Sensor controller, electronic device, and control method of sensor controller

Abstract

Provided are a sensor controller, an electronic device, and a method for controlling the sensor controller, which are capable of reducing the level of electromagnetic noise of a transmission signal transmitted to a touch sensor. The present invention is provided with: a transmission unit that transmits a transmission signal to a touch sensor during a third period including a first period for measuring electromagnetic noise and a second period for detecting the position of a passive indicator by the touch sensor; a measurement unit that measures the level of electromagnetic noise at a frequency corresponding to each of the periods during the first period and the second period; and a frequency selection unit that selects, for each third period, one of the first predetermined number of frequencies as a scanning frequency on the basis of the measurement result of the measurement unit, and selects, as preliminary frequencies, a second predetermined number of frequencies smaller than the first predetermined number from among the first predetermined number of frequencies different from the scanning frequency. The scan frequency is the frequency of the transmission signal in the second period, and the preliminary frequency is the frequency of the transmission signal in the first period.

Description

Technical Field

[0001] The present invention relates to a sensor controller, and in particular to a sensor controller, an electronic device and a control method of the electronic device. Background Art

[0002] In the past, there have been known touch sensors that detect position indications of fingers, styluses, etc., and sensor controllers that control the detection operation of the touch sensors. When detecting a position, an electronic device having such a touch sensor and a sensor controller detects the position by sending a transmission signal having a scanning frequency from the sensor controller to the touch sensor.

[0003] In this regard, patent document 1 discloses an indicator position detection device (sensor controller), which includes a plurality of conductor patterns (touch sensors) arranged in mutually intersecting directions, a signal supply circuit that sends signals to the conductor pattern arranged in a first direction, and a noise analysis circuit that performs frequency analysis on a noise signal received from the conductor pattern arranged in a second direction and detects and analyzes noise components.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent No. 5496735 Summary of the invention

[0007] Problems to be solved by the invention

[0008] In the technique described in Patent Document 1, the sensor controller needs to perform frequency analysis in order to analyze the noise component. Therefore, in the technique described in Patent Document 1, the circuit scale and manufacturing cost may increase according to the circuit for performing frequency analysis.

[0009] In addition, in the technology described in Patent Document 1, even if it is assumed that the sensor controller analyzes the noise component without frequency analysis, since the sensor controller described in Patent Document 1 determines the frequency of the transmitted signal based on the result of the frequency analysis at one frequency, when the noise level at the analyzed frequency is smaller than the noise level at other frequencies, the frequency of the transmitted signal is changed to another frequency. Therefore, in the technology described in Patent Document 1, the sensor controller may change the frequency of the transmitted signal relative to the touch sensor to a frequency with a high noise level.

[0010] The present invention has been made in view of the above problems, and an object of the present invention is to provide a sensor controller capable of efficiently reducing the level of electromagnetic noise of a transmission signal transmitted to a touch sensor.

[0011] Means for solving problems

[0012] In order to solve the above-mentioned problems, the first sensor controller involved in the present invention is a sensor controller that performs action control of position detection of a passive indicator by a touch sensor, wherein the sensor controller comprises: a sending unit that sends a sending signal to the touch sensor at a specified period in a third period including a first period for measuring electromagnetic noise and a second period for performing the position detection; a measuring unit that measures the level of electromagnetic noise having a frequency corresponding to each period during the first period and the second period; and a frequency selecting unit that selects, for each of the third period, one of a first specified number of frequencies as a scanning frequency based on the measurement result of the measuring unit, and selects a second specified number of frequencies that are less than the first specified number from the frequencies of the first specified number that are different from the scanning frequency as a preliminary frequency, the scanning frequency being the frequency of the sending signal during the second period, and the preliminary frequency being the frequency of the sending signal during the first period.

[0013] Furthermore, in the sensor controller according to the second aspect of the present invention, the frequency selection unit sequentially selects the second predetermined number of frequencies as the spare frequencies from among the first predetermined number of frequencies, frequencies different from the scanning frequency, for each of the third periods.

[0014] In the sensor controller according to the third aspect of the present invention, the frequency selection unit selects a frequency different from the scanning frequency selected last time as the current scanning frequency when the measurement result of the electromagnetic noise in the second period of the measurement unit is equal to or greater than a predetermined value.

[0015] In addition, in the sensor controller involved in the fourth present invention, the frequency selection unit determines whether the measurement result is less than the measurement result of the electromagnetic noise in the first period of the measurement unit when the measurement result is greater than the specified value, and when the determination is affirmative, the scanning frequency selected last time is selected again as the scanning frequency this time.

[0016] In addition, in the sensor controller involved in the fifth present invention, the frequency selection unit determines whether the measurement result is less than the measurement results of the electromagnetic noise in the multiple first periods of the measurement unit when the measurement result is greater than the specified value, and when the determination is affirmative, the scanning frequency selected last time is selected again as the scanning frequency this time.

[0017] In addition, in the sensor controller involved in the sixth embodiment of the present invention, the frequency selection unit determines whether the measurement result is less than the measurement results of the electromagnetic noise in the multiple first periods of the measurement unit when the measurement result is greater than the specified value. When the determination is negative, the frequency corresponding to the measurement result with the minimum value among the measurement results of the electromagnetic noise in the multiple first periods is selected as the scanning frequency this time.

[0018] In addition, in the sensor controller involved in the seventh present invention, the frequency selection unit determines whether the measurement result is less than the measurement results of the electromagnetic noise in the multiple first periods of the measurement unit when the measurement result is greater than the specified value. When the determination is negative, the frequency with the highest priority in the priority predetermined by the prior measurement results related to the level of electromagnetic noise is selected from the frequencies different from the scanning frequency among the first specified number of frequencies as the scanning frequency this time.

[0019] In addition, in the sensor controller involved in the eighth embodiment of the present invention, the frequency selection unit determines whether the measurement result is less than the measurement results of the electromagnetic noise in multiple first periods of the measurement unit when the measurement result is greater than the specified value. When the determination is negative, the frequency that is farthest from the scanning frequency selected last time is selected as the scanning frequency this time from the frequencies corresponding to the measurement results that are smaller than the specified value among the measurement results of the electromagnetic noise in multiple first periods.

[0020] In addition, in the sensor controller involved in the ninth invention, the frequency selection unit determines whether the measurement result is less than the measurement results of the electromagnetic noise in the multiple first periods of the measurement unit when the measurement result is greater than the specified value. When the determination is negative, the frequency closest to the scanning frequency selected last time is selected from the frequencies corresponding to the measurement results smaller than the specified value among the measurement results of the electromagnetic noise in the multiple first periods as the scanning frequency this time.

[0021] Furthermore, in the sensor controller according to the tenth aspect of the present invention, the second predetermined number is 1.

[0022] In addition, the eleventh electronic device involved in the present invention comprises: a touch sensor, which is arranged in a planar shape by multiple detection electrodes, and is used to detect the position of a passive indicator; and a sensor controller, which is connected to the touch sensor and has a sending unit, a measuring unit and a frequency selection unit, the sending unit sends a sending signal to the touch sensor in a specified period during a third period including a first period for measuring electromagnetic noise and a second period for performing the position detection, the measuring unit measures the level of electromagnetic noise having a frequency corresponding to each period during the first period and the second period, the frequency selection unit selects one of a first specified number of frequencies as a scanning frequency for each of the third periods based on the measurement result of the measuring unit, selects a second specified number of frequencies less than the first specified number from the frequencies of the first specified number of frequencies different from the scanning frequency as a preliminary frequency, the scanning frequency is the frequency of the sending signal during the second period, and the preliminary frequency is the frequency of the sending signal during the first period.

[0023] In addition, the twelfth embodiment of the present invention relates to a control method of a sensor controller for controlling the action of a touch sensor detecting the position of a passive indicator, which includes: sending a sending signal to the touch sensor in a third period including a first period for measuring electromagnetic noise and a second period for performing the position detection at a specified period; measuring the level of electromagnetic noise having a frequency corresponding to each period during the first period and the second period; and for each of the third period, based on the result of the measurement, selecting one of a first specified number of frequencies as a scanning frequency, selecting a second specified number of frequencies less than the first specified number from the frequencies of the first specified number of frequencies different from the scanning frequency as a preparatory frequency, the scanning frequency being the frequency of the sending signal during the second period, and the preparatory frequency being the frequency of the sending signal during the first period.

[0024] Effects of the Invention

[0025] According to the present invention, the sensor controller can efficiently reduce the level of electromagnetic noise of the transmission signal transmitted to the touch sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a diagram showing an example of an electronic device.

[0027] Figure 2 This is a diagram showing an example of a time chart showing the transition of a frequency used in a transmission signal transmitted to a touch sensor.

[0028] Figure 3: is a graph showing the distribution of electric potential detected by the touch sensor using the linear electrodes.

[0029] Figure 4 This is a diagram showing an example of the level of electromagnetic noise at each frequency used in the transmission signal.

[0030] Figure 5 This is a flowchart showing an example of a flow of a series of processes of the sensor controller.

[0031] Figure 6 FIG. 2 is a diagram showing another example of a time chart indicating the transition of a frequency used in a transmission signal transmitted to a touch sensor. DETAILED DESCRIPTION

[0032] Below, while referring to the attached Figure 1 An embodiment of the present invention (hereinafter referred to as "this embodiment") will be described. To facilitate understanding of the description, the same components and steps in the drawings are denoted by the same reference numerals as much as possible, and repeated descriptions are omitted.

[0033] <Circuit Structure>

[0034] Figure 1 1 is a diagram showing an example of an electronic device 1 according to the first embodiment. The electronic device 1 is a computer owned by a user, such as a tablet, a smartphone, a personal computer, etc. The user can write pictures and texts on the display surface of the electronic device 1 by pressing the tip of a stylus pen 2, which is a pen-shaped pointing device, or the user's finger 3 against the touch surface of the electronic device 1 and moving it. The stylus pen 2 is, for example, a non-active touch pen.

[0035] The electronic device 1 detects the indicated position of the stylus pen 2 or the finger 3, and performs various information processing according to the detection result. Specifically, the electronic device 1 detects the indicated position of the stylus pen 2 or the finger 3 based on the signal detected by the linear electrodes 21 and 22 provided on the display surface, and performs the generation processing of digital ink, the display processing of the pointer, etc. The electronic device 1 includes a sensor controller 10 and a touch sensor 20 in addition to a host processor, a memory, and a communication module (none of which are shown in the figure).

[0036] The touch sensor 20 is an electrostatic capacitance type sensor in which a plurality of detection electrodes are arranged in a planar shape. The touch sensor 20 is configured, for example, to include a plurality of X-line electrodes (hereinafter referred to as "linear electrodes 21") for detecting the position of the X-axis of the sensor coordinate system and a plurality of Y-line electrodes (hereinafter referred to as "linear electrodes 22") for detecting the position of the Y-axis. The linear electrodes 21 and 22 can be composed of a transparent conductive material including ITO (Indium Tin Oxide) or a wire mesh sensor. It should be noted that the touch sensor 20 can also replace the above-mentioned mutual capacitance type sensor with a self-capacitance type sensor in which block-shaped electrodes are arranged in a two-dimensional grid shape.

[0037] The sensor controller 10 controls the operation of the touch sensor 20 to detect the position of a passive pointer such as the stylus pen 2 or the finger 3. The sensor controller 10 includes, for example, an MCU (Micro Controller Unit) 11, a receiving unit 12, a transmitting unit 13, a detecting unit 14, and an output unit 15.

[0038] The detection unit 14 is a circuit that selects one of the plurality of linear electrodes 21 or a plurality of adjacent ones based on an instruction from the MCU 11. The output unit 15 is a circuit that selects one of the plurality of linear electrodes 22 or a plurality of adjacent ones based on an instruction from the MCU 11, amplifies an input signal sent from the MCU 11 into a predetermined voltage as an output signal, and outputs the output signal to the linear electrode 22.

[0039] The transmission unit 13 is connected to the linear electrode 22 selected by the output unit 15, and based on the instruction from the MCU 11, the transmission signal is transmitted to the linear electrode 21 via the output unit 15. Specifically, the transmission unit 13 transmits the transmission signal to the linear electrode 21 during the transmission period including the noise scanning period for measuring electromagnetic noise and the touch scanning period for position detection, which is a period following the noise scanning. It should be noted that, for the transmission signal transmitted from the transmission unit 13, the preparatory frequency for performing noise scanning during the noise scanning period is selected as the frequency, and the scanning frequency for performing position detection during the touch scanning period is selected as the frequency.

[0040] The receiving unit 12 is connected to the linear electrode 21 selected by the detecting unit 14 and receives detection signals generated on the linear electrode 21 when the stylus pen 2 or the finger 3 touches the sensor surface of the touch sensor 20 . The receiving unit 12 transmits the received detection signals to the MCU 11 .

[0041] The MCU 11 is a microprocessor having a ROM and a RAM inside and operating based on a predetermined program. The MCU controls, for example, the selection operation of the linear electrode 21 by the detection unit 14, the selection operation of the linear electrode 22 by the output unit 15, the reading process of the detection signal transmitted from the receiving unit 12 to the MCU, and the transmission operation of the transmission unit 13 to the touch sensor 20. The MCU is configured as a functional structure including, for example, a measuring unit 101, a frequency selecting unit 102, a control unit 103, and a storage unit 110.

[0042] The measuring unit 101 measures the level of electromagnetic noise at the frequency of the transmission signal transmitted from the transmitting unit 13 with respect to the detection signal transmitted from the receiving unit 12. Specifically, the measuring unit 101 measures the potential of the detection signal supplied from the linear electrode 21 via the receiving unit 12, and uses the measured potential as the level of electromagnetic noise at the frequency of the current transmission signal. In addition, the measuring unit 101 transmits the measured level of electromagnetic noise at the frequency of the current transmission signal to the frequency selecting unit 102.

[0043] The frequency selection unit 102 selects the frequency of the transmission signal sent from the transmission unit 13 based on the measurement result of the measurement unit 101. Specifically, for each transmission period, the frequency selection unit 102 selects one of the first prescribed number of frequencies as the scanning frequency during the touch scanning period based on the measurement result of the electromagnetic noise in the detection signal by the measurement unit 101. In addition, the frequency selection unit 102 selects a second prescribed number of frequencies that are different from the scanning frequency and are less than the first prescribed number from the first prescribed number of frequencies as the preparatory frequency during the noise scanning period. It should be noted that in the present embodiment, the second prescribed number is 1. It should be noted that how the frequency selection unit 102 selects the frequency based on the measurement result of the measurement unit 101 will be described later while referring to Figure 2 Therefore, the description is omitted here.

[0044] The control unit 103 controls the selection operation of the linear electrodes 21 by the detection unit 14. Specifically, the control unit 103 controls the operation of the detection unit 14 in a manner such as to sequentially select all the linear electrodes 21 on the touch sensor 20 during the touch scan period and the noise scan period. In addition, the control unit 103 controls the selection operation of the linear electrodes 22 by the output unit 15. Specifically, the control unit 103 controls the operation of the output unit 15 in a manner such as to sequentially select all the linear electrodes 22 on the touch sensor 20 during the touch scan period and the noise scan period. In addition, the control unit 103 controls the transmission of the frequency selected by the frequency selection unit 102 to the transmission unit 13 and the transmission operation of the transmission unit 13 for the transmission signal. In addition, the control unit 103 reads the detection signal transmitted from the receiving unit 12 and performs the detection operation of the position on the touch sensor 20. It should be noted that the control unit 103 may control the operations of the detection unit 14 and the output unit 15 in a manner to sequentially select a portion of the thinned-out linear electrodes 21 and 22 instead of all the linear electrodes 21 and 22 during the noise scanning period.

[0045] The storage unit 110 stores a program for the MCU 11 to operate, a program for controlling the operations of the transmitting unit 13, the detecting unit 14, and the output unit 15, a group of frequencies that can be selected as the frequencies of the transmitting signal, and the time variation of the level of electromagnetic noise in the detection signal measured by the measuring unit 101.

[0046] <Flow of a series of actions>

[0047] The configuration of the electronic device 1 has been described above. Next, the transition of the potentials of various signals in the electronic device 1 will be described in detail. Figure 2 1 is a diagram showing an example of a time chart indicating the transition of a frequency used in a transmission signal transmitted to the touch sensor 20 .

[0048] like Figure 2 As shown, the transmitting unit 13 transmits the transmission signal to the touch sensor 20 during the transmission period T3. In addition, the transmission period T3 includes a noise scanning period T1 for the measuring unit 101 to measure the electromagnetic noise at each preparatory frequency and a touch scanning period T2 for position detection, which is a period following the noise scanning. Figure 2 In the embodiment, the first predetermined number of frequencies are three frequencies f0, f1 and f2.

[0049] At time t0, the transmitting unit 13 refers to the frequency f1 selected by the frequency selecting unit 102 from the storage unit 110 as the preliminary frequency, and transmits the transmission signal having the frequency f1 to the touch sensor 20 during the noise scanning period T1. In addition, the measuring unit 101 measures the level of the electromagnetic noise of the detection signal transmitted from the touch sensor 20 during the noise scanning period T1. The measuring unit 101 stores the measurement result in the storage unit 110 as the level of the electromagnetic noise at the frequency f1 in the cycle of time t0.

[0050] It should be noted that, in the present embodiment, the control unit 103 controls the operation of the detection unit 14 and the output unit 15 by sequentially selecting all the linear electrodes 21 and 22, but the present invention is not limited thereto, and the operation of the output unit 15 may be controlled by sequentially selecting only the linear electrodes 21 and 22 remaining after thinning out of the plurality of linear electrodes 21 and 22. In addition, the control unit 103 may control the operation of the output unit 15 by simultaneously selecting all the linear electrodes 21 when transmitting a transmission signal from the transmission unit 13, and control the operation of the detection unit 14 by simultaneously selecting all the linear electrodes 22 when receiving a detection signal from the reception unit 12, instead of sequentially selecting all the linear electrodes 21 and 22. Furthermore, the control unit 103 may control the operation of the transmission unit 13 by simultaneously selecting all the linear electrodes 22 when simultaneously selecting all the linear electrodes 21, so that the transmission signals encoded by the orthogonal spread spectrum code are transmitted from all the linear electrodes 21.

[0051] At time t1, the transmitting unit 13 refers to the frequency f0 selected by the frequency selecting unit 102 from the storage unit 110 as the scanning frequency, and transmits the transmission signal having the frequency f0 to the touch sensor 20 during the touch scanning period T2. In addition, the measuring unit 101 measures the level of electromagnetic noise of the detection signal transmitted from the touch sensor 20 during the touch scanning period T2. The measuring unit 101 stores the measurement result as the level of electromagnetic noise at the frequency f0 at time t1 in the storage unit 110. In addition, the control unit 103 reads the detection signal transmitted from the receiving unit 12 during the touch scanning period T2, and performs a process of detecting the presence or absence of the position indication of the stylus pen 2 or the finger 3 on the touch sensor 20 and the indicated position.

[0052] At time t2, the frequency selection unit 102 refers to the storage unit 110 to obtain the measurement result of the measurement unit 101 related to the level of electromagnetic noise at the scanning frequency in the touch scanning period T2 from time t1 to time t2. Since the level of electromagnetic noise at the scanning frequency is less than a specified value and noise is not detected, the frequency selection unit 102 continues to select frequency f0 as the scanning frequency. In addition, since the level of electromagnetic noise at the scanning frequency is less than a specified value and noise is not detected, the frequency selection unit 102 selects frequency f2 that is different from the scanning frequency and different from the preliminary frequency measured this time as the preliminary frequency. It should be noted that details of the scanning frequency and the method for selecting the preliminary frequency of the frequency selection unit 102 will be described later with reference to Figure 3~Figure 5 Therefore, the description is omitted here.

[0053] At time t3-t5, the transmitter 13, the measuring unit 101 and the frequency selector 102 respectively perform the same operations as at time t0-t2 except that the preparatory frequency is changed from frequency f1 to frequency f2. It should be noted that at time t5, the frequency selector 102 selects frequency f0 as the scanning frequency and selects frequency f1 as the preparatory frequency.

[0054] At time t6 to t8 , the transmitting unit 13 , the measuring unit 101 , and the frequency selecting unit 102 perform the same operations as at time t0 to t2 , except that the preliminary frequency is changed from frequency f1 to frequency f2 .

[0055] At time t9 and t10, the transmitter 13 and the measuring unit 101 perform the same operations as at time t3 and t4, except that the preparatory frequency is changed from frequency f1 to frequency f2. At time t100, the measuring unit 101 detects that the level of electromagnetic noise at the sweep frequency, i.e., frequency f0, is above a predetermined value.

[0056] At time t11, the frequency selection unit 102 obtains the measurement result of the measurement unit 101 related to the level of electromagnetic noise at the scanning frequency f0 in the touch scanning period T2 from time t10 to time t11, by referring to the storage unit 110. Since the level of electromagnetic noise at the scanning frequency is above the specified value, the frequency selection unit 102 obtains the level of electromagnetic noise at the preliminary frequency f1 in the noise scanning period T1 from time t6 to time t7 and the preliminary frequency f2 in the noise scanning period T1 from time t9 to time t10, by referring to the storage unit 110.

[0057] Next, the frequency selector 102 selects frequency f1 having the lowest electromagnetic noise level as the sweep frequency among frequencies f0, f1, and f2. In addition, the frequency selector 102 selects frequency f0 which is different from frequency f1 selected as the sweep frequency and different from the preliminary frequency measured this time as the preliminary frequency.

[0058] At time t12 to t14, the transmitter 13, the measuring unit 101, and the frequency selector 102 perform the same operations as at time t0 to t2, except that the preparatory frequency is changed to frequency f0 and the scanning frequency is changed to frequency f1. It should be noted that at time t14, the frequency selector 102 continues to select frequency f1 as the scanning frequency and selects frequency f2 as the preparatory frequency.

[0059] At time t15 to t17, the transmitter 13, the measuring unit 101, and the frequency selector 102 perform the same operations as at time t0 to t2, except that the standby frequency is changed to frequency f2. It should be noted that at time t17, the frequency selector 102 continues to select frequency f1 as the scanning frequency and selects frequency f0 as the standby frequency.

[0060] The above has described the transition of the potentials of various signals in the electronic device 1. Next, the details of the measurement of the electromagnetic noise level by the measurement unit 101 will be described. Figure 3 is a graph showing the distribution of potentials detected by the touch sensor 20 using the linear electrodes 21 and 22. Figure 3 In FIG. 1 , the horizontal axis is the position in the X-line direction in the touch sensor 20 , indicating the position at which the linear electrode 22 is provided. Figure 3 In FIG. 1 , the vertical axis represents the potential of the detection signal transmitted from the linear electrode 21 to the measurement unit 101 via the receiving unit 12 .

[0061] In addition, Figure 3 In the area to the left of the linear electrode 22 set at the position Xth, no position indication based on the stylus pen 2 and the finger 3 is performed, and in the area to the right of the linear electrode 22 set at the position Xth, position indication based on the stylus pen 2 and the finger 3 is performed.

[0062] In addition, Figure 3 In FIG. 1 , potential Tth is a threshold indicating whether a position instruction is being made to the touch sensor 20 by the stylus pen 2 or the finger 3. When the potential of the detection signal is equal to or greater than potential Tth, the control unit 103 regards that a position instruction is made at the position indicated by the detected linear electrodes 21 and 22 and detects the position instruction.

[0063] During the noise scanning period T1, the measuring unit 101 measures the potential of the detection signal and extracts the measurement results that are lower than the potential Tth. Next, the measuring unit 101 calculates the difference between the maximum value and the minimum value of the extracted measurement results, that is, the potential difference Vms. Moreover, the measuring unit 101 stores the calculated potential difference Vms as the level of the electromagnetic noise at the current moment and the preparation frequency in the storage unit 110. In addition, in the touch scanning period T2, the measuring unit 101 calculates the potential difference Vms and stores the calculated potential difference Vms as the level of the electromagnetic noise at the current moment and the scanning frequency in the storage unit 110.

[0064] The above is a description of the details of the measurement of the electromagnetic noise level by the measurement unit 101. Figure 4 , while explaining the selection of frequency by the frequency selection unit 102. Figure 4 FIG. 1 is a diagram showing an example of the level of electromagnetic noise at each frequency used in the transmission signal. Figure 4 In FIG. 1 , the vertical axis and the horizontal axis respectively represent the level and frequency of the electromagnetic noise measured by the measuring unit 101. Figure 4 In the example, the current scanning frequency is frequency f0.

[0065] like Figure 4 As shown, the measurement result of the electromagnetic noise level at the frequency f0 as the scanning frequency is greater than the specified value Nth and is greater than the measurement results of the electromagnetic noise levels at the frequencies f1 and f2 as the preliminary frequencies. In addition, the measurement result of the electromagnetic noise level at the frequency f1 as the preliminary frequency is the smallest among the measurement results of the electromagnetic noise levels at the scanning frequency and each preliminary frequency.

[0066] The frequency selection unit 102 first determines whether the level of the electromagnetic noise of the current scanning frequency, i.e., frequency f0, is greater than the specified value Nth. Furthermore, when the level of the electromagnetic noise of the scanning frequency, i.e., frequency f0, is greater than the specified value Nth, the frequency selection unit 102 determines whether the level of the electromagnetic noise at frequency f0 is smaller than the levels of all electromagnetic noises at frequencies f1 and f2 as the preliminary frequencies. When the frequency selection unit 102 determines that the level of the electromagnetic noise at frequency f0 is greater than the level of any electromagnetic noise at frequencies f1 and f2, the frequency with the smallest level of electromagnetic noise among frequencies f1 and f2 is selected as the scanning frequency. Furthermore, the frequency selection unit 102 selects any one of the frequencies f0 and f2 that are not selected as the scanning frequency among frequencies f0~f2 as the preliminary frequency.

[0067] In addition, the frequency selection unit 102 continues to select the same frequency f0 as the scanning frequency when the level of the electromagnetic noise at the scanning frequency, i.e., the frequency f0, is less than the prescribed value Nth or the level of the electromagnetic noise at the frequency f0 is less than the level of all the electromagnetic noise at the preparatory frequencies, i.e., the frequencies f1 and f2. Furthermore, as long as the condition that the level of the electromagnetic noise at the frequency f0 is less than the prescribed value Nth or the level of the electromagnetic noise at the frequency f0 is less than the level of all the electromagnetic noise at the frequencies f1 and f2 is continuously satisfied, the frequency selection unit 102 sequentially selects the frequencies that are not selected from the plurality of preparatory frequencies as the preparatory frequencies for each transmission period T3.

[0068] It should be noted that in Figure 4 Since the level of electromagnetic noise at the scanning frequency, i.e., frequency f0, is greater than the specified value Nth and is greater than the level of any electromagnetic noise at the preparation frequencies, i.e., frequencies f1 and f2, the frequency selection unit 102 selects the frequency f1 having the smallest electromagnetic noise level among the preparation frequencies, i.e., frequencies f1 and f2, as the scanning frequency.

[0069] The selection of frequency by the frequency selection unit 102 has been described above. Next, the flow of a series of processes by the sensor controller 10 will be described in detail. Figure 5 This is a flowchart showing an example of a flow of a series of processes performed by the sensor controller 10 .

[0070] (Step SP10)

[0071] The sensor controller 10 uses the measuring unit 101 to measure the level of electromagnetic noise at the current preliminary frequency during the noise scanning period T1. The sensor controller 10 stores the measurement result of the electromagnetic noise level by the measuring unit 101 in the storage unit 110 in a form including information related to the time and the preliminary frequency. Then, the process moves to the process of step SP12.

[0072] (Step SP12)

[0073] The sensor controller 10 uses the measuring unit 101 to measure the level of electromagnetic noise at the current scanning frequency during the touch scanning period T2. The sensor controller 10 stores the measurement result of the electromagnetic noise level by the measuring unit 101 in the storage unit 110 in a form including information related to the time and the scanning frequency. Then, the process moves to the process of step SP14.

[0074] (Step SP14)

[0075] The sensor controller 10 uses the frequency selection unit 102 to obtain the measurement result of the electromagnetic noise level at the current scanning frequency in the most recent touch scanning period T2 from the storage unit 110. The sensor controller 10 uses the frequency selection unit 102 to determine whether the obtained measurement result is greater than a specified value. And, if the determination is positive, the process moves to the process of step SP16. On the other hand, if the determination is negative, the process moves to the process of step SP20.

[0076] (Step SP16)

[0077] The sensor controller 10 uses the frequency selection unit 102 to obtain the measurement results of the electromagnetic noise level at each preliminary frequency from the storage unit 110. The sensor controller 10 uses the frequency selection unit 102 to determine whether the level of the electromagnetic noise in the most recent touch scanning period T2 is less than all values ​​of the electromagnetic noise level at each preliminary frequency. And, if the determination is positive, the process moves to the process of step SP20. On the other hand, if the determination is negative, the process moves to the process of step SP18.

[0078] (Step SP18)

[0079] The sensor controller 10 uses the frequency selection unit 102 to select the frequency with the smallest measurement result of the electromagnetic noise level among the preliminary frequencies, and changes the scanning frequency to the selected frequency. Then, the process proceeds to the process of step SP20.

[0080] (Step SP20)

[0081] The sensor controller 10 uses the frequency selection unit 102 to select the frequency with the smallest measurement result of the electromagnetic noise level among the preliminary frequencies, and changes the scanning frequency to the selected frequency. Then, the process proceeds to the process of step SP22.

[0082] (Step SP22)

[0083] The sensor controller 10 uses the control unit 103 to determine whether a stop command for stopping the position detection operation of the sensor controller 10 and the touch sensor 20 has been transmitted from a component or the like outside the sensor controller 10 provided in the electronic device 1. And, if the determination is negative, the processing moves to the processing of step SP20. On the other hand, if the determination is positive, Figure 5 The series of processing shown ends.

[0084] <Effect>

[0085] As described above, in the present embodiment, the sensor controller 10 that performs the operation control of the touch sensor 20 for detecting the position of the stylus pen 2 (passive pointer) includes: a transmitting unit 13 that transmits a transmission signal to the touch sensor 20 in a transmission period T3 (third period) including a noise scanning period T1 (first period) for measuring electromagnetic noise and a touch scanning period T2 (second period) for performing position detection at a predetermined cycle; and a measuring unit 101 that measures the level of electromagnetic noise of a frequency corresponding to each period during the noise scanning period T1 and the touch scanning period T2. The sensor controller 10 further includes a frequency selecting unit 102 that selects one of the first predetermined number of frequencies as the frequency of the transmission signal in the touch scanning period T2, i.e., the scanning frequency, for each transmission period T3, based on the measurement result of the measuring unit 101, and selects a second predetermined number of frequencies less than the first predetermined number of frequencies from the frequencies different from the scanning frequency among the first predetermined number of frequencies as the frequency of the transmission signal in the noise scanning period T1, i.e., the preliminary frequency.

[0086] According to this structure, the sensor controller 10 selects a frequency different from the scanning frequency in the touch scanning period T2 as the preliminary frequency in the noise scanning period T1. Therefore, the sensor controller 10 measures the level of electromagnetic noise in a manner that the scanning frequency and the preliminary frequency do not overlap, thereby being able to efficiently reduce the level of electromagnetic noise of the transmission signal sent to the touch sensor 20.

[0087] In the present embodiment, the frequency selection unit 102 sequentially selects the second predetermined number of frequencies different from the scanning frequency from among the first predetermined number of frequencies as spare frequencies for each transmission period T3 (third period).

[0088] Therefore, the sensor controller 10 sequentially selects the spare frequencies from the frequencies different from the scanning frequency, and thus can more efficiently reduce the level of the electromagnetic noise of the transmission signal.

[0089] In this embodiment, when the measurement result of the electromagnetic noise in the touch scanning period T2 (second period) of the measuring unit 101 is equal to or greater than the predetermined value Nth, the frequency selecting unit 102 selects a frequency different from the scanning frequency selected last time as the current scanning frequency.

[0090] Therefore, the sensor controller 10 can reduce the level of electromagnetic noise of the transmission signal efficiently and accurately.

[0091] In addition, in this embodiment, when the measurement result is greater than the specified value Nth, the frequency selection unit 102 determines whether the measurement result is less than the measurement result of the electromagnetic noise in the noise scanning period T1 (first period) of the measuring unit 101. If the determination is affirmative, the scanning frequency selected last time is selected again as the scanning frequency this time.

[0092] According to this structure, even if the measurement result of the electromagnetic noise level during the touch scanning period T2 is above the specified value Nth, if it is below the measurement result of the electromagnetic noise level during the noise scanning period T1, the sensor controller 10 maintains the scanning frequency, thereby being able to reduce the electromagnetic noise level of the transmitted signal with higher accuracy.

[0093] In addition, in the present embodiment, the second predetermined number is 1.

[0094] According to this structure, the sensor controller 10 measures the level of electromagnetic noise relative to one preliminary frequency during the noise scanning period T1, so that the time of the touch scanning period T2 in the transmission period T3 can be ensured much more. Therefore, the sensor controller 10 can efficiently and accurately reduce the level of electromagnetic noise of the transmission signal while detecting the position indication relative to the touch sensor 20 with high accuracy.

[0095] ―――Modification―――

[0096] It should be noted that the present invention is not limited to the above-mentioned embodiments. That is, the technology obtained by appropriately adding design changes to the above-mentioned embodiments by those skilled in the art is also included in the scope of the present invention as long as it has the characteristics of the present invention. In addition, the various elements possessed by the above-mentioned embodiments and the modified examples described later can be combined within the technically feasible range, and the technology formed by combining them is also included in the scope of the present invention as long as it includes the characteristics of the present invention.

[0097] For example, in the above embodiment, the sensor controller 10 measures the electromagnetic noise level at one preliminary frequency in one transmission period T3, but the present invention is not limited thereto. The sensor controller 10 may measure the electromagnetic noise levels at a plurality of preliminary frequencies in one transmission period T3.

[0098] The frequency selection unit 102 in the sensor controller 10 may select, for each transmission period T3, a second predetermined number of frequencies that are less than the first predetermined number and have a value of 2 or more from the frequencies different from the scanning frequency among the first predetermined number of frequencies as the preliminary frequencies based on the measurement result of the measurement unit 101. That is, the second predetermined number may also be a value of 2 or more. In this case, the frequency selection unit 102 sequentially selects the second predetermined number of frequencies for each transmission period T3 from the frequencies obtained by removing the scanning frequency from the first predetermined number of frequencies.

[0099] Here, referring to Figure 6 , the operation of the sensor controller 10 when measuring the levels of electromagnetic noise at a plurality of preliminary frequencies in one transmission period T3 will be described. Figure 6 2 is a diagram showing another example of a time chart indicating the transition of the frequency used in the transmission signal transmitted to the touch sensor 20 .

[0100] like Figure 6 As shown, the transmitting unit 13 transmits the transmission signal to the touch sensor 20 during the transmission period T3. In addition, the transmission period T3 includes a plurality of noise scanning periods T4 and T5 and a touch scanning period T2 for the measuring unit 101 to measure the electromagnetic noise at each preparatory frequency. Figure 6 In the example, the first predetermined number of frequencies are the seven frequencies f0 to f6. Figure 6 , the second specified number is 2.

[0101] At time t50, the transmitting unit 13 refers to the frequency f1 selected by the frequency selecting unit 102 from the storage unit 110 as the preliminary frequency, and transmits the transmission signal having the frequency f1 to the touch sensor 20 during the noise scanning period T4. In addition, the measuring unit 101 measures the level of the electromagnetic noise of the detection signal transmitted from the touch sensor 20 during the noise scanning period T4. The measuring unit 101 stores the measurement result in the storage unit 110 as the level of the electromagnetic noise at the frequency f1 in the cycle of time t50.

[0102] At time t51, the sensor controller 10 performs the same operation as at time t50 except that the reference frequency is frequency f2. That is, the transmitting unit 13 transmits the transmission signal having frequency f2 to the touch sensor 20 during the noise scanning period T5. In addition, the measuring unit 101 measures the level of electromagnetic noise of the detection signal transmitted from the touch sensor 20 during the noise scanning period T5. The measuring unit 101 stores the measurement result in the storage unit 110 as the level of electromagnetic noise at frequency f2 in the cycle of time t51.

[0103] At time t52, the transmitter 13 transmits a transmission signal having a frequency f0 to the touch sensor 20. It should be noted that the operation of the sensor controller 10 in the touch scanning period T2 from time t52 to t53 is the same as that in Figure 2 The operation in the case where the second predetermined number described in is 1 is the same, so the description thereof is omitted.

[0104] At time t53, the frequency selection unit 102 refers to the storage unit 110 to obtain the measurement result of the measurement unit 101 related to the level of electromagnetic noise at the scanning frequency in the touch scanning period T2 from time t52 to time t53. Since the level of electromagnetic noise at the scanning frequency is less than the specified value and the noise is not detected, the frequency selection unit 102 continues to select the frequency f0 as the scanning frequency. In addition, since the level of electromagnetic noise at the scanning frequency is less than the specified value and the noise is not detected, the frequency selection unit 102 selects frequencies f3 and f4 that are different from the scanning frequency and different from the two preliminary frequencies measured this time as the preliminary frequencies.

[0105] At time t54 to t57, the transmitter 13, the measuring unit 101, and the frequency selector 102 perform the same operations as at time t50 to t53, except that the preparatory frequencies are changed from frequencies f1 and f2 to frequencies f3 and f4. It should be noted that at time t57, the frequency selector 102 selects frequency f0 as the scanning frequency and selects frequencies f5 and f6 as the preparatory frequencies.

[0106] At time t58 to t61, the transmitting unit 13, the measuring unit 101, and the frequency selecting unit 102 perform the same operations as at time t54 to t57, except that the preparatory frequencies are changed from frequencies f3 and f4 to frequencies f5 and f6. It should be noted that at time t61, the frequency selecting unit 102 selects frequency f0 as the scanning frequency, and selects frequencies f1 and f2 as the preparatory frequencies.

[0107] At time t62 to t64, the transmitter 13 and the measurement unit 101 perform the same operation as at time t50 to t52. At time t200, the measurement unit 101 detects that the level of electromagnetic noise at the frequency f0, which is the sweep frequency, is equal to or higher than a predetermined value.

[0108] At time t65, the frequency selection unit 102 refers to the storage unit 110 to obtain the measurement result of the measurement unit 101 related to the level of electromagnetic noise at the scanning frequency f0 in the touch scanning period T2 from time t64 to time t65. Since the level of electromagnetic noise at the scanning frequency is greater than the specified value, the frequency selection unit 102 refers to the storage unit 110. The frequency selection unit 102 obtains the level of electromagnetic noise at the preliminary frequencies f1 to f6 measured in each noise scanning period T4 and T5 during the period from time t54 to time t65.

[0109] Next, the frequency selector 102 selects frequency f4 having the lowest electromagnetic noise level among frequencies f0 to f6 as the sweep frequency. In addition, the frequency selector 102 selects frequencies f3 and f5 different from frequency f4 selected as the sweep frequency and different from the preliminary frequencies measured this time as preliminary frequencies.

[0110] At time t66 to t69, the transmitting unit 13, the measuring unit 101, and the frequency selecting unit 102 perform the same operations as at time t50 to t53, except that the preparatory frequencies are changed from frequencies f1 and f2 to frequencies f3 and f5, and the scanning frequency is changed from frequency f0 to frequency f4. It should be noted that at time t61, the frequency selecting unit 102 selects frequency f0 as the scanning frequency, and selects frequencies f1 and f2 as the preparatory frequencies.

[0111] According to this structure, the sensor controller 10 selects a plurality of frequencies as the preliminary frequencies, and therefore, when the level of electromagnetic noise at the scanning frequency becomes greater than the predetermined value Nth, the possibility of selecting a frequency with a low level of electromagnetic noise as the scanning frequency increases. Therefore, the sensor controller 10 can reduce the level of electromagnetic noise of the transmission signal with higher accuracy.

[0112] In addition, the frequency selection unit 102 may also determine whether the measurement result is less than the measurement results of the electromagnetic noise in multiple noise scanning periods T4~T5 (first period) of the measuring unit 101 when the measurement result is greater than the specified value Nth. If the determination is affirmative, the scanning frequency selected last time is selected again as the scanning frequency this time.

[0113] According to this configuration, the sensor controller 10 maintains the sweep frequency when the result of measuring the electromagnetic noise level at the sweep frequency is the smallest among the sweep frequency and the plurality of preliminary frequencies. Therefore, the sensor controller 10 can reduce the electromagnetic noise level of the transmission signal with higher accuracy.

[0114] In addition, when the measurement result is greater than the specified value Nth, the frequency selection unit 102 determines whether the measurement result is less than the measurement results of the electromagnetic noise in the multiple noise scanning periods T4~T5 (first period) of the measuring unit 101. When the determination is negative, the frequency corresponding to the measurement result with the minimum value among the measurement results of the electromagnetic noise in the multiple noise scanning periods T4~T5 is selected as the scanning frequency for this time.

[0115] According to this configuration, the sensor controller 10 selects the frequency with the smallest electromagnetic noise level among the plurality of preliminary frequencies as the scanning frequency, among the scanning frequency and the plurality of preliminary frequencies. Therefore, the sensor controller 10 can reduce the electromagnetic noise level of the transmission signal with higher accuracy.

[0116] In addition, in the above-mentioned embodiment, the electronic device 1 detects the position indication of a passive indicator such as the stylus 2 and the finger 3, but is not limited thereto. The electronic device 1 may also detect the position indication of a stylus of an active electrostatic coupling method, for example. The stylus of the active electrostatic coupling method, for example, has a power supply, a communication circuit, and electrodes for detecting an uplink signal sent from the electronic device 1 at a predetermined period and sending a downlink signal at a time indicated by taking the detected uplink signal as a reference moment. In addition, in addition to sending the signal, the electronic device 1 also sends the uplink signal to the touch sensor 20 and receives the downlink signal from the touch sensor 20.

[0117] According to this configuration, the sensor controller 10 can efficiently reduce the level of electromagnetic noise of the transmission signal even when the touch sensor 20 performs position indication by a passive indicator.

[0118] In addition, in the above-mentioned embodiment, the frequency selection unit 102 selects the scanning frequency and the preliminary frequency from the first predetermined number of frequencies, but the present invention is not limited thereto. The frequency selection unit 102 may be configured to change the first predetermined number of frequency candidates according to the use environment of the electronic device 1, the type of the electronic device 1, the type of the touch sensor 20 mounted on the electronic device 1, etc. The use environment of the electronic device 1 is, for example, the temperature, humidity, air pressure, cleanliness of the space where the electronic device 1 is arranged, the state of electromagnetic noise in the space, etc.

[0119] Specifically, the storage unit 110 stores a plurality of frequency groups corresponding to the use environments of the electronic device 1. In addition, the storage unit 110 stores a state related to the current frequency group set according to a setting command from an operator of the electronic device 1, an external device capable of communicating with the electronic device 1, or the like.

[0120] When selecting the scanning frequency and the backup frequency, the frequency selection unit 102 refers to the storage unit 110 and selects a scanning frequency from a predetermined number of frequencies corresponding to the set frequency group. In addition, the frequency selection unit 102 selects a frequency other than the scanning frequency from the predetermined number of frequencies as the backup frequency in sequence for each transmission period.

[0121] According to this structure, the sensor controller 10 can change the frequency candidates according to the use environment of the electronic device 1, the type of the electronic device 1, the type of the touch sensor 20 mounted on the electronic device 1, etc., thereby being able to reduce the level of electromagnetic noise of the transmitted signal with high accuracy and efficiency.

[0122] In addition, in the above-mentioned embodiment, when the level of electromagnetic noise at the scanning frequency is greater than the specified value Nth and is greater than the level of any electromagnetic noise at each of the preliminary frequencies, the frequency selection unit 102 selects the frequency with the smallest level of electromagnetic noise among the preliminary frequencies as the scanning frequency, but the present invention is not limited thereto. For example, the frequency selection unit 102 may select, as the scanning frequency, a frequency with the highest priority among the predetermined priorities among the preliminary frequencies with the level of electromagnetic noise less than the specified value Nth.

[0123] The priority is predetermined by, for example, a measurement program of the electronic device 1 stored in the storage unit 110, a device different from the electronic device 1 connected to the electronic device 1 in a communicable manner, etc., through the prior measurement results of each frequency in the frequency group stored in the storage unit 110, and is stored in the storage unit 110. "In advance" means before the electronic device 1 or the touch sensor 20 is used by the user, such as the time point of product shipment or the time point of setting change. The priority can be set, for example, in a manner such that [1] the lower the peak value, [2] the narrower the peak width, [3] the closer the noise generation distribution is to uniformity, or [4] the higher the reproducibility of the electromagnetic noise, the higher the priority. In addition, for example, the priority can also be set in a manner such that, after a prior measurement is performed in the touch sensor 20, the lower the reproducibility of the electromagnetic noise measured, the higher the priority.

[0124] According to this configuration, the sensor controller 10 can select, by the frequency selection unit 102 , a frequency having a low level of electromagnetic noise that is suitable for the characteristics of each electromagnetic noise of the electronic device 1 as the scanning frequency.

[0125] In addition, when the level of electromagnetic noise at the scanning frequency is greater than a specified value Nth and is greater than the level of any electromagnetic noise at each preliminary frequency, the frequency selection unit 102 may select as the scanning frequency a frequency among the preliminary frequencies having an electromagnetic noise level less than a specified value Nth and which is the value farthest from the current scanning frequency.

[0126] According to this configuration, the sensor controller 10 selects a frequency away from the current scanning frequency having a high electromagnetic noise level as the scanning frequency by the frequency selection unit 102. Therefore, the sensor controller 10 can select a frequency at which the electromagnetic noise level is more likely to be lowered from the preliminary frequencies as the scanning frequency.

[0127] In addition, when the level of electromagnetic noise at the scanning frequency is greater than a specified value Nth and is greater than the level of any electromagnetic noise at each preliminary frequency, the frequency selection unit 102 may select as the scanning frequency a frequency among the preliminary frequencies having an electromagnetic noise level less than a specified value Nth and which is closest to the current scanning frequency.

[0128] According to this configuration, the sensor controller 10 selects the frequency closest to the current scanning frequency having a high electromagnetic noise level as the scanning frequency by the frequency selection unit 102. Therefore, the sensor controller 10 can reduce the time required to change the scanning frequency or simplify the circuit configuration.

[0129] Description of Reference Numerals

[0130] 1 ... electronic device, 10 ... sensor controller, 13 ... transmitting unit, 20 ... touch sensor, 101 ... measuring unit, 102 ... frequency selecting unit, 21 ... linear electrode (detection electrode), 22 ... linear electrode (detection electrode).

Claims

1. A sensor controller is a sensor controller for controlling the motion of a touch sensor to detect the position of a passive indicator, wherein: have: a transmitting unit that transmits a transmission signal to the touch sensor at a predetermined period in a third period including a first period for measuring electromagnetic noise and a second period for performing the position detection; a measuring unit that measures, during the first period and the second period, a level of electromagnetic noise of a frequency associated with each period; and The frequency selection unit selects, for each of the third periods, one of the first prescribed number of frequencies as a scanning frequency based on the measurement result of the measurement unit, and selects a second prescribed number of frequencies less than the first prescribed number from the frequencies different from the scanning frequency among the first prescribed number of frequencies as preliminary frequencies, the scanning frequency being the frequency of the transmission signal in the second period, and the preliminary frequency being the frequency of the transmission signal in the first period.

2. The sensor controller according to claim 1, The frequency selection unit sequentially selects the second predetermined number of frequencies as the preliminary frequencies from among the first predetermined number of frequencies, which are different from the scanning frequency, for each of the third periods.

3. The sensor controller according to claim 2, The frequency selection unit selects a frequency different from the scanning frequency selected last time as the current scanning frequency when the measurement result of the electromagnetic noise in the second period by the measurement unit is equal to or greater than a predetermined value.

4. The sensor controller according to claim 3, When the measurement result is greater than the specified value, the frequency selection unit determines whether the measurement result is less than the measurement result of the electromagnetic noise in the first period of the measurement unit, and when the determination is affirmative, the scanning frequency selected last time is selected again as the scanning frequency this time.

5. The sensor controller according to claim 3, When the measurement result is greater than the specified value, the frequency selection unit determines whether the measurement result is less than the measurement results of the electromagnetic noise in the multiple first periods of the measurement unit. When the determination is affirmative, the scanning frequency selected last time is selected again as the scanning frequency this time.

6. The sensor controller according to claim 3, The frequency selection unit determines, when the measurement result is greater than the prescribed value, whether the measurement result is less than the measurement results of the electromagnetic noise in the multiple first periods of the measurement unit. When the determination is negative, the frequency corresponding to the minimum value of the measurement result among the multiple measurement results of the electromagnetic noise in the first periods is selected as the scanning frequency for this time.

7. The sensor controller according to claim 3, The frequency selection unit determines, when the measurement result is greater than the specified value, whether the measurement result is less than the measurement results of the electromagnetic noise in the multiple first periods of the measurement unit. When the determination is negative, the frequency with the highest priority in the priority predetermined by the prior measurement results related to the level of the electromagnetic noise is selected from the frequencies different from the scanning frequency among the first specified number of frequencies as the scanning frequency for this time.

8. The sensor controller according to claim 3, When the measurement result is greater than the prescribed value, the frequency selection unit determines whether the measurement result is less than the measurement results of the electromagnetic noise in the multiple first periods of the measurement unit. When the determination is negative, the frequency that is farthest from the scanning frequency selected last time is selected as the scanning frequency for this time from the frequencies corresponding to the measurement results that are smaller than the prescribed value among the measurement results of the electromagnetic noise in the multiple first periods.

9. The sensor controller according to claim 3, When the measurement result is greater than the prescribed value, the frequency selection unit determines whether the measurement result is less than the measurement results of the electromagnetic noise in the multiple first periods of the measurement unit. When the determination is negative, the frequency that is closest to the scanning frequency selected last time is selected as the scanning frequency for this time from the frequencies corresponding to the measurement results that are smaller than the prescribed value among the measurement results of the electromagnetic noise in the multiple first periods.

10. The sensor controller according to any one of claims 1 to 9, The second predetermined number is 1.

11. An electronic device comprising: A touch sensor, which is formed by a plurality of detection electrodes arranged in a planar shape, and is used for position detection of a passive pointer; and A sensor controller is connected to the touch sensor, and comprises a transmitting unit, a measuring unit and a frequency selecting unit. The transmitting unit transmits a transmission signal to the touch sensor at a predetermined period during a third period including a first period for measuring electromagnetic noise and a second period for performing the position detection. The measuring unit measures the level of electromagnetic noise having a frequency corresponding to each period during the first period and the second period. The frequency selecting unit selects one of a first predetermined number of frequencies as a scanning frequency for each of the third periods based on the measurement result of the measuring unit, and selects a second predetermined number of frequencies less than the first predetermined number from the frequencies of the first predetermined number of frequencies different from the scanning frequency as a preparatory frequency. The scanning frequency is the frequency of the transmission signal during the second period, and the preparatory frequency is the frequency of the transmission signal during the first period.

12. A method for controlling a sensor controller, which is a method for controlling a sensor controller for controlling a touch sensor to detect a position of a passive indicator, wherein: include: transmitting a transmission signal to the touch sensor at a predetermined period during a third period including a first period for measuring electromagnetic noise and a second period for performing the position detection; During the first period and the second period, measuring a level of electromagnetic noise of a frequency associated with each period; and For each of the third periods, based on the result of the measurement, one of the first specified number of frequencies is selected as the scanning frequency, and a second specified number of frequencies less than the first specified number are selected from the frequencies of the first specified number of frequencies that are different from the scanning frequency as the preliminary frequencies, the scanning frequency is the frequency of the sending signal in the second period, and the preliminary frequency is the frequency of the sending signal in the first period.

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