Patent Publication Number: US-2023137159-A1

Title: Biosensor, biosensor system and operation control method of biosensor

Description:
TECHNICAL FIELD 
     The present disclosure relates to a biosensor, a biosensor system and operation control method of biosensor. 
     BACKGROUND ART 
     A wearable biosensor that can be attached to a living body to obtain biological information such as an electrocardiographic signal over a long time is known. For example, a biosensor of this type has electrodes on both longitudinal directional sides, the electrodes are affixed to a chest of a living body with the longitudinal direction aligned with a sternum, and then, the biosensor automatically starts measuring biological information (see, for example, Patent Document 1). 
     PRIOR ART DOCUMENTS 
     Patent Documents 
     
         
         Patent Document 1: the specification of U.S. Patent Application Publication No. 2019/0254553 
       
    
     SUMMARY OF INVENTION 
     Problem to be Solved by Invention 
     When biological information is obtained for a long time by a biosensor affixed to a living body, measurement for a long time becomes useless if the biosensor cannot obtain biological information properly. In order to prevent the measurement for a long time being useless, it is preferable to check whether the biological information can be obtained normally before starting the measurement of biological information (actual measurement). 
     The present invention has been devised in view of the above-described points, and the present invention has an object to provide a biosensor having a function that enables to check whether the biological information can be obtained normally before starting the measurement of biological information. 
     Means for Solving Problem 
     A biosensor according to an embodiment of the present invention includes an electrode configured to be attached to a living body, an obtaining section configured to obtain biological information through the electrode, a memory configured to store the biological information obtained by the obtaining section, and a controller including an operation checking mode and a biological information recording mode. The controller, during the operation checking mode, wirelessly transmits the biological information obtained by the obtaining section, and transitions to the biological information recording mode upon receiving a recording start command from an outside, and during the biological information recording mode, writes the biological information obtained by the obtaining section to the memory. 
     Advantageous Effects of Invention 
     According to the disclosed technique, it is possible to provide a biosensor having a function that enables to check whether the biological information can be obtained normally before starting the measurement of biological information. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a diagram illustrating an example of an overall configuration of a biosensor system including a biosensor according to an embodiment; 
         FIG.  2    is a layout diagram illustrating an example of a flexible substrate of  FIG.  1   ; 
         FIG.  3    is a diagram illustrating a state in which the biosensor of  FIG.  1    is affixed to a chest of a subject; 
         FIG.  4    is a block diagram illustrating an example of a circuit configuration of the biosensor of  FIG.  1   ; 
         FIG.  5    is a state transition diagram illustrating an example of a transition of a mode of operation of the biosensor of  FIG.  1   ; 
         FIG.  6    is a flowchart illustrating an example of the operation of the biosensor of  FIG.  1   ; 
         FIG.  7    is a flowchart illustrating a continuation of the operation of  FIG.  6   ; 
         FIG.  8    is a flowchart illustrating a continuation of the operation of  FIG.  7   ; 
         FIG.  9    is a flowchart illustrating a continuation of the operation of  FIG.  8   ; 
         FIG.  10    is a sequence diagram illustrating an example of operation in a pairing mode of  FIG.  5    and  FIG.  7   ; 
         FIG.  11    is a data flow diagram illustrating an example of data transmission/reception between the biosensor of  FIG.  1    and an operation checking device; and 
         FIG.  12    is an explanatory diagram illustrating a display example of a screen of a PC connected to the operation checking device of  FIG.  1   . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments of the invention will be described with reference to the drawings. In each drawing, the same components are indicated by the same reference numerals and duplicate descriptions may be omitted. The same reference numerals as the signal name or voltage name is used for the signal line or voltage line through which information such as a signal or voltage is transmitted. Further, a signal line with the reference numerals “/” indicates a plurality of bits, but a signal line indicated by a single line may also transmit a signal of a plurality of bits. 
       FIG.  1    is a diagram illustrating an example of an overall configuration of a biosensor system including a biosensor according to an embodiment. A biosensor system SYS of  FIG.  1    includes a biosensor  100 , an operation checking device  310  for checking an initial operation, a personal computer (PC)  330 , a reading device  410  for reading biological information from the biosensor  100 , and a PC  420 . Each of the operation checking device  310  and the reading device  410  is an example of an external device. 
     For example, the biosensor  100  is a wearable electrocardiograph that obtains an electrocardiographic signal from a living body. The biosensor  100  may have a function of obtaining biological information other than an electrocardiographic signal, and may have a function of obtaining a plurality of types of biological information. 
     The operation checking device  310  is connected to the PC  320  via, for example, a universal serial bus (USB) interface (wired). The operation checking device  310  has a capability of wirelessly communicating with the biosensor  100  under the control of the PC  320 . For example, the PC  320  has a function of displaying a waveform representing a time change in received biological information (for example, an electrocardiographic waveform) on a display screen. 
     The reading device  410  is connected to the PC  420 , for example, via a USB interface (wired). The reading device  410  has a function of communicating with the biosensor  100  via a communication cable (wired communication). The details of the operation of the biosensor  100 , the operation checking device  310 , and the reading device  410  will be described later with reference to  FIG.  5   . 
     The biosensor  100  includes a flexible substrate (a resin substrate)  110  and a housing  120  (depicted by a dashed line) on which various components are mounted for obtaining biological information and processing the obtained biological information. The flexible substrate  110  includes a body section  121 , a constricted section  122  provided at one longitudinal directional end of the body section  121 , and a pad section  123  connected to the body section  121  via the constricted section  122 . The flexible substrate  110  also includes a constricted section  124  provided at the other longitudinal directional end of the body section  121  and a pad section  125  connected to the body section  121  via the constricted section  124 . 
     The body section  121  includes a component mounting section  126  at the constricted section  122  side and a battery setting section  127 , to which a battery  200  is set, at the constricted section  124  side. Various components mounted on the component mounting section  126  and circuit examples using the various components will be described with reference to  FIG.  4   . An external terminal  131 , to which a connector of a communication cable to be connected to the reading device  410  is connected, is formed in the component mounting section  126 . 
     For example, a coin-type battery  200  that supplies power to the component mounting section  126  is set at the battery setting section  127 . An electrode pattern  132  is formed on the pad section  123  to be affixed to a body surface of a living body, and an electrode pattern  133  is formed on the pad section  125  to be affixed to the body surface of the living body. Hereinafter, the electrode pattern  132  is also referred to as an electrode  132 , and the electrode pattern  133  is also referred to as an electrode  133 . 
       FIG.  2    is a layout diagram illustrating an example of the flexible substrate  110  of  FIG.  1   . On the component mounting section  126  of the flexible substrate  110 , an application specific integrated circuit (ASIC)  210 , a system on a chip (SoC)  220 , a NAND type flash memory  230 , a switch  240 , and light emitting diodes (LED)  250  are mounted. As illustrated in  FIG.  4   , a LED (G) that outputs green light and a LED (R) that outputs red light are mounted to the component mounting section  126  as the LED  250 . The LED (G) and the LED (R) are examples of light emitting elements. 
     The biosensor  100  includes a plate member  260  (depicted in  FIG.  2    as a frame drawn by a thick broken line), such as a stainless steel plate, on a surface (back side), included in the flexible substrate  110 , opposite to a component mounting surface (front side) on which the components such as the ASIC  210  and the SoC  220  are mounted. The switch  240  is, for example, a depression switch that is set to an on state when a protrusion is depressed and set to an off state when the protrusion is not depressed. The switch  240  is mounted at a position that is next to the constricted section  122  (at an edge of the body section  121 ) and is opposite the plate member  260 . Hereinafter, a living body to which the biosensor  100  is affixed and from which biological information is obtained by the biosensor  100  is also referred to as a subject P. 
     The constricted section  124  is formed to be longer than the constricted section  122 . As illustrated in  FIG.  3   , the biosensor  100  is affixed along a sternum of the subject P, while the pad section  123  is faced upward (i.e., toward the subject P neck side). Adhesion of electrodes  132  and  133  to a body surface of the subject P may be implemented with the use of an electrically conductive adhesive, or may be implemented with the use of a non-electrically-conductive adhesive to be applied to a part of each of the electrodes  132  and  133 . Alternatively, an electrode that is specially prepared for being affixed to a living body and is affixed to each of the electrodes  132  and  133  may be used to affix the electrodes  132  and  133  to the subject P with the use of an electrically conductive adhesive or a non-electrically-conductive adhesive. Note that the non-electrically-conductive adhesive is partially applied to the electrode that is specially prepared for being affixed to the living body. 
     The battery setting section  127  includes pad sections  127   a  and  127   b  and a constricted section  127   c . The pad section  127   a  is provided between the constricted section  124  and the component mounting section  126 . The pad section  127   b  is provided, in a direction orthogonal to the longitudinal direction, with respect to the pad section  127   a  (an upper direction of  FIG.  2   ) at a predetermined distance from the pad section  127   a . The constricted section  127   c  is provided between pad sections  127   a  and  127   b  to connect the pad sections  127   a  and  127   b  together. 
     The pad section  127   a  has a positive electrode pattern  134  to which a positive terminal of a battery  200  ( FIG.  1   ) is connected. The pad section  127   b  has a negative electrode pattern  135  to which a negative terminal of the battery  200  is connected. For example, the positive electrode pattern  134  has a square shape with corners chamfered, and the negative electrode pattern  135  has a circular shape corresponding to a size of a circular shape of the negative terminal of the battery  200 . For example, a diameter of the negative electrode pattern  135  is equal to a diameter of the battery  200  and is equal to a length of a diagonal of the positive electrode pattern 
     When a battery  200  is set in the biosensor  100 , an electrically conductive adhesive, such as an adhesive tape, is attached throughout the positive and negative electrode patterns  134  and  135 . Then, the battery  200  is mounted on the battery setting portion  127  by attaching the positive electrode terminal and the negative electrode terminal of the battery  200  to the positive electrode pattern  134  and the negative electrode pattern  135 , respectively, via the adhesive. The body section  121  depicted in  FIG.  1    is in a state where a battery  200  is set at the battery setting section  127  with the battery  200  sandwiched between the positive electrode pattern  134  and the negative electrode pattern  135  with the constricted section  127   c  bent. 
     The flexible substrate  110  has an antenna pattern  136  formed along the longitudinal direction of the flexible substrate  110  near one (at a lower side in  FIG.  2   ) of four sides of the rectangular component mounting section  126 . Although not depicted, one end of the antenna pattern  136  is connected to the SoC  220 . The flexible substrate  110  also has a wiring pattern  137  formed at an edge (at a lower side in  FIG.  2   ) of the body section  121  and extending from the electrode pattern  133  to near the switch  240  through the constricted section  124 . The wiring pattern  137  connects the electrode  133  to the ASIC  210 . 
     The antenna pattern  136  is formed at a wiring layer of the flexible substrate  110  at a component mounting surface side (the front side). Meanwhile, the wiring pattern  137  is formed at a wiring layer of the flexible substrate  110  at the back side. This prevents a DC current flowing through the wiring pattern  137  from flowing through the antenna pattern  136  even when, for example, the electrode pattern  133  contacts a charged object and a discharge toward the electrode pattern  133  occurs. Accordingly, the DC current flowing out due to the discharge can be prevented from flowing through the antenna pattern  136  into the SoC  220 , and thus, elements in the SoC  220  can be prevented from being electrostatically destroyed. The ASIC  210  includes a protective device against electrostatic discharge at an area where an input circuit to which the wiring pattern  137  is connected is formed. Hereinafter, the antenna pattern  136  is also simply referred to as an antenna  136 . 
     The flexible substrate  110  has a slit  128  extending toward the inside along a direction perpendicular to the longitudinal direction from an edge between the component mounting section  126  and the battery setting section  127  in order to be deformed by receiving stress from the outside. 
       FIG.  3    is a diagram illustrating a state in which the biosensor  100  of  FIG.  1    is affixed to a chest of the subject P. For example, the biosensor  100  is affixed to the subject P with the pad section  123  at an upper side and the pad section  125  at a lower side, with the longitudinal direction of the biosensor  100  extending along a sternum of the subject P. That is, the biosensor  100  is affixed to the subject P with the longer constricted section  124  at the lower side. On the back side of the body section  121  of the biosensor  100 , an adhesive tape or an adhesive agent is provided to affix the body section  121  to a body surface of the subject P. 
     The housing  120  of the biosensor  100 , with the body section  121  contained therein, has openings at least at positions corresponding to the electrodes  132 ,  133 . The electrodes  132 ,  133  exposed from the openings can be adhered to the subject P. The biosensor  100  wirelessly communicates with the operation checking device  310  ( FIG.  1   ) in a state in which the biosensor  100  has been affixed to the subject P, and the electrodes  132  and  133  have been adhered to a body surface of the subject P. The biosensor  100  transmits biological information, such as an electrocardiographic signal obtained from the subject P, to the PC  320  (see  FIG.  1   ) via the operation checking device  310 . 
     Subsequently, based on an electrocardiographic waveform or the like displayed on a display screen of the PC  320 , a physician or the like determines that the biosensor  100  has been affixed to a proper position. The biosensor  100  then starts an actual measurement of biological information in response to a recording start command transmitted from the PC  320  via the operation checking device  310  based on an operation of the PC  320  performed by the physician or the like. 
     The biosensor  100  writes biological information, which has been obtained sequentially from the subject P during the measurement, together with time information, to the flash memory  230 . When the switch  240  is depressed during the measurement, and then, the switch  240  is kept continuously in the on state, the biosensor  100  sequentially writes time information (indicating the turned-on state) corresponding to the current time to the flash memory  230 . For example, the time information is a time counter or the like that is sequentially updated with the passage of time after the start of the main measurement. 
     The subject P with the biosensor  100  attached thereto depresses the switch  240  if the subject P feels ill such as a palpitation or shortness of breath. While the subject P is feeling ill, the subject P may depress the switch  240  continuously. After the measurement is completed, the reading device  410  reads biological information, such as electrocardiographic signal data, time counter information accompanied by the biological information, and time counter information indicative of turned-on states of the switch  240 , for example, from the flash memory  230  of the biosensor  100 . 
     The reading device  410  ( FIG.  1   ) transfers various information read from the flash memory  230  to the PC  420  ( FIG.  1   ). The PC  420  that receives the various information displays biological information, such as an electrocardiographic waveform, on the display screen, and displays timings when the switch  240  has been depressed. This allows the physician or the like operating the PC  420  to determine whether abnormality is present in an electrocardiographic waveform or the like obtained when the subject P felt ill. 
     For example, a duration of the measurement is set according to a duration for which the biosensor  100  is operable by power supply from the battery  200 . For example, the duration of the measurement may be 24 hours (one day), but may be longer depending on the capacity of the battery  200  and the power consumption of the biosensor  100 . 
     In the present embodiment, since wireless communication is not performed during the measurement (a biological information recording mode, which will be described later), the wireless communication function of the SoC  220  is set to the off state. Therefore, the power consumption of the biosensor  100  can be reduced as compared with the case where the wireless communication function is operated during the measurement. 
       FIG.  4    is a block diagram illustrating an example of a circuit configuration of the biosensor  100  of  FIG.  1   . The various elements illustrated in  FIG.  4    are mounted on the component mounting section  126  illustrated in  FIG.  2   , except for the electrodes  132  and  133 . In addition to the elements described with reference to  FIG.  2   , the component mounting section  126  includes a DC/DC converter  10 , a power supply switch  12 , a DC/DC converter  14 , a thermistor  16 , filters  18 ,  20  and a resistor division section  22 . 
     The DC/DC converter  10  uses a power supply voltage VCC1 (for example, 3V) output from the battery  200  to generate a power supply voltage VCC2 lower than the power supply voltage VCC1. The DC/DC converter  10  supplies the generated power supply voltage VCC2 to the power supply terminal of the SoC  220 , the LED (G), the LED (R), the power supply switch  12 , and the power supply terminal of the ASIC  210 . 
     The SoC  220  always operates by receiving the power supply voltage VCC2 from the DC/DC converter  10  while the battery  200  outputs the power supply voltage VCC1. However, the SoC  220  includes, for example, a deep sleep mode (low power consumption mode) that disconnects the connection between the transistor of the built-in circuit block and the power supply line. Therefore, the SoC  220  does not consume power except for the interrupt function for detecting the pressing of the switch  240  in the deep sleep mode. 
     The power supply switch  12  is, for example, a p-channel Metal Oxide Semiconductor (MOS) transistor, and is set to the on state or the off state according to a switch control signal SCNT from the SoC  220 . When the power supply switch  12  is set to the on state, the power supply switch  12  connects the power supply line VCC2 to the power supply line VCC2 (S). While the power supply switch  12  is in the on state, the power supply voltage VCC2 is supplied to the flash memory  230  and the thermistor  16  as the power supply voltage VCC2 (S), and is supplied to an enable terminal EN of the DC/DC converter  14 . The timing at which the power supply switch  12  is turned on will be described with reference to  FIG.  6   . 
     In the deep sleep mode, as described later, the power supply switch  12  is kept in the off state until the switch  240  is depressed for a long time. Therefore, during the deep sleep mode, the DC/DC converter  14 , the ASIC  210 , and the flash memory  230  stop operating, and no current flows through the thermistor  16 . Accordingly, the power consumed by the biosensor  100  in the deep sleep mode can be limited to the power consumed by the SoC  220  in the deep sleep mode and the DC/DC converter  10 . By operating only the minimum number of elements, the life of the battery  200  can be extended, so the time during which the biological information can be recorded in the biological information recording mode can be extended. 
     The DC/DC converter  14  operates while receiving the power supply voltage VCC2 (S) with the enable terminal EN, and uses the power supply voltage VCC1 to generate a power supply voltage VCC3 which is lower than the power supply voltage VCC1. The DC/DC converter  14  stops the generation operation of the power supply voltage VCC3 while the power supply voltage VCC2 (S) is not received with the enable terminal EN. Specifically, the power supply voltage VCC3 is lower than the power supply voltage VCC2, but is not limited to this. The power supply voltage VCC3 is supplied to the ASIC  210 . In order to prevent the DC/DC converter  14  from malfunctioning, the enable terminal EN may be connected to a ground wire via a resistive element having a high resistance value that does not affect the power supply voltage VCC2 (S). 
     The ASIC  210  is connected to the SoC  220  by a Serial Peripheral Interface (SPI, registered trademark). The ASIC receives a master/slave signal M/S of the SPI from the SoC  220 . For example, the SoC  220  sets the master/slave signal M/S to a high level when the ASIC  210  is used as a master, and sets the master/slave signal M/S to a low level when the SoC  220  is used as a master. 
     The ASIC  210  includes an amplifier (hereinafter, AMP)  212 , an analog/digital converter (hereinafter, ADC)  214 , an input/output interface circuit (hereinafter, I/O)  216 , and a logic circuit (hereinafter, LOGIC)  218 . Further, the ASIC  210  includes an oscillation circuit (not illustrated) that generates a clock signal CLK, and the generated clock signal CLK is not only used in the ASIC  210  but also output to the SoC  220 . 
     The AMP  212  differentially amplifies voltage signals INP and INN respectively received from the plus electrode  132  and the minus electrode  133  via filters (FLT)  18  and  20  mounted on the flexible substrate  100 , and outputs the voltage signals obtained by the amplification to the ADC  214 . The ADC  214  converts the differentially amplified voltage signals into a digital value (voltage value), and outputs the voltage value obtained by the conversion to the I/O  216 . Then, biological information such as an electrocardiographic signal is output from the I/O  216  to the SoC  220  through the SPI signal line. 
     The ASIC  210  is operated by receiving the power supply voltages VCC2 and VCC3. For example, the AMP  212 , the ADC  214 , the LOGIC  218 , and the oscillation circuit (not illustrated) are operated by the power supply voltage VCC3. 
     The SoC  220  includes a Micro Controller Unit (MCU)  222  and a wireless communication section  224 . The MCU  222  controls the overall operation of the biosensor  100  by executing a control program stored in the built-in memory. For example, the MCU  222  controls the lighting, blinking, and extinguishing of the LED (G) and the LED (R), and receives the value of the current flowing through the thermistor  16  as temperature information TEMP. 
     The temperature indicated by the temperature information TEMP indicates the surrounding temperature of the biosensor  100 , and when the biosensor  100  is affixed to the subject P, indicates the body temperature of the subject P. Therefore, the body temperature of the subject P can be measured by the biosensor  100 . The measured body temperature may be written in the flash memory  230  as biological information together with the electrocardiographic signal and the like. 
     Further, the MCU  222  detects the value of the power supply voltage VCC1 output from the battery  200  based on a voltage VDET obtained by dividing the power supply voltage VCC1 by the resistor division section  22 . As a result, the MCU  222  can notify the decrease in the capacity of the battery  200  to the outside of the biosensor  100  by blinking the LED (R) or the like when the power supply voltage VCC1 is equal to or lower than a predetermined voltage. The MCU  222  may detect a failure of the DC/DC converters  10 ,  14  or the power supply switch  12  by detecting at least one of the power supply voltages VCC2, VCC2 (S), and VCC3 with the resistor division section (not illustrated). 
     Also in this case, the MCU  222  can notify the failure to the outside by blinking the LED (R). The MCU  222  may change at least one of the blinking cycle and the blinking pattern of the LED (G) instead of the LED (R) for each type of failure. In this case, the biosensor  100  can notify which element has failed to the outside of the biosensor  100  only by the LED (G) without the LED (R). 
     Further, the MCU  222  is connected to the switch  240  and can detect whether the switch  240  is pressed. For example, the switch  240  has one end connected to the SoC  220  and the other end connected to the ground wire. Therefore, the MCU  222  can detect the depressing of the switch  240  by the low level of the terminal to which the switch  240  is connected. Note that the terminal of the SoC  220  to which the switch  240  is connected is pulled up. By detecting the depressing time of the switch  240 , the MCU  222  can identify multiple events according to the depressing time. That is, a soft switch capable of detecting multiple events can be implemented with a single switch  240 . 
     The SoC  220  is connected to the flash memory  230  by a SPI signal line different from the SPI signal line connected to the ASIC  210 . The MCU  222  writes biological information such as an electrocardiographic signal received from the ASIC into the flash memory  230  via the SPI during the biological information recording mode which will be described later. 
     The wireless communication section  224  has a function of communicating with the operation checking device  310  illustrated in  FIG.  1    via the antenna  136  based on the instruction from the MCU  222 . Further, the wireless communication section  224  has a function of performing pairing with the operation checking device  310  based on the release of the deep sleep mode of the MCU  222 . The pairing between the wireless communication section  224  and the operation checking device  310  will be described with reference to  FIG.  7    and  FIG.  10   . 
     In the biosensor  100  illustrated in  FIG.  4   , the ASIC  210  functions as an obtaining section for obtaining biological information through the electrodes  132  and  133 . The flash memory  230  functions as a memory for storing biological information obtained by the ASIC  210 . The SoC  220  functions as a controller including an operation checking mode and a biological information recording mode. 
     The operation checking mode is a mode of checking as to whether the biosensor  100  can properly obtain biological information (whether the biosensor  100  is properly attached to the subject P and whether the biosensor  100  operates normally). For example, in the operation checking mode, the MCU  222  transmits biological information received from the ASIC  210  to the operation checking device  310  depicted in  FIG.  1    via the wireless communication section  224  without writing the biological information to the flash memory  230 . Therefore, the power consumption of the biosensor  100  can be reduced as compared with the case where the biological information is written to the flash memory  230  during the operation mode. 
     The biological information recording mode is a mode of operation switched from the operation checking mode based on a recording start instruction input from the operation checking device  310  when it is checked in the operation checking mode that biological information can be properly obtained by the biosensor  100 . During the biological information recording mode, the MCU  222  sequentially writes biological information obtained from the ASIC  210  to the flash memory  230 . 
       FIG.  5    is a state transition diagram illustrating an example of a transition of a mode of operation of the biosensor  100  of  FIG.  1   . That is,  FIG.  5    illustrates an example of an operation control method of the biosensor  100 , and illustrates an example of an operation implemented by a control program executed by the biosensor  100 . 
     The MCU  222  transitions to an initialization mode when the battery  200  is set at the battery setting section  127  and generation of the power supply voltage VCC2 is initiated. The MCU  222  performs initial settings of the hardware and the like in the initialization mode. After the completion of initialization, the operation mode transitions to a deep sleep mode. The deep sleep mode is a mode in which the MCU  222  receives an interrupt caused by the switch  240  being depressed, and is a low power consumption mode in which the operation of the ASIC  210  and the wireless communication section  224  is stopped. 
     In the deep sleep mode, the MCU  222  transitions to a pairing mode when depression of the switch  240  for a long time (for example, two seconds) is detected, and maintains the deep sleep mode in a case where a duration of the switch  240  being depressed is shorter than two seconds. In the deep sleep mode, the MCU  222  transitions to a data output mode when the reading device  410  is connected to the external terminal. 
     In the pairing mode, the MCU  222  causes the wireless communication section  224  to perform pairing with the operation checking device  310 . When the pairing is completed, the MCU  222  transitions to a waiting-for-command mode. If an error occurs during the pairing, the MCU  222  transitions to an error processing mode and performs error processing. The MCU  222  causes the LED (R) to blink in a predetermined pattern (for example, at one second intervals) while the MCU  222  is in the error processing mode. 
     The MCU  222  transitions from the pairing mode to the deep sleep mode when the pairing mode continues for a predetermined period. For example, the predetermined period is one minute. In the pairing mode, the power of the battery  200  can be prevented from being wasted by transitioning to the deep sleep mode when the state in which pairing is not performed continues. 
     In the waiting-for-command mode, the MCU  222  transitions to an operation checking mode when a waveform checking command is received from the PC  320  via the operation checking device  310 . If an error occurs in the waiting-for-command mode, the MCU  222  transitions to the error processing mode. 
     In the operation checking mode, the MCU  222  sends an instruction to the ASIC  210  to obtain biological information, and sequentially receives biological information obtained by the ASIC  210 . The MCU  222  transmits the received biological information to the PC  320  via the operation checking device  310 . When receiving instructions, to stop communication, from the PC  320  via the operation checking device  310  during the operation checking mode, the MCU  222  causes the ASIC  210  to stop obtaining biological information, and returns to the waiting-for-command mode. If an error occurs in the operation checking mode, the MCU  222  transitions to the error processing mode. 
     In the operation checking mode, when a recording start command is received from the PC  320  via the operation checking device  310 , the MCU  222  transitions to a biological information recording mode. Upon the transition from the operation checking mode to the biological information recording mode, obtaining of biological information by the ASIC  210  continues, for example. It is noted that, when the switch  240  is depressed for a long time (for example, ten seconds) in each of the pairing mode, the waiting-for-command mode, and the operation checking mode, the operation mode returns to the deep sleep mode. Further, it is noted that, when the switch  240  is depressed for a long time (for example, ten seconds) in the error processing mode, the operation mode returns to the initialization mode and initial settings are performed in the initialization mode. 
     The MCU  222  may transition to the deep sleep mode, during the waiting-for-command mode or the operation checking mode, when a sleep request is received from the outside, as well as when the switch  240  is depressed for a long time. For example, the sleep request from the outside is issued from the operation checking device  310  by operating the operation checking device  310  when the operator who operates a biosensor system SYS feels an abnormality during pairing or the like. This enables to prevent the power of the battery  200  from being wasted. 
     When the operation checking mode continues for a predetermined period, the MCU  222  transitions from the operation checking mode to the deep sleep mode. For example, the predetermined period is 25 minutes. In the operation checking mode, for example, by transitioning to the deep sleep mode when the period in which the biological information is not received continues, the power of the battery  200  can be prevented from being wasted. 
     Further, the MCU  222  sets a threshold value of the received signal strength in the pairing mode higher than the threshold value used for receiving the signal in the operation checking mode. As a result, the distance between the biosensor  100  capable of wireless communication and the operation checking device  310  can be made shorter than the distance capable of wireless communication in the operation checking mode. For example, the distance between the biosensor  100  capable of wireless communication and the operation checking device  310  is designed to be within 20 cm in the pairing mode and within several meters in the operation checking mode. 
     As a result, for example, even when pairing multiple biosensors  100  in the same room or the like, a possibility of misconnection with the unintended biosensor  100  can be reduced. In addition, the power consumption during the pairing mode can be reduced. On the other hand, in the operation checking mode after pairing, the distance capable of wireless communication is longer than in the pairing mode, so that wireless communication can be maintained even if the biosensor  100  is apart from the operation checking device  310 . 
     In the biological information recording mode, the MCU  222  sequentially writes biological information received from the ASIC  210  to the flash memory  230 . When depression of the switch is detected in the biological information recording mode, the MCU  222  transitions to an event recording mode and then continues to be in the event recording mode until the switch  240  comes to be in a turned-off state. For example, the subject P with the biosensor  100  attached thereto depresses the switch  240  if the subject P feels ill such as a palpitation or shortness of breath. That is, in the event recording mode, information indicating the time when the subject P feels ill such as a palpitation or shortness of breath can be recorded in the flash memory  230  together with the biological information. 
     When a predetermined set time has elapsed (for example, 24 hours) in the biological information recording mode, the MCU  222  sends an instruction to the ASIC  210  to stop obtaining biological information, and transitions to a waiting-for-data-output mode. In the waiting-for-data-output mode, the MCU  222  waits for the reading device  410  to be connected to the external terminal  131 . For example, during the data output mode, the MCU  222  continues to wait for the reading device  410  to be connected to the external terminal  131  by the interrupt terminal. The power consumption while waiting for the interrupt is similar to the power consumption in the deep sleep mode. 
     The reading device  410  connected to the external terminal  131  via the cable accesses the flash memory  230  through the external terminal  131  to read biological information, time information, and the like stored in the flash memory  230 . In each of the waiting-for-data-output mode and the data output mode, if the switch  240  is depressed for a long time (for example, 5 seconds), the operation mode returns to the initialization mode, and initial settings are performed. 
     In the data output mode, by directly connecting the reading device  410  to the external terminal  131  via the cable, the biological information can be read from the flash memory  230  to the reading device  410  without being controlled by the MCU  222 . Because the access to the flash memory  230  by the MCU  222  is not performed and the wireless communication by the wireless communication section  224  is not performed, the power consumption of the biosensor  100  in the data output mode can be minimized. 
     As illustrated in  FIG.  5   , the MCU  222  can transition the operation mode to various other operation modes depending on the depressing time of the switch  240  and the operation mode when the switch  240  is pressed. Therefore, as described above, a soft switch capable of detecting a plurality of events can be implemented by one switch  240 . As a result, as compared with the case where multiple switches are mounted on the biosensor  100 , the biosensor  100  can be miniaturized and the cost of the biosensor  100  can be reduced. 
       FIG.  6    to  FIG.  9    are flow charts illustrating an example of the operation of the biosensor  100  of  FIG.  1   . The processes illustrated in  FIG.  6    to  FIG.  9    are implemented by executing the control program by the MCU  222 , and correspond to the processes of the state transitions in each operation mode illustrated in  FIG.  5   . That is,  FIG.  6    to  FIG.  9    illustrate an example of an operation control method of the biosensor  100 . It is assumed that no error occurs in the processes illustrated in  FIG.  6    to  FIG.  9   , and the description of the error processing will be omitted. 
     When the battery  200  is set on the battery setting section  127  and the generation of the power supply voltage VCC2 is started, the MCU  222  transitions to the initialization mode to execute step S 10 . 
     In step S 10 , the MCU  222  performs setting of the I/O port to be used in the deep sleep mode. Next, in step S 12 , the MCU  222  sets an interrupt for the switch port to which the switch  240  is connected and the terminal port to which the external terminal  131  is connected. Next, in step S 14 , the MCU  222  sets a power mode in the deep sleep mode and transitions to the deep sleep mode. 
     Next, in step S 16 , the MCU  222  waits until the depression of the switch  240  is detected during the deep sleep mode. When the switch  240  is depressed, the MCU  222  blinks the LED (G) in the first pattern in step S 18  to notify the detection of the depression of the switch  240  to the outside. For example, in the first pattern, lighting is repeated at intervals of several tens of milliseconds. 
     In step S 20 , the MCU  222  transfers to step S 22  when the depressed time of the switch  240  exceeds two seconds. When the depression of the switch  240  is released (off state) before the depressed time exceeds two seconds, the MCU  222  turns off the LED (G) and returns to step S 10 . The MCU  222  may return to step S 16  when the depressed time of the switch  240  is two seconds or less. 
     In step S 22 , the MCU  222  turns on the LED (G) to notify the detection of the depression of the switch  240  for a long time to the outside. Next, in step S 24 , the MCU  222  waits until the depression of the switch  240  is released. When the depression of the switch  240  is released, the MCU  222  turns off the LED (G) in step S 26 . 
     Next, in step S 28 , the MCU  222  sets the power supply switch  12  to the on state, and supplies the power supply voltage VCC2 (S) to the enable terminal EN of the DC/DC converter  14 , the flash memory  230 , and the thermistor  16 . This enables the DC/DC converter  14  to start generating the power supply voltage VCC3, and the ASIC  210  to become enabled for operation. 
     Next, in step S 30 , the MCU  222  initializes settings of the ASIC  210  via the SPI. Next, in step S 32 , the MCU  222  blinks the LED (G) in the second pattern, and transfers to step S 34  of  FIG.  7   . For example, the blinking of the second pattern of the LED (G) indicates pairing with the operation checking device  310 . In the second pattern, lighting is repeated several times per second. After step S 32 , the operation mode transitions from the deep sleep mode to the pairing mode. 
     In  FIG.  7   , the pairing mode process is executed. For example, wireless communication between the wireless communication section  224  and the operation checking device  310  is carried out using the 2.4 GHz band, which is a frequency band for Industrial Scientific and Medical (ISM). In the 2.4 GHz band, any of 80 channels in which 2402-2481 MHz is divided into 1 MHz units can be selectively used. Although not particularly limited, the modulation method for wireless communication between the wireless communication section  224  and the operation checking device  310  is, for example, Minimum-Shift Keying (MSK). 
     In step S 34 , the MCU  222  waits for the reception of the pairing command “0xF1” transmitted from the operation checking device  310  and a channel number indicating one of the 80 channels in the 2.4 GHz band. In this regard, “Ox” at the beginning of the pairing command indicates that the last two digits “F1” are hexadecimal numbers, and are not included in the actual pairing command. 
     Upon the MCU  222  receiving the pairing command “0xF1” and the channel number, the MCU  222  turns on the LED (G) for the first period in step S 36 . For example, the lighting time of the LED (G) for the first period is several milliseconds. The lighting of the LED (G) for the first period indicates the reception of various commands transmitted from the operation checking device  310 . Next, in step S 38 , the MCU  222  sequentially searches for multiple channels assigned to each communication band to obtain the reception strength of each channel. 
     Next, in step S 40 , if there is a channel that matches the channel number received in step S 34  among the searched channels and the reception strength of the matched channel is equal to or higher than the predetermined intensity, the MCU  222  determines this channel as the channel to be used. Then, the MCU  222  transfers to step S 42 . On the other hand, if none of the searched channels match the channel number received in step S 34 , or if the reception strength of the matched channel is less than the predetermined strength, the MCU  222  returns to step S 34  and waits for the reception of a different channel number. 
     In step S 42 , the MCU  222  transmits the pairing command “0xF2” and a channel number indicating the channel determined in step S 40  to the operation checking device  310 . Next, in step S 44 , the MCU  222  waits for the reception of the pairing command “0xF3” transmitted from the operation checking device  310 . When the pairing command “0xF3” is received, the LED (G) is turned on for the first period. The pairing command “0xF3” is a board ID request command that requests a board ID. The board ID is identification information assigned to each biosensor  100  in advance, and, for example, is stored in a predetermined storage area of the flash memory  230  at the time of manufacturing the biosensor  100 . 
     Upon receiving the pairing command “0xF3”, in step S 46 , the MCU  222  transmits the pairing command “0xF4” and, for example, the last four digits of the board ID to the operation checking device  310 . Note that the number of digits and the digit position of the board ID to be transmitted are not limited to the above. 
     Next, in step S 48 , the MCU  222  waits for the reception of the pairing completion command “0xF5” transmitted from the operation checking device  310 . When the pairing completion command “0xF5” is received, the LED (G) is turned on for the first period. The pairing completion command “0xF5” is an example of the pairing completion notification. 
     Upon receiving the pairing command “0xF5”, in step S 50 , the MCU  222  transmits the pairing completion command “0xF6” indicating the completion of the pairing to the operation checking device  310 . Next, in step S 52 , the MCU  222  transmits internal information including information such as the current temperature of the biosensor  100  and the power supply voltage in use to the operation checking device  310 . 
     Next, in step S 54  of  FIG.  8   , the MCU  222  waits for the reception of a waveform checking command transmitted from the operation checking device  310 . The waveform checking command is issued from the PC  320  when a physician or the like selects a waveform checking button displayed on the screen of the PC  320  in order to check a waveform indicating a time change of the biological information. Upon receiving the waveform checking command, the MCU  222  transitions the operation mode from the pairing mode to the operation checking mode. Then, in step S 56 , the MCU  222  blinks the LED (G) for a second period in a third pattern in order to notify the outside that the biological information is transmitted to the PC  320 . For example, the second period is one minute to several minutes, and the number of blinks per second in the third pattern is different from the number of blinks per second in the second pattern. 
     Next, in step S 58 , the MCU  222  causes the ASIC  210  to obtain the biological information, and receives the biological information obtained by the ASIC  210 . Next, in step S 60 , the MCU  222  transmits the received biological information to the operation checking device  310  without writing the received biological information to the flash memory  230 . 
     Next, in step S 62 , when the MCU  222  receives a recording start command from the operation checking device  310 , the process transfers to step S 64 , and the operation mode transitions from the operation checking mode to the biological information recording mode. If the MCU  222  does not receive the recording start command, the process returns to step S 58 . That is, the MCU  222  repeatedly executes step S 58  and step S 60  until the recording start command is received, and transmits the biological information obtained by the ASIC  210  to the PC  320  via the operation checking device  310 . 
     In step S 64 , during the biological information recording mode, the MCU  222  receives the biological information obtained by the ASIC  210 . Next, in step S 66 , the MCU  222  writes the obtained biological information to the flash memory  230 . Writing the biological information to the flash memory  230  is performed during the biological information recording mode, and is not performed during the operation checking mode. 
     For example, the biological information obtained from the subject P during the operation checking mode is assumed to be written to the flash memory  230 . In this case, the MCU  222  is required to delete the biological information written in the flash memory  230  when transitioning from the operation checking mode to the biological information recording mode. In the present embodiment, it is not necessary to delete the biological information written in the flash memory  230  when transitioning from the operation checking mode to the biological information recording mode. Therefore, the storage capacity of the flash memory  230  can be saved, and the capacity of the battery  200  can be saved. 
     Next, in step S 68 , the MCU  222  performs step S 70  if the depression of the switch  240  is detected, and performs step S 72  if the depression of the switch  240  is not detected. Step S 70  is the operation of the event recording mode illustrated in  FIG.  5   , and the MCU  222  writes an event such as time information to the flash memory  230  and transfers to step S 72 . 
     In step S 72 , the MCU  222  transfers to step S 74  of  FIG.  9    if a predetermined set time (for example, 24 hours) has elapsed, and returns to step S 64  if the set time has not elapsed. That is, the MCU  222  repeatedly performs step S 64  to step S 70  until the set time elapses. Also, the MCU  222  sequentially writes the biological information obtained by the ASIC  210  to the flash memory  230 , or writes an event such as time information to the flash memory. After step S 72 , the MCU  222  transitions the operation mode from the biological information recording mode to the waiting-for-data-output mode. 
     In step S 74  of  FIG.  9   , the MCU  222  blinks the LED (G) in a fourth pattern in order to notify the outside that an obtainment period of the biological information has expired. For example, in the fourth pattern, lighting is repeated at intervals of several seconds. Next, in step S 76 , the MCU  222  waits for the reading device  410  to be connected to the external terminal  131 , and when the reading device  410  is connected, performs step S 78 . 
     In step S 78 , the MCU  222  turns on the LED (G) for a third period and transitions the operation mode from the waiting-for-data-output mode to the data output mode in order to notify the outside that the connection to the external terminal  131  of the reading device  410  has been detected. For example, the third period is one to several seconds. Next, in step S 80 , the flash memory  230  outputs stored biological information or the like to the reading device  410  via the external terminal  131  based on the reading access by the reading device  410 . Step S 80  is performed while the reading access from the reading device  410  to the flash memory  230  continues. 
     Next, in step S 82 , if depression of the switch  240  is detected for five seconds or longer, the MCU  222  returns to step S 10  of  FIG.  6    and transitions to the initialization mode. The MCU  222  repeatedly performs step S 82  if the switch  240  is not depressed for five seconds or longer. 
     As illustrated in  FIG.  6    to  FIG.  9   , the biosensor  100  changes the lighting time, blinking cycle, or blinking pattern of a single LED (G) according to the depression state of the switch  240  or the internal state of the biosensor  100 . This enables, for example, the physician or the like who operates the PC  320  to grasp which operation mode the biosensor  100  is in by observing the lighting state of the LED (G) and to confirm the biosensor  100  is operating correctly. 
       FIG.  10    is a sequence diagram illustrating an example of operation in a pairing mode of  FIG.  5    and  FIG.  7   . The sequence illustrated in  FIG.  10    corresponds to the operation in the operation checking mode of  FIG.  8    in addition to the operation in the pairing mode of  FIG.  7   . Since the operation of the biosensor  100  is the same as the operation of  FIG.  7    and  FIG.  8   , detailed description thereof will be omitted. 
     The operation checking device  310  is connected to the USB terminal of the PC  320  before the sequence of  FIG.  10    is started. Further, the biosensor  100  in transition to the deep sleep mode is attached to the chest of the subject P, and the switch  240  is depressed and held for two seconds or longer, so that the biosensor  100  transitions from the deep sleep mode to the pairing mode (e.g., (a) of  FIG.  10   ). Subsequently, the PC  320  is operated by an operator such as a physician, a pairing command is transmitted from the PC  320  to the operation checking device  310 , and the operation checking device  310  starts the pairing mode (e.g., (b) of  FIG.  10   ). 
     The operation checking device  310  collects the signal strength (for example, Received Signal Strength Indicator (RSSI) value) of each channel in the 2.4 GHz band (e.g., (c) of  FIG.  10   ). The operation checking device  310  determines that the channel having the smallest RSSI value is used for communication with the biosensor  100  as the least used channel (e.g., (d) of  FIG.  10   ). If multiple channels having the smallest RSSI value exist, the operation checking device  310  determines, for example, the channel having the smallest channel number as the channel to be used. 
     The operation checking device  310  repeatedly transmits the pairing command “0xF1” and the channel number indicating the determined channel together with a synchronization word (not illustrated) (e.g., (e) of  FIG.  10   ). After the pairing mode has been started, the biosensor  100  receives the pairing command “0xF1” and the channel number. Further, the biosensor  100  sequentially searches 80 channels in the 2.4 GHz band to obtain the reception strength of each channel. 
     If there is a channel whose reception strength is equal to or higher than the predetermined strength of the channel that matches the received channel number, the biosensor  100  transmits the channel number received from the operation checking device  310  together with the pairing command “0xF2” (e.g., (f) of  FIG.  10   ). This enables biological information or the like using a channel whose reception strength is less than the predetermined strength to be prevented from being transmitted/received. Therefore, communication between the biosensor  100  and the operation checking device  310  can be made of a predetermined quality or higher. 
     If there is no channel that matches the channel number received from the operation checking device  310 , or if the reception strength of the channel that matches the channel number is less than the predetermined strength, the biosensor  100  sets the synchronization word to the default value and returns to a restart point. If the pairing command “0xF2” is not received within a predetermined time after the pairing command “0xF1” being transmitted, the operation checking device  310  sets the synchronization word to the default value and returns to the restart point. 
     Upon receiving the pairing command “0xF2” and the channel number, the operation checking device  310  transmits the pairing command “0xF3” (board ID request command) (e.g., (g) of  FIG.  10   ). When the pairing command “0xF3” is received, the biosensor  100  transmits the pairing command “0xF4” and the last four digits of the board ID (e.g., (h) of  FIG.  10   ). 
     Upon receiving the pairing command “0xF4” and the part of the board ID, the operation checking device  310  transmits the pairing command “0xF5” (pairing completion command) (e.g., (i) of  FIG.  10   ). When the pairing command “0xF5” is received, the biosensor  100  transmits the pairing command “0xF6” (pairing completion command) (e.g., (j) of  FIG.  10   ). As a result, the pairing between the operation checking device  310  and the biosensor  100  is completed. 
     By performing pairing with the method illustrated in  FIG.  10   , communication can be performed between the biosensor  100  and the operation checking device  310  using a channel having a higher reception strength than the others. Therefore, for example, it is possible to increase the possibility of maintaining a predetermined reception strength as compared with the case of frequency hopping in which channels are switched sequentially. As a result, in the operation checking mode, the biological information obtained by the biosensor  100  can be wirelessly transmitted to the operation checking device  310  without making a communication error or the like. 
     Subsequently, the biosensor  100  transmits internal information including information such as the current temperature of the biosensor  100  and the power supply voltage in use (e.g., (k) of  FIG.  10   ). When the operation checking device  310  receives the internal information, the operation checking device  310  transmits the received internal information to the PC  320 . For example, the PC  320  displays the received internal information on the screen. Subsequently, the PC  320  is operated by the physician or the like, the waveform checking button displayed on the screen is selected, and the PC  320  transmits the waveform checking command to the operation checking device  310 . 
     Upon receiving the waveform checking command from the PC  320 , the operation checking device  310  transmits the waveform checking command and transitions the operation mode from the pairing mode to the operation checking mode (e.g., ( 1 ) of  FIG.  10   ). When the waveform checking command is received, the biosensor  100  transitions the operation mode from the pairing mode to the operation checking mode, and sequentially transmits biological information such as an electrocardiogram signal obtained by the ASIC  210  (e.g., (m) of  FIG.  10   ). The operation checking device  310  transmits the biological information received from the biosensor  100  to the PC  320  during the operation checking mode. Then, the waveform of the biological signal based on the biological information is displayed on the screen of the PC  320 . 
     If the sequence illustrated in  FIG.  10    cannot be continued, each of the operation checking device  310  and the biosensor  100  sets the synchronization word to the default value, and returns to the restart point to restart the sequence. For example, as an example in which the sequence cannot be continued, there is a case where the received response is different from the expected value, or a timeout occurs before the expected response is received. Further, after the transition to the pairing mode, for example, if the pairing is not completed within one minute, the biosensor  100  transitions to the deep sleep mode. 
       FIG.  11    is a data flow diagram illustrating an example of data transmission/reception between the biosensor of  FIG.  1    and the operation checking device  310 . In the example illustrated in  FIG.  10   , the biosensor  100  transmits the biological information obtained from the subject P to the operation checking device  310 , and the operation checking device  310  receives the biological information. 
     In the biosensor  100 , when the SoC  220  illustrated in  FIG.  4    receives the biological information from the ASIC  210 , a master-slave signal M/S is set to the logical value 1 in order to use the ASIC  210  as the master. 
     The ADC  214  of the ASIC  210  illustrated in  FIG.  4    performs A/D conversion of the biological information obtained from the subject P and amplified by the AMP  212  at a predetermined frequency. For example, the ADC  214  performs the A/D conversion eight times every 1.024 milliseconds. That is, the ASIC  210  obtains the biological information eight times every 1.024 milliseconds. In  FIG.  11   , groups of the biological information obtained eight times every 1.024 milliseconds are indicated by reference numerals # 1  to # 8 . 
     The I/O  216  uses the SPI to transmit A/D converted biological information to the SoC  220 . For example, the I/O  216  sets a chip select CS to the active level (for example, low level) for a predetermined period for each biological information, and outputs the biological information to the data terminal MOSI (i.e., Master Output Slave Input) in synchronization with the clock signal CLK during the active period. 
     The MCU  222  of the SoC  220  calculates the average value of 16 continuous biological information received from the ASIC  210 . That is, the MCU  222  calculates the average value of the biological information included in the two biological information groups (for example, # 1  and # 2 ). The MCU  222  outputs the calculated average value to the wireless communication section  224 . 
     The MCU  222  adds internal information to the biological information (e.g., average value) and transmits the average value of the biological information every time the average value of the biological information is transmitted to the operation checking device  310  at a predetermined number of times (for example, any number of times from 10 to 20 times). The wireless communication section  224  transmits the biological information (or the biological information to which the internal information is added) received from the MCU  222  to the operation checking device  310 . Although not particularly limited, for example, the time for transmitting the average value of the biological information is up to 320 microseconds, and the maximum time for internal information to be transmitted together with the average value of biological information is 470 microseconds. 
     When the operation checking device  310  receives the biological information from the biosensor  100 , the operation checking device  310  transmits the received biological information as two biological information groups to the data processing section in the operation checking device  310 . At this time, the SPI is used for transmission to the data processing section. For example, the operation checking device  310  transmits the biological information (average value) of two biological information groups to the built-in data processing section every 2.048 milliseconds. 
     The biosensor  100  (MCU  222 ) transitions to a command reception mode for receiving a control command from the operation checking device  310  at a predetermined frequency. For example, the frequency of transitioning to the command reception mode is set to be the same as the frequency of transmitting the internal information. For example, the operation checking device  310  transmits a stop instruction for transmitting biological information to the biosensor  100  as the control command. 
     The operation checking device  310  continuously transmits the control command. A transmission interval of the control command is set shorter than the period for transitioning to the command reception mode (for example, up to 200 microseconds). As a result, even when the operation checking device  310  transmits the control command without recognizing the transition timing of the command reception mode, the biosensor  100  can reliably receive the control command. 
       FIG.  12    is an explanatory diagram illustrating a display example of a screen of the PC  320  connected to the operation checking device  310  of  FIG.  1   . When the operation checking program of the biosensor  100  is started on the PC  320 , the operation checking screen illustrated in  FIG.  12    is displayed on the screen of the PC  320 . The operation checking screen includes an input field for inputting information such as a hospital name, a patient ID, a patient name, and a date of birth, a waveform checking button, a recording start button, and a waveform display window. 
     For example, an operator such as a physician who operates the biosensor system SYS connects the operation checking device  310  to the PC  320 , and after attaching the biosensor  100  to the subject P, the switch  240  of the biosensor  100  is depressed for a long time. By depressing the switch  240  for a long time, the biosensor  100  and the operation checking device  310  perform a pairing process. The operation checking program executed by the PC  320  is started by the operation of the operator before or after the depression of the switch  240  for a long time. 
     Subsequently, as described above, when the waveform checking button is selected by the operator, the PC  320  transmits an operation checking command to the biosensor  100  via the operation checking device  310 . Upon receiving the operation checking command, the biosensor  100  transitions to the operation checking mode and wirelessly transmits the biological information obtained from the subject P to the operation checking device  310 . The operation checking device  310  that has received the biological information transmits the received biological information to the PC  320 . The PC  320  generates a waveform using the received biological information, and displays the generated waveform in the waveform display window. 
     The operator checks that the biosensor  100  is affixed to the correct position of the subject P and that the biosensor  100  is operating normally by observing the waveform displayed in the waveform display window. That is, it is confirmed that the biosensor  100  obtains biological information normally. 
     Subsequently, as described above, when the recording start button is selected by the operator, the PC  320  transmits a recording start command to the biosensor  100  via the operation checking device  310 . Upon receiving the recording start command, the biosensor  100  transitions from the operation checking mode to the biological information recording mode, and stops transmitting the biological information obtained from the subject P to the PC  320 . Then, the biosensor  100  starts the actual measurement of the biological information, and sequentially writes the biological information obtained by the ASIC  210  to the flash memory  230 . Subsequently, the operation checking program is terminated by the physician or the like who operates the PC  420 . 
     For example, after 24 hours have elapsed from the start of writing the biological information to the flash memory due to the start of the biological information recording mode, the reading device  410  (of  FIG.  1   ) is connected to the external terminal  131  of the biosensor  100 . The reading device  410  reads the biological information and the like recorded in the flash memory  230  of the biosensor  100  based on the reading instruction from the PC  420 , and transfers the read biological information and the like to the PC  420 . 
     For example, the PC  420  displays a waveform (electrocardiogram waveform, etc.) indicating a time change of the received biological information on the screen. When the PC  420  receives accompanying information accompanying the biological information together with the biological information, the PC  420  may display the accompanying information together with the waveform on the screen. Then, the waveform displayed on the screen is observed by the physician or the like who operates the PC  420 . 
     As described above, in the embodiment illustrated in  FIG.  1    to  FIG.  12   , the biosensor  100  transitions to the operation checking mode that enables checking of whether the biological information can be normally obtained before the biological information recording mode for the actual measurement of the biological information. This enables, in the operation confirmation mode, after the physician or the like checks whether the biosensor  100  is correctly attached to the subject P and whether the biosensor  100  operates normally, the biosensor  100  to start the actual measurement of the biological information. As a result, a problem that the biosensor  100  cannot correctly record the biological information during the biological information recording mode can be prevented. Also, a problem that the correct biological information is not written to the flash memory can be prevented. 
     The biological information obtained during the operation checking mode is wirelessly transmitted to the operation checking device  310  and transferred to the PC  320 . Then, by displaying the waveform or the like on the screen of the PC  320 , a physician or the like can observe the waveform and check whether the biosensor  100  normally obtains the biological information. Further, after checking that the biological information is normally obtained, the recording start button is pressed by the physician or the like, so that the biosensor  100  transitions from the operation checking mode to the biological information recording mode and the biological information can be written in the flash memory  230 . At this time, since the wireless communication section  224  does not operate during the biological information recording mode, the power consumption of the biosensor  100  can be reduced. 
     As described with reference to  FIG.  5   , the biosensor  100  can transition the operation mode to various other operation modes according to the depressing time of the switch  240  and the operation mode when the switch  240  is pressed. Therefore, a soft switch capable of detecting a plurality of events can be implemented by one switch  240 . Accordingly, the biosensor  100  can be miniaturized and the cost of the biosensor  100  can be reduced. 
     By performing pairing with the method illustrated in  FIG.  10   , communication can be performed between the biosensor  100  and the operation checking device  310  using a channel having a higher reception strength than the others. Therefore, in the operation checking mode, the biological information obtained by the biosensor  100  can be wirelessly transmitted to the operation checking device  310  without making a communication error or the like. 
     The biosensor  100  changes the lighting time, blinking cycle, or blinking pattern of a single LED (G) according to the depression state of the switch  240  or the internal state of the biosensor  100 . This enables, for example, the physician or the like who operates the PC  320  to grasp which operation mode the biosensor  100  is in by observing the lighting state of the LED (G) and to check the biosensor  100  being operating correctly. 
     By directly connecting the external terminal  131  to the flash memory  230 , in the data output mode, by connecting the reading device  410  to the external terminal  131  via the cable, the biological information can be read directly from the flash memory  230  to the reading device  410 . Since the control by the MCU  222  is not performed and the wireless communication by the wireless communication section  224  is not performed when the biological information is read from the flash memory  230 , the power consumption of the biosensor  100  can be minimized. 
     When the switch  240  is depressed during the biological information recording mode, by writing the time information corresponding to the current time to the flash memory  230 , the time when the subject P feels ill such as a palpitation or shortness of breath can be recorded in the flash memory  230  together with the biological information. This enables the physician or the like to determine whether abnormality is present in an electrocardiographic waveform or the like obtained when the subject P felt ill based on such as a depression timing of the switch  240  read from the flash memory  230  and displayed on the screen. 
     By providing the power supply switch  12  that is kept in the off state until the switch  240  is depressed for a long time during the deep sleep mode, unnecessary power consumption during the deep sleep mode can be prevented. As a result, the life of the battery  200  can be extended, so the time during which the biological information can be recorded in the biological information recording mode can be extended. 
     Although the above-described embodiment describes an example of using the SPI for data transmission between devices, for example, another serial interface such as an Inter-Integrated Circuit (I2C) may be used. 
     Although the present invention has been described based on the embodiments, the present invention is not limited to the specifically disclosed embodiments. In these respects, modifications/changes can be made without departing from the spirit of the present invention. 
     The present application claims priority under Japanese Patent Application No. 2020-059655 filed Mar. 30, 2020. The contents of which are incorporated herein by reference in their entirety. 
     REFERENCE SIGNS LIST 
     
         
           10  DC/DC converter 
           12  power supply switch 
           14  DC/DC converter 
           16  thermistor 
           18 ,  20  filters 
           22  resistor division section 
           100  biosensor 
           110  flexible substrate 
           120  housing 
           121  body section 
           122  constricted section 
           123  pad section 
           124  constricted section 
           125  pad section 
           126  component mounting section 
           127  battery setting section 
           127   a ,  127   b  pad sections 
           127   c  constricted section 
           128  slit 
           131  external terminal 
           132 ,  133  electrode patterns 
           134  positive electrode pattern 
           135  negative electrode pattern 
           136  antenna pattern 
           200  battery 
           210  ASIC 
           212  amplifier 
           214  analog/digital converter (ADC) 
           216  input/output interface circuit (I/O) 
           218  logic circuit (LOGIC) 
           250  LED 
           260  plate member 
           310  operation checking device 
           320  PC 
           410  reading device 
           420  PC 
         P Subject 
         SCNT switch control signal 
         SYS Living body sensor system 
         TEMP temperature information 
         VCC1, VCC2, VCC2 (S), VCC3 supply voltage 
         VDET voltage