines the plug surface and switches the USB communication path according to the plug surface. In addition, the source device 401 returns a connection response and enables the VBUS power supply. Thereafter, the sink device 451 receives the VBUS power supply, determines the plug surface from the connection response, and switches the USB communication path according to the determined plug surface. In addition, the sink device 451 stops outputting the connection notification signal, enables the USB communication function, and when the connection notification signal is no longer detected by the source device 401, the source device 401 enables the USB communication function.

[0095] Thus, when the connection of the cable 121 by the CC line is not detected, the connection of the cable 121 can be detected by using the USB2.0 communication line for alternative detection. Furthermore, the USB communication path can be correctly switched by detecting the plug surface. Therefore, USB3.2 communication and USB2.0 communication become possible.

[0096] Note that in Embodiment 3, in addition to the above-described configuration, a configuration in which the relationship between the "connection notification detection unit 402 and connection response unit 403 of the source device 401" and the "connection notification unit 452 and plug surface detection unit 453 of the sink device 451" is swapped is also realizable.

[0097] <Embodiment 4> In Embodiments 1 to 3, the source device and the sink device are connected by a cable compatible with USB Type-C. On the other hand, in Embodiment 4, the source device and the sink device are connected by a cable that changes USB Type-A to Type-C (USB Type-A / USB Type-C conversion cable). The source device has a USB Type-A port, and the sink device has a USB Type-C port.

[0098] FIG. 7 is a configuration diagram of a communication system 700 according to Embodiment 4. The communication system 700 includes a source device 701 having a USB Type-A host port and a sink device 751 having a USB Type-C device port.

[0099] The source device 701 includes a first CPU 702, a host controller 703, and a USB Type-A port 704.

[0100] The sink device 751 includes a second CPU 152, a device controller 153, a second control unit 154, a second multiplexer 155, a multiplexer control unit 752, and a second port 157.

[0101] The USB Type-A port 704 and the second port 157 are connected by a conversion cable 712. The conversion cable 712 is a cable that connects a USB Type-A port and a USB Type-C port. The conversion cable 712 conforms to the USB Type-C standard. A 56 kΩ pull-up resistor is implemented between the VBUS line and the CC line in the cable plug of the conversion cable 712.

[0102] The second CPU 152, the device controller 153, the second control unit 154, and the second multiplexer 155 have the same functions as the components with the same names in Embodiment 1.

[0103] The multiplexer control unit 752 is an inversion control unit that inverts the plug surface signal output from the second control unit 154 to the second multiplexer 155 according to the control of the second CPU 152.

[0104] Next, the process of realizing USB communication will be described using the flowchart of FIG. 8. Note that the flowchart of FIG. 8 is a flowchart for explaining the process of the sink device 751. Since the process of the source device 701 is the same as the general process of a device having a USB Type-A port, the description of the process of the source device 701 will be omitted.

[0105] In step S801, the second control unit 154 attempts to detect the connection of the cable based on the CC1 / CC2 terminal voltage. In Embodiment 4, both the conversion cable 712 and the cable 121 can be connected to the sink device 751. Therefore, in the following description, when the type of the cable is not specified, the "cable" will not be numbered. If the connection of the cable is detected, the process proceeds to step S802. If the connection of the cable is not detected, the process proceeds to step S803.

[0106] In step S802, since there is no disconnection in the CC line, the second control unit 154 shifts to the normal operation.

[0107] In step S803, the second control unit 154 attempts to detect VBUS power supply. If VBUS power supply is not detected, and the connection of the cable based on the CC1 / CC2 terminal voltage has not been detected either, it means it is not in a state of being connected to the source device 701. Therefore, in this case, the process returns to step S801. If VBUS power supply is detected, the process proceeds to step S804.

[0108] The source device 701 has a USB Type-A port. Therefore, without detecting the connection of the cable through the CC line, the host controller 703 turns on the VBUS switch to enable VBUS power supply. Thus, even if a connection failure occurs in the CC line, the sink device 751 can receive VBUS power supply. That is, when the connection of the cable based on the CC1 / CC2 terminal voltage of the second control unit 154 has not been detected and VBUS power reception has been detected, there is a possibility that the USB Typa-A / USB Type-C conversion cable 712 is connected.

[0109] In step S804, the second CPU 152 enables the USB communication function of the device controller 153. When the connection notification function is in an enabled state, the switch of the connection notification unit 156 is turned on, and a connection notification signal is output.

[0110] In step S805, the host controller 703 turns on the VBUS power supply. Also, the host controller 703 determines whether the USB2.0 communication between the host controller 703 and the device controller 153 is in a link-up state (a state where USB2.0 communication can be executed). If it is determined that the USB2.0 communication is in a link-up state, the process proceeds to step S806. If it is determined that the USB2.0 communication is not in a link-up state, the process of step S805 is repeated.

[0111] In step S806, host controller 703 determines whether the USB3.2 communication is in a link-up state. Here, assume that the host controller 703 supports USB3.2 communication. In this case, if the setting of the plug surface of the second multiplexer 155 matches the plug surface of the conversion cable 712 connected to the actual second port 157, the USB3.2 communication path from the host controller 703 to the device controller 153 is connected. Therefore, in such a case, the USB3.2 communication is in a link-up state. If it is determined that the USB3.2 communication is in a link-up state, the process proceeds to step S810. If it is determined that the USB3.2 communication is not in a link-up state, the process proceeds to step S807. Note that the device controller 153 notifies the second CPU 152 whether the USB3.2 communication is in a link-up state.

[0112] In step S807, in response to the notification that the USB3.2 communication is not in a link-up state, the second CPU 152 outputs a signal (inversion signal) instructing the multiplexer control unit 752 to invert the plug surface signal. When the multiplexer control unit 752 acquires the inversion signal, it inverts the logic ("0" or "1" value) of the plug surface signal output from the second control unit 154 to the second multiplexer 155. As a result, the setting of the plug surface of the second multiplexer 155 is inverted. Therefore, even if the setting of the plug surface of the second multiplexer 155 does not match the plug surface of the conversion cable 712 connected to the actual second port 157, the USB3.2 communication path from the host controller 703 to the device controller 153 is connected.

[0113] In step S808, it is determined again whether the USB3.2 communication is in a link-up state. If it is determined that the USB3.2 communication is in a link-up state, the process proceeds to step S810. If it is determined that the USB3.2 communication is not in a link-up state, the process proceeds to step S809.

[0114] In step S809, the host controller 703 starts USB2.0 communication.

[0115] In step S810, the host controller 703 starts USB3.2 communication.

[0116] As described above, in Embodiment 4, when the USB2.0 communication is in the link-up state and the USB3.2 communication is not in the link-up state, the multiplexer control unit 752 switches the signal path of the second multiplexer 155. As a result, even if the connection of the cable by the CC line is not detected, when receiving VBUS power supply, USB3.2 and USB2.0 communications become possible.

[0117] (Modification example) It is possible to combine Embodiment 4 with Embodiments 1 to 3. For example, when combining Embodiment 4 and Embodiment 2, as shown in FIG. 9, the sink device 951 further has the multiplexer control unit 752 according to Embodiment 4 in addition to the configuration of the sink device 151.

[0118] Then, the processing according to the flowchart of FIG. 10, which is a combination of the flowchart of FIG. 3 of Embodiment 2 and the flowchart of FIG. 8 of Embodiment 4, is executed.

[0119] In such an example, when VBUS power supply is not detected in step S352, it is not determined as a connection abnormality, and after proceeding to step S804, the link-up state of USB communication is determined in steps S805 and S806. As a result, the sink device 951 can perform USB3.2 communication or USB2.0 communication even when a connection failure occurs in the CC line and the connection by the CC line cannot be detected due to the connection of the cable 121 or the conversion cable 712.

[0120] As described above, the present invention has been described in detail based on its preferred embodiments. However, the present invention is not limited to these specific embodiments, and various forms within the scope not departing from the gist of the present invention are also included in the present invention. Some of the above-described embodiments may be appropriately combined.

[0121] Also, in the above, “when A is greater than or equal to B, proceed to step S1, and when A is less than B, proceed to step S2” may be read as “when A is greater than B, proceed to step S1, and when A is less than or equal to B, proceed to step S2”. Conversely, “when A is greater than B, proceed to step S1, and when A is less than or equal to B, proceed to step S2” may be read as “when A is greater than or equal to B, proceed to step S1, and when A is less than B, proceed to step S2”. Therefore, as long as there is no contradiction, “A or more” may be read as “greater than (higher; longer; more) than A”, and “A or less” may be read as “less than (lower; shorter; less) than A”. And “greater than (higher; longer; more) than A” may be read as “A or more”, and “less than (lower; shorter; less) than A” may be read as “A or less”.

[0122] Note that each functional part of each of the above embodiments (each modification example) may be individual hardware, or may not be. The functions of two or more functional parts may be realized by common hardware. Each of the multiple functions of one functional part may be realized by individual hardware. Two or more functions of one functional part may be realized by common hardware. Also, each functional part may be realized by hardware such as an ASIC, FPGA, DSP, etc., or may not be. For example, the device may have a processor and a memory (storage medium) in which a control program is stored. And the functions of at least some of the functional parts of the device may be realized by the processor reading out and executing the control program from the memory.

[0123] (Other Embodiments) The present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiment to a system or apparatus via a network or a storage medium, and causing one or more processors in a computer of the system or apparatus to read and execute the program. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

[0124] The disclosure of the above embodiment includes the following configurations, methods, programs, and media. (Configuration 1) A communication system having a first device and a second device that can communicate with each other by being connected by a USB (Universal Serial Bus) cable having a first communication line, a second communication line, and a third communication line, when the first device and the second device are connected by the first communication line, USB communication is possible on the second communication line, the first device determination means for determining whether or not it is connected to the second device by the first communication line, when it is not determined by the determination means that it is connected to the second device by the first communication line, first control means for controlling to output a first signal to the third communication line, and has the second device detection means for detecting the first signal when the first signal is output to the third communication line, detection means for detecting that a connection failure has occurred in the first communication line when the detection means detects the first signal, and A communication system characterized by the above. (Configuration 2) The first communication line is a CC (Configuration Channel) line, The communication system according to Configuration 1, characterized by the above. (Configuration 3) The determination means determines whether the first device is connected to the second device via the first communication line according to a voltage change of a terminal connected to the first communication line. The communication system according to Configuration 1 or 2, characterized in that. (Configuration 4) When the detection means detects that a connection failure has occurred in the first communication line in the first case, the second device further includes notification means for notifying the user that a connection failure has occurred in the first communication line. The communication system according to any one of Configurations 1 to 3, characterized in that. (Configuration 5) When the detection means detects that a connection failure has occurred in the first communication line in the first case, the second device further includes second control means for controlling the USB communication between the first device and the second device to be performed via the third communication line. The communication system according to any one of Configurations 1 to 4, characterized in that. (Configuration 6) The USB cable includes a first plug for connecting to the first device and a second plug for connecting to the second device. The first device has first direction detection means for detecting the direction in which the first plug is connected to the first device, and the second device further has second direction detection means for detecting the direction in which the second plug is connected to the second device. In the first case, the first control means controls the USB communication in the third communication line based on the direction in which the first plug is connected to the first device. In the first case, the second control means controls the USB communication in the third communication line based on the direction in which the second plug is connected to the second device. The communication system according to Configuration 5, characterized in that. (Configuration 7) The first device has a first multiplexer for selecting a signal connected to the third communication line from a plurality of signals. The second device has a second multiplexer that selects a signal among the plurality of signals and is connected to the third communication line. In the first case, the first control means realizes USB communication on the third communication line by controlling the first multiplexer. In the first case, the second control means realizes USB communication on the third communication line by controlling the second multiplexer. The communication system according to Configuration 6, characterized in that. (Configuration 8) The first orientation detection means detects the orientation in which the first plug is connected to the first device based on the first signal. The second orientation detection means detects the orientation in which the second plug is connected to the second device based on the first signal. The communication system according to Configuration 6 or 7, characterized in that. (Configuration 9) In the first case, the first control means further controls so that USB communication between the first device and the second device is performed by the second communication line based on the orientation in which the first plug is connected to the first device. In the first case, the second control means further controls so that USB communication between the first device and the second device is performed by the second communication line based on the orientation in which the second plug is connected to the second device. The communication system according to any one of Configurations 6 to 8, characterized in that. (Configuration 10) The first control means When it is not determined by the determination means that it is connected to the second device by the first communication line and no specific power supply from the second device is detected, the first signal is output to the third communication line. When it is not determined by the determination means that the first communication line is connected to the second device, and when power supply of the specific power from the second device is detected, control is performed so as not to output the first signal to the third communication line. The communication system according to any one of Configurations 1 to 9, characterized in that. (Configuration 11) The USB cable is a cable compatible with USB Type-C. The communication system according to any one of Configurations 1 to 10, characterized in that. (Configuration 12) The first control means When it is not determined by the determination means that the first communication line is connected to the second device, and when power supply of the specific power from the second device is detected, the first signal is output to the third communication line. When it is not determined by the determination means that the first communication line is connected to the second device, and when power supply of the specific power from the second device is not detected, control is performed so as not to output the first signal to the third communication line. The communication system according to any one of Configurations 1 to 9, characterized in that. (Configuration 13) The USB cable is a cable connecting a USB Type-A port and a USB Type-C port. The communication system according to Configuration 12, characterized in that. (Method) A control method for a communication system having a first device and a second device capable of communicating with each other, connected by a USB (Universal Serial Bus) cable having a first communication line, a second communication line, and a third communication line, When the first device and the second device are connected by the first communication line, USB communication is possible on the second communication line, In the first device, a determination step of determining whether or not it is connected to the second device via the first communication line; In the first device, an output step of outputting a first signal to the third communication line when it is not determined in the determination step that it is connected to the second device via the first communication line; In the second device, a detection step of detecting the first signal when the first signal is output to the third communication line; In the second device, a detection step of detecting that a connection failure has occurred in the first communication line when the first signal is detected in the detection step; A control method for a communication system, characterized by comprising the above. (Program) A program for causing a computer to function as each means of the communication system according to any one of Configurations 1 to 13. (Medium) A computer-readable storage medium storing a program for causing a computer to function as each means of the communication system according to any one of Configurations 1 to 13.

Explanation of Signs

[0125] 100: Communication system, 101: Source device, 151: Sink device, 104: First control unit, 106: Connection notification detection unit, 154: Second control unit, 156: Connection notification unit

Claims

1. A communication system having a first device and a second device capable of communicating with each other, connected by a USB (Universal Serial Bus) cable having a first communication line, a second communication line, and a third communication line, wherein when the first device and the second device are connected by the first communication line, USB communication is possible on the second communication line, and the first device includes determination means for determining whether or not it is connected to the second device by the first communication line, and first control means for controlling to output a first signal to the third communication line when it is not determined by the determination means that it is connected to the second device by the first communication line, and the second device includes detection means for detecting the first signal when the first signal is output to the third communication line, and detection means for detecting that a connection failure has occurred in the first communication line when the detection means detects the first signal, and a communication system characterized by the above.

2. The first communication line is a CC (Configuration Channel) line. The communication system according to claim 1, characterized by the above.

3. The determination means determines whether or not it is connected to the second device by the first communication line according to a voltage change of a terminal connected to the first communication line. The communication system according to claim 1, characterized by the above.

4. When the second device detects, by the detection means, that a connection failure has occurred in the first communication line in a first case, the second device further includes notification means for notifying the user that a connection failure has occurred in the first communication line. The communication system according to claim 1, characterized by the above.

5. When the second device detects, by the detection means, that a connection failure has occurred in the first communication line in a first case, the second device further includes second control means for controlling USB communication between the first device and the second device to be performed by the third communication line. The communication system according to claim 1, characterized by the above.

6. The USB cable includes a first plug for connecting to the first device and a second plug for connecting to the second device. The first device has first orientation detection means for detecting the orientation in which the first plug is connected to the first device, and the second device further has second orientation detection means for detecting the orientation in which the second plug is connected to the second device. In the first case, the first control means controls USB communication on the third communication line based on the orientation in which the first plug is connected to the first device. In the first case, the second control means controls USB communication on the third communication line based on the orientation in which the second plug is connected to the second device. The communication system according to claim 5, characterized in that.

7. The first device has a first multiplexer for selecting a signal connected to the third communication line from among a plurality of signals. The second device has a second multiplexer for selecting a signal connected to the third communication line from among the plurality of signals. In the first case, the first control means realizes USB communication on the third communication line by controlling the first multiplexer. In the first case, the second control means realizes USB communication on the third communication line by controlling the second multiplexer. The communication system according to claim 6, characterized in that.

8. The first orientation detection means detects the orientation in which the first plug is connected to the first device based on the first signal. The second orientation detection means detects the orientation in which the second plug is connected to the second device based on the first signal. The communication system according to claim 6, characterized in that.

9. In the first case, the first control means further controls such that USB communication between the first device and the second device is performed via the second communication line based on the orientation in which the first plug is connected to the first device. In the first case, the second control means further controls such that USB communication between the first device and the second device is performed via the second communication line based on the orientation in which the second plug is connected to the second device. The communication system according to claim 6, characterized in that.

10. The first control means When it is not determined by the determination means that the connection to the second device is made via the first communication line, and when power supply of specific power from the second device is not detected, the first signal is output to the third communication line. When it is not determined by the determination means that the connection to the second device is made via the first communication line, and when power supply of the specific power from the second device is detected, control is performed so as not to output the first signal to the third communication line. The communication system according to claim 1, characterized in that.

11. The USB cable is a cable corresponding to USB Type-C. The communication system according to claim 1, characterized in that.

12. The first control means. When it is not determined by the determination means that the connection to the second device is made via the first communication line, and when power supply of specific power from the second device is detected, the first signal is output to the third communication line. When it is not determined by the determination means that the connection to the second device is made via the first communication line, and when power supply of the specific power from the second device is not detected, control is performed so as not to output the first signal to the third communication line. The communication system according to claim 1, characterized in that.

13. The USB cable is a cable connecting a USB Type-A port and a USB Type-C port. The communication system according to claim 12, characterized in that.

14. A control method for a communication system having a first device and a second device capable of communicating with each other by being connected by a USB (Universal Serial Bus) cable having a first communication line, a second communication line, and a third communication line, When the first device and the second device are connected by the first communication line, USB communication is possible on the second communication line. A determination step of determining in the first device whether or not the first device is connected to the second device via the first communication line. An output step of outputting a first signal to the third communication line when it is not determined in the determination step that the first device is connected to the second device via the first communication line in the first device. In the second device, when the first signal is output to the third communication line, a detection step of detecting the first signal; In the second device, when the first signal is detected in the detection step, a detection step of detecting that a connection failure has occurred in the first communication line; A control method for a communication system, characterized by comprising:

15. A program for causing a computer to function as each means of the communication system according to any one of claims 1 to 13.

16. A computer-readable storage medium storing a program for causing a computer to function as each means of the communication system according to any one of claims 1 to 13.

Images