Patent Publication Number: US-2021168298-A1

Title: Electronic devices and program

Description:
CLAIM OF PRIORITY 
     The present application claims priority from Japanese patent application JP 2018-144083 filed on Jul. 31, 2018, the content of which is hereby incorporated by reference into this application. 
     BACKGROUND 
     This invention relates to electronic devices and a program therefor. 
     There is known an information communication system that transmits positional information (positional data) between a camera and a mobile phone (JP 2008-252212 A). Such an existing information communication system does not perform fine control to meet the device conditions. 
     SUMMARY 
     First aspect of the disclosure of an electronic device in this application is an electronic device configured to send positional information to an external device configured to set the positional information to data, the electronic device comprising: an acquisition unit configured to acquire positional information; and a sender unit configured to send information to the external device, wherein the sender unit is configured to send the external device a command not to set positional information received from the electronic device in a case where a mode not allowing the external device to set positional information to data is chosen. 
     Second aspect of the disclosure of an electronic device in this application is an electronic device configured to send positional information to an external device configured to set the positional information to data, the electronic device comprising: an acquisition unit configured to acquire positional information; and a sender unit configured to send information to the external device, wherein the sender unit is configured to send the external device invalid positional information in a case where a mode not allowing the external device to set positional information to data is chosen. 
     Third aspect of the disclosure of an electronic device in this application is an electronic device comprising: a generator unit configured to generate data; a receiver unit configured to receive information from an external device; a storage unit configured to store positional information sent by the external device and received by the receiver unit; and a control unit configured to set positional information to data generated by the generator unit, wherein the control unit is configured not to set positional information stored in the storage unit to data in a case where the receiver unit receives a command not to set positional information to data. 
     Fourth aspect of the disclosure of an electronic device in this application is an electronic device comprising: a generator unit configured to generate data; a receiver unit configured to receive information from an external device; a storage unit configured to store positional information sent from the external device and received by the receiver unit; and a control unit configured to set positional information to data generated by the generator unit, wherein the control unit is configured not to set positional information stored in the storage unit to data in a case where the receiver unit receives invalid positional information from the external device. 
     An aspect of the disclosure of a computer program in this application is a computer program configured to make a processor of an electronic device configured to send positional information to an external device configured to set positional information to data perform the processing of: acquiring positional information; and sending the external device a command not to set positional information received from the electronic device to data in a case where a mode not allowing the external device to set positional information to data is chosen. 
     Another aspect of the disclosure of a computer program in this application is a computer program configured to make a processor of an electronic device configured to send positional information to an external device configured to set positional information to data perform the processing of: acquiring positional information; and sending invalid positional information to the external device in a case where a mode not allowing the external device to set positional information to data is chosen. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an explanatory diagram illustrating an example of setting positional information and an example of canceling the positional information. 
         FIG. 2  is an explanatory diagram providing examples of information stored in the cache memory of the digital camera. 
         FIG. 3  is a block diagram illustrating an example of the hardware configuration of the smartphone. 
         FIG. 4  is a block diagram illustrating an example of the hardware configuration of the digital camera. 
         FIG. 5  is a block diagram illustrating an example of the functional configuration of a communication system. 
         FIG. 6  is a sequence diagram illustrating an example of a connection sequence in the communication system. 
         FIG. 7  is a flowchart of an example of scanning and connecting by the smartphone. 
         FIG. 8  is a flowchart of an example of data processing by the digital camera at Step S 612  in  FIG. 6 . 
         FIG. 9  is a flowchart of an example of generating an image file by the digital camera. 
         FIG. 10  is a flowchart of Example 1 of updating the cache memory. 
         FIG. 11  is a flowchart of Example 2 of updating the cache memory. 
         FIG. 12  is an explanatory diagram illustrating an example of retroactively deleting positional information. 
         FIG. 13  is a flowchart of an example of sending a time of mode change by the smartphone. 
         FIG. 14  is a flowchart of an example of retroactively deleting positional information by the digital camera. 
         FIG. 15  is a sequence diagram illustrating an example of setting positional information in Embodiment 3. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Hereinafter, electronic devices and a program according to the embodiments of this invention are described with reference to the accompanying drawings. The following embodiments are described employing a smartphone as an example of an electronic device and a digital camera (imaging device) as an external electronic device (hereinafter, external device) capable of communicating with the electronic device. The electronic device is not limited to a smartphone but can be a portable device or an autonomous movable device, as far as it is capable of communicating with an external device and acquiring its positional information. Examples of the portable device include a mobile phone, a gaming machine, and a tablet computer and examples of the autonomous movable device includes a drone and a robot. 
     The external device is not limited to a digital camera but can be a digital video camera, a gaming machine, a tablet computer, a drone, or a robot, as far as it is capable of communicating with the electronic device and generating data to be associated with positional information sent from the electronic device. The external device has to be a device that is incapable of generating positional information by itself or can choose not to acquire its positional information even though it is capable of acquiring its positional information like the electronic device. 
     Embodiment 1 
     Examples of Setting and Canceling Positional Information 
       FIG. 1  is an explanatory diagram illustrating an example of setting positional information and an example of canceling the positional information. The example (A) illustrates that a smartphone  101  makes a digital camera  102  set positional information P and the example (B) illustrates that the smartphone  101  makes the digital camera  102  cancel the positional information. The user takes an image of an object with the digital camera  102  while carrying the smartphone  101 . The positional information P is information for identifying the position of the smartphone  101  with a latitude and a longitude, for example. 
     The configuration screen  111  includes a slider  113  in a positional information setting mode field  112 . The slider  113  is an interface that slides horizontally in accordance with user operation. When the slider  113  is located at the right end, it means positional information is to be set (ON). When the slider is located at the left end, it means positional information is not to be set (OFF). The digital camera  102  does not have a function to choose whether to set positional information P. 
     In the example (A), the positional information setting mode of the smartphone  101  is ON. Accordingly, the smartphone  101  successively acquires positional information P by satellite positioning, for example, and sends it to the digital camera  102 . The digital camera  102  stacks the successively received positional information P in a cache memory. The digital camera  102  takes an image of an object and generates image data  121  of the object. 
     The digital camera  102  retrieves the latest positional information P from the cache memory and sets the retrieved positional information P to the image data  121  to generate an image file  122 . The positional information P can be stored to the image file  122  in the form of exchangeable image file (Exif) information. Hence, the digital camera  102  can associate the positional information P on the place where the image data  121  is generated with the image data  121  even though the digital camera  102  does not have a satellite positioning function. 
     In the example (B), the smartphone  101  is in a state where the positional information setting mode is changed from ON to OFF. In this state, the smartphone  101  does not send positional information P but instead, sends cancellation data to cancel the positional information P already sent to the digital camera  102 . 
     The cancellation data can be a command to discard the positional information P. Upon receipt of the command to discard the positional information P, the digital camera  102  clears its cache memory. The digital camera  102  takes an image of an object to generate image data  121 . The digital camera  102  tries to retrieve the latest positional information P from the cache memory but cannot because the cache memory is cleared. Accordingly, the digital camera  102  generates an image file  123  without setting positional information P to the image data  121 . When the mode not to set positional information P is chosen in the smartphone  101 , positional information P is not set to image data  121 . 
     This configuration enables choosing to set or not to set positional information P to image data  121  generated by the digital camera  102  with the smartphone  101  only. In other words, choosing whether to set positional information P with the digital camera  102  becomes unnecessary; the digital camera  102  does not require complicated user operation, increasing the convenience for the user. 
     The foregoing description employs a command to discard positional information P as an example of cancellation data to clear the cache memory in which positional information P is stacked; however, the cancellation data is not limited to this example. For example, the smartphone  101  can send invalid positional information PX as another example of cancellation data to the digital camera  102  so that the digital camera  102  stores the invalid positional information PX to the cache memory. 
     The invalid positional information PX can be impossible values of latitude and longitude. As a result, the digital camera  102  retrieves the invalid positional information PX from the cache memory as the latest positional information and sets the retrieved invalid positional information PX to the image data  121  to generate an image file  123 . 
     Examples of Information Stored in Cache Memory 
       FIG. 2  is an explanatory diagram providing examples of information stored in the cache memory of the digital camera  102 . The example (A) illustrates an example of information stored in the cache memory  200  of the digital camera  102  when the positional information setting mode is ON, like the example (A) in  FIG. 1 . The examples (B1) and (B2) illustrate examples of information stored in the cache memory  200  of the digital camera  102  when the positional information setting mode is switched from ON to OFF, like the example (B) in  FIG. 1 . 
     The digital camera  102  associates a position  202  with a time  201  and stores them as a record to the cache memory  200 . The position  202  is the position of the smartphone  101  at the time  201 . Since the user in this example carries the smartphone  101  and the digital camera  102 , the position  202  corresponds to the position of the digital camera  102 . 
     As to the example (A), the smartphone  101  sends the values T 1  to Tn (n is an integer greater than 1) for the time  201  together with positions  202  indicated by positional information P to the digital camera  102 . In this example, a smaller value for n represents an older value; the time T 1  and the position P 1  when n=1 are the oldest values. 
     The time  201  can be a time at which the smartphone  101  acquires positional information by satellite positioning or a time at which the smartphone  101  sends out the positional information P to the digital camera  102 . As a result, accurate positional information P of the smartphone  101  at acquisition of the positional information can be set to data generated by the digital camera  102  at acquisition of the positional information. In the example where the smartphone  101  does not send the time  201 , the time  201  can be a time at which the digital camera  102  receives positional information P. This configuration reduces the amount of data to be transmitted from the smartphone  101 . 
     The example (B1) illustrates an example of information stored in the cache memory  200  after the positional information P is discarded in accordance with a command to discard positional information P as cancellation data. Upon receipt of the command to discard positional information P from the smartphone  101 , the digital camera  102  discards the times  201  and the positions  202 . 
     The example (B2) illustrates an example of information stored in the cache memory  200  after invalid positional information PX as cancellation data is recorded. Upon receipt of the invalid positional information PX from the smartphone  101 , the digital camera  102  records the time of reception Tn as a time  201  and the invalid positional information PX as a position  202 . 
     The digital camera  102  retrieves the position  202  in the cache memory  200  every time no matter whether the mode to set positional information P is ON or OFF in the smartphone  101 . Accordingly, if the cache memory  200  is in the state of example (A), the digital camera  102  retrieves the positional information Pn; if in the state of example (B1), the digital camera  102  retrieves nothing; and if in the state of example (B2), the digital camera  102  retrieves the invalid positional information PX. This configuration eliminates the necessity to choose whether to set positional information P with the digital camera  102 , increasing the user-friendliness of the digital camera  102 . 
     Example of Hardware Configuration of Smartphone  101   FIG. 3  is a block diagram illustrating an example of the hardware configuration of the smartphone  101 . The smartphone  101  includes a processor  301 , a storage device  302 , an operation device  303 , a display device  304 , an imager  305 , a satellite signal receiver  306 , a first communication interface (IF)  307 , a second communication IF  308 , and a third communication IF  309 . These are connected by a bus  310  to be able to communicate with one another. 
     The processor  301  controls the smartphone  101 . The processor  301  executes programs. The processor  301  generates positional information P based on a received satellite signal, for example. The storage device  302  serves as a working area for the processor  301 . The storage device  302  is a non-transitory or transitory recording medium for storing programs and data. Examples of the storage device  302  include a read only memory (ROM), a random access memory (RAM), a hard disk drive (HDD), and a flash memory. 
     The operation device  303  receives input of data. Examples of the operation device  303  include a button and a touch panel. The display device  304  displays information on a display screen. The display device  304  displays the configuration screen  111 . The imager  305  includes a lens and an image sensor for taking an image of an object and outputting an image signal. The satellite signal receiver  306  receives a satellite signal transmitted from a positioning satellite. 
     The first communication IF  307  is a communication module connectable to the Internet through a router for a wireless local area network (LAN), such as a Wi-Fi module. In the case where the digital camera  102  functions as a software-based access point like in the case of ad hoc Wi-Fi connection, the first communication IF  307  is connected with the digital camera  102 . 
     The second communication IF  308  is a communication module for lower-speed communication than the first communication IF  307 , for example for Bluetooth™ Low Energy (BLE) (“™” will be omitted hereinafter). The third communication IF  309  is a communication module connectable to the Internet via a wireless base station, such as a 4G module or a Long-Term Evolution (LTE) module. 
     Example of Hardware Configuration of Digital Camera  102   
       FIG. 4  is a block diagram illustrating an example of the hardware configuration of the digital camera  102 . The digital camera  102  is an imaging device that can take a still image and a motion video. 
     The digital camera  102  includes a processor  401 , a storage device  402 , a driver  403 , an optical system  404 , an image sensor  405 , an analog front-end (AFE)  406 , a large-scale integration (LSI)  407 , an operation device  408 , a sensor  409 , a display device  410 , a first communication IF  411 , a second communication IF  412 , and a bus  413 . The processor  401 , the storage device  402 , the driver  403 , the LSI  407 , the operation device  408 , the sensor  409 , the display device  410 , the first communication IF  411 , and the second communication IF  412  are connected with the bus  413 . 
     The processor  401  controls the digital camera  102 . The processor  401  executes programs. The storage device  402  serves as a working area for the processor  401 . The storage device  402  is a non-transitory or transitory recording medium for storing programs and data. Examples of the storage device  402  include a ROM, a RAM, an HDD, and a flash memory. The cache memory  200  illustrated in  FIG. 2  is included in the storage device  402 . The digital camera  102  can include a plurality of storage devices  402  and at least one of them can be removable from the digital camera  102 . 
     The driver  403  drives and controls the optical system  404 . The driver  403  includes a driver circuit  403   a  and a driving source  403   b . The driver circuit  403   a  controls the driving source  403   b  in accordance with instructions from the processor  401 . The driving source  403   b  can be a motor; it moves a zooming lens  441   b  and a focusing lens  441   c  in the optical system  404  along the optical axis and also, opens and closes a diaphragm  442  in accordance with control of the driver circuit  403   a.    
     The optical system  404  includes a plurality of lenses (a lens  441   a , a zooming lens  441   b , and a focusing lens  441   c ) disposed along the optical axis, and a diaphragm  442 . The optical system  404  collects light from an object and emits the light to the image sensor  405 . 
     The image sensor  405  receives the object light from the optical system  404  and converts it to electric signals. The image sensor  405  can be a solid-state image sensor employing an X-Y address method (for example a complementary metal-oxide semiconductor (CMOS) sensor) or a solid-state image sensor employing a progressive scanning method (for example, a charge coupled device (CCD)). 
     The image sensor  405  has a plurality of photosensitive elements (pixels) arrayed in a matrix on its light-receiving surface. Each pixel of the image sensor  405  is provided with one of a plurality of kinds of color filters disposed in a specific color arrangement (for example, Bayer arrangement) so that the pixel transmits a specific color component. Accordingly, each pixel of the image sensor  405  outputs an analog electric signal corresponding to a color component obtained by color separation with the color filter. 
     The AFE  406  is an analog front-end circuit for processing analog electric signals from the image sensor  405 . The AFE  406  performs gain adjustment for the electric signals, analog signal processing (such as correlated double sampling and black level correction), A/D conversion, digital signal processing (such as defective pixel correction) one after another to generate raw image data and outputs the row image data to the LSI  407 . The above-described driver  403 , the optical system  404 , the image sensor  405 , and the AFE  406  are included in an imager  420 . 
     The LSI  407  is an integrated circuit for specific processing including image processing such as color interpolation, white balance adjustment, contour enhancement, gamma correction, and grayscale conversion, encoding, decoding, and compressing/decompressing on the raw image data received from the AFE  407 . Specifically, the LSI  407  can be a programmable logic device (PLD) such as an application-specific integrated circuit (ASIC) or a field-programmable gate array (FPGA). 
     The operation device  408  inputs commands and data. Examples of the operation device  408  include various kinds of buttons including a release button, a switch, a dial, and a touch panel. The sensor  409  is a device for detecting information. Examples of the sensor  409  include an automatic focus (AF) sensor, an automatic exposure (AE) sensor, a gyro sensor, an acceleration sensor, and a temperature sensor. The display device  140  displays image data  121  and a configuration screen. Examples of the display device  140  include a backside monitor provided on the backside of the digital camera  102  and an electronic viewfinder. 
     The first communication IF  411  is a communication module that can communicate with the smartphone  101  by ad hoc Wi-Fi connection, for example. The second communication IF  412  is a communication module for lower-speed communication than the first communication IF  411 , such as a BLE module. 
     Example of Functional Configuration of Communication System 
       FIG. 5  is a block diagram illustrating an example of the functional configuration of a communication system. The communication system  500  consists of a smartphone  101  and a digital camera  102 . The configuration of the smartphone  101  is described first. 
     Configuration Example of Smartphone  101   
     The smartphone  101  includes a first sender unit  511 , a first receiver unit  512 , a first storage unit  513 , an acquisition unit  514 , and a configuration unit  515 . The first sender unit  511  sends positional information P or cancellation data to the digital camera  102 . Specifically, the first sender unit  511  sends positional information P or cancellation data to the digital camera  102  through BLE or ad hoc Wi-Fi connection. 
     Transmission by BLE saves power consumption. Transmission by ad hoc Wi-Fi connection enables high-speed direct data transfer to the digital camera  102 . The first sender unit  511  may send the time of acquisition or the time of sending of the positional information P to the digital camera  102 . Specifically, the first sender unit  511  can be implemented by the first communication IF  307  or the second communication IF  308  illustrated in  FIG. 3 . 
     The first receiver unit  512  receives data from the digital camera  102 . The data from the digital camera  102  can be an image file or a motion video file generated by the digital camera  102 . Specifically, the first receiver unit  512  receives data from the digital camera  102  through ad hoc Wi-Fi connection. The ad hoc Wi-Fi connection enables direct reception of large data from the digital camera  102 . Specifically, the first receiver unit  512  can be implemented by the first communication IF  307  illustrated in  FIG. 3 . 
     The first storage unit  513  stores data received by the first receiver unit  512 . Specifically, the first storage unit  513  can be implemented by the storage device  302  illustrated in  FIG. 3 . 
     The acquisition unit  514  acquires positional information P. Specifically, the acquisition unit  514  acquires a latitude and a longitude as positional information P by determining the latitude and the longitude from satellite signals from four positioning satellites received by the satellite signal receiver  306 . Each time the acquisition unit  514  acquires positional information P, the positional information P is sent from the first sender unit  511 . Specifically, the acquisition unit  514  can be implemented by the processor  301  executing a program stored in the storage device  302 . 
     The configuration unit  515  activates either a mode (first mode) to set positional information P to the data generated by the digital camera  102  or mode (second mode) not to set positional information P. Specifically, the configuration unit  515  activates the first mode, or turns on the positional information setting mode in response to the slider  113  being slid to the right end as shown in the example (A) in  FIG. 1  and activates the second mode, or turns off the positional information setting mode in response to the slider  113  being slid to the left end as shown in the example (B) in  FIG. 1 . 
     Under the first mode (when the positional information setting mode is ON), the acquisition unit  514  repeatedly acquires positional information P and the first sender unit  511  successively sends the positional information P acquired by the acquisition unit  514  to the digital camera  102 . Under the second mode (when the positional information setting mode is OFF), the configuration unit  515  sets cancellation data to the first sender unit  511  and the first sender unit  511  sends the cancellation data to the digital camera  102 . 
     When communication with the digital camera  102  is not available under the first mode (when the positional information setting mode is ON), the configuration unit  515  changes the first mode to the second mode (turns the positional information setting mode from ON to OFF). “Communication is not available” means that connection to the digital camera  102  has not been established or that the connection to the digital camera  102  is disconnected because of communication failure. As a result of this operation, the first sender unit  511  does not send positional information P when communication is unavailable. 
     When communication becomes available later, the configuration unit  515  changes the second mode to the first mode (turns the positional information setting mode from OFF to ON). As a result of this operation, the acquisition unit  514  restarts repeatedly acquiring positional information P and the first sender unit  511  successively sends the positional information P acquired by the acquisition unit  514  to the digital camera  102 . 
     When communication with the digital camera  102  is not available, the smartphone  101  may notify the user of it by sound or image. As a result, the user is informed of the automatic change from the first mode to the second mode (that the positional information setting mode is automatically turned from ON to OFF). 
     When communication with the digital camera  102  is not available, the configuration unit  515  may disable the user operation to choose the first mode or the second mode. Specifically, the smartphone  101  does not display the positional information setting mode field  112  in the configuration screen  111  in  FIG. 1  or makes the slider  113  inoperative although the smartphone  101  displays the configuration screen  111 . 
     Not displaying the positional information setting mode field  112  prevents the user from reflecting his/her intention to set positional information when communication is unavailable. Disabling the operation of the slider  113  prevents the user from reflecting his/her intention to set positional information when communication is unavailable and further, allows the user to know whether the current mode is the first mode (the positional information setting mode: ON) or the second mode (the positional information setting mode: OFF). 
     The configuration unit  515  can disable the user operation to choose the first mode (the positional information setting mode: ON) or the second mode (the positional information setting mode: OFF) and change the mode from the first mode (the positional information setting mode: ON) to the second mode (the positional information setting mode: OFF) when connected communication with the digital camera  102  is disconnected because of communication failure or the communication is terminated. This configuration saves the power consumption by sending positional information P against the user&#39;s intention after the smartphone  101  and the digital camera  102  are reconnected. Specifically, the configuration unit  515  is implemented by the processor  301  executing a program stored in the storage device  302 . 
     Configuration Example of Digital Camera  102   
     The digital camera  102  includes a second receiver unit  521 , a second storage unit  522 , a second sender unit  523 , a generator unit  524 , and a control unit  525 . The second receiver unit  521  receives information from the smartphone  101 . The information from the smartphone  101  can be positional information acquired by the smartphone  101  or cancellation data (a command to discard positional information P or invalid positional information PX) set by the smartphone  101 . Specifically, the second receiver unit  521  receives information from the smartphone  101  through BLE or ad hoc Wi-Fi connection. Specifically, the second receiver unit  521  can be implemented by the first communication IF  411  or the second communication IF  412  illustrated in  FIG. 4 . 
     The second storage unit  522  stores information received by the second receiver unit  521 . Specifically, the second storage unit  522  stores positional information P and times of acquisition of the positional information P as positions  202  and times  201  as illustrated in  FIG. 2 . The second storage unit  522  further stores data generated by the generator unit  524 . Specifically, the second storage unit can be implemented by the storage device  402  illustrated in  FIG. 4 . 
     The second sender unit  523  sends information stored in the second storage unit  522  to the smartphone  101 . Specifically, the second sender unit  523  sends data generated by the generator unit  524  and stored in the second storage unit  522 , for example. More specifically, the second sender unit  523  sends image files  122 ,  123 , and motion video files stored in the second storage unit  522  to the smartphone  101  through ad hoc Wi-Fi connection. Transmission by ad hoc Wi-Fi connection enables high-speed direct transfer of large data. Specifically, the second sender unit  523  can be implemented by the first communication IF  411  illustrated in  FIG. 4 . 
     The generator unit  524  generates data. Specifically, the generator unit  524  includes an imager  420  and generates image data  121  based on an image signal from the imager  420 . Further, the generator unit  524  generates an image file  122  or  123  from the image data  121  or generates a motion video file by sorting a series of image data  121  in time series. 
     The control unit  525  controls the cache memory  200 . Specifically, the control unit  525  stores positional information P to the top of the stack in the cache memory  200  as illustrated in the example (A) in  FIG. 2  when the second receiver unit  521  receives the positional information P. This configuration makes the control unit  525  retrieve the last stored positional information P. 
     In the case where the second receiver unit  521  receives the time of acquisition together, the control unit  525  also stores the time of acquisition with the positional information P to the cache memory  200 . As a result of this operation, the control unit  525  retrieves the last stored time of acquisition together with the positional information P. The control unit  525  may accumulate a certain number of records (combinations of a time  201  and a position  202 ) in the cache memory  200  and delete them one by one from the oldest record when the number of records exceeds the certain number. This configuration allows the cache memory  200  to have a limited capacity. 
     The control unit  525  deletes positional information P from the cache memory  200  when a certain time (for example, two hours) has elapsed since the positional information P is stored. Specifically, the control unit  525  deletes the record of a position  202  that has been in the cache memory  200  for the certain time since the time  201 . 
     When a long time has elapsed since a position  202  is stored, it is considered that the user is no longer at the position  202 . However, the user may leave the digital camera  102  while carrying the smartphone  101 , so that the communication between the smartphone  101  and the digital camera  102  could be disconnected. In this case, if the user returns to the digital camera  102  within a certain period, the smartphone  101  and the digital camera  102  will be reconnected. Accordingly, in consideration of the user&#39;s convenience, it is preferable that the digital camera  102  hold the positional information P in the cache memory  200  for a certain period before deleting it from the cache memory  200 . 
     Furthermore, the control unit  525  retrieves the positional information P stored last in the cache memory  200  and sets the positional information P to data generated by the generator unit  524  when the data is stored to the second storage unit  522 . Specifically, the control unit  525  sets the positional information P to the generated image data  121  to generate an image file  122  as illustrated in the example (A) in  FIG. 1 . 
     This configuration enables positional information P to be associated with image data  121  even if the digital camera  102  does not include a satellite signal receiver  306  like the smartphone  101 . Accordingly, where the image data  121  is taken can be located by referring to the image file  122 . 
     In the case where the second receiver unit  521  receives cancellation data, the control unit  525  controls the cache memory  200  depending on the kind of the cancellation data. Specifically, in the case where the cancellation data is a command to discard positional information P, the control unit  525  clears the cache memory  200  as illustrated in the example (B1) in  FIG. 2 . 
     After this operation, the control unit  525  cannot retrieve positional information P when the control unit  525  accesses the cache memory  200 , because the cache memory  200  does not include any record. Accordingly, data from the generator unit  524  will not be provided with positional information P even if the digital camera  102  does not have a mode not to set positional information P. 
     In the case where the cancellation data is invalid positional information PX, the control unit  525  stores invalid positional information PX to the top of the stack in the cache memory  200  as illustrated in the example (B2) in  FIG. 2 . After this operation, the control unit  525  retrieves the invalid positional information PX when the control unit  525  accesses the cache memory  200 . 
     Accordingly, even if the digital camera  102  does not have a mode not to set positional information P, data from the generator unit  524  will be provided with invalid positional information PX. Since this invalid positional information PX indicates a position that does not exist actually, the data with the invalid positional information PX will not be recognized erroneously as data generated at a position indicated by the positional information P. 
     In addition, the control unit  525  may discard positional information stored in the cache memory  200  in the second storage unit  522  if the second receiver unit  521  cannot receive information from the smartphone  101 . Specifically, when established BLE connection with the smartphone  101  is disconnected because of communication failure or the smartphone  101  leaving the communication range, for example, the control unit  525  discards the positional information P accumulated in the cache memory  200 . 
     As a result of this operation, image data  121  generated during the disconnection is not provided with positional information. The smartphone  101  and the digital camera  102  could be at different positions during the disconnection and accordingly, discarding the positional information P in response to disconnection prevents wrong positional information P from being set. After reconnection, the cache memory  200  stores the latest positional information P newly received from the smartphone  101  and therefore, setting positional information P to image data  121  becomes available. 
     Example of Connection Sequence in Communication System  500   
       FIG. 6  is a sequence diagram illustrating an example of a connection sequence in the communication system  500 .  FIG. 6  illustrates an example of a sequence to connect the digital camera  102  and the smartphone  101  by BLE to be able to communicate with each other. In  FIG. 6 , the digital camera  102  is an advertiser (also referred to as broadcaster) that broadcasts an advertisement packet and the smartphone  101  is a scanner (also referred to as observer) that scans for the advertisement packet. 
     The smartphone  101  starts scanning for an advertisement packet in accordance with presetting or in response to an operation input from the user (Step S 601 ). The digital camera  102  starts advertising in accordance with presetting or in response to an operation input from the user (Step S 602 ). Hence, the digital camera  102  repetitively broadcasts an advertisement packet ADV_IND indicating that the digital camera  102  is connectable    1   0   2  with constant intervals (Step S 602 ). The advertisement packet ADV_IND includes identification information specifying that the digital camera  102  requests positional information P. 
     In the case of active scanning, the smartphone  101  that has received the advertisement packet ADV_IND sends a scanning request SCAN_REQ to the digital camera  102  (Step S 604 ) and the digital camera  102  that has received the scanning request SCAN_REQ returns a scanning response SCAN RSP to the smartphone  101  (Step S 605 ). 
     In the case of passive scanning, Steps S 604  and S 605  are not performed. In the passive scanning, the digital camera  102  broadcasts an advertisement packet ADV_DIRECT_IND specifying that the digital camera  102  is connectable and does not allow scanning at Step S 603 . 
     Subsequently, the smartphone  101  verifies the BLE connection request (Step S 606 ). Specifically, the smartphone  101  checks whether the received advertisement packet ADV_IND includes identification information specifying that the digital camera  102  requests positional information P. If the advertisement packet ADV_IND includes such identification information, the smartphone  101  sends a connection request CONNECT_REQ to the source of the advertisement packet ADV_IND, or the digital camera  102  (Step S 607 ). 
     The smartphone  101  determines that the smartphone  101  itself is a master (Step S 608 ) and the digital camera  102  that has received the connection request CONNECT_REQ determines that the digital camera  102  itself is a slave (Step S 609 ). Through these operations, BLE connection is established between the smartphone  101  and the digital camera  102 . 
     Subsequently, the smartphone  101  checks the positional information setting mode (Step S 610 ). Specifically, if the positional information setting mode is ON, the smartphone  101  can acquire positional information P and send it to the slave (digital camera  102 ); if the positional information setting mode is OFF, the smartphone  101  can send cancellation data to the slave (digital camera  102 ). 
     The smartphone  101  sends data (positional information P or cancellation data) to the digital camera  102  of the slave in accordance with the result of checking the positional information setting mode at Step S 610  (Step S 611 ). The digital camera  102  performs data processing as illustrated in  FIG. 1  based on the received data (Step S 612 ). An example of a detailed procedure of data processing (Step S 612 ) will be described later with  FIG. 8 . 
     Example of Scanning and Connecting by Smartphone  101   
       FIG. 7  is a flowchart of an example of scanning and connecting by the smartphone  101 . The flowchart of  FIG. 7  is an example of processing of an application program to be executed by the processor  301  when scanning is started at Step S 601  in  FIG. 6 . The processor of the smartphone  101  can execute this application program in the background or the foreground. In the case of the foreground, this application program has to be explicitly started. Further in the case of the foreground, the positional information setting mode can be manually changed between ON and OFF. 
     If the smartphone  101  receives an advertisement packet at Step S 603  (Step S 701 : Yes) and determines to be a master (Step S 702 : Yes), connection with the digital camera  102  is established. In this case, the smartphone  101  checks whether the mode to set positional information P is ON or OFF (Step S 703 ). 
     If the positional information setting mode is ON (Step S 703 : ON), the smartphone  101  successively acquires positional information with the acquisition unit  514  and sends the acquired positional information to the digital camera  102  in series (Step S 705 ). The smartphone  101  can send the time of acquisition of positional information P together with the positional information P. 
     Optionally, the smartphone  101  can generate an empty packet that does not include acquired positional information P with the configuration unit  515  and send the empty packet to the digital camera  102  if the acquired positional information P is identical to the previous positional information P or the difference of the acquired positional information P from the previous positional information P is within an acceptable range. 
     This configuration reduces the amount of transmitted data. The digital camera  102  that has received the empty packet does not store positional information P to the cache memory  200  because there is no positional information P to be stored. As a result, the power consumption in the digital camera  102  can be saved. 
     If the determination at Step S 703  is that the positional information setting mode is OFF (Step S 703 : OFF), the smartphone  101  sets cancellation data for canceling the already sent positional information P with the configuration unit  515  (Step S 706 ) and sends the cancellation data to the digital camera  102  (Step S 707 ). 
     If the smartphone  101  receives an advertisement packet sent at Step S 603  (Step S 701 : Yes) but has not determined to be a master (Step S 702 : No), connection with the digital camera  102  is not established. In this case, the smartphone  101  returns to Step S 701 . 
     If the smartphone  101  does not receive an advertisement packet sent at Step S 603  (Step S 701 : No), the smartphone  101  is located outside the communication range of the advertisement packet of the digital camera  102 . In this case, the smartphone  101  disables changing the positional information setting mode (Step S 708 ) and returns to Step S 701 . 
     Specifically, the smartphone  101  displays the positional information setting mode field  112  (including the slider  113 ) in an inoperative state for the user or does not display the slider  113 . As a result, the smartphone  101  rejects accepting the user&#39;s intension whether to set positional information P. Particularly displaying an inoperative state enables the user to see whether the positional information setting mode is currently ON or OFF. 
     Example of Data Processing by Digital Camera  102   
       FIG. 8  is a flowchart of an example of data processing by the digital camera  102  at Step S 612  in  FIG. 6 . The flowchart of  FIG. 8  is an example of processing of firmware to be executed by the processor  401  of the digital camera  102 . The digital camera  102  waits for data (positional information P or cancellation data) sent from the smartphone  101  at Step  611  (Step S 801 : No). 
     Upon receipt of such data (Step S 801 : Yes), the digital camera  102  identifies the kind of the received data (Step S 802 ). If the received data is positional information P or invalid positional information PX (Step S 802 : positional information or invalid positional information), the digital camera  102  stores the received data (positional information P or invalid positional information PX) to the top of the stack in the cache memory  200  as illustrated in the example (A) or (B2) in  FIG. 2  (Step S 803 ) and terminates the data processing of Step S 612 . 
     In the case where the received data includes the time of acquisition, the digital camera  102  stores the time of acquisition to the cache memory  200  together with the positional information P or invalid positional information PX. As a result, the digital camera  102  can manage the positional information P in association with the time of acquisition. 
     In the case where the received data does not include the time of acquisition, the digital camera  102  may store the time of reception of the data to the cache memory  200 , in place of the time of acquisition. This configuration reduces the amount of data transferred from the smartphone  101  to the digital camera  102 . 
     If the received data is a command to discard positional information P (Step S 802 : discard command), the digital camera  102  clears the cache memory  200  as illustrated in the example (B1) in  FIG. 2  (Step S 804 ) and terminates the data processing of Step S 612 . 
     Example of Generating Image File by Digital Camera  102   
       FIG. 9  is a flowchart of an example of generating an image file by the digital camera  102 . The digital camera  102  retrieves positional information P without noting whether the positional information stored in the cache memory  200  is information on an actually existing location or invalid positional information PX. Accordingly, the “positional information” shown in  FIG. 9  includes positional information P on an actually existing location and invalid positional information PX. 
     The digital camera  102  waits for the release button to be pressed manually or by a self-timer (Step S 901 : No). Upon detection of press of the release button (Step S 901 : Yes), the digital camera  102  takes an image of the object and outputs an image signal with the imager  420 , and generates image data  121  with the LSI  407  (Step S 902 ). The digital camera  102  further tries to retrieve the latest positional information P from the cache memory  200  (Step S 903 ). 
     If positional information P is retrieved (Step S 904 : Yes), the digital camera  102  sets the positional information P to the image data  121  (Step S 905 ) to generate an image file  122  as illustrated in the example (A) in  FIG. 1  and records the image file  122  to the storage device  402  (Step S 906 ). 
     If positional information P is not retrieved (Step S 904 : No), or the cache memory  200  is empty as illustrated in the example (B1) in  FIG. 2 , the digital camera  102  generates an image file  123  that does not include positional information P as illustrated in the example (B) in  FIG. 1 , and records the image file  123  to the storage device  402  (Step S 906 ). 
     Examples of Updating Cache Memory  200   
       FIG. 10  is a flowchart of Example 1 of updating the cache memory  200 . First, the digital camera  102  waits for the time to update the cache memory  200  (Step S 1001 : No). The time to update is a time scheduled in a cycle or specified in accordance with the user operation. If the time to update has come (Step S 1001 : Yes), the digital camera  102  acquires the current time from its internal clock (Step S 1002 ). 
     To correct the current time of the internal clock of the digital camera  102 , the digital camera  102  can adjust the internal clock based on the time of acquisition sent from the smartphone  101  together with positional information P so that the current time of the internal clock will be the time of acquisition. As a result, the clock in the digital camera  102  is synchronized with the clock in the smartphone  101 . 
     Upon acquisition of the current time (Step S 1002 ), the digital camera  102  deletes positional information P stored earlier than a predetermined time (for example, two hours as mentioned above) before the current time from the cache memory  200  (Step S 1003 ). As a result, positional information P that has not been in the cache memory  200  for the predetermined time since the time of acquisition of the latest positional information P is kept in the cache memory  200 . 
       FIG. 11  is a flowchart of Example  2  of updating the cache memory  200 . The flowchart of  FIG. 11  is triggered by establishment of BLE connection between the digital camera  102  and the smartphone  101  in  FIG. 6 . The digital camera  102  determines whether the connected smartphone  101  is changed (Step S 1101 ). If the smartphone  101  is not changed (Step S 1101 : No), the digital camera  102  terminates the updating. If the smartphone  101  is changed (Step S 1101 : Yes), the digital camera  102  clears the cache memory  200  (Step S 1102 ). 
     After the connected smartphone  101  is changed, the digital camera  102  does not need the positional information P of the smartphone  101  connected before the change. Accordingly, the digital camera  102  deletes all positional information P even before the aforementioned time elapses. However, if the connected smartphone  101  is not changed, the communication could be temporarily disconnected and reconnected because the user once leaves the digital camera  102  while carrying the smartphone  101  and then returns to the digital camera  102 . Accordingly, the digital camera  102  does not clear the cache memory  200  like the operation at Step S 1102  but updates the cache memory  200  like the operation in  FIG. 10 . 
     As described above, Embodiment 1 enables image data  121  of an object generated by a digital camera  102  that has neither a function to choose whether to set positional information P nor a positioning function to be provided with positional information P at the time when the image is taken in accordance with a positional information setting mode (ON or OFF) in the smartphone  101 . Not installing the function to choose whether to set positional information P in the digital camera  102  but managing the function with the positional information setting mode of the smartphone  101  eliminates complicated operations on both the smartphone  101  and the digital camera  102  and improves the usability. Furthermore, even if the digital camera  102  does not have a positioning function to acquire positional information P, the digital camera  102  can acquire the positional information P at the time of taking an image from the smartphone  101 ; the digital camera  102  can be reduced in weight, size, and cost. 
     Embodiment 2 
     Embodiment 2 is an example where the digital camera  102  deletes positional information P from an image file  122  retroactively. To mainly explain retroactively deleting positional information P, the elements common to Embodiment 1 are denoted by the same reference signs and description thereof is omitted in Embodiment 2. 
       FIG. 12  is an explanatory diagram illustrating an example of retroactively deleting positional information P. The digital camera  102  and the smartphone  101  are connected by BLE and the positional information setting mode of the smartphone  101  is ON. Hence, the digital camera  102  acquires the latest positional information P immediately before the time t 0 . The communication between the digital camera  102  and the smartphone  101  is disconnected at a time t 0  because of communication failure or the smartphone  101  exiting the communication range. 
     After the time t 0 , the latest positional information in the cache memory  200  of the digital camera  102  is P. The digital camera  102  restarts broadcasting an advertisement packet at the time t 0 . The digital camera  102  reads the cache memory  200  every time image data  121  is generated no matter whether the positional information setting mode of the smartphone  101  is ON or OFF after the time t 0 , even if the communication is disconnected. 
     At a time t 1 , the positional information setting mode of the smartphone  101  is changed from ON to OFF. The smartphone  101  records the time t 1  to the storage device  302  as a time of mode change. At a time t 2 , the digital camera  102  takes an image of an object and sets the latest positional information P in the cache memory  200  to the image data to generate an image file  122 . 
     At a time t 3 , BLE connection between the digital camera  102  and the smartphone  101  is established. The smartphone  101  immediately sends the time t 1  of the time of mode change to the digital camera  102 . Since the positional information setting mode is OFF, the smartphone  101  also sends cancellation data to the digital camera  102 . 
     Upon receipt of the time of mode change t 1 , the digital camera  102  deletes the positional information P set later than the time of mode change t 1  from the image file generated during the disconnection. The position of the digital camera  102  at the time t 2  is not necessarily the position indicated by the positional information P. However, the digital camera  102  cannot receive information from the smartphone  101  during the disconnection. 
     Accordingly, the digital camera  102  retroactively deletes the positional information P. As a result of this operation, erroneous setting of the positional information P can be avoided. Further, the digital camera  102  receives cancellation data at the time t 3 . Hence, the positional information P will be never set to image data  121  generated by taking an image after the time t 3 . 
     Example of Sending Time of Mode Change 
       FIG. 13  is a flowchart of an example of sending a time of mode change by the smartphone  101 . The flowchart of  FIG. 13  is an example of the processing of an application program to be executed by the processor  301  when the positional information setting mode is checked at Step S 610  in  FIG. 6 . 
     The smartphone  101  determines whether the smartphone  101  is being connected with the digital camera  102  by BLE (Step S 1301 ). If the smartphone  101  is being connected by BLE (Step S 1301 : Yes), the smartphone  101  returns to Step S 1301  to repeat the determination. If the smartphone  101  is not being connected by BLE (Step S 1301 : No), the BLE connection between the smartphone  101  and the digital camera  102  is disconnected. 
     Subsequently, the smartphone  101  determines whether the positional information setting mode is changed from ON to OFF (Step S 1302 ). If it is not changed (Step S 1302 : No), the smartphone  101  returns to Step S 1301 . If it is changed (Step S 1302 : Yes), the smartphone  101  records the time of mode change to the storage device  302  (Step S 1303 ). 
     The smartphone  101  waits to be reconnected with the digital camera  102  after recording the time of mode change (Step S 1304 : No). If the connection is reestablished (Step S 1304 : Yes), the smartphone  101  retrieves the time of mode change from the storage device  302  and sends it to the digital camera  102  (Step S 1305 ). 
     Example of Retroactively Deleting Positional Information 
       FIG. 14  is a flowchart of an example of retroactively deleting positional information by the digital camera  102 . The digital camera  102  waits to receive a time of mode change when being reconnected with the smartphone  101  (Step S 1401 : No). Upon receipt of a time of mode change (Step S 1401 : Yes), the digital camera  102  searches the storage device  402  to identify image files  122  of the images taken after the time of mode change (Step S 1402 ). Then, the digital camera  102  deletes positional information P from the identified image files  122  (Step S 1403 ) and terminates the retroactively deleting positional information. 
     Since the digital camera  102  has neither a function to set positional information P nor a positioning function, it cannot stop setting positional information P when the communication with the smartphone  101  is disconnected and therefore, reads the positional information P before the disconnection. However, the digital camera  102  in Embodiment 2 receives the time of mode change after being reconnected to find out the time at which the positional information setting mode in the smartphone  101  is changed from ON to OFF during the disconnection. Accordingly, even if positional information P received before the disconnection is set to image data  121  generated during the disconnection, the digital camera  102  can delete the positional information P later. This operation reduces the frequency to set erroneous positional information P. 
     Like the digital camera in Embodiment 1, the digital camera  102  in Embodiment 2 has neither a function to choose whether to set positional information P or a positioning function. Accordingly, not installing the function to choose whether to set positional information P in the digital camera  102  but managing the function with the positional information setting mode of the smartphone  101  eliminates complicated operations on both the smartphone  101  and the digital camera  102  and improves the usability. Furthermore, even if the digital camera  102  does not have a positioning function to acquire positional information P, the digital camera  102  can acquire the positional information P at the time of taking an image from the smartphone  101 ; the digital camera  102  can be reduced in weight, size, and cost. 
     Embodiment 3 
     Embodiment 3 provides an example of setting positional information in the case where the digital camera  102  changes the connection with the smartphone  101  from BLE connection to ad hoc Wi-Fi connection to transfer an image file  122  or  123  to the smartphone  101 . Embodiment 3 employs BLE as an example of a first communication method for sending positional information P and ad hoc Wi-Fi connection as an example of a second communication method for transferring an image file  122  or  123 ; however, the first communication method can be any other communication method such as Bluetooth as far as it is slower than the second communication method. In similar, the second communication method can be any other communication method such as Wi-Fi Direct™ (“™” will be omitted hereinafter), as far as the second communication method is faster than the first communication method. To mainly explain this example of setting positional information, the elements same as those in Embodiment 1 or 2 are denoted by the same reference signs and description thereof is omitted in Embodiment 3. 
     Sequence of Setting Positional Information 
       FIG. 15  is a sequence diagram illustrating an example of setting positional information in Embodiment 3. In the beginning of  FIG. 15 , the digital camera  102  and the smartphone  101  are already connected by BLE and the positional information setting mode of the smartphone  101  is ON. Each time the smartphone  101  acquires positional information with the acquisition unit  514  (Step S 1501 ), the smartphone  101  transfers the acquired positional information to the digital camera  102  by BLE communication (Step S 1502 ). 
     Each time positional information P is transferred (Step S 1502 ), the digital camera  102  stores it to the top of the stack in the cache memory  200   
     (Step S 1503 ). Subsequently, the digital camera  102  receives an instruction to start ad hoc Wi-Fi connection (Step S 1504 ). This instruction to start ad hoc Wi-Fi connection (Step S 1504 ) can be received through explicit operation by the user, for example. 
     The digital camera  102  may also receive an instruction to start Wi-Fi connection (Step S 1504 ) that is triggered by completion of generation of an image file  122  as a result of taking an image of an object. The digital camera  102  may display a screen to recommend ad hoc Wi-Fi connection on the backside monitor upon completion of generation of an image file  122  as a result of taking an image of an object to receive an instruction to start Wi-Fi connection (Step S 1504 ) through explicit operation by the user. 
     Upon receipt of the instruction to start Wi-Fi connection (Step S 1504 ), the digital camera  102  sends a request to disconnect BLE (a TERMINATE packet) to the smartphone  101  (Step S 1505 ). With this operation, the smartphone  101  and the digital camera  102  disconnect the BLE connection (Step S 1506 ). Such disconnecting the BLE connection before starting ad hoc Wi-Fi connection reduces the wasteful power consumption of the smartphone  101  and the digital camera  102 . 
     Subsequently, the smartphone  101  and the digital camera  102  establish ad hoc Wi-Fi connection (Step S 1507 ). 
     After establishment of ad hoc Wi-Fi connection (Step S 1507 ), the smartphone  101  acquires positional information with the acquisition unit (Step S 1508 ) and each time, the smartphone  101  transfers the positional information to the digital camera  102  through the ad hoc Wi-Fi connection (Step S 1509 ). Each time positional information P is transferred (Step S 1509 ), the digital camera  102  stores the positional information P to the top of the stack in the cache memory  200  (Step S 1510 ). 
     Subsequently, the digital camera  102  receives an instruction to transfer image files by ad hoc Wi-Fi connection (Step S 1511 ). Specifically, the digital camera  102  may receive the instruction to transfer image files with designation of the image files  122  to be transferred through user operation. This transfer instruction (Step S 1511 ) can be received through explicit operation by the user. 
     The digital camera  102  may also receive a transfer instruction (Step S 1511 ) triggered by accumulation of image files  122  exceeding a predetermined volume in the storage device  402 . When the image files  122  accumulated in the storage device  402  exceed a predetermined volume, the digital camera  102  can display a screen to recommend transfer of files by ad hoc Wi-Fi connection and receive designation of the image files  122  to be transferred on the backside monitor to receive designation of the image files  122  to be transferred and a transfer instruction (Step S 1511 ) through explicit operation by the user. 
     Upon receipt of the transfer instruction (Step S 1511 ), the digital camera  102  transfers an image file  122  (Step S 1512 ). Upon completion of the transfer of the image file  122  (Step S 1512 ), the smartphone  101  acquires positional information P with the acquisition unit  514  (Step S 1513 ) and transfers the acquired positional information P to the digital camera  102  through ad hoc Wi-Fi connection (Step S 1514 ). 
     Each time positional information P is transferred (Step S 1514 ), the digital camera  102  stores the positional information P to the cache memory  200  (Step S 1515 ). Upon completion of transfer of positional information P (Step S 1514 ), the digital camera  102  transfers the next image file  122  to the smartphone  101  through ad hoc Wi-Fi connection (Step S 1512 ). 
     The smartphone  101  and the digital camera  102  repeat transfer of an image file  122  in units of file at Steps S 1512  to S 1515 ; however, the file transfer can be performed in units of certain size, instead of in units of file. In the case of transfer in units of file, image files  122  have different sizes and therefore, the intervals for the smartphone  101  to transfer positional information P are varied. However, in the case of transfer in units of certain size, the variation among the transfer intervals can be reduced. Further in the case of transfer in units of certain size, the frequency for the smartphone  101  to transfer positional information P can be increased by determining a smaller size for a unit. 
     When a user riding on a moving object such as a car or a train takes images with the digital camera  102  and transfers their image files  122  from the digital camera  102  to the smartphone  101 , the digital camera cannot acquire positional information P until transfer of an image file  122  is completed and therefore, the last stored positional information P could be different from the current position. For this reason, the digital camera  102  may suspend transferring image files  122  in ad hoc Wi-Fi connection (Step S 1512 ) if the speed of the moving object is higher than a predetermined speed. 
     Specifically, the smartphone  101  calculates the speed of the moving object based on the successively acquired positional information P and the time intervals of the acquisition. The smartphone  101  transfers the calculated speed together with or instead of positional information P to the digital camera  102  through ad hoc Wi-Fi connection (Step S 1514 ). 
     Upon being notified of the movement speed, the digital camera  102  suspends transferring image files if the speed is higher than a predetermined speed. As a result of this operation, the smartphone  101  can transfer positional information P to the digital camera  102  through ad hoc Wi-Fi connection without waiting for completion of transfer of an image file. In this case, the digital camera  102  resumes the transfer of image files  122  when the received movement speed becomes lower than the predetermined speed. 
     Instead of sending the speed of the moving object to the digital camera  102 , the smartphone  101  can send an instruction to suspend transfer of image files together with or instead of positional information P to the digital camera  102  through ad hoc Wi-Fi connection, if the speed of the moving object is higher than a predetermined speed (Step S 1514 ). 
     In this case, the digital camera  102  that receives the instruction to suspend transfer of image files  122  suspends transfer of image files  122 . As a result, the smartphone  101  can transfer positional information P to the digital camera  102  through ad hoc Wi-Fi connection without waiting for completion of transfer of an image file  122 . 
     The smartphone  101  sends an instruction to resume transfer of image files  122  to the digital camera  102  when the calculated movement speed becomes lower than the predetermined speed. The digital camera  102  resumes the transfer of the image file  122  upon receipt of the instruction to resume transfer. 
     Although the above-described two examples of transfer control control suspension and resumption of transfer of image files  122 , the control may decrease the unit size as the movement speed becomes higher. 
     Specifically, the smartphone  101  calculates the speed of a moving object based on the successively acquired positional information P and the time intervals in acquiring positional information P. The smartphone  101  transfers the calculated movement speed together with or instead of positional information P to the digital camera  102  through ad hoc Wi-Fi connection (Step S 1514 ). 
     In these cases, the digital camera  102  decreases the unit size if the received movement speed is higher than the previous one, and increases the unit size if the received movement speed is lower than the previous one. This configuration enables the smartphone  101  to control the frequency of transferring positional information P depending on the speed of the moving object. 
     Instead of sending the speed of the moving object to the digital camera  102 , the smartphone  101  can send an instruction to decrease the unit size if the calculated speed is higher than the previous one and an instruction to increase the unit size if the calculated speed is lower than the previous one together with or instead of positional information P to the digital camera  102  through ad hoc Wi-Fi connection (Step S 1514 ). 
     In these cases, the digital camera  102  that receives an instruction to decrease the unit size decreases the unit size and transfers image files to the smartphone  101  through ad hoc Wi-Fi connection in units of the decreased size and the digital camera  102  that receives an instruction to increase the unit size increases the unit size and transfers image files to the smartphone  101  through ad hoc Wi-Fi connection in units of the increased size. This configuration enables the smartphone  101  to control the frequency of transferring positional information P depending on the speed of transportation. 
     The foregoing description has explained assuming that the positional information setting mode of the smartphone  101  is ON. If the positional information setting mode is changed from ON to OFF, the smartphone  101  sends the digital camera  102  cancellation data, instead of positional information P (Steps S 1502 , S 1508 , and S 1513 ). 
     In this case, if the cancellation data is a command to discard positional information P, the digital camera  102  discards the positional information P in the cache memory  200  as illustrated in the example (B1) in  FIG. 2 , like in Embodiment 1. Accordingly, the image files  123  to be transferred do not include positional information P as illustrated in the example (B) in  FIG. 1 . 
     If the cancellation data is invalid positional information PX, the digital camera  102  stacks invalid positional information PX to the cache memory  200  as illustrated in the example (B2) in  FIG. 2 . Accordingly, the image files  123  to be transferred include invalid positional information PX as illustrated in the example (B) in  FIG. 1 . 
     As understood from the above, Embodiment 3 enables the smartphone  101  to transfer positional information P or cancellation data to the digital camera  102  through ad hoc Wi-Fi connection in the intervals of transferring image files from the digital camera  102  to the smartphone  101  through ad hoc Wi-Fi connection. Accordingly, BLE connection that is not used to transfer positional information P or cancellation data is disconnected to reduce the wasteful power consumption in the smartphone  101  and the digital camera  102 . 
     The above-described Embodiments 1 to 3 have described examples where the smartphone  101  sends cancellation data to the digital camera  102 . However, the smartphone  101  can send a command not to set positional information P to data (hereinafter, a non-setting command) to the digital camera  102 . Upon receipt of the non-setting command, the digital camera  102  performs either one of two kinds of data processing. 
     One kind of data processing is that the digital camera  102  regards the non-setting command as the aforementioned command to discard positional information P and clears the cache memory  200  as illustrated in the example (B) in  FIG. 2 . 
     The other kind of data processing is that the digital camera  102  does not regard the non-setting command as a command to discard positional information P and does not set the latest positional information Pn (as of the time Tn) to the image data  121 . In other words, after receiving a non-setting command, the digital camera  102  stops retrieving the latest positional information Pn (as of the time Tn) from the cache memory  200 . This configuration reduces the load to retrieve positional information P. 
     When the mode of the smartphone  101  is subsequently changed from the second mode (the positional information setting mode: OFF) to the first mode (the positional information setting mode: ON), the digital camera  102  receives positional information P from the smartphone  101 . Upon receipt of the new positional information P, the digital camera  102  cancels the stop of retrieval of positional information Pn from the cache memory  200 . As understood from the above, the digital camera  102  stops retrieving positional information P from the cache memory  200  when the smartphone  101  is in the second mode (the positional information setting mode: OFF) to reduce the processing load and wasteful power consumption. 
     It should be noted that this invention is not limited to the configurations described above but can be achieved by desirably combining these configurations. This invention also includes other possible aspects within the technical scope of this invention. 
     EXPLANATION OF REFERENCES 
       101  smartphone,  102  digital camera,  121  image data,  122 ,  123  image file,  200  cache memory,  420  imager,  511  first sender unit,  512  first receiver unit,  513  first storage unit,  514  acquisition unit,  515  configuration unit,  521  second receiver unit,  522  second storage unit,  523  second sender unit,  524  generator unit,  525  control unit