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

Abstract

To provide a sensor controller that can highly efficiently lower a level of electromagnetic noise of a transmission signal to be transmitted to a touch sensor.SOLUTION: A sensor controller includes: a transmission unit that transmits a transmission signal to a touch sensor in a third period including a first period for measuring electromagnetic noise and a second period for detecting the position of a passive pointer by the touch sensor, at a predetermined cycle; a measurement unit that measures a level of electromagnetic noise at a frequency associated with each period, in the first period and the second period; and a frequency selection unit that selects, as a scan frequency that is a frequency of the transmission signal in the second period every third period, one of a first predetermined number of frequencies, and selects, as backup frequencies that are frequencies of the transmission signal in the first period, a second predetermined number of frequencies fewer than the first predetermined number from frequencies different from the scan frequency among the first predetermined number of frequencies, based on the measurement result of the measurement unit.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a sensor controller, and more particularly to a sensor controller, an electronic device, and a method for controlling an electronic device. [Background technology]

[0002] Conventionally, there are known touch sensors that detect position indication by a finger, a stylus, etc., and sensor controllers that control the detection operation of the touch sensors. In electronic devices equipped with such touch sensors and sensor controllers, position detection is performed by transmitting a transmission signal having a scan frequency from the sensor controller to the touch sensor.

[0003] In this regard, Patent Document 1 discloses an indicator position detection device (sensor controller) including a plurality of conductor patterns (touch sensors) arranged in intersecting directions, a signal supply circuit that transmits signals to the conductor patterns arranged in a first direction, and a noise analysis circuit that performs frequency analysis on noise signals received by the conductor patterns arranged in a second direction, and further detects and analyzes noise components. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5496735 Summary of the Invention [Problem to be solved by the invention]

[0005] In the technology described in Patent Document 1, the sensor controller needs to perform frequency analysis to analyze noise components. Therefore, in the technology described in Patent Document 1, there is a possibility that the circuit size and manufacturing costs will increase due to the circuit for performing frequency analysis.

[0006] In addition, in the technology described in Patent Document 1, even if the sensor controller were to analyze noise components without performing frequency analysis, the sensor controller described in Patent Document 1 would determine the frequency of the transmission signal based on the result of frequency analysis at one frequency, and would change the frequency of the transmission signal to another frequency even if the noise level at the analyzed frequency is smaller than the noise level at another frequency. Therefore, in the technology described in Patent Document 1, the sensor controller may change the frequency of the transmission signal for the touch sensor to a frequency with a high noise level.

[0007] The present invention has been made in consideration of the above problems, and has an object to provide a sensor controller that can highly efficiently reduce the level of electromagnetic noise in a transmission signal sent to a touch sensor. [Means for solving the problem]

[0008] In order to solve the above problems, a first sensor controller according to the present invention is a sensor controller that controls the operation of detecting the position of a passive pointer using a touch sensor, and includes a transmission unit that transmits a transmission signal to the touch sensor at a predetermined cycle during a third period including a first period for measuring electromagnetic noise and a second period for performing the position detection, a measurement unit that measures the level of electromagnetic noise at a frequency associated with each period during the first period and the second period, and a frequency selection unit that selects, for each third period, one frequency out of a first predetermined number of frequencies as a scan frequency, which is the frequency of the transmission signal in the second period, based on the measurement result of the measurement unit, and selects a second predetermined number of frequencies less than the first predetermined number from among the first predetermined number of frequencies that are different from the scan frequency, as backup frequencies, which are the frequencies of the transmission signal in the first period.

[0009] In addition, in the sensor controller according to the second aspect of the present invention, the frequency selection unit selects, in sequence for each third period, the second predetermined number of frequencies from among the first predetermined number of frequencies that are different from the scan frequency, as the backup frequencies.

[0010] In addition, in the sensor controller of the third invention, when the measurement result of the electromagnetic noise during the second period by the measurement unit is equal to or greater than a predetermined value, the frequency selection unit selects a frequency different from the scan frequency selected previously as the current scan frequency.

[0011] In addition, in the sensor controller of the fourth invention, when the measurement result is greater than or equal to the predetermined value, the frequency selection unit determines whether the measurement result is less than or equal to the measurement result of the electromagnetic noise in the first period by the measurement unit, and if the determination is positive, selects the scan frequency selected last time as the current scan frequency again.

[0012] In addition, in the sensor controller of the fifth invention, when the measurement result is greater than or equal to the predetermined value, the frequency selection unit determines whether the measurement result is less than or equal to each of the measurement results of the electromagnetic noise during the multiple first periods by the measurement unit, and if the determination is positive, selects the scan frequency selected last time as the current scan frequency again.

[0013] In addition, in a sixth sensor controller according to the present invention, when the measurement result is greater than or equal to the predetermined value, the frequency selection unit determines whether the measurement result is less than or equal to each of the measurement results of the electromagnetic noise during the multiple first periods by the measurement unit, and if the determination is negative, selects as the current scan frequency a frequency corresponding to the measurement result that is the smallest among the measurement results of the electromagnetic noise during the multiple first periods.

[0014] In addition, in the sensor controller of the seventh invention, when the measurement result is greater than or equal to the predetermined value, the frequency selection unit determines whether the measurement result is less than or equal to each of the measurement results of the electromagnetic noise in the multiple first periods by the measurement unit, and if the determination is negative, selects as the current scan frequency the frequency with the highest priority in terms of a priority predetermined based on prior measurement results regarding the level of electromagnetic noise from among the first predetermined number of frequencies that are different from the scan frequency.

[0015] In addition, in the sensor controller of the eighth invention, when the measurement result is greater than or equal to the predetermined value, the frequency selection unit determines whether the measurement result is less than or equal to each of the measurement results of the electromagnetic noise in the multiple first periods by the measurement unit, and if the determination is negative, selects as the current scan frequency the frequency that is the furthest from the previously selected scan frequency from among the frequencies corresponding to the measurement results of the electromagnetic noise in the multiple first periods that are smaller than the predetermined value.

[0016] In addition, in a ninth sensor controller according to the present invention, when the measurement result is greater than or equal to the predetermined value, the frequency selection unit determines whether the measurement result is less than or equal to each of the measurement results of electromagnetic noise in the multiple first periods by the measurement unit, and if the determination is negative, selects as the current scan frequency the frequency that is closest to the previously selected scan frequency from the frequencies corresponding to the measurement results of electromagnetic noise in the multiple first periods that are smaller than the predetermined value.

[0017] In addition, in a sensor controller according to a tenth aspect of the present invention, the second predetermined number is one.

[0018] In addition, an electronic device of an eleventh aspect of the present invention comprises a touch sensor having a plurality of detection electrodes arranged in a planar shape for detecting the position of a passive pointer, a transmission unit connected to the touch sensor and transmitting a transmission signal to the touch sensor at a predetermined cycle during a third period including a first period for measuring electromagnetic noise and a second period for performing the position detection, a measurement unit measuring the level of electromagnetic noise at a frequency corresponding to each period during the first period and the second period, and a frequency selection unit selecting, for each third period, one frequency out of a first predetermined number of frequencies as a scan frequency, which is the frequency of the transmission signal in the second period, based on a measurement result of the measurement unit, and selecting a second predetermined number of frequencies less than the first predetermined number from among the first predetermined number of frequencies that are different from the scan frequency, as backup frequencies, which are the frequencies of the transmission signal in the first period.

[0019] In addition, a twelfth aspect of the present invention is a control method for a sensor controller that controls the operation of detecting the position of a passive pointer using a touch sensor, and includes the steps of: transmitting a transmission signal to the touch sensor at a predetermined cycle during a third period including a first period for measuring electromagnetic noise and a second period for performing the position detection; measuring the level of electromagnetic noise at a frequency corresponding to each period during the first period and the second period; and selecting, for each of the third periods based on a result of the measurement, one frequency from a first predetermined number of frequencies as a scan frequency, which is the frequency of the transmission signal in the second period, and selecting a second predetermined number of frequencies less than the first predetermined number from among the first predetermined number of frequencies that are different from the scan frequency, as backup frequencies, which are the frequencies of the transmission signal in the first period. Effect of the Invention

[0020] According to the present invention, the sensor controller can highly efficiently reduce the level of electromagnetic noise in the transmission signal transmitted to the touch sensor. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 illustrates an example of an electronic device. [Diagram 2] 11 is a diagram illustrating an example of a timing chart showing a transition of a frequency used in a transmission signal transmitted to a touch sensor. [Diagram 3] 11 is a graph showing a distribution of electric potential detected by a linear electrode of a touch sensor. [Figure 4] 1 is a diagram showing an example of the level of electromagnetic noise for each frequency used in a transmission signal; [Diagram 5] 10 is a flowchart showing an example of a flow of a series of processes performed by a sensor controller. [Figure 6] 11 is a diagram showing another example of a timing chart showing a transition of a frequency used in a transmission signal transmitted to a touch sensor. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Hereinafter, an embodiment of the present invention (hereinafter, referred to as "the present embodiment") will be described with reference to the accompanying drawings. In order to facilitate understanding of the description, the same components and steps in each drawing are denoted by the same reference numerals as much as possible, and duplicated descriptions will be omitted.

[0023] <Circuit configuration> FIG. 1 is a diagram showing an example of an electronic device 1 according to a first embodiment. The electronic device 1 is a computer owned by a user, and is configured, for example, as a tablet, a smartphone, or a personal computer. A user can write pictures or characters on the display surface of the electronic device 1 by pressing and moving the tip of a stylus 2, which is a pen-shaped pointing device, or the user's finger 3, against the touch surface of the electronic device 1. The stylus 2 is, for example, a non-active touch pen.

[0024] The electronic device 1 detects the position pointed to by the stylus 2 or finger 3, and performs various information processing according to the detection results. Specifically, the electronic device 1 detects the position pointed to by the stylus 2 or finger 3 based on signals detected by linear electrodes 21 and 22 provided on the display surface, and performs digital ink generation processing, pointer display processing, and the like. 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).

[0025] The touch sensor 20 is a capacitance type sensor in which a plurality of detection electrodes are arranged in a planar shape. The touch sensor 20 includes, for example, a plurality of X-line electrodes (hereinafter referred to as "linear electrodes 21") for detecting the position of the X-axis of a 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 may be made of a transparent conductive material including ITO (Indium Tin Oxide), or may be made of a wire mesh sensor. Note that the touch sensor 20 may be a self-capacitance type sensor in which block-shaped electrodes are arranged in a two-dimensional lattice shape, instead of the mutual capacitance type sensor described above.

[0026] The sensor controller 10 controls the operation of detecting the position of a passive pointer such as a stylus 2 or a finger 3 using a touch sensor 20. 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.

[0027] The detection unit 14 is a circuit that selects one or adjacent ones of the plurality of linear electrodes 21 based on an instruction from the MCU 11. The output unit 15 is a circuit that selects one or adjacent ones of the plurality of linear electrodes 22 based on an instruction from the MCU 11, amplifies an input signal transmitted from the MCU 11 to a predetermined voltage, and outputs the output signal to the linear electrode 22.

[0028] The transmitting unit 13 is connected to the linear electrode 22 selected by the output unit 15, and transmits a transmission signal to the linear electrode 21 via the output unit 15 based on an instruction from the MCU 11. Specifically, the transmitting unit 13 transmits a transmission signal to the linear electrode 21 in a transmission period including a noise scan period for measuring electromagnetic noise and a touch scan period following the noise scan for performing position detection, in response to an instruction from the MCU 11. Note that, for the transmission signal transmitted from the transmitting unit 13, a backup frequency for performing noise scanning is selected as the frequency during the noise scan period, and a scan frequency for performing position detection is selected as the frequency during the touch scan period.

[0029] The receiving unit 12 is connected to the linear electrode 21 selected by the detecting unit 14, and receives from the linear electrode 21 a detection signal generated in the linear electrode 21 when the stylus 2 or the finger 3 touches the sensor surface of the touch sensor 20. The receiving unit 12 transmits the received detection signal to the MCU 11.

[0030] The MCU 11 is a microprocessor having an internal ROM and RAM and operating based on a predetermined program. The MCU, for example, controls the selection operation of the linear electrode 21 by the detection unit 14, controls the selection operation of the linear electrode 22 by the output unit 15, reads the detection signal transmitted from the receiving unit 12 to the MCU, and controls the transmission operation of the transmission unit 13 to the touch sensor 20. The MCU is configured to include, for example, a measurement unit 101, a frequency selection unit 102, a control unit 103, and a storage unit 110 as functional components.

[0031] The measuring unit 101 measures the level of electromagnetic noise at the frequency of the transmission signal transmitted from the transmitting unit 13, in response 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 sets 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.

[0032] The frequency selection unit 102 selects the frequency of the transmission signal to be transmitted from the transmission unit 13 based on the measurement result of the measurement unit 101. Specifically, the frequency selection unit 102 selects one of the first predetermined number of frequencies as a scan frequency in the touch scan period based on the measurement result of the electromagnetic noise in the detection signal by the measurement unit 101 for each transmission period. The frequency selection unit 102 also selects a second predetermined number of frequencies, which is different from the scan frequency and is smaller than the first predetermined number, from the first predetermined number of frequencies as spare frequencies in the noise scan period. In this embodiment, the second predetermined number is 1. How the frequency selection unit 102 selects the frequency based on the measurement result of the measurement unit 101 will be described later with reference to FIG. 2, so the description will be omitted here.

[0033] 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 so as to select, for example, all the linear electrodes 21 on the touch sensor 20 in sequence during the touch scan period and the noise scan period. The control unit 103 also 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 so as to select, for example, all the linear electrodes 22 on the touch sensor 20 in sequence during the touch scan period and the noise scan period. The control unit 103 also 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 signal by the transmission unit 13. The control unit 103 also reads the detection signal transmitted from the reception unit 12 and performs the detection operation of the position on the touch sensor 20. In addition, during the noise scan period, the control unit 103 may control the operation of the detection unit 14 and the output unit 15 so as to select in sequence some of the linear electrodes 21 and 22 after thinning out, rather than all of the linear electrodes 21 and 22.

[0034] The memory unit 110 stores programs for operating the MCU 11, programs for controlling the operation of the transmission unit 13, the detection unit 14 and the output unit 15, a set of frequencies that can be selected as the frequency of the transmission signal, and the time transition of the level of electromagnetic noise in the detection signal measured by the measurement unit 101.

[0035] <Flow of operations> Above, we have described the configuration of the electronic device 1. Next, we will explain in detail the transition of potentials of various signals in the electronic device 1. Figure 2 is a diagram showing an example of a timing chart showing the transition of frequencies used in transmission signals transmitted to the touch sensor 20.

[0036] 2, the transmitter 13 transmits a transmission signal to the touch sensor 20 during a transmission period T3. The transmission period T3 includes a noise scan period T1 during which the measurement unit 101 measures electromagnetic noise at each auxiliary frequency, and a touch scan period T2 following the noise scan and during which position detection is performed. In FIG. 2, the first predetermined number of frequencies are three frequencies, f0, f1, and f2.

[0037] At time t0, the transmission unit 13 refers to the frequency f1 selected by the frequency selection unit 102 as a backup frequency from the storage unit 110, and transmits a transmission signal having the frequency f1 to the touch sensor 20 during the noise scan period T1. In addition, the measurement unit 101 measures the level of electromagnetic noise in the detection signal transmitted from the touch sensor 20 during the noise scan period T1. The measurement unit 101 stores the measurement result in the storage unit 110 as the level of electromagnetic noise at the frequency f1 in the cycle of time t0.

[0038] In the present embodiment, the control unit 103 controls the operation of the detection unit 14 and the output unit 15 to sequentially select all the linear electrodes 21 and 22, but this is not limited thereto, and the control unit 103 may control the operation of the output unit 15 to sequentially select only the remaining linear electrodes 21 and 22 that have been thinned out among the plurality of linear electrodes 21 and 22. The control unit 103 may also control the operation of the output unit 15 to simultaneously select all the linear electrodes 21 when transmitting a transmission signal from the transmission unit 13, rather than sequentially selecting all the linear electrodes 21 and 22, and control the operation of the detection unit 14 to simultaneously select all the linear electrodes 22 when receiving a detection signal from the reception unit 12. Furthermore, when selecting all the linear electrodes 21 simultaneously, the control unit 103 may control the operation of the transmission unit 13 so that a transmission signal encoded by an orthogonal spread code is transmitted from all the linear electrodes 21.

[0039] At time t1, the transmitting unit 13 refers to the frequency f0 selected by the frequency selecting unit 102 as the scan frequency from the storage unit 110, and transmits a transmission signal having the frequency f0 to the touch sensor 20 during the touch scan period T2. Furthermore, the measuring unit 101 measures the level of electromagnetic noise of the detection signal transmitted from the touch sensor 20 during the touch scan period T2. The measuring unit 101 stores the measurement result in the storage unit 110 as the level of electromagnetic noise at the frequency f0 at time t1. Furthermore, the control unit 103 reads the detection signal transmitted from the receiving unit 12 during the touch scan period T2, and performs processing to detect the presence or absence of a position indication by the stylus 2 or finger 3 on the touch sensor 20 and the operation to detect the indicated position.

[0040] At time t2, the frequency selection unit 102 refers to the storage unit 110 and acquires the measurement result by the measurement unit 101 regarding the level of electromagnetic noise at the scan frequency during the touch scan period T2 from time t1 to time t2. The frequency selection unit 102 continues to select the frequency f0 as the scan frequency because the level of electromagnetic noise at the scan frequency is less than a predetermined value and noise is not detected. In addition, the frequency selection unit 102 selects a frequency f2, which is different from the scan frequency and different from the currently measured backup frequency, as the backup frequency because the level of electromagnetic noise at the scan frequency is less than a predetermined value and noise is not detected. Note that the details of the method of selecting the scan frequency and the backup frequency by the frequency selection unit 102 will be described later with reference to Figs. 3 to 5, so the description thereof will be omitted here.

[0041] From time t3 to t5, the transmitting unit 13, the measurement unit 101, and the frequency selecting unit 102 each perform the same operations as those from time t0 to t2, except that the backup frequency has changed from frequency f1 to frequency f2. Note that, at time t5, the frequency selecting unit 102 selects frequency f0 as the scan frequency and frequency f1 as the backup frequency.

[0042] From time t6 to t8, the transmitting unit 13, the measurement unit 101, and the frequency selecting unit 102 perform the same operations as from time t0 to t2, except that the backup frequency has changed from frequency f1 to frequency f2.

[0043] At times t9 and t10, the transmitting unit 13 and the measuring unit 101 perform the same operations as at times t3 and t4, respectively, except that the backup frequency has changed from frequency f1 to frequency f2. Also, at time t100, the measuring unit 101 detects that the level of electromagnetic noise at frequency f0, which is the scan frequency, is equal to or higher than a predetermined value.

[0044] At time t11, the frequency selection unit 102 refers to the storage unit 110 and acquires the measurement result by the measurement unit 101 regarding the level of electromagnetic noise at frequency f0, which is the scan frequency in the touch scan period T2 from time t10 to time t11. Because the level of electromagnetic noise at the scan frequency is equal to or higher than a predetermined value, the frequency selection unit 102 refers to the storage unit 110 and acquires the levels of electromagnetic noise at frequency f1, which is the backup frequency in the noise scan period T1 from time t6 to time t7, and at frequency f2, which is the backup frequency in the noise scan period T1 from time t9 to time t10.

[0045] Next, the frequency selection unit 102 selects, as the scan frequency, the frequency f1 that has the smallest level of electromagnetic noise among the frequencies f0, f1, and f2. The frequency selection unit 102 also selects, as the backup frequency, the frequency f0 that is different from the frequency f1 selected as the scan frequency and different from the currently measured backup frequency.

[0046] From time t12 to t14, the transmitting unit 13, the measurement unit 101, and the frequency selecting unit 102 each perform the same operations as those from time t0 to t2, except that the backup frequency has changed to frequency f0 and the scanning frequency has changed to frequency f1. Note that, at time t14, the frequency selecting unit 102 continues to select frequency f1 as the scanning frequency and selects frequency f2 as the backup frequency.

[0047] From time t15 to t17, the transmitting unit 13, the measurement unit 101, and the frequency selecting unit 102 perform the same operations as those from time t0 to t2, except that the backup frequency has been changed to frequency f2. Note that, at time t17, the frequency selecting unit 102 continues to select frequency f1 as the scan frequency, and selects frequency f0 as the backup frequency.

[0048] The above describes the transition of the potential of various signals in the electronic device 1. Next, the details of the measurement of the level of electromagnetic noise by the measurement unit 101 will be described. FIG. 3 is a graph showing the distribution of the potential detected by the linear electrodes 21 and 22 of the touch sensor 20. In FIG. 3, the horizontal axis indicates the position in the X-line direction on the touch sensor 20, and indicates the position at which the linear electrode 22 is provided. Also, in FIG. 3, the vertical axis indicates the potential of the detection signal transmitted from the linear electrode 21 to the measurement unit 101 via the receiving unit 12.

[0049] Also, in FIG. 3, it is assumed that in the area to the left of position Xth, including the linear electrode 22 provided at position Xth, no position indication is made by the stylus 2 or finger 3, and that in the area to the right of the linear electrode 22 provided at position Xth, position indication is made by the stylus 2 or finger 3.

[0050] 3, potential Tth is a threshold value indicating whether or not a position is specified by the stylus 2 or the finger 3 on the touch sensor 20. When the potential of the detection signal is equal to or higher than potential Tth, the control unit 103 detects the position specification as a position specification being specified at the position indicated by the detected linear electrodes 21 and 22.

[0051] During the noise scan period T1, the measurement unit 101 measures the potential of the detection signal and extracts a measurement result that is less than the potential Tth. Next, the measurement unit 101 calculates a potential difference Vms, which is the difference between the maximum and minimum values ​​of the extracted measurement results. Furthermore, the measurement unit 101 stores the calculated potential difference Vms in the storage unit 110 as the level of electromagnetic noise at the current time and the backup frequency. Similarly, during the touch scan period T2, the measurement unit 101 calculates the potential difference Vms and stores the calculated potential difference Vms in the storage unit 110 as the level of electromagnetic noise at the current time and the scan frequency.

[0052] The details of the measurement of the electromagnetic noise level by the measurement unit 101 have been described above. Next, the selection of the frequency by the frequency selection unit 102 will be described with reference to Fig. 4. Fig. 4 is a diagram showing an example of the electromagnetic noise level for each frequency used in the transmission signal. In Fig. 4, the vertical axis and the horizontal axis respectively indicate the electromagnetic noise level and frequency measured by the measurement unit 101. Also, in Fig. 4, it is assumed that the current scan frequency is frequency f0.

[0053] 4, the measurement result of the electromagnetic noise level at frequency f0, which is the scan frequency, is equal to or greater than the predetermined value Nth, and is greater than the measurement results of the electromagnetic noise level at frequencies f1 and f2, which are the backup frequencies. Moreover, the measurement result of the electromagnetic noise level at frequency f1, which is the backup frequency, is the smallest among the measurement results of the electromagnetic noise level at the scan frequency and each backup frequency.

[0054] The frequency selection unit 102 first judges whether the level of electromagnetic noise at the frequency f0, which is the current scan frequency, is equal to or greater than a predetermined value Nth. If the level of electromagnetic noise at the frequency f0, which is the scan frequency, is equal to or greater than the predetermined value Nth, the frequency selection unit 102 judges whether the level of electromagnetic noise at the frequency f0 is smaller than the levels of electromagnetic noise at the frequencies f1 and f2, which are the backup frequencies. If the frequency selection unit 102 judges that the level of electromagnetic noise at the frequency f0 is equal to or greater than the levels of electromagnetic noise at either of the frequencies f1 and f2, it selects the frequency of the frequencies f1 and f2, which has the smallest level of electromagnetic noise, as the scan frequency. Furthermore, the frequency selection unit 102 selects one of the frequencies f0 and f2, which has not been selected as the scan frequency, as the backup frequency, from among the frequencies f0 to f2.

[0055] Furthermore, if the electromagnetic noise level at frequency f0, which is the scan frequency, is less than a predetermined value Nth, or the electromagnetic noise level at frequency f0 is lower than the electromagnetic noise level at both of the backup frequencies f1 and f2, the frequency selection unit 102 continues to select the same frequency f0 as the scan frequency. Furthermore, as long as the condition that the electromagnetic noise level at frequency f0 is less than a predetermined value Nth, or the electromagnetic noise level at frequency f0 is lower than the electromagnetic noise level at both of the frequencies f1 and f2 continues to be satisfied, the frequency selection unit 102 selects an unselected frequency from the multiple backup frequencies as a backup frequency in turn for each transmission period T3.

[0056] In FIG. 4, since the electromagnetic noise level at frequency f0, which is the scan frequency, is greater than the predetermined value Nth and is equal to or greater than the electromagnetic noise level at either of the backup frequencies f1 and f2, the frequency selection unit 102 selects frequency f1, which has the smallest electromagnetic noise level, as the scan frequency among the backup frequencies f1 and f2.

[0057] The above describes the selection of frequencies by the frequency selection unit 102. Next, a detailed description will be given of the flow of a series of processes in the sensor controller 10. FIG.

[0058] (Step SP10) The sensor controller 10 measures the level of electromagnetic noise at the current backup frequency during the noise scan period T1 by the measurement unit 101. The sensor controller 10 stores the measurement result of the level of electromagnetic noise by the measurement unit 101 together with information related to the time and the backup frequency in the storage unit 110. Then, the process proceeds to step SP12.

[0059] (Step SP12) The sensor controller 10 measures the level of electromagnetic noise at the current scan frequency during the touch scan period T2 by the measurement unit 101. The sensor controller 10 stores the measurement result of the level of electromagnetic noise by the measurement unit 101 together with information on the time and the scan frequency in the storage unit 110. Then, the process proceeds to step SP14.

[0060] (Step SP14) The sensor controller 10 acquires a measurement result of the level of electromagnetic noise at the current scan frequency in the most recent touch scan period T2 from the storage unit 110 by the frequency selection unit 102. The sensor controller 10 determines whether the acquired measurement result is equal to or greater than a predetermined value by the frequency selection unit 102. If the determination is positive, the process proceeds to step SP16. On the other hand, if the determination is negative, the process proceeds to step SP20.

[0061] (Step SP16) The sensor controller 10 acquires the measurement result of the level of the electromagnetic noise at each auxiliary frequency from the storage unit 110 by the frequency selection unit 102. The sensor controller 10 determines whether the level of the electromagnetic noise in the most recent touch scan period T2 is equal to or lower than any one of the values ​​of the level of the electromagnetic noise at each auxiliary frequency by the frequency selection unit 102. If the determination is positive, the process proceeds to step SP20. On the other hand, if the determination is negative, the process proceeds to step SP18.

[0062] (Step SP18) The sensor controller 10 selects the frequency that provides the minimum measurement result of the electromagnetic noise level from among the auxiliary frequencies using the frequency selection unit 102, and changes the scan frequency to the selected frequency. Then, the process proceeds to step SP20.

[0063] (Step SP20) The sensor controller 10 selects the frequency that provides the minimum measurement result of the electromagnetic noise level from among the auxiliary frequencies using the frequency selection unit 102, and changes the scan frequency to the selected frequency. Then, the process proceeds to step SP22.

[0064] (Step SP22) The sensor controller 10 determines whether or not a stop command for stopping the position detection operation by the sensor controller 10 and the touch sensor 20 has been transmitted from an external component of the sensor controller 10 provided in the electronic device 1 by the control unit 103. If the determination is negative, the process proceeds to step SP20. On the other hand, if the determination is positive, the series of processes shown in FIG. 5 ends.

[0065] <Effects> As described above, in this embodiment, the sensor controller 10 that controls the operation of detecting the position of the stylus 2 (passive pointer) by the touch sensor 20 includes a transmission unit 13 that transmits a transmission signal to the touch sensor 20 during a transmission period T3 (third period) including a noise scan period T1 (first period) for measuring electromagnetic noise and a touch scan period T2 (second period) for position detection at a predetermined cycle, and a measurement unit 101 that measures the level of electromagnetic noise at a frequency associated with each period during the noise scan period T1 and the touch scan period T2. Furthermore, the sensor controller 10 includes a frequency selection unit 102 that selects one frequency from a first predetermined number of frequencies as a scan frequency that is a frequency of a transmission signal in the touch scan period T2 based on the measurement result of the measurement unit 101, and selects a second predetermined number of frequencies that is less than the first predetermined number from among the first predetermined number of frequencies that are different from the scan frequency as spare frequencies that are frequencies of a transmission signal in the noise scan period T1, based on the measurement result of the measurement unit 101, for each transmission period T3.

[0066] According to this configuration, the sensor controller 10 selects a frequency different from the scan frequency in the touch scan period T2 as the backup frequency in the noise scan period T1. Therefore, the sensor controller 10 measures the level of electromagnetic noise without overlapping the scan frequency and the backup frequency, and therefore, the level of electromagnetic noise in the transmission signal transmitted to the touch sensor 20 can be reduced with high efficiency.

[0067] Furthermore, in this embodiment, the frequency selection unit 102 selects, in order for each transmission period T3 (third period), a second predetermined number of frequencies that are different from the scan frequency among the first predetermined number of frequencies, as backup frequencies.

[0068] Therefore, the sensor controller 10 selects the backup frequency in order from the frequencies different from the scan frequency, and therefore the level of electromagnetic noise in the transmission signal can be reduced with higher efficiency.

[0069] In addition, in this embodiment, when the measurement result of the electromagnetic noise during the touch scan period T2 (second period) by the measurement unit 101 is equal to or greater than a predetermined value Nth, the frequency selection unit 102 selects a frequency different from the previously selected scan frequency as the current scan frequency.

[0070] Therefore, the sensor controller 10 can reduce the level of electromagnetic noise in the transmission signal with high efficiency and precision.

[0071] Furthermore, in this embodiment, when the measurement result is equal to or greater than a predetermined value Nth, the frequency selection unit 102 determines whether the measurement result is equal to or less than the measurement result of the electromagnetic noise during the noise scan period T1 (first period) by the measurement unit 101, and when the determination is positive, selects again the previously selected scan frequency as the current scan frequency.

[0072] According to this configuration, even if the measurement result of the electromagnetic noise level during the touch scan period T2 is equal to or greater than a predetermined value Nth, the sensor controller 10 maintains the scan frequency as long as the measurement result of the electromagnetic noise level during the noise scan period T1 is equal to or less than the measurement result of the electromagnetic noise level during the noise scan period T1, thereby enabling the electromagnetic noise level of the transmission signal to be reduced with higher accuracy.

[0073] In this embodiment, the second predetermined number is one.

[0074] According to this configuration, the sensor controller 10 measures the level of electromagnetic noise for one auxiliary frequency during the noise scan period T1, and therefore, a long time can be secured for the touch scan period T2 in the transmission period T3. Therefore, the sensor controller 10 can detect the position indication for the touch sensor 20 with high accuracy while reducing the level of electromagnetic noise in the transmission signal with high efficiency and high accuracy.

[0075] --- Variation --- The present invention is not limited to the above-described embodiment. In other words, the above-described embodiment may be modified by a person skilled in the art as appropriate, and the modifications may be included within the scope of the present invention as long as they include the characteristics of the present invention. In addition, the elements of the above-described embodiment and the modifications described below may be combined to the extent technically possible, and the combinations of these may be included within the scope of the present invention as long as they include the characteristics of the present invention.

[0076] For example, in the above embodiment, the sensor controller 10 measures the level of electromagnetic noise at one auxiliary frequency in one transmission period T3, but this is not limited to this. The sensor controller 10 may measure the levels of electromagnetic noise at multiple auxiliary frequencies in one transmission period T3.

[0077] The frequency selection unit 102 in the sensor controller 10 may select, for each transmission period T3, a second predetermined number of frequencies that is less than the first predetermined number and is a value of 2 or more from among the first predetermined number of frequencies that are different from the scan frequency, as backup frequencies, based on the measurement result of the measurement unit 101. That is, the second predetermined number may be a value of 2 or more. In this case, the frequency selection unit 102 selects the second predetermined number of frequencies in order for each transmission period T3 from the frequencies remaining after excluding the scan frequency from the first predetermined number of frequencies.

[0078] Here, the operation of the sensor controller 10 in the case of measuring the levels of electromagnetic noise at a plurality of auxiliary frequencies in one transmission period T3 will be described with reference to Fig. 6. Fig. 6 is a diagram showing another example of a timing chart showing the transition of the frequency used in the transmission signal transmitted to the touch sensor 20.

[0079] As shown in Fig. 6, the transmitter 13 transmits a transmission signal to the touch sensor 20 during a transmission period T3. The transmission period T3 includes a plurality of noise scan periods T4 and T5 for the measurement unit 101 to measure electromagnetic noise at each auxiliary frequency, and a touch scan period T2. In Fig. 6, the first predetermined number of frequencies is assumed to be seven frequencies f0 to f6. In Fig. 6, the second predetermined number is assumed to be two.

[0080] At time t50, the transmission unit 13 refers to the frequency f1 selected by the frequency selection unit 102 as a backup frequency from the storage unit 110, and transmits a transmission signal having the frequency f1 to the touch sensor 20 during the noise scan period T4. In addition, the measurement unit 101 measures the level of electromagnetic noise in the detection signal transmitted from the touch sensor 20 during the noise scan period T4. The measurement unit 101 stores the measurement result in the storage unit 110 as the level of electromagnetic noise at the frequency f1 in the cycle of time t50.

[0081] 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 transmitter 13 transmits a transmission signal having frequency f2 to the touch sensor 20 during a noise scan period T5. Also, the measurement unit 101 measures the level of electromagnetic noise in the detection signal transmitted from the touch sensor 20 during the noise scan period T5. The measurement 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.

[0082] At time t52, the transmitter 13 transmits a transmission signal having a frequency f0 to the touch sensor 20. Note that the operation of the sensor controller 10 in the touch scan period T2 from time t52 to t53 is similar to the operation when the second predetermined number is 1 described in FIG. 2, and therefore the description thereof will be omitted.

[0083] At time t53, the frequency selection unit 102 refers to the storage unit 110 and acquires the measurement result by the measurement unit 101 regarding the level of electromagnetic noise at the scan frequency during the touch scan period T2 from time t52 to time t53. The frequency selection unit 102 continues to select frequency f0 as the scan frequency because the level of electromagnetic noise at the scan frequency is less than a predetermined value and noise is undetected. In addition, the frequency selection unit 102 selects frequencies f3 and f4, which are different from the scan frequency and different from the two auxiliary frequencies measured this time, as auxiliary frequencies because the level of electromagnetic noise at the scan frequency is less than a predetermined value and noise is undetected.

[0084] From time t54 to t57, the transmitting unit 13, the measurement unit 101, and the frequency selecting unit 102 perform the same operations as those from time t50 to t53, except that the backup frequencies are changed from frequencies f1 and f2 to frequencies f3 and f4. Note that at time t57, the frequency selecting unit 102 selects frequency f0 as the scan frequency, and frequencies f5 and f6 as the backup frequencies.

[0085] From time t58 to t61, the transmitting unit 13, the measurement unit 101, and the frequency selecting unit 102 perform the same operations as those from time t54 to t57, except that the backup frequencies have changed from frequencies f3 and f4 to frequencies f5 and f6. Note that, at time t61, the frequency selecting unit 102 selects frequency f0 as the scan frequency, and frequencies f1 and f2 as the backup frequencies.

[0086] From time t62 to t64, the transmitting unit 13 and the measuring unit 101 perform the same operations as those from time t50 to t52. Also, at time t200, the measuring unit 101 detects that the level of electromagnetic noise at the frequency f0, which is the scan frequency, is equal to or higher than a predetermined value.

[0087] At time t65, the frequency selection unit 102 refers to the storage unit 110 and acquires the measurement result by the measurement unit 101 regarding the level of electromagnetic noise at frequency f0, which is the scan frequency during touch scan period T2 from time t64 to time t65. Since the level of electromagnetic noise at the scan frequency is equal to or higher than a predetermined value, the frequency selection unit 102 refers to the storage unit 110. The frequency selection unit 102 acquires the levels of electromagnetic noise at frequencies f1 to f6, which are auxiliary frequencies, measured during each noise scan period T4 and T5 between time t54 and time t65.

[0088] Next, the frequency selection unit 102 selects, as the scan frequency, the frequency f4 having the smallest electromagnetic noise level among the frequencies f0 to f6. The frequency selection unit 102 also selects, as the backup frequencies, the frequencies f3 and f5 which are different from the frequency f4 selected as the scan frequency and different from the currently measured backup frequencies.

[0089] From time t66 to t69, the transmitting unit 13, the measurement unit 101, and the frequency selecting unit 102 perform the same operations as those from time t50 to t53, except that the backup frequencies change from frequencies f1 and f2 to frequencies f3 and f5, and the scan frequency changes from frequency f0 to frequency f4. At time t61, the frequency selecting unit 102 selects frequency f0 as the scan frequency, and frequencies f1 and f2 as the backup frequencies.

[0090] According to this configuration, the sensor controller 10 selects multiple frequencies as the backup frequencies, so that when the level of electromagnetic noise at the scan frequency exceeds a predetermined value Nth, the sensor controller 10 is more likely to be able to select a frequency with a low level of electromagnetic noise as the scan frequency. Therefore, the sensor controller 10 can reduce the level of electromagnetic noise in the transmission signal with higher accuracy.

[0091] Furthermore, when the measurement result is equal to or greater than a predetermined value Nth, the frequency selection unit 102 determines whether or not the measurement result is equal to or less than each of the electromagnetic noise measurement results during multiple noise scan periods T4 to T5 (first period) by the measurement unit 101, and when the determination is positive, may again select the previously selected scan frequency as the current scan frequency.

[0092] According to this configuration, the sensor controller 10 maintains the scan frequency when the measurement result of the electromagnetic noise level at the scan frequency is the smallest among the scan frequency and the multiple auxiliary frequencies. Therefore, the sensor controller 10 can reduce the electromagnetic noise level of the transmission signal with higher accuracy.

[0093] Furthermore, if the measurement result is equal to or greater than a predetermined value Nth, the frequency selection unit 102 determines whether or not the measurement result is equal to or less than each of the measurement results of the electromagnetic noise during multiple noise scan periods T4 to T5 (first period) by the measurement unit 101, and if the determination is negative, selects the frequency corresponding to the measurement result that is the smallest value among the measurement results of the electromagnetic noise during the multiple noise scan periods T4 to T5 as the current scan frequency.

[0094] According to this configuration, the sensor controller 10 selects, as the scan frequency, a frequency among the multiple auxiliary frequencies at which the measurement result of the electromagnetic noise level is the smallest, thereby enabling the sensor controller 10 to reduce the electromagnetic noise level of the transmission signal with higher accuracy.

[0095] In the above embodiment, the electronic device 1 detects a position indication by a passive pointer such as the stylus 2 or the finger 3, but is not limited thereto. The electronic device 1 may detect a position indication by, for example, an active electrostatic coupling stylus. The active electrostatic coupling stylus includes a power source, a communication circuit, and electrodes for detecting an uplink signal transmitted from the electronic device 1 at a predetermined cycle and transmitting a downlink signal at a specified time using the detected uplink signal as a reference time. In addition to transmitting a transmission signal, the electronic device 1 transmits an uplink signal to the touch sensor 20 and receives a downlink signal from the touch sensor 20.

[0096] According to this configuration, the sensor controller 10 can reduce the level of electromagnetic noise in the transmission signal with high efficiency even when the position of the touch sensor 20 is specified by a passive pointer.

[0097] In the above embodiment, the frequency selection unit 102 selects the scan frequency and the backup frequency from a first predetermined number of frequencies, but the present invention is not limited to this. The frequency selection unit 102 may be configured to be able to change the first predetermined number of frequency candidates according to, for example, the usage 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 usage environment of the electronic device 1 is, for example, the temperature, humidity, air pressure, cleanliness of the space in which the electronic device 1 is placed, the state of electromagnetic noise in the space, etc.

[0098] Specifically, the storage unit 110 stores a set of a plurality of frequencies associated with each of the usage environments of the electronic device 1. The storage unit 110 also stores a state related to the current set of frequencies that is set according to a setting command from an operator of the electronic device 1 or an external device that can communicate with the electronic device 1.

[0099] When selecting the scan frequency and the backup frequency, the frequency selection unit 102 refers to the storage unit 110 and selects one scan frequency from a predetermined number of frequencies associated with each set of frequencies according to the set of frequencies. In addition, the frequency selection unit 102 selects a frequency other than the scan frequency as a backup frequency from the predetermined number of frequencies in order for each transmission period.

[0100] According to this configuration, the sensor controller 10 can change the frequency candidates depending on the usage 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 enabling the level of electromagnetic noise in the transmission signal to be reduced with high accuracy and efficiency.

[0101] In the above embodiment, when the electromagnetic noise level at the scan frequency is greater than the predetermined value Nth and is equal to or greater than the electromagnetic noise level at any of the auxiliary frequencies, the frequency selection unit 102 selects the auxiliary frequency with the smallest electromagnetic noise level as the scan frequency, but this is not limited to the above. For example, the frequency selection unit 102 may select the frequency with the highest priority in terms of a predetermined priority order as the scan frequency from among the auxiliary frequencies with the electromagnetic noise level smaller than the predetermined value Nth.

[0102] The priority order is determined in advance by a measurement result of each frequency in the frequency set stored in the storage unit 110, for example, by a program for measuring the electronic device 1 stored in the storage unit 110 or a device other than the electronic device 1 communicably connected to the electronic device 1, and is stored in the storage unit 110. "In advance" means before the electronic device 1 or the touch sensor 20 is used by a user, for example, at the time of product shipment or at the time of change of settings. For example, the priority order may be set so that the lower the peak, the narrower the peak width, the closer the noise generation distribution is to uniform, or the higher the reproducibility of the electromagnetic noise is, with respect to the electromagnetic noise measured in advance. In addition, the priority order may be set so that the lower the reproducibility of the electromagnetic noise is, with respect to the electromagnetic noise measured after performing a measurement in advance on the touch sensor 20, the higher the priority order.

[0103] According to this configuration, the sensor controller 10 can use the frequency selection unit 102 to select a frequency at which the level of electromagnetic noise is small and which is suitable for the individual electromagnetic noise characteristics of the electronic device 1 as the scan frequency.

[0104] In addition, when the electromagnetic noise level at the scan frequency is greater than a predetermined value Nth and is equal to or greater than the electromagnetic noise level at any of the auxiliary frequencies, the frequency selection unit 102 may select as the scan frequency the frequency that is the furthest from the current scan frequency among the auxiliary frequencies whose electromagnetic noise level is smaller than the predetermined value Nth.

[0105] According to this configuration, the sensor controller 10 selects, as the scan frequency, a frequency that is far from the current scan frequency at which the level of electromagnetic noise is high, by the frequency selection unit 102. Therefore, the sensor controller 10 can select, as the scan frequency, a frequency that is more likely to have a lower level of electromagnetic noise from among the backup frequencies.

[0106] In addition, when the electromagnetic noise level at the scan frequency is greater than a predetermined value Nth and is equal to or greater than the electromagnetic noise level at any of the auxiliary frequencies, the frequency selection unit 102 may select as the scan frequency a frequency that is closest to the current scan frequency among the auxiliary frequencies having an electromagnetic noise level smaller than the predetermined value Nth.

[0107] According to this configuration, the sensor controller 10 selects, as the scan frequency, a frequency that is closest to the current scan frequency at which the electromagnetic noise level is high, by the frequency selection unit 102. Therefore, the sensor controller 10 can reduce the time required to change the scan frequency and simplify the circuit configuration. [Explanation of symbols]

[0108] 1...electronic device, 10...sensor controller, 13...transmitter, 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 that controls an operation of detecting a position of a passive pointer using a touch sensor, a transmitter configured to transmit a transmission signal to the touch sensor during a third period including a first period for measuring electromagnetic noise and a second period for performing the position detection at a predetermined cycle; a measurement unit that measures a level of electromagnetic noise of a frequency associated with each of the first and second periods during the first and second periods; a frequency selection unit that selects, for each of the third time periods, one of a first predetermined number of frequencies as a scan frequency that is the frequency of the transmission signal in the second time period based on a measurement result of the measurement unit, and selects, from among the first predetermined number of frequencies, a second predetermined number of frequencies that is less than the first predetermined number and that are different from the scan frequency, as backup frequencies that are the frequencies of the transmission signal in the first time period; A sensor controller comprising:

2. the frequency selection unit selects, in order for each third period, the second predetermined number of frequencies as the backup frequencies from among the first predetermined number of frequencies that are different from the scan frequency; The sensor controller of claim 1 .

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

4. When the measurement result is equal to or greater than the predetermined value, the frequency selection unit determines whether or not the measurement result is equal to or less than a measurement result of the electromagnetic noise in the first period by the measurement unit, and when the determination is positive, selects the previously selected scan frequency as the current scan frequency again. The sensor controller according to claim 3 .

5. When the measurement result is equal to or greater than the predetermined value, the frequency selection unit determines whether or not the measurement result is equal to or less than each measurement result of the electromagnetic noise in the plurality of first time periods by the measurement unit, and when the determination is positive, selects the previously selected scan frequency again as the current scan frequency. The sensor controller according to claim 3 .

6. When the measurement result is equal to or greater than the predetermined value, the frequency selection unit determines whether or not the measurement result is equal to or less than each of the measurement results of the electromagnetic noise in the plurality of first time periods by the measurement unit, and when the determination is negative, selects a frequency corresponding to the measurement result that is the smallest value among the measurement results of the electromagnetic noise in the plurality of first time periods as the current scan frequency. The sensor controller according to claim 3 .

7. When the measurement result is equal to or greater than the predetermined value, the frequency selection unit determines whether or not the measurement result is equal to or less than each of the measurement results of the electromagnetic noise in the plurality of first time periods by the measurement unit, and when the determination is negative, selects, as the current scan frequency, from among the first predetermined number of frequencies different from the scan frequency, a frequency having the highest priority in terms of a priority order predetermined based on a previous measurement result regarding the level of the electromagnetic noise. The sensor controller according to claim 3 .

8. When the measurement result is equal to or greater than the predetermined value, the frequency selection unit determines whether or not the measurement result is equal to or less than each of the measurement results of the electromagnetic noise in the plurality of first time periods by the measurement unit, and when the determination is negative, selects, as the current scan frequency, a frequency that is the furthest from the previously selected scan frequency among the frequencies corresponding to the measurement results of the electromagnetic noise in the plurality of first time periods that are smaller than the predetermined value. The sensor controller according to claim 3 .

9. When the measurement result is equal to or greater than the predetermined value, the frequency selection unit determines whether or not the measurement result is equal to or less than each of the measurement results of the electromagnetic noise in the plurality of first time periods by the measurement unit, and when the determination is negative, selects, as the current scan frequency, a frequency that is closest to the previously selected scan frequency from among the frequencies corresponding to the measurement results of the electromagnetic noise in the plurality of first time periods that are smaller than the predetermined value. The sensor controller according to claim 3 .

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

11. a touch sensor having a plurality of detection electrodes arranged in a planar shape, for detecting the position of a passive pointer; a sensor controller including: a transmitting unit connected to the touch sensor, the transmitting unit transmitting a transmission signal to the touch sensor at a predetermined cycle during a third period including a first period for measuring electromagnetic noise and a second period for performing the position detection; a measuring unit measuring an electromagnetic noise level at a frequency associated with each of the first and second periods; and a frequency selecting unit selecting, for each of the third periods, one of a first predetermined number of frequencies as a scan frequency that is the frequency of the transmission signal in the second period based on a measurement result of the measuring unit, and selecting, for each of the third periods, a second predetermined number of frequencies that is less than the first predetermined number from among the first predetermined number of frequencies that are different from the scan frequency, as spare frequencies that are the frequencies of the transmission signal in the first period; An electronic device comprising:

12. A method for controlling a sensor controller that controls operation of detecting a position of a passive pointer using a touch sensor, comprising the steps of: transmitting a transmission signal to the touch sensor during a third period including a first period for measuring electromagnetic noise and a second period for performing the position detection at a predetermined cycle; measuring a level of electromagnetic noise at a frequency associated with each of the first and second periods; selecting, for each of the third time periods, one frequency from among a first predetermined number of frequencies as a scan frequency that is a frequency of the transmission signal in the second time period based on a result of the measurement, and selecting, from among the first predetermined number of frequencies, a second predetermined number of frequencies that is less than the first predetermined number and that are different from the scan frequency, as backup frequencies that are frequencies of the transmission signal in the first time period; A control method for a sensor controller comprising:

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