JP2020065188A - Communication device, method of controlling the same, and program - Google Patents

Abstract

To reduce power consumption while executing time synchronization with another communication device.SOLUTION: A communication device receives a first synchronization message from another communication device, transmits a second synchronization message to the other communication device, receives a third synchronization message transmitted from the other communication device in response to the transmitted second synchronization message, and performs time synchronization with the other communication device on the basis of the received first and third synchronization messages. After a mode is switched from a first operation mode to a second operation mode in which power consumption is lower than that in the first operation mode, control is performed so that a frequency of transmission of the second synchronization message to the other communication device becomes lower than that during a time period when the communication device operates in the first operation mode.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a communication device capable of time synchronization with another communication device.

In recent years, video display has become higher in quality and larger in screen size, and a video that realizes high-resolution video display exceeding the resolution of a single video output device by using multiple video output devices. Display systems are known.
In such a video display system, a plurality of video output devices (hereinafter referred to as “projectors”) are connected to each other on a network and receive video data distributed from a video distribution device via the network. To project. High-resolution image display is realized by arranging the images projected from a plurality of projectors side by side to form one projected image.

As described above, in order to synchronize the projection of images from a plurality of projectors to form one projected image, it is necessary to synchronize the time among all the projectors. As a mechanism for performing such time synchronization between a plurality of devices on the network, there is a time synchronization protocol (Precision Time Protocol: PTP) defined by IEEE 1588 of the Institute of Electrical and Electronics Engineers (IEEE).
In PTP, first, a plurality of slave devices respectively receive a periodic synchronization message transmitted from one master clock device. The slave device then sends a periodic delay request message to the master clock device and receives a delay response message in response to the delay request message from the master clock device.
The slave device analyzes the information acquired by exchanging these messages, estimates the transmission delay time and time offset of the network, corrects the time of the self device, and synchronizes with the time of the master clock device. A plurality of slave devices each perform time synchronization with the master clock device in this manner, whereby time synchronization is performed for all slave devices (projectors) in the system.

Patent Document 1 discloses a communication control device that performs time synchronization with a plurality of communication control devices connected by a network using such a time synchronization procedure according to PTP.
Specifically, the communication control device of Patent Document 1 measures the reception intervals of request packets from a plurality of communication control devices, and based on the measured reception intervals of the request packets, any of the plurality of communication control devices is detected. Detects collision of request packets from the communication control device. According to the detection result of the request packet collision, the communication control device determines whether or not to send a response packet to the request packet.

  When a collision of request packets is detected, the communication control device also transmits a re-request packet for requesting time synchronization to the communication control device that transmitted the request packet in which the collision was detected.

JP, 2014-78781, A

However, the communication control device described in Patent Document 1 corresponds to the master clock device on the side that receives the delay request message in PTP, and does not consider the control of the time synchronization message transmission on the slave device side. .
For example, in the case where a plurality of projectors are synchronously linked to form one projection image as described above, time synchronization with other projectors is not necessarily required while each projector as a slave device is not projecting an image. Conventionally, even while the time synchronization is not required, the slave device periodically transmits a delay request message to the master clock device in order to synchronize the time, which may consume unnecessary power. was there.

  The present invention has been made in view of the above problems, and an object thereof is to reduce power consumption while performing time synchronization with another communication device.

  In order to solve the above problems, according to an aspect of a communication device of the present invention, a first receiving unit that receives a first synchronization message from another communication device and a second synchronization to the other communication device. Transmitting means for transmitting a message, second receiving means for receiving a third synchronization message transmitted from the other communication device in response to the second synchronization message transmitted by the transmitting means, and reception Synchronization means for time-synchronizing with the other communication device based on the generated first synchronization message and the third synchronization message, a first operation mode, and power consumption lower than that of the first operation mode Switching means for switching the operation of the communication device between the second operation mode and the second operation mode; and the other communication after the switching from the first operation mode to the second operation mode by the switching means. And a control means for controlling the transmitting means so that the frequency of transmitting the second synchronization message to the device is lower than that during the operation of the communication apparatus in the first operation mode. It

  According to the present invention, it is possible to reduce power consumption while performing time synchronization with another communication device.

Block diagram showing an example of a network configuration of the projection system according to the present embodiment Block diagram showing an example of the hardware and functional configuration of a projector that is a slave device The figure which shows an example of the process sequence of the time synchronization process performed between a master clock device and a projector. 3 is a flowchart showing an example of an operation processing procedure of the projector according to the first embodiment. A flowchart showing an example of an operation processing procedure of the projector in the first embodiment together with FIG. FIG. 3 is a diagram for explaining a difference in operation between operation modes of respective units configuring the projector. Diagram illustrating the differences in communication modes of the projector for each operation mode 6 is a flowchart showing an example of the operation processing procedure of the projector in the second embodiment. A flowchart showing an example of the operation processing procedure of the projector in the second embodiment together with FIG. FIG. 10 is a diagram showing an example of a configuration of application execution history information referenced by a projector in the second embodiment.

  Hereinafter, an embodiment for carrying out the present invention will be described in detail with reference to the accompanying drawings. The embodiment described below is an example as a means for realizing the present invention, and should be appropriately modified or changed according to the configuration of the device to which the present invention is applied and various conditions. It is not necessarily limited to the embodiment. Moreover, not all combinations of the features described in the present embodiment are essential to the solving means of the present invention. The same configurations will be described with the same reference numerals.

(Embodiment 1)
In the present embodiment, an example will be described in which the communication device is a slave device that synchronizes with the time of a master clock device connected via a network, using a time synchronization protocol (Precision Time Protocol: PTP) defined by IEEE1588. . However, the time synchronization protocol that can be used in this embodiment is not limited to PTP, and NTP (Network Network Protocol), SNTP (Simple Network Time Protocol), or the like may be used, for example.

  Further, in the present embodiment, the “first operation mode” may be a normal mode in which a normal application including an application requiring time synchronization can operate. On the other hand, the “second operation mode” is an operation mode that consumes less power than the first operation mode, and for example, activates only a communication function with a network or only a part of functions including a communication function with a network. Network standby mode.

<Network configuration of this embodiment>
FIG. 1 is a diagram showing an example of a network configuration of a projection system according to this embodiment.
The projection system 100 shown in FIG. 1 includes slave devices 1a, 1b, 1c, and 1d, a master clock device 2, and a slave device 3. The slave devices 1a, 1b, 1c, and 1d, the master clock device 2, and the slave device 3 are connected to each other via a network 4.

In FIG. 1, slave devices 1a, 1b, 1c, and 1d may be projectors that project images 5a, 5b, 5c, and 5d, respectively. Although four projectors are shown as an example in FIG. 1, the number of projectors is not limited to four and may be two or more.
The master clock device 2 has a time that serves as a reference for the entire projection system 100, and executes time synchronization with each of the slave devices 1a to 1d and 3.
The slave device 3 may be a video distribution device (for example, a PC) that distributes video data projected by the projectors 1a to 1d.

Each video data distributed from the video distribution device 3 is received by each of the projectors 1 a to 1 d and projected on the screen 5. By arranging the four projected images 5a to 5d to form one image, a high-resolution image display over the entire screen 5 is realized.
In order to realize such high-resolution image display, it is necessary for the projectors 1a to 1d to project on the screen 5 at the timings synchronized with each other. In the present embodiment, therefore, the time synchronization sequence is executed between the master clock device 2 and the plurality of slave devices 1a to 1d and 3 accommodated in the projection system 100 to synchronize the time in the projection system 100. I am letting you.

<Projector hardware and functional configuration>
FIG. 2 is a diagram showing an example of a hardware configuration and a functional configuration of projectors 1a, 1b, 1c, and 1d (hereinafter collectively referred to as “projector 1”) that are slave devices according to the present embodiment. Note that any of the projectors 1a, 1b, 1c, and 1d may have the same structure shown in FIG.
Among the function modules of the projector 1 shown in FIG. 2, for functions realized by software, a program for providing the function of each function module is stored in a memory such as a ROM, read out to the RAM, and executed by the CPU. It is realized by doing. Regarding the function realized by the hardware, for example, by using a predetermined compiler, a dedicated circuit may be automatically generated on the FPGA from a program for realizing the function of each functional module. FPGA is an abbreviation for Field Programmable Gate Array. Alternatively, a Gate Array circuit may be formed in the same manner as the FPGA and realized as hardware. Moreover, you may make it implement | achieve by ASIC (Application Specific Integrated Circuit). Note that the configuration of the functional blocks shown in FIG. 1 is an example, and a plurality of functional blocks may constitute one functional block, or one of the functional blocks may be divided into blocks that perform a plurality of functions. Good.

The projector 1 includes a control unit 11, a storage device 12, a temporary storage unit 13, a projection unit 14, a timer / clock unit 15, a communication I / F 16, an operation clock generation unit 17, and a power supply unit 18.
The functional blocks 12 to 18 inside the projector 1 are controlled by the control unit 11, respectively. Power is supplied to each of the functional blocks 11 to 17 inside the projector 1 by the power supply unit 18. Further, an operation clock is supplied from the operation clock generation unit 17 to each of the functional blocks 11 to 16 and 18 inside the projector 1.
In this embodiment, the functional blocks 11 to 18 inside the projector 1 operate in either a normal mode or a standby mode, which will be described later.

The control unit 11 executes a program stored in the storage device 12 and controls each of the functional blocks 12 to 18 to operate.
The storage device 12 stores various programs executed by the control unit 11 and various data. Various types of data stored in the storage device 12 include the type of application executed during operation, the operating status during execution, and the like. The storage device 12 has a memory structure in which the information stored therein is not erased even when the power of the projector 1 is shut down.

The temporary storage unit 13 is a storage unit that temporarily stores various information in executing the functions of the functional blocks 11 to 18 of the projector 1, and is configured by a semiconductor memory or the like. The temporary storage unit 13 has a memory structure that erases the information stored therein when the power is shut down.
The temporary storage unit 13 mainly temporarily stores video data received from the video distribution device (PC) 3, which is another slave device, and can also store some programs.
In the present embodiment, particularly when the projector 1 is operating in the standby mode, the control unit 11 executes the program stored in the temporary storage unit 13 to perform various controls. The temporary storage unit 13 also stores the values of the transmission delay time and the time offset of the network obtained by executing the time synchronization sequence described later with reference to FIG.

The projection unit 14 includes an image display element, a lens, and a light source, and projects an image displayed by the image display element onto the screen 5 or the like using the light source and the lens.
The timer / clock section 15 is composed of a clock function that indicates the date and time, and a timer that can measure a certain fixed period. The timer / clock section 15 provides necessary information such as date and time, time, and timer according to an instruction from the control section 11. The timer / clock unit 15 also uses the values of the transmission delay time and the time offset of the network obtained by executing the time synchronization sequence described later with reference to FIG. 3 to synchronize the time of the entire projection system 100. It also has a function to correct the time.

  The communication I / F 16 is a communication interface that connects to a wired network 10 such as a LAN (Local Area Network) that complies with the IEEE802.3-related standards. The projector 1 is connected to the network 4 shown in FIG. 1 via the communication I / F 16. In the present embodiment, the communication I / F 16 is used as a communication interface when receiving video data from the video distribution device 3 and executing the time synchronization sequence shown in FIG. 3 with the master clock device 2. It

Alternatively, the communication I / F 16 may be configured by Host_IF that connects to a wireless LAN module that conforms to the IEEE 802.11 related standards. This Host_IF may be USB (Universal Serial Bus) or SDIO (Secure Digital Input / Output). Alternatively, Host_IF may be PCIe (Peripheral Component Interconnect-Express).
The control unit 11 uses the communication I / F 16 as an interface for controlling the control LSI mounted on these wireless LAN modules. In this case, the projector 1, which is a slave device, is connected to the video distribution device 3 and the master clock device 2 having the system configuration shown in FIG. 1 via an access point.

The operation clock generation unit 17 supplies the operation clock internally generated to each of the functional blocks 11 to 16 and 18. In the present embodiment, the operation clock generation unit 17 can generate two or more operation clocks having different frequencies. The generated two or more operation clocks having different frequencies are selected by the control of the control unit 11 and are supplied to the respective functional blocks 11 to 16 and 18.
The operation clock generation unit 17 supplies an operation clock having a lower frequency in the standby mode than in the normal mode. In this standby mode, it is also possible to individually stop the supply of the operation clock to each of the functional blocks 11 to 16 and 18 under the control of the control unit 11.

  The power supply unit 18 supplies power for operating the respective functional blocks 11 to 17 inside the projector 1. A switch that can turn on / off the power of the entire projector 1 is provided inside the projector 1, and the user can turn on / off the power by operating the switch. Further, it is possible to individually set the power supply on / off to each of the functional blocks 11 to 17 inside the projector 1. The on / off of the individual power supply is controlled by the control unit 11. Executed by

<Processing sequence for time synchronization>
FIG. 3 is a sequence chart showing an example of details of the processing procedure of the time synchronization executed between the master clock device 2 and each of the devices 1a to 1d and 3 which are slave devices in the system in the present embodiment. .
In the PTP defined in the IEEE1588 standard, four types of synchronization messages are defined for time synchronization between the master clock device 2 and each of the devices 1a to 1d and 3 which are slave devices in the system. These four types of synchronization messages are the Sync message, Follow_up message, Delay_Req message, and Delay_Resp message shown in FIG.
Among these, the Sync message and the Follow_up message are used to measure the communication delay from the master clock device 2 to each of the devices 1a to 1d and 3. On the other hand, the Delay_Req message and the Delay_Resp message are used to measure the communication delay from each of the devices 1a to 1d and 3 to the master clock device 2.
The Sync message is periodically transmitted from the master clock device 2, for example, once every two seconds. The Delay_Req message is periodically transmitted from the devices 1a to 1d and 3 which are slave devices in the normal mode, for example, once a minute. Hereinafter, the Delay_Req message transmitted from the slave device is also referred to as “delay request message” or “delay request”. The Sync message and the Follow_up message transmitted from the master clock device 2 can be collectively referred to as “Sync message”.

In S431, the master clock device 2 transmits a Sync message to each of the devices 1a to 1d and 3 at time T1.
In step S432, when the master clock device 2 transmits the Sync message, the master clock device 2 stores the time T1 at which the Sync message was transmitted.
In S433, the master clock device 2 then inserts the time T1 into the Follow_up message and transmits the message to the devices 1a to 1d and 3.

In S434, each of the devices 1a to 1d and 3 receives the Sync message from the master clock device 2 and stores the reception time T2. Each of the devices 1a to 1d and 3 also acquires the transmission time T1 of the Sync message from the Follow_up message that is continuously received.
Next, in S435, each of the devices 1a to 1d and 3 transmits a Delay_Req message to the master clock device 2 at time T3.
In S436, each of the devices 1a to 1d and 3 stores the time T3 at which the Delay_Req message was transmitted.

In S437, when the master clock device 2 receives the Delay_Req message, the master clock device 2 stores the reception time T4 of the Delay_Req message.
In S438, the master clock device 2 then inserts the reception time T4 into the Delay_Resp message and transmits the message to the devices 1a to 1d and 3, respectively.
Each of the devices 1a to 1d and 3 receives the Delay_Resp message from the master clock device 2 and acquires the reception time T4 from this Delay_Resp message.

  By executing the above sequence, each of the devices 1a to 1d and 3 acquires the message transmission / reception times T1 to T4, respectively. As a result, it becomes possible to calculate the transmission delay and time offset of the network between the master clock device 2 and each of the devices 1a to 1d, which are slave devices, and time synchronization as described below. .

  Here, the difference Tmsd between the Sync message transmission time T1 and the Sync message reception time T2 and the difference Tsmd between the Delay_Req message transmission time T3 and the Delay_Req message reception time T4 are respectively expressed by the following equations (1) and (2). As shown.

Tmsd = (T2 + Tms) -T1 = (T2-T1) + Tms (1)
Tsmd = T4- (T3 + Tms) = (T4-T3) -Tms (2)

In the above, Tms represents the time offset of each of the devices 1a to 1d and 3 with respect to the master clock device 2. Here, since the values of Tmsd and Tsmd cannot be obtained from the above equations (1) and (2), it is assumed that the communication paths are symmetrical and the transmission delay of the network is Td.
Tmsd = Tsmd = Td (3)

The transmission delay Td and the time offset Tms are obtained from the following equations (4) and (5) by solving the simultaneous equations of the equations (1), (2), and (3).
Td = ((T2-T1) + (T4-T3)) / 2 (4)
Tms = ((T4-T3)-(T2-T1)) / 2 (5)

  It is the devices 1a to 1d and 3 that are slave devices that must be time-synchronized with the master clock device 2. Therefore, each of the devices 1a to 1d and 3 which are slave devices derives the transmission delay and the time offset based on the above equations (4) and (5), respectively, and corrects the time of its own device. , And time synchronization with the master clock device 2.

<Slave device operation mode switching operation procedure>
FIG. 4 and FIG. 5 show an example of the processing procedure of the operation mode switching process of the projector 1 which is a slave device and the time synchronization process executed by connecting to the master clock device 2 via the network in the present embodiment. It is a flowchart shown. In the following, an example will be described in which the projector 1 uses PTP defined by the IEEE1588 standard as a time synchronization protocol with the master clock device 2, but the present embodiment is also applicable to protocols other than the PTP protocol. In the following, an example will be described in which the control unit 11 of the projector 1 variably controls the timing at which the Delay_Req (delay request) message illustrated in FIG. 3 is transmitted according to the switching of the operation mode.

In S41, the projector 1 makes a state transition from the power-off state in which all the functions of the projector 1 are stopped, on condition that the user has performed an operation to turn on the power. When the power-on operation is executed (S41: Y), the process proceeds to S42, while when the power-on operation is not executed (S41: N), the process returns to S41 and the current state is maintained, and the process of S41 is repeated.
The operation of turning on the power, which should be determined in S41, is, for example, an operation of connecting the power supply to the power supply unit 18 of the projector 1 by the user, or turning on the power-on / off switch provided in the power supply unit 18. Including switching operations.

In S42, the projector 1 shifts to the normal mode. Specifically, first, the storage device 12 of the projector 1 is activated, and the control unit 11 executes a predetermined program stored in the storage device 12 to start the control of each functional block of the projector 1.
The control unit 11 makes necessary settings for each functional block so that various applications can be executed.

  In step S43, the control unit 11 of the projector 1 executes the time synchronization sequence shown in FIG. 3 via the timer / clock unit 15 to synchronize the time of the own device with the master clock device 2 included in the projection system 100. Correct to the time you did. Specifically, the control unit 11 of the projector 1 receives the Sync message and the Follow_up message from the master clock device 2. After that, the control unit 11 of the projector 1 transmits a Delay_Req message to the master clock device 2 and receives a Delay_Resp message as a response from the master clock device 2. After that, the control unit 11 of the projector 1 corrects the time of its own device by calculating the transmission delay and the time offset of the network from the synchronization message and the transmission / reception time of the synchronization message.

In the present embodiment, the control unit 11 of the projector 1 transmits the Delay_Req (delay request) message transmitted to the master clock device 2 during the operation in the normal mode and in the standby mode described below. Control to be different.
Specifically, while operating in the normal mode, the control unit 11 of the projector 1 may transmit a Delay_Req message to the master clock device 2 each time a Sync message and a Follow_up message are received from the master clock device 2.

  Alternatively, in the normal mode, the Delay_Req message may be transmitted to the master clock device 2 after receiving the Sync message and the Follow_up message from the master clock device 2 a predetermined number of times. Alternatively, the Delay_Req message may be transmitted to the master clock device 2 each time the Sync message and the Follow_up message are received from the master clock device 2 when the time accuracy of the own device is deteriorated to a certain level or more. In any case, the control unit 11 of the projector 1 controls the transmission of the Delay_Req message so that the frequency of transmitting the Delay_Req message is lower during the standby mode than when operating in the normal mode. .

In S44, the control unit 11 of the projector 1 determines whether the user has performed an operation of activating a predetermined application, or whether the predetermined application is already being executed. If the user has performed an operation of activating a predetermined application, or if the predetermined application is already being executed (S44: Y), the process proceeds to S45. On the other hand, when the predetermined application is not being executed and the operation to start is not executed (S44: N), S45 is skipped and the process proceeds to S51.
The predetermined application to be determined in S44 includes an application that does not operate normally unless the time is synchronized in the system, such as the projection system 100 shown in FIG.

  Note that in FIG. 4, the time synchronization sequence is executed in S43 prior to S44, and the time synchronization is completed before the predetermined application is activated. By executing S43 and S44 in such an order, the time synchronization has already been executed at the time of shifting to the normal mode. Therefore, when the application start operation that requires the time synchronization is performed, the application is quickly started. can do.

  In S45, the projection unit 14 of the projector 1 executes an application or the like that projects the video data received from the video distribution device 3 onto the screen 5 as shown in FIG. In S43, since the time of each of the projectors 1a to 1d has already been synchronized with the master clock device 2, it is possible to project the image data from the plurality of projectors 1a to 1d onto the screen 5 to form one image. Becomes

  Referring to FIG. 5, in S51, the state transition is performed on condition that the user has performed an operation of turning off the power. When the power-off operation is executed (S51: Y), the process proceeds to S58 to execute the shutdown process, while when the power-off operation is not executed (S51: N), the process proceeds to S52.

In S52, the control unit 11 of the projector 1 determines whether or not the operation of shifting to the standby mode has been performed by the user. If the operation to shift to the standby mode is performed by the user (S52: Y), the process proceeds to S52. On the other hand, if the operation to shift to the standby mode is not performed (S52: N), the process returns to S43 and the processes from S43 to S51. repeat.
Through S51 and S52, the time synchronization sequence of S43 is continuously executed until the user performs an operation of turning off the power or an operation of shifting to the standby mode.

In S53, the control unit 11 of the projector 1 stops the application currently being executed, for example, which projects the video data received from the video distribution device 3 on the screen 5, and then shifts (switches) to the standby mode.
Specifically, the control unit 11 instructs the communication I / F 16 to stop the reception of the video data from the video distribution device 3, and instructs the projection unit 14 to stop the projection onto the screen 5. And stop the application.

In S54, the control unit 11 of the projector 1 sends Delay_Req (delay request) to the projector 1 to measure the transmission delay between the slave device and the master clock device in the time synchronization sequence shown in FIG. Stop sending messages.
In S53, the application that requires time synchronization in the system is already stopped, so the transmission of the Delay_Req (delay request) message for measuring the transmission delay may be stopped in S54. In the standby mode, it is required to suppress the power consumption to be low. Therefore, the power consumption can be reduced by stopping the transmission of the Delay_Req message, which is an unnecessary operation.

  Alternatively, in the standby mode, the Delay_Req (delay request) message may be transmitted at a lower frequency than when the time synchronization sequence is executed in S43 in the normal mode. Alternatively, in the standby mode, the transmission of the Delay_Req message may be stopped when the time precision of the own device is a certain precision or higher.

S55 is a state of operating in the standby mode, and during this standby mode, unnecessary operations are stopped so that the power consumption is lower than that in the normal mode.
In S55, the frequency of the operation clock of the entire projector 1 is set low by the control of the control unit 11. The control unit 11 may also shift the power supply of the functional blocks with large power consumption, such as the projection unit 14 and the storage device 12, to the state in which the power is also stopped. The control unit 11 may shift the timer / clock unit 15 and the communication I / F 16 to a state in which the functions are narrowed to such an extent that an activation packet or the like from the outside can be received. The operation control in the standby mode in S55 will be described later with reference to FIGS. 6 and 7.

In S56, the state transition is made on the condition that the user performs the operation of turning off the power. When the power-off operation is performed (S56: Y), the process proceeds to S58 to execute the shutdown process, while when the power-off operation is not performed (S56: N), the process proceeds to S57.
In S57, the control unit 11 of the projector 1 determines whether or not the operation of shifting to the normal mode has been performed by the user. When the operation of shifting to the normal mode is performed by the user (S57: Y), the process returns to S42 and the processing of S42 to S56 is repeated, while when the operation of shifting to the normal mode is not performed (S57: N), S54. The process returns to S54 to S56 and is repeated.
Through S56 and S57, the transmission stop of the Delay_Req (delay request) message in S54 is maintained until the user performs an operation of turning off the power or an operation of shifting (switching) to the normal mode.

  In S58, the projector 1 shifts to the instructed power-off state and shuts down. Specifically, the projector 1 terminates the program executed by the control unit 11 so that the storage device 12 can be stopped normally, and transfers a part of the information stored in the temporary storage unit 13 to the storage device 12. Write. After that, the projector 1 stops the supply of the operation clock and the power to each functional block, shifts to the power-off state in which all the functions are stopped, and completes the shutdown.

<Operation difference between normal mode and standby mode>
FIG. 6 is a diagram showing an example of a power supply state and an operation clock frequency depending on the operation modes of the respective functional blocks 11 to 16 inside the projector 1 which constitutes the slave device. As shown in FIG. 6, by controlling the power supply and operation clock frequency of each functional block, it is possible to reduce power consumption in the standby mode as compared with the normal mode. The numerical values shown in FIG. 6 are examples, and the present embodiment is not limited to the numerical values shown in FIG.

  During operation in the normal mode, the control unit 11 of the projector is supplied with power and is supplied with a high operation clock frequency of 400 MHz. On the other hand, the control unit 11 is supplied with power during operation in the standby mode, but is supplied with an operation clock frequency of 50 MHz, which is lower than that in the normal mode. As described above, in the standby mode, the operating clock is set to a frequency lower than that in the normal mode, so that the reduction of power consumption is prioritized over the operating performance.

  During operation in the normal mode, the storage device 12 of the projector 1 is supplied with power and is supplied with a high operation clock frequency of 400 MHz. On the other hand, while the storage device 12 is operating in the standby mode, both the power supply and the operation clock supply are stopped. As described above, in the standby mode, the power consumption is reduced by completely stopping the supply of the power supply and the operation clock.

  During operation in the normal mode, the temporary storage unit 13 of the projector 1 is supplied with power and is supplied with a high operation clock frequency of 400 MHz. On the other hand, the temporary storage unit 13 is supplied with power during operation in the standby mode, but is supplied with an operation clock frequency of 50 MHz, which is lower than that in the normal mode. As described above, in the standby mode, the operating clock is set to a frequency lower than that in the normal mode, so that the reduction of power consumption is prioritized over the operating performance.

  During operation in the normal mode, the projection unit 14 of the projector 1 is supplied with power and is supplied with a high operation clock frequency of 200 MHz. On the other hand, while the projection unit 14 is operating in the standby mode, both the power supply and the operation clock supply are stopped. As described above, in the standby mode, the power consumption is reduced by completely stopping the supply of the power supply and the operation clock.

  During operation in the normal mode, the timer / clock section 15 of the projector 1 is supplied with power and is supplied with a high operation clock frequency of 200 MHz. On the other hand, the timer / clock section 15 is supplied with power during operation in the standby mode, but is supplied with an operation clock frequency of 25 MHz, which is lower than that in the normal mode. As described above, in the standby mode, the operating clock is set to a frequency lower than that in the normal mode, so that the reduction of power consumption is prioritized over the operating performance.

  The communication I / F 16 of the projector 1 is supplied with power and is supplied with a high operation clock frequency of 200 MHz while operating in the normal mode. On the other hand, the communication I / F 16 is supplied with power during operation in the standby mode, but is supplied with a lower operation clock frequency than in the normal mode, such as 25 MHz for the operation clock. As described above, in the standby mode, the operating clock is set to a frequency lower than that in the normal mode, so that the reduction of power consumption is prioritized over the operating performance.

  As shown in the operation mode table 6 of FIG. 6 as an example, in the standby mode in which the projection application that requires time synchronization does not operate, it is not necessary to supply the power supply and the operation clock to the projection unit 14 and the storage device 12. Further, in the standby mode, it is sufficient if a specific packet can be received from another device connected via the network. Therefore, the operation clock frequency supplied to the control unit 11, the temporary storage unit 13, the timer / clock unit 15, and the communication I / F 16 which should be operated for receiving these packets is set lower than in the normal mode. Good.

  FIG. 7 is a diagram showing an example of a control pattern for the communication function and performance of the projector 1 constituting the slave device depending on the difference in operation mode. As shown in FIG. 7, in the standby mode, the power consumption can be reduced by limiting the communication function and performance as compared with the normal mode. The numerical values shown in FIG. 7 are examples, and the present embodiment is not limited to the numerical values shown in FIG.

Regarding the time synchronization 71, the projector 1 executes the time synchronization sequence shown in FIG. 3 in the normal mode, while in the standby mode, stops transmitting the Delay_Req message as shown in FIG. 4 and only receives the Sync message. Run.
In the standby mode, an application that requires time synchronization is not executed. Therefore, although the Sync message is received, the transmission of the Delay_Req message for time synchronization is stopped to suppress unnecessary power consumption.

Regarding the communication packet 72, in the normal mode, the projector 1 can transmit / receive all communication packets supported by the projector 1 via the communication I / F 16. On the other hand, in the standby mode, only specific communication packets are transmitted and received.
The specific communication packet that can be transmitted and received in the standby mode includes, for example, an ARP (Address Resolution Protocol) response defined in the TCP / IP protocol. Further, the specific packet includes, for example, reception of an ICMP (Internet Control Message Protocol) Ping response and a wake-up packet (Magic Packet).
As described above, in the standby mode, it suffices to be able to communicate with other devices for a specific purpose such as transmission and reception of control communication packets for managing and maintaining the system, reception of activation packets, and the like. For this reason, in the present embodiment, it is possible to send and receive only the communication packets required in the standby mode, thereby suppressing unnecessary power consumption.

The maximum number of connections 73 is the total number that the projector 1 can form a virtual communication path (connection) with a communication partner via the network. Regarding the maximum number of connections 73, the projector 1 can handle up to 128 connections in the normal mode. On the other hand, the standby mode may be limited to 10 connections.
As described above, in the standby mode, it suffices to be able to perform communication only for a specific purpose such as transmission / reception of control communication packets for managing and maintaining the system, reception of activation packets, and the like. Therefore, in the present embodiment, unnecessary power consumption is suppressed by limiting the number of connections required for transmitting and receiving communication packets for a specific purpose.

For the maximum wireless (PHY) rate 74, the projector 1 connects to the network in the normal mode using the communication standard of the speed of 1 Gbps. On the other hand, in the standby mode, the communication standard of 100 Mbps speed may be used to connect to the network.
As described above, in the standby mode, communication may be limited to a specific application, and therefore, in the present embodiment, a communication standard of 100 Mpbs with low power consumption is selected to suppress unnecessary power consumption.

As described above, according to the present embodiment, the communication device (slave device (projector) 1) sends a delay request to another communication device (master clock device 2) after switching from the normal mode to the standby mode. The transmission frequency is controlled to be lower than that during the communication device operates in the normal mode.
Further, in the present embodiment, when the standby mode is switched to the normal mode, the frequency of transmitting the delay request to another communication device is controlled to be higher than that during the operation in the standby mode.

With this, in the communication device that transmits the delayed request, it is possible to suppress the frequency of transmission of the delayed request used for time synchronization to another communication device after switching to the standby mode. For example, it is possible to suppress the transmission frequency of the delayed request from the time when the standby mode is switched to the time when the normal mode is restored. As a result, when time synchronization is not required, it is possible to reduce the power consumed by each process of time delay synchronization and transmission of the delayed request.
Further, when returning from the standby mode to the normal mode, it is possible to restart the transmission of the delay request used for time synchronization. As a result, when returning to the normal mode, it is possible to quickly perform time synchronization and quickly start an application that requires time synchronization. Therefore, it is possible to reduce power consumption while performing time synchronization with another communication device.

(Embodiment 2)
Hereinafter, Embodiment 2 of the present invention will be described regarding differences from Embodiment 1.
In the present embodiment, the communication device on the side that transmits the second synchronization message (delay request) records the execution history of the application that requires time synchronization on the network in the normal mode. Then, when the communication device shifts to the normal mode, it determines whether or not there is an execution history of an application that requires time synchronization, and if there is an execution history, sends the second synchronization message to another communication device. Send. On the other hand, when the execution history of the application requiring the time synchronization is not yet present, the communication device does not move to the normal mode but at the timing when the time synchronization is required, the second synchronization message (delay request). To another communication device.
An application that requires time synchronization is not always executed immediately after shifting to the normal mode. According to the present embodiment, the second synchronization message (delayed request) is not transmitted when the application that requires time synchronization is not yet executed even after the transition to the normal mode. Power consumption can be reduced.

The hardware configuration and the functional configuration of the communication device, which is the slave device according to the present embodiment, are the same as those of the communication device according to the first embodiment shown in FIG.
FIG. 8 and FIG. 9 show an example of the processing procedure of the operation mode switching process of the projector 1 which is a slave device and the time synchronization process executed by connecting to the master clock device 2 via the network in the present embodiment. It is a flowchart shown. In this embodiment, the control unit 11 of the projector 1 controls the timing of transmitting the Delay_Req (delay request) message to the master clock device 2 based on the execution history of the application.

  Referring to FIG. 8, the processing of S41 and S42 is the same as S41 and S42 of the first embodiment shown in FIG. However, in the present embodiment, in S42, the control unit 11 of the projector 1 copies the application execution history information stored in advance in the storage device 12 to the temporary storage unit 13.

FIG. 10 is a diagram showing an example of execution history information of an application referred to by the control unit 11 of the projector 1 in the second embodiment. The application execution history information shown in FIG. 10 records history information about what application the projector 1 executed and when.
In FIG. 10, the application 1 may be, for example, a projection application that projects video data received from the video distribution device 3 from each of the projectors 1a to 1d and projects it on the screen 5 to form one video. In order to execute such an application 1, it is a condition that the respective times of the plurality of projectors 1a to 1d are synchronized with the master clock device 2.

  On the other hand, the application 2 may be, for example, a projection application in which only one projector 1 independently projects the video data received from the video distribution device 3 onto the screen 5. Such an application 2 operates normally even if the time is not synchronized with the master clock device 2 because, for example, only the projector 1a is activated and the other projectors 1b to 1d are not activated.

  Similarly, the application 3 may be, for example, an application that performs various settings for each of the projectors 1. Specifically, the application 3 may be an application that independently activates the projector 1 to project the setting contents on the screen 5 and adjusts brightness and keystone by a user operation. Such an application 3 operates normally even if the time is not synchronized with the master clock device 2 because, for example, only the projector 1a is activated and the other projectors 1b to 1d are not activated.

  Referring to FIG. 10, the execution history information of application 1 indicates that the application 1 was executed on December 1, 2015, November 30, 2015, and October 21, 2015. Similarly, the execution history information of the application 2 indicates that it was executed on November 6, 2015, and the execution history information of the application 3 indicates that it was executed on November 13, 2015 and September 16, 2015, respectively. There is.

  Returning to FIG. 8, after shifting to the normal mode in S42, the control unit 11 of the projector 1 refers to the execution history information of FIG. 10 stored in the temporary storage unit 13 and requires time synchronization in S46. Determine whether the history of application execution is included. When the execution history information includes a history of execution of an application that requires time synchronization (S46: Y), the process proceeds to S43, the time synchronization sequence is executed, and a Delay_Req (delay request) message is transmitted to the master clock device. Send to 2.

On the other hand, if the execution history information does not include the history of execution of the application that requires time synchronization (S46: N), the time synchronization processing of S43 is skipped and the process proceeds to S44.
For example, assume that the confirmation of the execution history information is performed on December 10, 2015. In this case, since the execution history of the application 1 remains as of December 1, the same year, the control unit 11 determines that there is an execution history of the application that requires time synchronization.
Alternatively, it is assumed that the confirmation of the execution history information is performed on September 30, 2015. In this case, since the history information after October 21st of the same year does not exist yet and the execution history of the application 1 does not remain, the control unit 11 does not have the execution history of the application requiring the time synchronization. To determine.

Alternatively, it is assumed that the confirmation of the execution history information is performed on November 22, 2015. In this case, since the execution history of the application 1 remains as of October 21, the same year, the control unit 11 may determine that there is an execution history of the application that requires time synchronization.
Alternatively, if there is no execution history of the application 1 within the predetermined period, it may be considered that there is no execution history of the application that requires time synchronization. For example, in FIG. 10, since there is no execution history of the application 1 when the execution history information is limited to the past one month from November 22 of the same year, it may be determined that there is no execution history of the application that requires time synchronization. .

In S46, if the execution history information includes a history of execution of an application that requires time synchronization (S46: Y), the process proceeds to S43, and the control unit 11 of the projector 1 sets the time to the master clock device 2. Execute the synchronous sequence process to correct the time. S43 and S44 are the same as S43 and S44 of the first embodiment shown in FIG.
In S44, if the start of the application is instructed or is being executed (S44: Y), in S47, the control unit 11 of the projector 1 selects the application for which the time synchronization is necessary and the time synchronization is still performed. Is not executed.

When the application requiring the time synchronization is selected and the time synchronization with the master clock device 2 is not yet executed (S47: Y), the process returns to S43 to execute the time synchronization sequence. On the other hand, if the application requiring the time synchronization is not selected, or if the time synchronization to the master clock device 2 has already been executed (S47: N), the process proceeds to S45 without executing the time synchronization sequence. Run the application.
In S45, the application selected in S44 is executed. In the present embodiment, the control unit 11 of the projector 1 stores the type and date information of the application executed in S45 in the temporary storage unit 13 and the storage device 12 as the execution history information of the application. The application type recorded as the execution history information includes at least a type indicating whether or not time synchronization is necessary.

  When the application 1 of FIG. 10 is selected in S44, the application 1 displays on the screen 5 such that the video data received from the video distribution device 3 is projected from each of the projectors 1a to 1d to form one video. It is an application to project. In order to execute the application 1, it is a condition that the time of each of the projectors 1a to 1d is synchronized with the master clock device 2.

Referring to FIG. 9, the processing of S51 to S53 is the same as the processing of S51 to S53 of the first embodiment shown in FIG.
After stopping the currently executing application and shifting to the standby mode in S53, the control unit 11 of the projector 1 determines in the execution history information that the history of execution of the application requiring time synchronization is included in the execution history information. Determine if there is. If there is a history of execution of an application that requires time synchronization in the execution history information (S59: Y), the process proceeds to S54, and the transmission of the Delay_Req (delay request) message to the master clock device 2 is stopped. On the other hand, in the execution history information, when there is no history of execution of the application that requires time synchronization (S59: N), S54 is skipped and the process proceeds to S55.

In S59, the latest execution history information in the execution history information stored in the temporary storage unit 13 is referred to, and it can be determined whether the application 1 or not. When the latest execution history information is the application 1, the process proceeds to S54, while when the latest execution history information is other than the application 1, the process skips S54 and proceeds to S55.
The processing from S54 to S58 is the same as the processing from S54 to S58 in the first embodiment shown in FIG.

As described above, according to the present embodiment, the communication device on the side that transmits the delayed request records the execution history of the application that requires time synchronization on the network in the normal mode. Then, when shifting to the normal mode, the communication device determines whether or not there is an execution history of an application that requires time synchronization, and if there is an execution history, transmits a delay request to another communication device. On the other hand, if the execution history of the application that requires time synchronization has not yet been reached, the communication device sends a delay request to another communication device at the timing when time synchronization is required, not when the application shifts to the normal mode. To do.
As a result, even after the transition to the normal mode, if the application that requires time synchronization is not yet executed, the delayed request is not transmitted, so that the power consumption in the normal mode can be reduced.

Each of the above-described embodiments can be realized by combining a plurality of them.
The present invention can also be realized by a program that realizes a part of the above-described embodiments or one or more functions. That is, the program can be realized by a process of supplying the program to a system or an apparatus via a network or a storage medium, and reading and executing the program by one or more processors in a computer (or CPU, MPU, etc.) of the system or the apparatus. is there. Further, the program may be recorded in a computer-readable recording medium and provided.
Further, the functions of the embodiments are not limited to being realized by executing the program read by the computer. For example, an operating system (OS) running on a computer may perform a part or all of the actual processing based on the instructions of the program, and the processing may realize the functions of the above-described embodiments.

  DESCRIPTION OF SYMBOLS 1 ... Slave device (projector), 2 ... Master clock device, 3 ... Slave device (PC), 4 ... Network, 5 ... Screen, 11 ... Control part, 12 ... Storage device, 13 ... Temporary storage part, 14 ... Projection part , 15 ... Timer / clock generation unit, 16 ... Communication I / F, 17 ... Operation clock generation unit, 18 ... Power supply unit

Claims (12)

A communication device,
First receiving means for receiving a first synchronization message from another communication device;
Transmitting means for transmitting a second synchronization message to the other communication device;
Second receiving means for receiving a third synchronization message transmitted from the other communication device in response to the second synchronization message transmitted by the transmitting means,
Synchronization means for time synchronization with the other communication device based on the received first synchronization message and the received third synchronization message;
Switching means for switching the operation of the communication device between a first operation mode and a second operation mode that consumes less power than the first operation mode;
After the switching unit has switched from the first operation mode to the second operation mode, the frequency at which the second synchronization message is transmitted to the other communication device is set by the communication device to the first frequency. Control means for controlling the transmitting means so as to be lower than that during operation in the operation mode,
A communication device comprising: When the control unit switches to the first operation mode by the switching unit, the frequency at which the second synchronization message is transmitted to the other communication device is determined by the communication device to the second operation mode. Control the transmitting means to be higher during operation
The communication device according to claim 1, wherein: The control means stops transmission of the second synchronization message to the other communication device after the switching means switches from the first operation mode to the second operation mode;
The communication device according to claim 1, wherein the communication device is a communication device. The control means controls the second communication device to the second communication device during the period from the switching from the first operation mode to the second operation mode by the switching means until the return to the first operation mode. Controlling the transmitting means such that the frequency of transmitting the synchronization message is lower than during the operation of the communication device in the first operation mode;
The communication device according to claim 1, wherein the communication device is a communication device. The first operation mode is a normal mode in which an application that requires time synchronization with the other communication device can operate, and the second operation mode can operate at least a communication function with a network. The application is in a non-operational standby mode,
The communication device according to any one of claims 1 to 4, wherein: Further comprising storage means for storing the execution history of the application,
The control means controls the frequency of transmitting the second synchronization message to the other communication device based on the execution history stored in the storage means,
The communication device according to any one of claims 1 to 5, wherein: The control means refers to the execution history stored in the storage means when the switching means switches to the first operation mode, and the execution history is time-synchronized with the other communication device. When the execution history of the required application is included, the transmission means is caused to transmit the second synchronization message to the other communication device,
The communication device according to claim 6, wherein: The control means refers to the execution history stored in the storage means when the first operation mode is switched to the second operation mode by the switching means, and the execution history is different from the execution history. When the execution history of an application that requires time synchronization with another communication device is included, the frequency at which the second synchronization message is transmitted to the other communication device is such that the communication device operates in the first operation mode. Controlling the transmitting means to be lower than the interval,
The communication device according to claim 6 or 7, characterized in that. The communication device is a slave device in PTP (Precision Time Protocol), and the other communication device is a master clock device in PTP,
The communication device according to claim 1, wherein the communication device is a communication device. The first synchronization message includes a Sync message in PTP, the second synchronization message includes a Delay_Req message in PTP, and the third synchronization message includes a Delay_Resp message in PTP.
The communication device according to claim 9, wherein A method for controlling a communication device for time synchronization with another communication device, comprising:
Receiving a first synchronization message from the other communication device;
Sending a second synchronization message to the other communication device;
Receiving a third synchronization message transmitted from the other communication device in response to the transmitted second synchronization message;
Time-synchronizing with the other communication device based on the received first synchronization message and the third synchronization message;
Switching the operation of the communication device between a first operating mode and a second operating mode that consumes less power than the first operating mode;
The frequency at which the second synchronization message is transmitted to the other communication device after the first operation mode is switched to the second operation mode is such that the communication device operates in the first operation mode. Controlling to be lower than the interval,
A method for controlling a communication device, comprising:   A program for causing a computer to function as each unit of the communication device according to claim 1.

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