Noise suppression method of stylus and mobile device

Abstract

The invention relates to a noise suppression method of a stylus and a mobile device. The noise suppression method of the touch pen comprises the following steps: sampling a signal received by a touch sensing electrode as a sampling signal; comparing the sampling signal with the sampling signal at the adjacent time; when the difference value between the sampling signal and the sampling signal in the adjacent time is larger than a signal allowable value, a first noise suppression signal is output, and the first noise suppression signal is equal to the sampling signal; and when the difference between the sampling signal and the sampling signal of the adjacent time is smaller than a signal allowable value, outputting a second noise suppression signal, and the value of the second noise suppression signal is between the sampling signal and the sampling signal of the adjacent time.

Description

Technical Field

[0001] The present invention relates to a wireless sensing technology, and in particular to a noise suppression method of a touch pen and a mobile device with the touch pen using the same. Background Art

[0002] A stylus is an input device for mobile devices or tablet computers that looks like a traditional pen or pencil, but is specially designed to interact with a touch screen. A stylus usually has a sharp tip that allows the user to accurately touch, draw, write or operate on the screen without using a finger.

[0003] The design and function of a stylus can vary from device to device, but generally speaking, the working principle of a stylus is to use capacitive touch technology with a modulated digital signal so that the signal contains information about the position, pressure, tilt angle, etc. of the stylus. Once the stylus signal is transmitted to the mobile device, the touch controller on the device decodes the signal. The touch controller identifies the position, movement, and other relevant information of the stylus and converts it into data that the application can understand.

[0004] Figure 1 is a circuit diagram of a decoding circuit of a touch pen system in the prior art. Figure 1 , the decoding circuit of this stylus system includes a stylus 101 and a stylus receiving device 102. The stylus 101 is the signal transmitting end, and the stylus receiving device 102 is the receiving end. The stylus 101 (transmitting end) transmits the transmission data through phase shift modulation (PSK modulation) and added carrier modulation, and the stylus receiving device 102 (receiving end) enters the digital system demodulation (de-modulation) after ADC sampling. However, there are many noise sources in the whole machine environment. If the sampling frequency is not high enough, it will cause various high-frequency noise reflection probabilities to increase and the (white) noise level to be too high. Although after digital demodulation, the receiving end can use a filter (IIR or FIR filter) to filter out noise and improve performance, the bandwidth of the filter is related to the number of sampling points. When the sampling rate is not high, the effect of the filter will be greatly reduced. Summary of the invention

[0005] The invention provides a noise suppression method for a touch pen and a mobile device with a touch pen using the method, which are used to suppress and inhibit the noise of a sampled touch pen signal before down-sampling.

[0006] An embodiment of the present invention provides a mobile device, which includes a stylus pen and a display touch device. The stylus pen is used to transmit a stylus pen signal. The display touch device includes a plurality of touch electrodes, a plurality of signal sampling devices, and a plurality of noise suppression circuits. Each signal sampling device includes an input end and an output end, wherein the input ends of the plurality of signal sampling devices are respectively coupled to the plurality of touch electrodes. Each noise suppression circuit includes an input end and an output end, wherein the input ends of the plurality of noise suppression circuits are respectively coupled to the output ends of the plurality of signal sampling devices.

[0007] A specific noise suppression circuit among the plurality of noise suppression circuits is used to compare a sampling signal sampled by a corresponding signal sampling device with a sampling signal sampled by the corresponding signal sampling device at an adjacent time. When the difference between the sampling signal sampled by the corresponding signal sampling device and the sampling signal sampled by the corresponding signal sampling device at an adjacent time is greater than a signal allowable value, the specific noise suppression circuit outputs the sampling signal sampled by the corresponding signal sampling device as a first noise suppression signal as an output signal. When the difference between the sampling signal sampled by the corresponding signal sampling device and the sampling signal sampled by the corresponding signal sampling device at an adjacent time is less than a signal allowable value, the specific noise suppression circuit outputs a second noise suppression signal as the output signal, wherein the value of the second noise suppression signal is between the sampling signal sampled by the corresponding signal sampling device and the sampling signal sampled by the corresponding signal sampling device at an adjacent time.

[0008] According to the mobile device described in the preferred embodiment of the present invention, each of the above-mentioned signal sampling devices further includes a charge amplifier and an analog-to-digital converter. The charge amplifier includes an input terminal and an output terminal, wherein the input terminal of the charge amplifier is coupled to the input terminal of the signal sampling device, and the charge amplifier is used to receive the signal of the coupled touch electrode to output an amplified touch signal. The analog-to-digital converter includes an input terminal and an output terminal, wherein the input terminal of the analog-to-digital converter is coupled to the output terminal of the charge amplifier to receive the amplified touch signal, and the output terminal of the analog-to-digital converter is coupled to the output terminal of the signal sampling device to output a sampling signal corresponding to the signal sampling device.

[0009] According to the mobile device described in the preferred embodiment of the present invention, each of the noise suppression circuits further includes a pre-register, a post-register, a digital comparison circuit, an addition and subtraction circuit, and a multi-task selection circuit. The pre-register receives the sampling signal corresponding to the signal sampling device and temporarily stores it. The post-register is used to store the previously output sampling signal and to output the output signal. The first input port of the digital comparison circuit is coupled to the pre-register to receive the sampling signal corresponding to the signal sampling device, the second input port of the digital comparison circuit is coupled to the post-register, and the output end of the digital comparison circuit outputs a selection signal, wherein the digital comparison circuit determines the logic of the selection signal according to the difference between the input values ​​of the first input port of the digital comparison circuit and the second input port of the digital comparison circuit.

[0010] The first input port of the addition and subtraction circuit is coupled to the post-register to receive the previously output sampling signal, the second input port of the addition and subtraction circuit receives a variation allowable value, and the output end thereof outputs a second noise suppression signal. The first input port of the multi-task selection circuit is coupled to the pre-register to receive the sampling signal corresponding to the signal sampling device, the second input port of the multi-task selection circuit is coupled to the output port of the addition and subtraction circuit to receive the second noise suppression signal, and the selection end of the multi-task selection circuit is coupled to the output end of the digital comparison circuit to receive the selection signal, wherein the output port of the multi-task selection circuit determines to output the data of the first input port of the multi-task selection circuit or the data of the second input port of the multi-task selection circuit according to the logic of the selection signal.

[0011] According to the mobile device described in the preferred embodiment of the present invention, the input port of the above-mentioned post-buffer is coupled to the output port of the multi-task selection circuit to receive the data output by the output port of the multi-task selection circuit as the above-mentioned previously output sampling signal, wherein the output port of the post-buffer outputs the first noise suppression signal or the second noise suppression signal according to the temporarily stored data.

[0012] According to the mobile device described in the preferred embodiment of the present invention, the above-mentioned pre-buffer further includes a storage block coupled to the output port of the post-buffer for storing data outputted by the output port of the post-buffer as a second previously outputted sampling signal, wherein each noise suppression circuit further includes a second multi-task selection circuit, wherein a first input port of the second multi-task selection circuit is coupled to the storage block of the pre-buffer for receiving the second previously outputted sampling signal, a second input port of the second multi-task selection circuit is coupled to the output port of the post-buffer for receiving data outputted by the output port of the post-buffer, a selection end of the multi-task selection circuit receives a delay selection signal, and an output port of the second multi-task selection circuit is coupled to a second input port of the multi-task selection circuit and a second input port of the digital comparison circuit.

[0013] The embodiment of the present invention further provides a noise suppression method for a stylus. The noise suppression method for the stylus includes: sampling a signal received by a touch sensing electrode as a sampling signal; comparing the sampling signal with a sampling signal at an adjacent time; when the difference between the sampling signal and the sampling signal at the adjacent time is greater than a signal allowable value, outputting a first noise suppression signal, wherein the first noise suppression signal is equal to the sampling signal; and when the difference between the sampling signal and the sampling signal at the adjacent time is less than the signal allowable value, outputting a second noise suppression signal, wherein the value of the second noise suppression signal is between the sampling signal and the sampling signal at the adjacent time.

[0014] In summary, the embodiments of the present invention adopt the method of sampling the received signal and comparing it with the previously sampled signal, and determining whether the currently sampled signal changes according to whether the comparison result is greater than the signal allowable value. When the comparison result is greater than the signal allowable value, the currently sampled signal is directly output. When the comparison result is less than the signal allowable value, the previously sampled signal is added or subtracted by a change allowable value as the output signal. In this way, the processed signal can maintain the change within the above-mentioned change allowable value under the influence of noise, and the currently sampled signal will be output only when there is a real change. In this way, the energy of various noises is reduced and the signal-to-noise ratio is increased.

[0015] In order to further understand the technology, means and effects of the present invention, reference may be made to the following detailed description and accompanying drawings, so that the purpose, features and concepts of the present invention can be thoroughly and specifically understood. However, the following detailed description and accompanying drawings are only used for reference and explanation of the implementation of the present invention, and are not intended to limit the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings are provided to enable those skilled in the art to further understand the present invention and are incorporated into and constitute a part of the specification of the present invention. The accompanying drawings illustrate exemplary embodiments of the present invention and are used to explain the principles of the present invention together with the description of the present invention.

[0017] Figure 1 It is a circuit diagram of a decoding circuit of a touch pen system in the prior art.

[0018] Figure 2 FIG. 1 is a circuit diagram of a decoding circuit of a mobile device using a stylus pen according to a preferred embodiment of the present invention.

[0019] Figure 3 FIG. 1 is a schematic diagram showing an ideal situation of a signal sampled by the signal sampling device 204 of a mobile device using a stylus pen according to a preferred embodiment of the present invention.

[0020] Figure 4 FIG. 1 is a schematic diagram showing a signal sampled by the signal sampling device 204 of a mobile device using a stylus pen according to a preferred embodiment of the present invention.

[0021] Figure 5 FIG. 4 is a circuit block diagram of a noise suppression circuit according to a preferred embodiment of the present invention.

[0022] Figure 6 FIG. 4 is a schematic diagram showing a signal output by a noise suppression circuit according to a preferred embodiment of the present invention.

[0023] Figure 7 FIG. 4 is a circuit block diagram of a noise suppression circuit according to a preferred embodiment of the present invention.

[0024] Figure 8 FIG. 4 is a flow chart of a noise suppression method for a stylus pen according to a preferred embodiment of the present invention.

[0025] Explanation of symbols:

[0026] 101: Stylus

[0027] 102: Stylus receiving device

[0028] 201: Stylus

[0029] 202: Mobile devices

[0030] 203: Touch electrode

[0031] 204: Signal sampling device

[0032] 205: Noise suppression circuit

[0033] 206: Charge Amplifier

[0034] 207: Analog-to-digital converter

[0035] 501: Pre-Cache

[0036] 502: Post-Cache

[0037] 503: Digital Comparator Circuit

[0038] 504: Addition and subtraction circuits

[0039] 505: Multi-task selection circuit

[0040] A[n]: sampling signal of the signal sampling device

[0041] B[n-1]: The sampling signal of the previous time

[0042] VAR: Variation Allowable Value

[0043] 601, 602, 603: Sampling signals with reduced variation after being processed by the noise suppression circuit

[0044] S800-S804: Process steps of a noise suppression method for a stylus pen according to a preferred embodiment of the present invention DETAILED DESCRIPTION

[0045] Reference will now be made in detail to exemplary embodiments of the present invention, which are illustrated in the accompanying drawings. Where possible, the same component symbols are used in the drawings and the specification to refer to the same or similar components. In addition, the exemplary embodiments are only one of the implementation methods of the design concept of the present invention, and the following examples are not intended to limit the present invention.

[0046] Figure 2 FIG. 1 is a block diagram of a decoding circuit of a mobile device using a stylus pen according to a preferred embodiment of the present invention. Figure 2 In an embodiment of a decoding circuit of a mobile device using a stylus pen, a stylus pen 201 and a mobile device 202 are included. The decoding circuit is disposed in the mobile device 202. The decoding circuit includes a plurality of touch electrodes 203, a plurality of signal sampling devices 204, and a plurality of noise suppression circuits 205. Each of the signal sampling devices 204 includes a charge amplifier (CA) 206 and a plurality of analog-to-digital converters (ADC) 207.

[0047] Figure 3 FIG. 2 is a schematic diagram of a signal sampled by a signal sampling device 204 of a mobile device using a stylus pen in an ideal situation according to a preferred embodiment of the present invention. Figure 3 ,Depend on Figure 3It can be seen that, ideally, the signal received by the touch electrode 203 from the stylus 201 should be a perfect square wave after passing through the analog-to-digital converter. Therefore, ideally, only two values ​​will be obtained during sampling.

[0048] Figure 4 FIG. 2 is a schematic diagram of a signal sampled by a signal sampling device 204 of a mobile device using a stylus pen in a preferred embodiment of the present invention under the condition of signal interference. Figure 4 ,Depend on Figure 4 It can be seen that in the case of actual signal transmission, the signal of the stylus 201 received by the touch electrode 203 will be affected by high-frequency noise, aliasing effect and white noise, so that the perfect square wave that should originally contain only two values ​​will actually become a signal with other high and low fluctuations after being received and analog-to-digital converted.

[0049] Figure 5 FIG. 2 is a block diagram of a noise suppression circuit 205 according to a preferred embodiment of the present invention. Figure 5 The noise suppression circuit 205 includes a pre-buffer 501, a post-buffer 502, a digital comparison circuit 503, an addition and subtraction circuit 504, and a multi-task selection circuit 505. The pre-buffer 501 receives the sampling signal A[n] from the corresponding signal sampling device and temporarily stores it. The post-buffer 502 is used to store the previously output and processed sampling signal B[n-1].

[0050] In this embodiment, the digital comparison circuit 503 receives the sampling signal A[n] stored in the pre-register 501 and the sampling signal B[n-1] stored in the post-register 502 at the previous time, and compares the two. When the difference between the sampling signal A[n] and the sampling signal B[n-1] is large enough to exceed a set signal tolerance value, it means that the signal transition occurs from sampling time n-1 to sampling time n. At this time, the selection signal SEL_1 output by the digital comparison circuit 503 is set to logic 1. At this time, the sampling signal A[n] input to the input terminal corresponding to logic 1 of the multi-task selection circuit 505 will be introduced into the output terminal of the multi-task selection circuit 505, so the post-register 502 will treat the received sampling signal A[n] as the output signal B[n] of the next time, that is, A[n]=B[n].

[0051] However, when the difference between the sampling signal A[n] and the sampling signal B[n-1] is insufficient and does not exceed a set signal tolerance value, it indicates that the signal difference from sampling time n-1 to sampling time n may be affected by interference and change. At this time, the selection signal SEL_1 output by the digital comparison circuit 503 will be set to logic 0. At this time, the signal input to the input multiplexer 505 corresponding to the logic 0 input terminal will be introduced to the output terminal of the multiplexer 505. Since the signal input to the input multiplexer 505 corresponding to the logic 0 input terminal is operated by the addition and subtraction circuit 504. In this embodiment, the output of the addition and subtraction circuit 504 can be regarded as B[n-1]+VAR, where VAR represents the allowable change value in this embodiment. That is to say, although there is actually a difference between the sampling signal A[n] and the sampling signal B[n-1], this difference is considered to be possibly noise. Therefore, in this embodiment, only this signal is allowed to change partially within the limit of the allowable change value VAR. The rule of the above allowable change value VAR is that when A[n]>B[n-1], B[n]=B[n-1]+VAR, and when A[n]<B[n-1], B[n]=B[n-1]-VAR. After that, the post buffer 502 will regard the received sampling signal B[n-1]+VAR or B[n-1]-VAR as the output signal B[n] for the next time.

[0052] Figure 6 It is a schematic diagram of the signal output by the noise suppression circuit 205 according to a preferred embodiment of the present invention. Please refer to Figure 6 , those of ordinary skill in the art should be able to see that after being processed by the noise suppression circuit 205, the variation amounts of the reference numerals 601, 602, and 603 are greatly reduced. Thereby, the influence of noise is also suppressed, making the output signal closer to the ideal.

[0053] Figure 7 It is a circuit block diagram of the noise suppression circuit 205 according to a preferred embodiment of the present invention. Please refer to Figure 7In addition to the above-mentioned pre-register 501, post-register 502, digital comparison circuit 503, addition and subtraction circuit 504, and multi-task selection circuit 505, the noise suppression circuit 205 further includes a second multi-task selection circuit 701. In addition, the pre-register 501 further includes an additional storage block 702 coupled to the output port of the post-register for storing the data B[n-2] outputted from the output port of the post-register. The first input port of the second multi-task selection circuit 701 is coupled to the storage block 702 of the pre-register 501 to receive the previously outputted sampling signal B[n-2]. The second input port of the second multi-task selection circuit 701 is coupled to the output port of the post-register 502 to receive the data B[n-1] outputted from the output port of the post-register. The selection end of the second multi-task selection circuit 701 receives a delay selection signal SEL_2. The delay selection signal SEL_2 is used to determine whether the sampling signal received by the digital comparison circuit 503 is the sampling signal B[n-1] delayed by one unit time or the sampling signal B[n-2] delayed by two unit times.

[0054] In a preferred embodiment of the present invention, when the sampling rate is high enough, the current sampled signal A[n] is compared with the signal B[n-1] delayed by one unit time or with the signal B[n-2] delayed by two unit time, which does not affect the operation of the present invention. Therefore, the user can choose to compare signals delayed by different unit time to obtain better results according to different implementation environments. The present invention is not limited to this.

[0055] The above embodiments can be summarized into a noise suppression method for a stylus pen. Figure 8 FIG. 1 is a flowchart of a noise suppression method for a stylus pen according to a preferred embodiment of the present invention. Figure 8 , the noise suppression method of the stylus comprises the following steps:

[0056] Step S800: Start.

[0057] Step S801: sampling a signal received by a touch sensing electrode as a sampling signal A[n].

[0058] Step S802: Compare the sampled signal A[n] with the sampled signal B[n-1] of the adjacent time to determine whether the comparison result is greater than the signal allowable value VT. If the comparison result is greater than the signal allowable value VT, proceed to step S803; if the comparison result is less than the signal allowable value VT, proceed to step S804.

[0059] Step S803: When the difference between the sampling signal A[n] and the adjacent sampling signal B[n-1] is greater than the signal tolerance value VT, a first noise suppression signal is output, wherein the first noise suppression signal is equal to the sampling signal A[n].

[0060] Step S804: When the difference between the sampled signal A[n] and the sampled signal B[n-1] at the adjacent time is less than the signal tolerance value VT, a second noise suppression signal is output, wherein the value of the second noise suppression signal is between the sampled signal A[n] and the sampled signal B[n-1] at the adjacent time, such as B[n-1]+VAR or B[n-1]-VAR, so that the signal fluctuation is suppressed within the variation tolerance value VAR.

[0061] In the above-mentioned noise suppression method of the stylus, although the sampling signal A[n] is compared with the sampling signal B[n-1] of the adjacent time, that is, the previous time, those with ordinary knowledge in the technical field should know, after referring to the above-mentioned embodiments, that the first two unit times, three unit times, or the first N unit times are all feasible methods. It depends on the sampling rate and the application. Therefore, the present invention is not limited to this. In addition, although the above-mentioned embodiments use the processed signal B[n-1] as an example, those with ordinary knowledge in the technical field should know that the unprocessed adjacent time sampling signal A[n-1] can also be used as an embodiment. Therefore, the present invention is not limited to this.

[0062] In summary, the embodiment of the present invention samples the received signal and compares it with the previously sampled signal, and determines whether the currently sampled signal changes according to whether the comparison result is greater than the signal allowable value. When the comparison result is greater than the signal allowable value, the currently sampled signal is directly output. When the comparison result is less than the signal allowable value, the previously sampled signal is added or subtracted by a change allowable value as the output signal. In this way, the processed signal can maintain the change within the above-mentioned change allowable value under the influence of noise, and the currently sampled signal will be output only when there is a real change. In this way, the energy of various noises is reduced and the signal-to-noise ratio is increased.

[0063] It should be understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in view thereof will be suggested to those skilled in the art and are to be included within the spirit and scope of the present application and the scope of the appended claims.

Claims

1. A mobile device, characterized in that: include: A stylus pen, used to transmit a stylus pen signal; A display touch device, comprising: A plurality of touch electrodes; a plurality of signal sampling devices, wherein each signal sampling device comprises an input terminal and an output terminal, wherein the input terminals of the plurality of signal sampling devices are respectively coupled to the plurality of touch electrodes; and A plurality of noise suppression circuits, wherein each noise suppression circuit comprises an input terminal and an output terminal, wherein the input terminals of the plurality of noise suppression circuits are respectively coupled to the output terminals of the plurality of signal sampling devices, Among the above-mentioned multiple noise suppression circuits, a specific noise suppression circuit is used to compare the sampling signal sampled by the corresponding signal sampling device with the sampling signal sampled by the corresponding signal sampling device at an adjacent time. When the difference between the sampling signal sampled by the corresponding signal sampling device and the sampling signal sampled by the corresponding signal sampling device at an adjacent time is greater than a signal allowable value, the specific noise suppression circuit outputs the sampling signal sampled by the corresponding signal sampling device as a first noise suppression signal as an output signal; When the difference between the sampling signal sampled by the corresponding signal sampling device and the sampling signal sampled by the corresponding signal sampling device at an adjacent time is less than a signal allowable value, the specific noise suppression circuit outputs a second noise suppression signal as the output signal, wherein the value of the second noise suppression signal is between the sampling signal sampled by the corresponding signal sampling device and the sampling signal sampled by the corresponding signal sampling device at an adjacent time.

2. The mobile device according to claim 1, characterized in that: Each signal sampling device further comprises: a charge amplifier, comprising an input terminal and an output terminal, wherein the input terminal of the charge amplifier is coupled to the input terminal of the signal sampling device, and the charge amplifier is used to receive a signal from the coupled touch electrode to output an amplified touch signal; and An analog-to-digital converter includes an input terminal and an output terminal, wherein the input terminal of the analog-to-digital converter is coupled to the output terminal of the charge amplifier to receive the amplified touch signal, and the output terminal of the analog-to-digital converter is coupled to the output terminal of the signal sampling device to output a sampling signal corresponding to the signal sampling device.

3. The mobile device according to claim 1, characterized in that: Each noise suppression circuit further comprises: a pre-register, receiving the sampling signal corresponding to the signal sampling device and temporarily storing it; and A post buffer for storing the previously output sampled signal and for outputting the output signal; A digital comparison circuit, comprising a first input port, a second input port and an output port, wherein the first input port of the digital comparison circuit is coupled to the pre-register to receive the sampling signal corresponding to the signal sampling device, the second input port of the digital comparison circuit is coupled to the post-register, and the output port of the digital comparison circuit outputs a selection signal, wherein the digital comparison circuit determines the logic of the selection signal according to whether the difference between the input values ​​of the first input port of the digital comparison circuit and the second input port of the digital comparison circuit is greater than the signal allowable value; an addition-subtraction circuit, comprising a first input port, a second input port and an output port, wherein the first input port of the addition-subtraction circuit is coupled to the post-buffer to receive the previously output sampling signal, the second input port of the addition-subtraction circuit receives a variation allowable value, and the output port thereof outputs the second noise suppression signal; and A multi-task selection circuit comprises a selection end, a first input port, a second input port and an output port, wherein the first input port of the multi-task selection circuit is coupled to the pre-register to receive the sampling signal corresponding to the signal sampling device, the second input port of the multi-task selection circuit is coupled to the output port of the addition and subtraction circuit to receive the second noise suppression signal, and the selection end of the multi-task selection circuit is coupled to the output end of the digital comparison circuit to receive the selection signal. The output port of the multi-task selection circuit determines to output data of the first input port of the multi-task selection circuit or data of the second input port of the multi-task selection circuit according to the logic of the selection signal.

4. The mobile device according to claim 3, characterized in that: The input port of the post-buffer is coupled to the output port of the multi-task selection circuit to receive data outputted by the output port of the multi-task selection circuit as the previously outputted sampling signal, wherein the output port of the post-buffer outputs the first noise suppression signal or the second noise suppression signal according to the temporarily stored data.

5. The mobile device according to claim 4, characterized in that: The pre-register further includes a storage block coupled to the output port of the post-register for storing data outputted from the output port of the post-register as a second previously outputted sampling signal. Wherein, each noise suppression circuit further comprises: A second multi-task selection circuit includes a selection end, a first input port, a second input port and an output port, wherein the first input port of the second multi-task selection circuit is coupled to the storage block of the pre-buffer to receive the second previously output sampling signal, the second input port of the second multi-task selection circuit is coupled to the output port of the post-buffer to receive data output by the output port of the post-buffer, the selection end of the second multi-task selection circuit receives a delayed selection signal, and the output port of the second multi-task selection circuit is coupled to the second input port of the multi-task selection circuit and the second input port of the digital comparison circuit.

6. A method for suppressing noise of a stylus pen, characterized in that: include: sampling a signal received by a touch sensing electrode as a sampling signal; comparing the sampled signal with sampled signals at adjacent times; When the difference between the sampling signal and the adjacent sampling signal is greater than a signal tolerance value, a first noise suppression signal is output as an output signal, wherein the first noise suppression signal is equal to the sampling signal; and When the difference between the sampling signal and the sampling signal at the adjacent time is less than the signal allowable value, a second noise suppression signal is output as an output signal, wherein the value of the second noise suppression signal is between the sampling signal and the sampling signal at the adjacent time.

7. The noise suppression method of a stylus pen according to claim 6, wherein: When the difference between the sampling signal and the sampling signal at the adjacent time is less than the signal tolerance value, comprising: When the difference is positive, adding a variation tolerance value to the adjacent time sampling signal to serve as the second noise suppression signal; and When the difference is positive or negative, the variation tolerance value is subtracted from the adjacent time sampling signal to obtain the second noise suppression signal. The variation tolerance value is between the difference between the sampling signal and the sampling signal at the adjacent time.

8. The noise suppression method of a stylus pen according to claim 6, characterized in that: The sampling signal at the adjacent time includes the output signal at the previous time.

9. The noise suppression method of a stylus pen according to claim 6, characterized in that: The sampling signal of the adjacent time includes the output signal of the previous N time periods, wherein N is a natural number.

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