JP2015045580A - Electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electronic apparatus which can acquire time information for a GPS module while saving power.SOLUTION: An electronic apparatus 10 comprises: a communication unit 112 which communicates with a position measurement unit 113 that acquires position information and time information on the basis of signals from satellites 30A to 30D; a clocking unit 112 which clocks the current time; a time calculation unit 112 which calculates the reference time on the basis of the time information received from the position measurement unit 113 via the communication unit 112 and clocking information clocked by the clocking unit 112; and a control unit 112 which controls the communication unit 112, the clocking unit 112 and the time calculation unit 112 so as to receive the time information via the position measurement unit 113 at first timing, calculate the reference time at second timing and output the reference time to the position measurement unit 113.

Description

  The present invention relates to an electronic device.

  For positioning using a GPS satellite, time information is also required on the side of the GPS module that receives radio waves from the GPS satellite. Therefore, it is disclosed that power is always supplied to the timer circuit for the GPS module so that the time can be measured even when the power switch of the electronic device including the GPS module is turned off and the power supply to the GPS module is stopped. (See Patent Document 1).

JP 2012-154872 A

  However, there is room for improvement in terms of power saving to constantly supply power to the timer circuit for the GPS module in the electronic device.

  An electronic device according to the present invention is input from a position measurement unit via a communication unit that communicates with a position measurement unit that acquires position information and time information based on a signal from a satellite, a timer unit that measures time, and a communication unit. Based on the time information and the time information measured by the time measuring unit, the time calculation unit that calculates the reference time, and the time information from the position measurement unit at the first timing are input, and the reference time is calculated at the second timing. And a control unit for controlling the communication unit, the time measuring unit, and the time calculating unit so as to output the reference time to the position measuring unit.

  The electronic device according to the present invention can achieve both acquisition of time information for the GPS module and power saving.

It is a block diagram which illustrates the principal part structure of a digital camera. It is a flowchart explaining the flow of the positioning by a GPS module.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
<Outline of GPS positioning>
Positioning using a GPS satellite is performed based on distance measurement. In general, the GPS module receives a signal with the exact position and time of the GPS satellite transmitted from the GPS satellite, and measures the time (signal propagation time) until the signal reaches the GPS module from the GPS satellite. To do. The distance from the GPS satellite to the GPS module is calculated by taking the product of the signal propagation time and the propagation speed (= light speed).

  Since the position of the GPS module may be considered that the radius centered on the position of the GPS satellite is on the spherical surface of the measurement distance, when distance measurement is performed for each of the three GPS satellites, the intersection of the three spherical surfaces The position of the GPS module is determined. In the above distance measurement, accurate time information equivalent to that of an atomic clock mounted on a GPS satellite is required to accurately measure the signal propagation time. However, since it is unrealistic to provide the GPS module with an atomic clock, the GPS module is equipped with a low-accuracy clock, and the time difference between the GPS module clock and the GPS satellite atomic clock is calculated. Is adopted.

  Specifically, the distance measurement is simultaneously performed for four GPS satellites, and a positioning calculation is performed to obtain four unknowns based on information received from the four GPS satellites. Of the four unknowns, three correspond to three-dimensional position information, and the remaining one corresponds to time difference information from the GPS satellite. As described above, the positioning calculation is performed based on the reception information from the four GPS satellites, and as a result, the low-accuracy time information of the GPS module can be matched with the accurate time information of the GPS satellites. In this description, time information used for positioning calculation in the GPS module is referred to as GPS reference time.

  Conventionally, a low-precision clock (for example, a clock circuit) always keeps time in the GPS module so that the GPS reference time is not lost. On the other hand, in this embodiment, when the power supply to the GPS module is stopped, the power supply to the timer circuit of the GPS module is also stopped, and the time measurement in the GPS module is stopped. And while the time measurement of the GPS module is stopped, the GPS reference time information is maintained using a clock (for example, RTC (real time clock)) provided in the host device combined with the GPS module.

  Since the present embodiment is characterized in that the GPS reference time information is maintained while the power supply to the GPS module is stopped, the following description will be focused on this point.

<Description of digital camera>
In the present embodiment, the host device combined with the GPS module is configured by the digital camera 10. FIG. 1 is a block diagram illustrating the main configuration of the digital camera 10. The digital camera 10 repeats positioning at predetermined time intervals by the GPS module 113 and stores positioning results such as latitude and longitude in the flash memory 111. When the release operation is performed, the digital camera 10 records the captured image data as an image file in a storage medium such as a memory card. At this time, the latest positioning result stored in the flash memory 111 is included in the image file as shooting position information.

  In FIG. 1, a digital camera 10 includes a photographing optical system 101, an image sensor 102, an AFE (Analog front end) circuit 103, an image processing circuit 104, an LCD monitor 105, a RAM 110, a flash memory 111, and a CPU 112. A GPS module 113, an external interface 114, an operation member 115, and an RTC 116.

  The photographing optical system 101 includes a plurality of lens groups including a zoom lens and a focusing lens, and forms a subject image on the imaging surface of the image sensor 102. In order to simplify FIG. 1, the photographing optical system 101 is illustrated as a single lens.

  The imaging element 102 is configured by a CMOS image sensor or the like in which light receiving elements are two-dimensionally arranged on the imaging surface. The image sensor 102 photoelectrically converts the subject image to generate an image signal. The image signal is input to the AFE circuit 103.

  The AFE circuit 103 performs predetermined signal processing on the image signal and converts the image signal after the signal processing into digital data. Digital data is input to the image processing circuit 104. The image processing circuit 104 performs various types of image processing (color interpolation processing, gradation conversion processing, contour enhancement processing, white balance adjustment processing, image compression processing, image expansion processing, etc.) on digital data.

  The LCD monitor 105 is constituted by a liquid crystal panel, and displays an image, an operation menu screen, and the like according to an instruction from the CPU 112. The RAM 110 is used as a work memory for the CPU 112. The RAM 110 temporarily stores digital image data in the image processing step performed by the image processing circuit 104.

  The flash memory 111 is a nonvolatile memory, and is used for storing various data in addition to storing a program executed by the CPU 112. The flash memory 111 is provided with an area 111a for storing GPS reference time information and an area 111b for storing in-camera reference time information. The GPS reference time information is a time used for positioning calculation by the GPS module 113 as described above.

  The in-camera reference time information is information indicating a local time (for example, Japanese standard time) set in the digital camera 10 by the user. The CPU 112 controls an operation performed by the digital camera 10 by executing a program stored in the flash memory 111. The CPU 112 also performs AF (autofocus) operation control and automatic exposure (AE) calculation.

  The operation member 115 includes a main switch, a release button, a menu switch, and the like. The operation member 115 sends an operation signal corresponding to each operation, such as a main switch operation, a release operation, and a menu selection operation, to the CPU 112. In addition to monitoring input of operation signals from the operation member 115, the CPU 112 acquires positioning data (including GPS reference time) from the GPS module 113.

  The GPS module 113 includes a CPU 113a in the GPS module and an RF unit 113b. The RF unit 113b receives radio waves from the four GPS satellites 30A to 30D, and the CPU 113a in the GPS module calculates positioning data (latitude, longitude, altitude, and time) using information carried on the received radio waves. . The CPU 112 receives positioning data from the GPS module 113 every predetermined time (for example, 5 seconds), and overwrites and stores the positioning data in a predetermined area of the nonvolatile memory (flash memory 111).

  The GPS module 113 includes an energization control terminal 113c, and switches between energization (power supply) and non-energization (power cutoff) in accordance with a control signal from the CPU 112. For example, when the energization control terminal 113c is controlled to H level, the GPS module 113 starts supplying power to the inside of the module. When the energization control terminal 113c is controlled to L level, the GPS module 113 cuts off the power supply to the inside of the module. The CPU 112 normally controls the energization control terminal 113c to H level at the timing when the main switch is turned on and energization of each part in the camera is started. Further, when the main switch is turned off, the CPU 112 requests the GPS module 113 to stop positioning, and then controls the energization control terminal 113c to the L level.

  The CPU 112 when the information indicating the positioning data of the shooting point is set to be stored in association with the shot image, the exif format including the shot image data, the positioning data, and the shooting time information (for example, the reference time in the camera) The image file is generated, and the image file is controlled to be recorded on a storage medium (not shown). Specifically, when the CPU 112 receives a release button pressing operation signal, it sends an instruction to each block in FIG. 1 to start the shooting process, and records the shot image file in a storage medium (not shown).

  The external interface 114 transmits / receives data to / from an external device (such as a personal computer or a cradle) according to an instruction from the CPU 112 via a cable (not shown). The RTC 116 counts a clock signal having a predetermined frequency generated by a built-in crystal oscillator, and outputs a count value in response to a request from the CPU 112. The RTC 116 is supplied with electric power from a battery (not shown), and is configured to continue the counting operation regardless of the on / off state of the main switch.

  When the main switch is turned on, for example, the CPU 112 adds a time based on the latest count value by the RTC 116 to the GPS reference time stored in the area 111a of the flash memory 111, and replaces it with a new GPS reference time. . When the main switch is turned off, the CPU 112 overwrites and stores in the area 111a the latest time information (GPS reference time transmitted together with the positioning data from the GPS module 113) stored in a predetermined area of the flash memory 111.

  Further, when the main switch is turned on, the CPU 112 adds a time based on the latest count value by the RTC 116 to the reference time in the camera stored in the area 111b of the flash memory 111, for example, and creates a new local Replace as time. The CPU 112 measures the local time based on the replaced local time and the count value by the RTC 116. When the main switch is turned off, the CPU 112 overwrites and stores the latest local time in the area 111b.

<Position measurement control>
The flow of positioning by the GPS module 113 executed by the CPU 112 of the digital camera 10 will be described with reference to the flowchart illustrated in FIG. In FIG. 2, the process flow on the digital camera 10 side is shown on the left side, and the process flow on the GPS module 113 side is shown on the right side.

<Processing on the digital camera 10>
The CPU 112 activates the process shown in FIG. 2 at a timing when the main switch constituting the operation member 115 is turned on and energization of each part in the camera is started. The processing according to FIG. 2 is performed in parallel even when other processing such as photographing processing is performed. In step S11 of FIG. 2, the CPU 112 sets the output of the GPS module 113 to the energization control terminal 113c to H level, starts energization inside the GPS module 113, and proceeds to step S12. As a result, the GPS module 113 is activated.

  In step S <b> 12, the CPU 112 determines whether GPS reference time information is stored in the flash memory 111. If the GPS reference time is stored in the area 111a, the CPU 112 makes a positive determination in step S12 and proceeds to step S13. If the GPS reference time is not stored in the area 111a, the CPU 112 makes a negative determination in step S12 and proceeds to step S14.

  In step S13, the CPU 112 reads the GPS reference time from the area 111a of the flash memory 111, adds a time based on the latest count value by the RTC 116, and replaces it with a new GPS reference time. The CPU 112 transmits the replaced GPS reference time information to the GPS module 113, and proceeds to step S14. In step S14, the CPU 112 requests the GPS module 113 to drive and proceeds to step S15. Thereby, the GPS module 113 starts positioning.

  In step S15, the CPU 112 acquires positioning data (including the GPS reference time) from the GPS module 113, and proceeds to step S16. In step S16, the CPU 112 stores the positioning data (including the GPS reference time) in a predetermined area of the flash memory 111, and proceeds to step S17.

  In step S17, the CPU 112 determines whether or not to perform a power-off process. When the main switch constituting the operation member 115 is turned off, the CPU 112 makes an affirmative decision in step S17 and proceeds to step S18. When the main switch constituting the operation member 115 is not turned off, the CPU 112 makes a negative determination in step S17, returns to step S15, and repeats the above-described processing.

  In step S18, the CPU 112 stores the GPS reference time information in the flash memory 111, and proceeds to step S19. Specifically, of the latest positioning data stored in a predetermined area of the flash memory 111, the GPS reference time is overwritten and stored in the flash memory 111 area 111a.

  In step S19, the CPU 112 requests the GPS module 113 to stop driving and proceeds to step S20. In step S20, the CPU 112 sets the output of the GPS module 113 to the energization control terminal 113c to L level, terminates the energization of the GPS module 113, and ends the process of FIG.

<Processing on the GPS module 113 side>
The GPS module CPU 113a activates the processing shown in FIG. 2 when energization of the GPS module 113 is started. In step S51 of FIG. 2, the CPU 113a in the GPS module acquires GPS reference time information from the CPU 112, and proceeds to step S52. The GPS module 113 uses the GPS reference time acquired here for positioning calculation in step S53.

  In step S52, the CPU 113a in the GPS module determines whether or not the CPU 112 has requested driving. The CPU 113a in the GPS module makes an affirmative decision in step S52 when a drive request is made, and proceeds to step S53. If a drive request is not made, the CPU 113a waits for a drive request while repeating the decision process.

  In step S53, the CPU 113a in the GPS module obtains positioning data (including GPS reference time) by performing positioning calculation based on information received from the four GPS satellites, and proceeds to step S54. The CPU 113a in the GPS module calibrates the GPS reference time used for the positioning calculation based on the time difference information obtained by the positioning calculation, so that each time the positioning is performed, it is about the same as the atomic clock possessed by the GPS satellites 30A to 30D. Update to the correct time.

  In step S54, the CPU 113a in the GPS module transmits the positioning data (including the GPS reference time) to the CPU 112, and proceeds to step S55. In step S55, the CPU 113a in the GPS module determines whether or not the CPU 112 has requested stop of driving. The CPU 113a in the GPS module makes an affirmative decision in step S55 when a stop request is made, and proceeds to step S56. If a stop request is not made, the CPU 113a in the GPS module makes a negative decision in step S55 and returns to step S53. In this case, the GPS reference time is updated while positioning is repeated every predetermined time. In step S56, the CPU 113a in the GPS module stops positioning and ends the process shown in FIG.

According to the embodiment described above, the following operational effects can be obtained.
(1) The digital camera 10 is input from the GPS module 113 via the CPU 112 that communicates with the GPS module 113 that acquires position information and time information based on signals from the GPS satellites 30A to 30D, the CPU 112 that measures time, and the CPU 112. The time information is input from the GPS module 113 at the timing of the CPU 112 that calculates the GPS reference time based on the measured time information and the time information measured by the CPU 112, and the first (the energization stop for the GPS module 113), And a CPU 112 for controlling the GPS reference time to be calculated and the GPS reference time to be output to the GPS module 113 at the second timing (the start of energization of the GPS module 113). As a result, the GPS reference time can be maintained without providing a time keeping circuit to the GPS module 113 and constantly energizing it.

(2) The time information input from the GPS module 113 is the time when the GPS reference time output to the GPS module 113 is calibrated in the GPS module 113 based on signals from the GPS satellites 30A to 30D. Thereby, an accurate GPS reference time can be maintained.

(3) The first timing is when energization is stopped for the GPS module 113, and the second timing is when energization is started after the energization is stopped. Thereby, the GPS reference time can be maintained while the energization of the GPS module 113 is stopped.

(Modification 1)
In the above description, the digital camera 10 is described as an example of the host device combined with the GPS module. However, in addition to the digital camera 10, an electronic device such as a high-function mobile phone or a tablet terminal may be used as the host device.

(Modification 2)
In the above embodiment, an example in which the GPS module 113 is built in the digital camera 10 has been described. However, the GPS module may be a type that is mounted (or connected) to an electronic device such as the digital camera 10.

(Modification 3)
In the above description, an example in which time information is not transmitted to the GPS module 113 when a negative determination is made in step S12 has been described. In this case, for example, the GPS module 113 treats the time put on the signal transmitted from any one of the four GPS satellites as the GPS reference time, and performs the first positioning calculation after starting energization. . As described above, when the positioning calculation is performed, the GPS reference time can be calibrated based on the time difference information obtained by the positioning calculation. Use it.

  If a negative determination is made in step S12, the in-camera reference time information may be transmitted to the GPS module 113. In this case, the GPS module 113 treats the in-camera reference time (for example, Japan standard time) as the GPS reference time, and performs the first positioning calculation after the start of energization. As described above, when the positioning calculation is performed, the GPS reference time can be calibrated based on the time difference information obtained by the positioning calculation. Use it.

  The CPU 112 of the modification 3 calculates the in-camera reference time different from the GPS reference time based on the local time input by the user operation and the time information measured by the CPU 112. Then, the CPU 112 performs control so as to calculate the in-camera reference time and output the in-camera reference time to the GPS module 113 when the time information from the GPS module 113 does not exist. As a result, the GPS reference time can be maintained without providing a time keeping circuit to the GPS module 113 and constantly energizing it.

(Modification 4)
In the above description, when the CPU 112 starts energizing the GPS module 113 (S11), the example in which the GPS reference time information is transmitted from the CPU 112 to the GPS module 113 (S13) has been described. In addition to this, the GPS reference time information may be transmitted from the CPU 112 to the GPS module 113 when the GPS module 113 requires a cold start. The cold start means that the almanac information and the ephemeris information are newly acquired from the transmission signal by the GPS satellite when the time elapsed from the previous positioning exceeds a predetermined time.

  Since the CPU 112 of the modification 4 includes the case where the GPS module 113 performs a cold start at the second timing, a new calculation is performed when a long time elapses from the previous positioning while the GPS module 113 is energized. The GPS reference time can be transmitted to the GPS module 113.

  The above description is merely an example, and is not limited to the configuration of the above embodiment.

DESCRIPTION OF SYMBOLS 10 ... Digital camera 30A-30D ... GPS satellite 102 ... Image pick-up element 111 ... Flash memory 112 ... CPU
113 ... GPS module 113a ... CPU in the GPS module
113b ... RF unit 113c ... energization control terminal 115 ... operation member 116 ... RTC

Claims (6)

A communication unit that communicates with a position measurement unit that acquires position information and time information based on a signal from a satellite;
A timekeeping section for timing,
A time calculation unit that calculates a reference time based on the time information input from the position measurement unit via the communication unit and the time information timed by the time measurement unit;
The communication unit, the time measuring unit, so as to input the time information from the position measurement unit at a first timing, and to calculate the reference time and output the reference time to the position measurement unit at a second timing. And a control unit for controlling each of the time calculation units,
An electronic device comprising: The electronic device according to claim 1,
The time information input from the position measuring unit is the time when the reference time output to the position measuring unit is calibrated based on a signal from the satellite in the position measuring unit. . The electronic device according to claim 1 or 2,
The electronic device according to claim 1, wherein the first timing is when energization is stopped for the position measurement unit, and the second timing is when energization is started after the energization is stopped. The electronic device according to claim 3,
The electronic device according to claim 2, wherein the second timing is a case where a cold start is performed in the position measurement unit. In the electronic device as described in any one of Claims 1-4,
The time calculation unit further calculates a second reference time different from the reference time based on information input by a user operation and time information measured by the time measurement unit,
The control unit is configured to calculate the second reference time and output the second reference time to the position measurement unit when the time information from the position measurement unit does not exist. An electronic device that controls a time measuring unit and the time calculating unit, respectively. The electronic device according to claim 5,
When the second reference time is output to the position measurement unit, the time information input from the position measurement unit is the second reference time output to the position measurement unit from the satellite in the position measurement unit. An electronic device characterized in that the time is calibrated based on a signal.

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