JP6591017B1 - Wireless sensor device and wireless sensor system - Google Patents

Abstract

In a wireless sensor device configured such that a sensor control unit does not share an oscillator with a wireless communication unit, a sensor control clock is synchronized with another wireless sensor device. According to one aspect of the present invention, a wireless sensor device includes first and second oscillators, first and second clock control units, an interrupt generation unit, and a sensor control unit. The first clock control unit corrects the first counter value based on the clock signal of the first oscillator based on the reference clock value included in the radio signal received from the hub device at the first interval. The interrupt generation unit generates an interrupt signal at the second interval. The second clock control unit corrects the second counter value based on the clock signal of the second oscillator based on the second interval every time an interrupt signal is received. The sensor control unit generates time data associated with the sensor value based on the second counter value. [Selection] Figure 1

Description

  The present invention relates to time synchronization between wireless sensor devices.

  By synchronizing the times of a plurality of sensors installed at physically separated positions, for example, a plurality of sensor values associated with the same time can be identified. Thereby, for example, it is possible to contrast different biological data such as electrocardiographic data and pulse wave data at the same time of the same person.

  Conventionally, such time synchronization has been realized by the following two techniques, for example. A first technique is to connect a plurality of sensors to a sensor control unit realized by a single SoC (System on Chip) using a cable, and perform processing intensively by the sensor control unit. According to this technique, processing is performed using the single oscillator connected to the SoC as a base clock, so that there is almost no time lag between sensor data handled by the sensor control unit.

  In Patent Document 1, analog data output by a physical quantity measuring means M1 corresponding to various sensors such as an intake pressure sensor 3 is equivalent to an AD converter 17 at each trigger signal detection timing corresponding to each rotation signal. The transfer to the AD conversion means M3 is disclosed.

  In the second technique, a plurality of sensors are respectively connected to a wireless communication interface (I / F) and synchronized using a general wireless protocol such as a wireless LAN (Local Area Network) or Bluetooth (registered trademark). It is to exchange wireless signals for use. This technique allows time synchronization without the need for a physical cable.

JP 63-19008 A Special table 2014-504485 gazette

  According to the first technique described above, a cable for connecting a plurality of sensors to the sensor control unit may be a problem. For example, when a plurality of biometric sensors are installed at various parts of the user's body, the user may feel bothered with these cables or physically limit the movement of the body. That is, when a plurality of biometric sensors are installed in various parts of the user's body, in particular, the cable may be a factor that impairs the user's QoL (Quality of Life). Further, the cable is required to be made of a material having a small influence on the human body, to have a high resistance to disconnection, and to have a low resistance value, and there is a problem of an increase in cost for responding to these.

  Furthermore, when the total number of sensors connected to the SoC exceeds the number of interfaces installed in the SoC, for example, the number of ADC (Analog Digital Converter) channels, it is necessary to use a plurality of SoCs in combination. . In this case, the circuit configuration becomes complicated, such as sharing an oscillator.

  On the other hand, according to the second technique, wireless signals for synchronization are exchanged using a general-purpose wireless protocol. In wireless LAN and Bluetooth (registered trademark), which are typical examples of such a wireless protocol, However, since contention-type wireless communication is performed, there is a problem that the communication latency is unstable. For example, in an environment where communication channels are congested, collisions are likely to occur, and latency is likely to increase. As the latency increases, the arrival timing of the synchronization radio signal is delayed, and the accuracy of time synchronization deteriorates.

  On the other hand, it is possible to stabilize the latency by exchanging wireless signals for synchronization by TDMA (Time Division Multiple Access) wireless communication in which communication bandwidth is guaranteed instead of such contention wireless communication. It is.

  Patent Document 2 discloses that in a TDMA-based communication system, a base station transmits a synchronization signal to a client, and this synchronization signal causes the client to adjust (eg, reset) the clock according to the base station clock. Yes. However, Patent Document 2 merely discloses a clock synchronization method for wireless communication. Therefore, even if such a synchronization method is applied, the sensor control clock cannot be synchronized in a configuration in which the sensor control unit and the wireless communication unit do not share an oscillator.

  An object of the present invention is to synchronize a sensor control clock with a sensor control clock in another wireless sensor device in a wireless sensor device in which the sensor control unit does not share an oscillator with the wireless communication unit.

  According to one aspect of the present invention, the wireless sensor device is wirelessly connected to the hub device. The wireless sensor device includes a first oscillator, a first counter, a wireless communication unit, a first clock control unit, an interrupt generation unit, a second oscillator, a second counter, a second counter, A clock control unit and a sensor control unit are included. The first oscillator generates a first clock signal. The first counter counts the first counter value based on the first clock signal. The wireless communication unit performs wireless communication in synchronization with the first counter value, and receives a wireless signal including a reference clock value from the hub device at a first interval. The first clock control unit corrects the first counter value based on the reference clock value. The interrupt generation unit generates a first interrupt signal at a second interval. The second oscillator generates a second clock signal. The second counter counts the second counter value based on the second clock signal. The second clock control unit corrects the second counter value based on the second interval every time the first interrupt signal is received. A sensor control part produces | generates the time data linked | related with the sensor value showing the measurement result of the physical quantity by a sensor based on a 2nd counter value, and obtains sensor data containing a sensor value and time data.

  According to another aspect of the present invention, a wireless sensor system includes a hub device and a plurality of wireless sensor devices wirelessly connected to the hub device. Each of the plurality of wireless sensor devices includes a first oscillator, a first counter, a wireless communication unit, a first clock control unit, an interrupt generation unit, a second oscillator, and a second counter. , A second clock control unit, and a sensor control unit. The first oscillator generates a first clock signal. The first counter counts the first counter value based on the first clock signal. The wireless communication unit performs wireless communication in synchronization with the first counter value, and receives a wireless signal including a reference clock value from the hub device at a first interval. The first clock control unit corrects the first counter value based on the reference clock value. The interrupt generation unit generates a first interrupt signal at a second interval. The second oscillator generates a second clock signal. The second counter counts the second counter value based on the second clock signal. The second clock control unit corrects the second counter value based on the second interval every time the first interrupt signal is received. A sensor control part produces | generates the time data linked | related with the sensor value showing the measurement result of the physical quantity by a sensor based on a 2nd counter value, and produces | generates the sensor data containing a sensor value and time data.

  According to the present invention, in the wireless sensor device in which the sensor control unit does not share the oscillator with the wireless communication unit, the sensor control clock can be synchronized with the sensor control clock in the other wireless sensor devices.

1 is a block diagram illustrating a wireless sensor device according to an embodiment. The figure which illustrates the wireless sensor system containing the wireless sensor apparatus of FIG. Explanatory drawing of the clock correction in the wireless sensor apparatus of FIG. Explanatory drawing of the clock correction in the wireless sensor apparatus of FIG. The flowchart which illustrates operation | movement of the hub apparatus in FIG. 3 is a flowchart illustrating a part of the clock correction operation related to the first oscillator in the wireless sensor device of FIG. 1. 6 is a flowchart illustrating the remainder of the clock correction operation related to the first oscillator in the wireless sensor device of FIG. 1. 6 is a flowchart illustrating a clock correction operation related to a second oscillator in the wireless sensor device of FIG. 1. Explanatory drawing of the timing synchronization of A / D conversion over a some wireless sensor apparatus.

  Hereinafter, embodiments will be described with reference to the drawings. Hereinafter, elements that are the same as or similar to elements already described are denoted by the same or similar reference numerals, and redundant descriptions are basically omitted. For example, when there are a plurality of identical or similar elements, a common reference may be used to explain each element without distinction, and the common reference may be used to distinguish each element. In addition, branch numbers may be used.

(Embodiment)
The wireless sensor device according to the embodiment can be incorporated into the wireless sensor system shown in FIG. 2, for example. In this wireless sensor system, a star-type network topology is adopted. That is, in this wireless sensor system, a plurality of wireless sensor devices 100 (nodes) are wirelessly connected around the hub device 200. Details of the wireless sensor device 100 will be described later.

  The hub device 200 may be, for example, a mobile terminal (for example, a smartphone, a tablet, a laptop, a smart watch, or other wearable device), a stationary PC (Personal Computer), and the like, but is not limited thereto. . The hub device 200 may be the same as or similar to the wireless sensor device 100 except for its role. For example, any one of the plurality of wireless sensor devices 100 can function as the hub device 200.

  Hub device 200 includes at least a wireless communication unit and an oscillator. The oscillator generates a clock signal. The wireless communication unit performs TDMA wireless communication and broadcasts a wireless signal including a clock value based on the clock signal to the plurality of wireless sensor devices 100 at a predetermined interval. Further, the wireless communication unit may receive sensor data from a plurality of wireless sensor devices 100.

  The oscillator included in the hub device 200, a clock signal generated by the oscillator, and a clock value based on the clock signal can be referred to as a reference oscillator, a reference clock signal, and a reference clock value, respectively. Further, the radio signal including the reference clock value and the transmission interval of the radio signal can be referred to as a beacon signal and a beacon interval, respectively.

  Hereinafter, the operation of the hub device 200 will be described with reference to FIG. The operation of FIG. 5 can be started, for example, when a predetermined application with clock synchronization of the plurality of wireless sensor devices 100 is started. First, the wireless communication unit of the hub device 200 sets a beacon (transmission) interval (step S301), and the process proceeds to step S302.

  In step S302, the wireless communication unit of the hub device 200 reads the reference clock value. Subsequently, the wireless communication unit determines whether or not the beacon transmission timing has arrived based on the reference clock value read in step S302 (step S303). The beacon transmission timing can be derived, for example, by adding the beacon interval set in step S301 to the previous beacon transmission timing. If it is determined that the beacon transmission timing has arrived, the process proceeds to step S304; otherwise, the process proceeds to step S305.

  In step S <b> 304, the wireless communication unit of the hub device 200 generates a beacon signal including a reference clock value and broadcasts the signal to the wireless sensor device 100. After step S304, the process proceeds to step S305.

  In step S305, it is determined whether or not to end the operation of FIG. The operation of FIG. 5 can be terminated in conjunction with the termination of the application, for example. If the operation of FIG. 5 is not terminated, the process returns to step S302.

  As illustrated in FIG. 1, the wireless sensor device 100 includes a first oscillator 101, a first counter 102, an antenna 103, a wireless communication unit 104, a first clock control unit 105, and an interrupt generation. Unit 106, sensor 107, A / D converter 108, second oscillator 109, second counter 110, second clock control unit 111, and sensor control unit 112.

  The wireless sensor device 100 includes, as hardware elements, a first SoC, a second SoC, a first oscillator 101, a first counter 102, an antenna 103, a sensor 107, an A / D converter 108, and a second oscillator. 109 and a second counter 110.

  The wireless sensor device 100 may be, for example, a health care device such as a sphygmomanometer, an electrocardiograph, a pedometer, a weight scale, a mobile device including a biosensor, or an electronic device including a sensor other than the biosensor. It may be a device.

  The first oscillator 101 can be an arbitrary oscillation circuit, for example, an oscillation circuit to which a solid oscillator such as a crystal oscillator is connected. The first oscillator 101 generates a first clock signal and supplies it to the first counter 102. The first clock signal can be, for example, a square wave with a fixed period. The first oscillator 101 may be built in (mounted on) the first SoC or may be externally attached to the first SoC.

  The first counter 102 counts the first counter value based on the first clock signal from the first oscillator 101. The first counter 102 notifies the wireless communication unit 104 and the interrupt generation unit 106 of the first counter value. Specifically, the first counter 102 includes a logic circuit configured to count up the first counter value in response to (in synchronization with) the rising edge or falling edge of the first clock signal. Can be realized. The first counter 102 may be built in the first SoC or may be externally attached to the first SoC. Note that the first counter 102 may count down instead of counting up, but in the following description, it is counted up.

  Further, the first clock control unit 105 performs start / stop control of the first counter 102. Further, the first counter value held by the first counter 102 can be rewritten (corrected) by the first clock control unit 105.

  The antenna 103 is connected to the wireless communication unit 104. The antenna 103 receives a radio signal transmitted from an external device such as the hub device 200 and sends it to the radio communication unit 104, or conversely transmits a radio signal supplied from the radio communication unit 104 to the external device. The antenna 103 may be built in the first SoC or may be externally attached to the first SoC.

  The wireless communication unit 104 performs wireless communication in synchronization with the first counter value notified by the first counter 102. For example, the wireless communication unit 104 can receive the above-described beacon signal from the hub device 200 via the antenna 103 and reproduce the reference clock value included in the beacon signal. This reference clock value is used as a synchronization target of the first counter value in each of the plurality of wireless sensor devices 100, as will be described later. The wireless communication unit 104 notifies the first clock control unit 105 of the reference clock value. Note that since the beacon signal is transmitted at every beacon interval, the wireless communication unit 104 can periodically receive the beacon signal.

  On the other hand, for example, the wireless communication unit 104 can receive sensor data from the sensor control unit 112 and transmit the sensor data to the hub device 200 via the antenna 103. Thereby, the hub device 200 can collect sensor data from the plurality of wireless sensor devices 100.

  The wireless communication unit 104 includes an analog circuit, an A / D converter, a D / A converter, a digital signal processing unit, and the like in order to realize such processing. Each of the analog circuit, the A / D converter, and the D / A converter may be incorporated in the first SoC or may be externally attached to the first SoC. On the other hand, the digital signal processing unit can be realized by a processor and a memory mounted on the first SoC.

  A processor implement | achieves the various processes mentioned later by running a program. The processor is typically a CPU (Central Processing Unit) and / or a GPU (Graphics Processing Unit), but may be a microcomputer, an FPGA (Field Programmable Gate Array), or a DSP (Digital Signal Processor), etc. .

  The memory may temporarily store programs executed by the processor and data used by the processor. The memory may include a RAM (Random Access Memory) having a work area where such programs / data are expanded.

  The analog circuit receives a radio signal from the antenna 103, performs analog signal processing such as low-noise amplification, filtering, and down-conversion, and sends the processed analog signal to the A / D converter. The A / D converter converts the input analog signal into a digital signal and sends it to the digital signal processing unit. The digital signal processing unit performs digital signal processing such as demodulation and decoding on the input digital signal to reproduce received data. In the example beacon signal described above, the received data may include a reference clock value.

  On the other hand, the digital signal processing unit receives transmission data (for example, including sensor data) from the sensor control unit 112 or other elements (not shown), performs digital signal processing such as encoding and modulation, and the processed digital signal To the D / A converter. The D / A converter converts an input digital signal into an analog signal and sends it to an analog circuit. The analog circuit performs analog processing such as up-conversion, filtering, and power amplification on the input analog signal, and sends the processed analog signal to the antenna 103.

  The first clock control unit 105 controls the first counter value held by the first counter 102. The first clock control unit 105 can be realized by an input / output interface such as a processor, a memory, and a UART (Universal Asynchronous Receiver / Transmitter) mounted on the first SoC.

  Specifically, the first clock control unit 105 receives the reference clock value from the wireless communication unit 104 and corrects the first counter value held by the first counter 102 based on the reference clock value. For example, the first clock control unit 105 may rewrite the first counter value with the reference clock value.

  Further, the first clock control unit 105 can perform start / stop control and initial setting of the first counter 102. For example, the first clock control unit 105 can perform initial setting of the first counter 102 in response to reception of the first beacon signal after the wireless sensor device 100 transitions to the clock synchronization mode. Here, the clock synchronization mode is an operation mode for performing clock synchronization between the plurality of wireless sensor devices 100. For example, a predetermined application is executed in the hub device 200, and the wireless sensor device 100 and the hub device 200. The wireless sensor device 100 may transition to the clock synchronization mode, triggered by the establishment of a wireless connection with

  Specifically, the first clock control unit 105 corrects the first counter value based on the reference clock value included in the first beacon signal after the wireless sensor device 100 transitions to the clock synchronization mode. Further, the first clock control unit 105 sets a start clock value for starting the synchronization of the first counter value and the second counter value described later, and an interval for performing an interrupt described later to maintain the synchronization. The interrupt interval shown is set for the interrupt generator 106. The start clock value is determined so as to represent a time in the future from the first counter value at the time when the start clock value is set. Then, the first clock control unit 105 notifies the second clock control unit 111 of the set start clock value and interrupt interval. The notification of the start clock value and the interrupt interval is performed using an input / output interface such as UART installed in the first SoC.

  In the example of FIG. 1, the first clock control unit 105 directly corrects the first counter value held by the first counter 102, but controls the first oscillator 101. Thus, the first counter value may be corrected indirectly. For example, when the first oscillator 101 is an oscillator capable of controlling the oscillation frequency, the first clock control unit 105 may control the oscillation frequency. Specifically, when the first counter value is delayed with respect to the reference clock value, that is, when the period of the first clock signal is larger than the period of the reference clock signal as illustrated in FIG. The first clock control unit 105 may raise the oscillation frequency of the first oscillator 101. Conversely, when the first counter value is advanced with respect to the reference clock value, the first clock control unit 105 may lower the oscillation frequency of the first oscillator 101.

  The interrupt generation unit 106 operates according to the start clock value and the interrupt interval set by the first clock control unit 105. The interrupt generation unit 106 can be realized by a processor, a memory, and an input / output interface such as GPIO (General Purpose Input / Output) mounted on the first SoC.

  Specifically, when the interrupt generation unit 106 detects that the first counter value has reached the start clock value, the interrupt generation unit 106 generates a (startup) interrupt signal and transmits it to the second clock control unit 111. The interrupt signal is transmitted using an input / output interface such as GPIO mounted on the first SoC.

  Thereafter, the interrupt generation unit 106 generates an (synchronous) interrupt signal at every interrupt interval and transmits the interrupt signal to the second clock control unit 111. That is, the interrupt generation unit 106 generates and transmits an interrupt signal at the timing when the first counter value reaches the sum of the start clock value and the natural number multiple of the interrupt interval.

  The sensor 107 measures a predetermined physical quantity and generates an (analog) sensing signal representing the measurement result. The sensor 107 sends a sensing signal to the A / D converter 108. The sensor 107 can be controlled, for example, by measurement conditions by the sensor control unit 112. The sensor 107 may be a biological sensor such as a sphygmomanometer or an electrocardiograph, a motion sensor such as an acceleration sensor, a gyro sensor, or a pedometer, or a temperature sensor, a humidity sensor, an illuminance sensor, or the like. It may be an environmental sensor. The sensor 107 may be incorporated in the second SoC or may be externally attached to the second SoC.

  The A / D converter 108 receives a sensing signal from the sensor 107, and analog / digital converts it to generate a sensor value. The A / D converter 108 sends the sensor value to the sensor control unit 112. The A / D converter 108 may be built in the second SoC or may be externally attached to the second SoC.

  The A / D converter 108 periodically captures and digitizes the sensing signal according to the sampling period. This sampling period is controlled by the sensor control unit 112 based on the second counter value. That is, if the second counter value is synchronized among the plurality of wireless sensor devices 100, for example, as shown in FIG. 9, the A / D converter 108- included in the wireless sensor device 100-1 is used. 1 and the A / D converter 108-2 included in the wireless sensor device 100-2 can synchronize the sampling period (Δf), that is, the A / D conversion timing of the sensing data.

  When the sensor 107 outputs a digital sensing signal (which corresponds to the sensor value) instead of an analog sensing signal, the A / D converter 108 can be omitted.

  The second oscillator 109 may be an arbitrary oscillation circuit independent of the first oscillator 101, for example, an oscillation circuit to which a solid vibrator such as a crystal vibrator is connected. The second oscillator 109 generates a second clock signal and supplies it to the second counter 110. The second clock signal can be, for example, a square wave with a fixed period. The second oscillator 109 may be built in the second SoC or may be externally attached to the second SoC.

  The second counter 110 counts the second counter value based on the second clock signal from the second oscillator 109. The second counter 110 notifies the sensor control unit 112 of the second counter value. Specifically, the second counter 110 can be realized by a logic circuit configured to count up the second counter value in response to a rising edge or a falling edge of the second clock signal. The second counter 110 may be built in the second SoC or may be externally attached to the second SoC. The second counter 110 may count down instead of counting up. However, in the following description, it is assumed that the second counter 110 counts up.

  In addition, the start / stop control of the second counter 110 is performed by the second clock control unit 111. Note that the second counter 110 can be in a stopped state from when the wireless sensor device 100 transitions to the clock synchronization mode until it is activated by the second clock control unit 111. Further, the second counter value held by the second counter 110 can be rewritten (corrected) by the second clock control unit 111.

  The second clock control unit 111 controls the second counter value held by the second counter 110. The second clock control unit 111 can be realized by a processor, a memory, and an input / output interface (for example, UART, GPIO, etc.) mounted on the second SoC.

  For example, the second clock control unit 111 can perform the initial setting of the second counter 110 based on the start clock value notified from the first clock control unit 105 via, for example, UART. Specifically, the second clock control unit 111 rewrites the second counter value (initial value) held by the second counter 110 in the stopped state to the start clock value in response to the notification. When the second clock control unit 111 receives an (activation) interrupt signal from the interrupt generation unit 106 via, for example, GPIO, the second clock control unit 111 activates the second counter 110. As a result, the second counter value is counted starting from the start clock value.

  Further, the second clock control unit 111 corrects the second counter value based on the interrupt interval every time a (synchronous) interrupt signal is received from the interrupt generation unit 106 via, for example, GPIO. For example, the second clock control unit 111 may rewrite the second counter value by the sum of the previous correction value of the second counter value and the interrupt interval. In other words, the second clock control unit 111 can rewrite the second counter value to the sum of the start clock value and the natural number of interrupt intervals (which is equal to the number of times of correction execution).

  In the example of FIG. 1, the second clock control unit 111 directly corrects the second counter value held by the second counter 110, but controls the second oscillator 109. Thus, the second counter value may be corrected indirectly. For example, when the second oscillator 109 is an oscillator that can control the oscillation frequency, the second clock control unit 111 may control the oscillation frequency. Specifically, when the second counter value is delayed with respect to the reference clock value, the second clock control unit 111 may increase the oscillation frequency of the second oscillator 109. Conversely, when the second counter value is advanced with respect to the reference clock value, the second clock control unit 111 may lower the oscillation frequency of the second oscillator 109.

  The sensor control unit 112 receives the sensor value from the A / D converter 108, generates time data (time stamp) associated with the sensor value, and obtains sensor data including the sensor value and the time data. If the second counter value is appropriately synchronized among a plurality of different wireless sensor devices 100, this time data indicates the measurement date and time of the sensor value on the substantially same time axis between these wireless sensor devices 100. Can be expressed in standards. This time data may be, for example, the second counter value at the time of acquiring the sensor value. The sensor control unit 112 sends this sensor data to the wireless communication unit 104. As described above, the sensor control unit 112 can control the sampling period of the A / D converter 108 based on the second counter value. The sensor control unit 112 can be realized by a processor and a memory mounted on the second SoC.

  Hereinafter, the operation of the wireless sensor device 100 will be described with reference to FIGS. 6 to 8. 6 and 7 show an example of clock correction operation related to the first oscillator 101, and FIG. 8 shows an example of clock correction operation related to the second oscillator 109. First, the operation of FIGS. 6 and 7 will be described. 6 and 7 may be triggered by the wireless sensor device 100 transitioning to the clock synchronization mode.

  First, the wireless communication unit 104 sets a beacon (reception) interval (step S401) and waits for a beacon signal (step S402). If a beacon signal has not been received, the process proceeds to step S409 in FIG. On the other hand, if a beacon signal is received, it is determined whether or not it is the first reception (after the start of the operation of FIG. 6) (step S403). If it is the first reception, the process proceeds to step S404, and if it is the second or subsequent reception, the process proceeds to step S408.

  In step S <b> 404, the first clock control unit 105 performs initial setting of the first counter 102. For example, the first clock control unit 105 can correct the first counter value based on the reference clock value included in the received beacon signal.

  Next, the first clock control unit 105 sets the start clock value and the interrupt interval to the interrupt generation unit 106 and notifies the second clock control unit 111 of the set start clock value and interrupt interval ( Step S405). After step S405, the process proceeds to step S406.

  Here, the interrupt interval can be determined independently of the beacon interval. As the interrupt interval is shorter, the synchronization shift between the first counter value and the second counter value can be suppressed. For example, when the accuracy of the second oscillator 109 is lower than the accuracy of the first oscillator 101 (generally within about ± 10 to 20 ppm), by setting the interrupt interval to a sufficiently small value, The error of time data included in the sensor data can be within an allowable range. Further, the interrupt interval may be different among the plurality of wireless sensor devices 100. Therefore, when there are variations in the accuracy of the second oscillator 109, the allowable error range of time data, and the like among the plurality of wireless sensor devices 100, an appropriate interrupt interval is set individually in each wireless sensor device 100. By doing so, it is possible to balance the required synchronization accuracy and the load of the synchronization processing.

  FIG. 4 exemplifies how the correction of the first counter value and the second counter value is performed when the interrupt interval is set to half the beacon interval. In the example of FIG. 4, the first counter value is corrected every beacon interval (I1), and the second counter value is corrected every interrupt interval (I2 = I1 / 2). In this way, by setting the interrupt interval to be small, the second counter value is frequently corrected to match the first counter value, so even if the accuracy of the second oscillator 109 is low, Deviation between the first counter value and the second counter value can be suppressed. In other words, since the accuracy required for the second oscillator 109 can be relaxed, the cost can be reduced.

  In step S406, the interrupt generation unit 106 waits for the first counter value to reach the start clock value set in step S405. When the first counter value reaches the start clock value, the process proceeds to step S407.

  In step S <b> 407, the interrupt generation unit 106 generates a (startup) interrupt signal and transmits it to the second clock control unit 111. After step S407, the process proceeds to step S409 in FIG.

  In step S408, the first clock control unit 105 corrects the first counter value based on the reference clock value included in the received beacon signal. For example, the first clock control unit 105 can rewrite the first counter value with the reference clock value. After step S408, the process proceeds to step S409 in FIG.

  In step S409 in FIG. 7, the interrupt generation unit 106 determines whether or not the interrupt timing has arrived. The interrupt timing can be derived, for example, by adding the interrupt interval set in step S405 in FIG. 6 to the previous interrupt timing. If the interrupt timing has arrived, the process proceeds to step S410; otherwise, the process proceeds to step S411.

  In step S 410, the interrupt generation unit 106 generates a (synchronous) interrupt signal and transmits it to the second clock control unit 111. After step S410, the process proceeds to step S411.

  In step S411, it is determined whether or not to end the operations in FIGS. This operation can be terminated with, for example, a termination instruction from the hub device 200, completion of transmission of necessary sensor data, or the like as a trigger. If the operations in FIGS. 6 and 7 are not terminated, the process returns to step S402 in FIG.

  Next, the operation of FIG. 8 will be described. The operation of FIG. 8 may be triggered by the wireless sensor device 100 transitioning to the clock synchronization mode. When the operation of FIG. 8 starts, the process proceeds to step S501.

  In step S <b> 501, the second clock control unit 111 waits for the start clock value / interrupt interval to be notified from the first clock control unit 105. This notification is performed in step S405 in FIG. When the start clock value / interrupt interval is notified, the process proceeds to step S502.

  In step S502, the second clock control unit 111 rewrites the second counter value held by the second counter 110 (stopped state) to the notified start clock value. After step S502, the process proceeds to step S503.

  In step S503, the second clock control unit 111 waits to receive an (activation) interrupt signal from the interrupt generation unit 106. This interrupt signal is transmitted in step S407 in FIG. When the interrupt signal is received, the process proceeds to step S504.

  In step S504, the second clock control unit 111 starts the second counter 110. Thereby, the first counter 102 and the second counter 110 respectively count the first counter value and the second counter value from the same value (which is equal to the start clock value) at substantially the same timing. Can do. After step S504, the process proceeds to step S505.

  In step S505, if the second clock control unit 111 receives a (synchronous) interrupt signal from the interrupt generation unit 106, the process proceeds to step S506. Otherwise, the process proceeds to step S507. This interrupt signal is transmitted in step S410 in FIG.

  In step S506, the second clock control unit 111 corrects the second counter value based on the interrupt interval notified in step S501. For example, the second clock control unit 111 can rewrite the second counter value by the sum of the previous correction value of the second counter value and the interrupt interval. After step S506, the process proceeds to step S507.

  In step S507, it is determined whether or not to end the operation of FIG. This operation can be terminated with, for example, a termination instruction from the hub device 200, completion of transmission of necessary sensor data, or the like as a trigger. If the operation of FIG. 8 is not terminated, the process returns to step S505.

  As described above, the wireless sensor device according to the embodiment employs a configuration in which the sensor control unit does not share the oscillator with the wireless communication unit, and the reference clock value included in the wireless signal periodically received from the hub device. Based on the above, clock correction related to the oscillator for the wireless communication unit is performed. The wireless sensor device periodically generates an interrupt signal at an interval that can be set independently of the transmission interval of the wireless signal, and performs clock correction on the oscillator for the sensor control unit using the interrupt signal as a trigger. Therefore, according to this wireless sensor device, it is possible to synchronize the clock for sensor control with the clock for sensor control in other wireless sensor devices.

  The above-described embodiments are merely specific examples for helping understanding of the concept of the present invention, and are not intended to limit the scope of the present invention. The embodiment can add, delete, or convert various components without departing from the gist of the present invention.

  In the above-described embodiment, several functional units have been described. However, these are merely examples of mounting each functional unit. For example, a plurality of functional units described to be mounted on one device may be mounted over a plurality of separate devices, or conversely described as mounted over a plurality of separate devices. It is also possible that the functional unit thus configured is implemented in one apparatus.

  The various functional units described in the above embodiments may be realized by using a circuit. The circuit may be a dedicated circuit that realizes a specific function, or may be a general-purpose circuit such as a processor.

  At least a part of the processing of each embodiment described above can be realized by using, for example, a processor mounted on a general-purpose computer as basic hardware. A program for realizing the above processing may be provided by being stored in a computer-readable recording medium. The program is stored in the recording medium as an installable file or an executable file. Examples of the recording medium include a magnetic disk, an optical disk (CD-ROM, CD-R, DVD, etc.), a magneto-optical disk (MO, etc.), and a semiconductor memory. The recording medium may be any recording medium as long as it can store the program and can be read by the computer. The program for realizing the above processing may be stored on a computer (server) connected to a network such as the Internet and downloaded to the computer (client) via the network.

DESCRIPTION OF SYMBOLS 100 ... Wireless sensor apparatus 101 ... 1st oscillator 102 ... 1st counter 103 ... Antenna 104 ... Wireless communication part 105 ... 1st clock control part 106 ... Interrupt Generation unit 107 ... sensor 108 ... A / D converter 109 ... second oscillator 110 ... second counter 111 ... second clock control unit 112 ... sensor control unit 200 ... Hub devices

Claims (5)

A wireless sensor device wirelessly connected to a hub device,
A first oscillator for generating a first clock signal;
A first counter that counts a first counter value based on the first clock signal;
A wireless communication unit that performs wireless communication in synchronization with the first counter value and receives a wireless signal including a reference clock value from the hub device at a first interval;
A first clock controller that corrects the first counter value based on the reference clock value;
An interrupt generator for generating a first interrupt signal at a second interval;
A second oscillator for generating a second clock signal;
A second counter that counts a second counter value based on the second clock signal;
A second clock control unit that corrects the second counter value based on the second interval each time the first interrupt signal is received;
Time data associated with the sensor values representing the measured value of the physical quantity obtained by the sensor generated based on the second counter value, comprising a sensor control unit for obtaining sensor data including the sensor value and the time data,
The second counter is activated by the second clock controller after the wireless sensor device transitions to a clock synchronization mode in which the first counter value synchronization process and the second counter value synchronization process are performed. Until it is stopped,
The first clock control unit sets a start clock value and the second interval in response to reception of the first radio signal after the wireless sensor device transitions to the clock synchronization mode, and the set start Notifying the second clock control unit of the clock value and the second interval;
The second clock control unit rewrites the second counter value to the start clock value in response to the notification of the start clock value and the second interval,
The interrupt generation unit generates a second interrupt signal when detecting that the first counter value has reached the start clock value,
The second clock control unit activates the second counter in response to reception of the second interrupt signal.
Wireless sensor device. An analog / digital converter,
The sensor generates a sensing signal representing a measurement result of the physical quantity,
The analog / digital converter performs analog / digital conversion on the sensing signal to generate the sensor value,
The sensor control unit controls a sampling period of the analog / digital converter based on the second counter value;
The wireless sensor device according to claim 1. Said second clock control unit, each time it receives the first interrupt signal, said second counter value is rewritten to the sum of the natural number times of the start clock value and the second distance, wherein Item 2. The wireless sensor device according to Item 1 . A hub device;
A plurality of wireless sensor devices wirelessly connected to the hub device,
Each of the plurality of wireless sensor devices is
A first oscillator for generating a first clock signal;
A first counter that counts a first counter value based on the first clock signal;
A wireless communication unit that performs wireless communication in synchronization with the first counter value and receives a wireless signal including a reference clock value from the hub device at a first interval;
A first clock controller that corrects the first counter value based on the reference clock value;
An interrupt generator for generating a first interrupt signal at a second interval;
A second oscillator for generating a second clock signal;
A second counter that counts a second counter value based on the second clock signal;
A second clock control unit that corrects the second counter value based on the second interval each time the first interrupt signal is received;
Time data associated with the sensor values representing the measured value of the physical quantity obtained by the sensor generated based on the second counter value, look including a sensor control unit which generates a sensor data including the sensor value and the time data,
In each of the plurality of wireless sensor devices,
The second counter is activated by the second clock controller after the wireless sensor device transitions to a clock synchronization mode in which the first counter value synchronization process and the second counter value synchronization process are performed. Until it is stopped,
The first clock control unit sets a start clock value and the second interval in response to reception of the first radio signal after the wireless sensor device transitions to the clock synchronization mode, and the set start Notifying the second clock control unit of the clock value and the second interval;
The second clock control unit rewrites the second counter value to the start clock value in response to the notification of the start clock value and the second interval,
The interrupt generation unit generates a second interrupt signal when detecting that the first counter value has reached the start clock value,
The second clock control unit activates the second counter in response to reception of the second interrupt signal.
Wireless sensor system. The wireless sensor system according to claim 4 , wherein the plurality of wireless sensor devices perform wireless communication with the hub device by a TDI (Time Division Multiple Access) method.