CN210724736U - Anti-interference detection device for capacitive touch keys - Google Patents
Anti-interference detection device for capacitive touch keys Download PDFInfo
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- CN210724736U CN210724736U CN201920321732.9U CN201920321732U CN210724736U CN 210724736 U CN210724736 U CN 210724736U CN 201920321732 U CN201920321732 U CN 201920321732U CN 210724736 U CN210724736 U CN 210724736U
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Abstract
The utility model relates to an anti-interference detection device of electric capacity touch button, receive and filtering unit, reference clock, button state detecting element, current reference cell, modulating unit, frequency calculator, demodulation unit and signal comparison unit including detection port, RC oscillation unit, feedback waveform, current reference cell be connected with detection port, RC oscillation unit respectively, detection port receive and filtering unit with the feedback waveform is connected, modulating unit be connected with RC oscillation unit, signal comparison unit, reference clock respectively, reference clock be connected with frequency calculator, demodulation unit respectively, the frequency calculator receive and filtering unit, demodulation unit, button state detecting element are connected with the feedback waveform respectively, button state detecting element be connected with signal comparison unit. Compared with the prior art, the utility model discloses can eliminate noise jamming, improve and detect the accuracy.
Description
Technical Field
The utility model belongs to the technical field of the anti-interference technique of touch and specifically relates to an anti-interference detection device of electric capacity touch button is related to.
Background
The touch key has the advantages of attractive appearance, durability, low cost, long service life and the like, is applied to more and more devices, and is a capacitive touch key which is widely adopted at present.
The capacitive touch detection is based on the principle that the frequency of the RC oscillator changes, and when a hand of a person touches a touch key, the equivalent capacitance of the touch key to the ground is increased, so that the frequency of the RC oscillator connected with the touch key changes along with the change.
The traditional detection mode is that the MCU system samples the number of cycles output by the RC oscillator at regular time, and whether the touch key is pressed down is judged according to the change of the number of cycles. As shown in fig. 1, includes: the existing touch key 101 is equivalent to a capacitance of a detection port to the ground, and when a finger touches the existing touch key, the capacitance changes; an existing RC oscillation unit 102 that sends out an oscillation waveform to the detection port, and a capacitance inside the RC oscillation unit is associated with an equivalent capacitance of the existing touch key 101; a conventional feedback waveform receiving and filtering unit 103 for detecting a port; an existing reference clock 104; an existing waveform counter 105; the existing key state detection unit 106. The working principle of the detection mode is as follows: the method comprises the steps of counting by using a reference clock to obtain a fixed time length, counting port feedback waveforms by using a waveform counter within the fixed time length to obtain a count value, identifying and judging the change of capacitance of a detection port according to the change of the count value, and judging that a touch key is pressed down when the change value reaches a certain threshold value relative to a measured reference value. This touch detection method has the advantage of high sensitivity, but it has the inherent disadvantage of weak resistance to strong noise. Noise from a power supply or strong environmental noise interference is superimposed on the oscillation waveform, which easily causes erroneous judgment of the touch key state.
SUMMERY OF THE UTILITY MODEL
The utility model aims at providing an anti-interference detection device of electric capacity touch button in order to overcome the defect that above-mentioned prior art exists, utilize the mode of carrier modulation and demodulation, the strong noise interference of filtering avoids touching the erroneous judgement of button state.
The purpose of the utility model can be realized through the following technical scheme:
the utility model provides a capacitance touch button anti-interference detection device, includes detection port, RC oscillation unit, feedback waveform receiving and filtering unit, reference clock and button state detecting element, detection device still include current reference cell, modulating unit, frequency calculator, demodulation unit and signal comparison unit, current reference cell be connected with detection port, RC oscillation unit respectively, detection port be connected with feedback waveform receiving and filtering unit, modulating unit be connected with RC oscillation unit, signal comparison unit, reference clock respectively, the reference clock be connected with frequency calculator, demodulation unit respectively, the frequency calculator be connected with feedback waveform receiving and filtering unit, demodulation unit, button state detecting element be connected with signal comparison unit respectively.
Preferably, the first output terminal of the reference clock is connected to the input terminal of the modulation unit, and is used for controlling the modulation unit to output the modulation signal.
Preferably, the first output terminal of the modulation unit is connected to the input terminal of the RC oscillating unit, and is configured to control the RC oscillating unit to be enabled, and superimpose the modulation signal on the oscillating signal of the RC oscillating unit to generate the feedback signal.
Preferably, the output end of the RC oscillating unit is connected to the input end of the current reference unit, and is used for transmitting the feedback signal to the current reference unit so as to control the current reference unit to output a corresponding current value.
Preferably, the output end of the current reference unit is connected to the detection port, and is used for charging and discharging the detection port to generate a feedback waveform at the detection port.
Preferably, an input end of the feedback waveform receiving and filtering unit is connected to the detection port, and is configured to receive the feedback waveform from the detection port and perform filtering processing on the waveform.
Preferably, a first input terminal of the frequency calculator is connected to the output terminal of the feedback waveform receiving and filtering unit, a second input terminal thereof is connected to the second output terminal of the reference clock, and a first output terminal thereof is connected to the first input terminal of the key state detecting unit, and is configured to calculate a frequency of the filtered feedback waveform, and compare the frequency with the frequency of the reference clock, so as to output a frequency fluctuation value to the key state detecting unit.
Preferably, a first input of the demodulation unit is connected to a third output of the reference clock, and a second input of the demodulation unit is connected to a second output of the frequency calculator, for detecting a demodulation signal from the filtered feedback waveform.
Preferably, a first input end of the signal comparing unit is connected to a second output end of the modulating unit, a second input end of the signal comparing unit is connected to an output end of the demodulating unit, and an output end of the signal comparing unit is connected to a second input end of the key state detecting unit, and is configured to compare the modulated signal with the demodulated signal and output a signal comparison result to the key state detecting unit.
Preferably, the current reference unit has configurable current steps, and the current steps correspond to different external capacitance values of the detection port respectively.
Compared with the prior art, the utility model discloses following beneficial effect has:
the touch control method includes the steps that a current reference unit with configurable current steps is added, and the touch control method can be adapted to touch peripheries with different capacitance values.
Secondly, the influence of strong noise interference can be effectively eliminated by modulating to generate a feedback waveform and demodulating the feedback waveform.
And thirdly, through double comparison of the frequency fluctuation value and the modulation and demodulation signal, the accuracy of analyzing and judging the state of the touch key can be improved.
Drawings
FIG. 1 is a schematic structural diagram of a prior art detecting device;
fig. 2 is a schematic structural diagram of the detection device of the present invention.
In the figure, 101 is the existing touch key, 102 is the existing RC oscillation unit, 103 is the existing feedback waveform receiving and filtering unit, 104 is the existing reference clock, 105 is the existing waveform counter, 106 is the existing key state detecting unit;
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, not all, of the embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative efforts shall fall within the protection scope of the present invention.
As shown in fig. 2, the capacitive touch key anti-interference detection device includes a current reference unit 202, an RC oscillation unit 203, a feedback waveform receiving and filtering unit 204, a modulation unit 205, a reference clock 206, a frequency calculator 207, a demodulation unit 208, a signal comparison unit 209, and a key state detection unit 210.
A first output end of the reference clock 206 is connected to an input end of the modulation unit 205, and is used for controlling the modulation unit 205 to output a modulation signal L1, where the modulation signal L1 is a set of binary sequences;
a first output terminal of the modulation unit 205 is connected to an input terminal of the RC oscillating unit 203, and is configured to control the RC oscillating unit 203 to be enabled, and to superimpose the modulation signal on the oscillating signal of the RC oscillating unit 203 to generate a feedback signal;
the output end of the RC oscillation unit 203 is connected to the input end of the current reference unit 202, and is configured to transmit a feedback signal to the current reference unit 202 to control the current reference unit 202 to output a corresponding current value, the current reference unit 202 has configurable current steps, and each current step corresponds to a different external capacitance value of the detection port;
the output end of the current reference unit 202 is connected to the detection port 201, and is used for charging and discharging the detection port 201 to generate a feedback waveform at the detection port 201;
the input end of the feedback waveform receiving and filtering unit 204 is connected to the detection port 201, and is configured to receive the feedback waveform from the detection port 201 and perform filtering processing on the waveform;
the frequency calculator 207 has a first input terminal connected to the output terminal of the feedback waveform receiving and filtering unit 204, a second input terminal connected to the second output terminal of the reference clock 206, and a first output terminal connected to the first input terminal of the key state detecting unit 210, and is configured to calculate the frequency f0 of the filtered feedback waveform, and compare the frequency f0 with the frequency f of the reference clock, so as to output a frequency fluctuation Df to the key state detecting unit 210;
a demodulation unit 208 having a first input terminal connected to the third output terminal of the reference clock 206 and a second input terminal connected to the second output terminal of the frequency calculator 207 for detecting a demodulated signal L2 from the filtered feedback waveform, the modulated signal L2 being a set of binary sequences;
the first input terminal of the signal comparing unit 209 is connected to the second output terminal of the modulating unit 205, the second input terminal thereof is connected to the output terminal of the demodulating unit 208, and the output terminal thereof is connected to the second input terminal of the key state detecting unit 210, for comparing whether the binary sequences of the modulated signal L1 and the demodulated signal L2, specifically, the modulated signal L1 and the demodulated signal L2 are consistent, and outputting the signal comparison result to the key state detecting unit 210;
and the key state detection unit 210 is used for analyzing, judging and outputting the touch key state.
The utility model discloses a work flow as follows:
step 1, modulating to generate a feedback waveform: superimposing the modulation signal on the oscillation signal to form a feedback signal so as to generate a feedback waveform at the detection port;
step 2, processing the demodulation feedback waveform: filtering the feedback waveform generated in the step 1, calculating the frequency of the feedback waveform, comparing the frequency with a reference frequency, outputting a frequency fluctuation value, and then detecting a demodulation signal in the feedback waveform;
step 3, comparing signals: comparing the demodulation signal in the step 2 with the modulation signal in the step 1, and simultaneously outputting a signal comparison result;
step 4, analyzing and judging the state of the touch key: and if the frequency fluctuation value in the step 2 exceeds a preset threshold value and the signal comparison result in the step 3 is consistent, judging that the touch key is pressed at the moment, otherwise, judging that the touch key is not pressed at the moment.
Wherein, the step 1 specifically comprises:
step 1.1, enabling the modulation unit 205 to generate a modulation signal L1 according to the frequency of the reference clock 206, enabling the RC oscillation unit 203 under the control of the modulation unit 205, and superposing the modulation signal L1 on the oscillation signal of the RC oscillation unit 203 to form a feedback signal;
in step 1.2, the RC oscillating unit 203 transmits the feedback signal in step 1.1 to the current reference unit 202 to control the current reference unit 202 to output a corresponding current value to charge and discharge the detection port 201, so as to generate a feedback waveform.
The step 2 specifically comprises:
step 2.1, the feedback receiving and filtering unit 204 filters the feedback waveform and transmits the filtered feedback waveform to the frequency calculator 207;
step 2.2, calculating the frequency f0 of the filtered feedback waveform by the frequency calculator 207, comparing the frequency f with the frequency f of the reference clock 206 and outputting a frequency fluctuation value Df;
step 2.3, according to the frequency division mf of the reference clock, the frequency division value mf is approximately equal to the frequency f0 of the filtered feedback waveform calculated by the frequency calculator in the step 2.2, and a demodulation signal L2 is detected from the filtered feedback waveform.
In this embodiment, the configurable gear range of the current reference unit 202 is 100nA to 100uA, and corresponds to different external capacitance values respectively. The frequency f of the reference clock 206 is 8MHz, and the corresponding period is 125 ns.
When the current reference is 10uA, the external capacitance of the corresponding detection port is C0-1 nF, a feedback waveform with f 0-16 kHz is obtained on the detection port, and the corresponding period is 6.25 us. According to the formula: f ≧ I/C, where the current reference I does not change and the frequency f changes inversely proportionally as the capacitance C changes.
Assuming that the minimum capacitance value of 1/5000, i.e. 0.2pF, is increased by finger touch, the frequency of the feedback waveform is decreased by 1/5000, which corresponds to an increase of about 12.5ns, so that the frequency calculator 207 needs to count the waveform to be fed back at least 10 times before it corresponds to 125ns of 1 cycle of the reference clock 206. The frequency calculator 207 therefore needs to calculate the frequency of the filtered feedback waveform after 10 cycles of 16kHz (i.e. 6.25us × 10 ═ 625 us).
In fact, because the frequency of the filtered feedback waveform is used as the input of the demodulation unit 208, a relatively precise frequency value is often obtained by performing a relatively long-time average calculation.
For ease of illustration, assuming a finger touch increases capacitance by 600pF, i.e., the total sense port capacitance reaches 1.6nF, the sense port feedback waveform frequency f0 becomes 10 kHz.
The filtered feedback waveform is demodulated with the clock base of the demodulation unit 208 being 800 divisions, i.e., 10kHz, of the reference clock 206. Even if the circuit periphery has the influence of strong noise, the demodulation unit 208 can demodulate the same envelope code as the modulation unit 205, thereby achieving the effect of filtering the strong noise interference.
The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily think of various equivalent modifications or replacements within the technical scope of the present invention, and these modifications or replacements should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (10)
1. An anti-interference detection device for capacitive touch keys comprises a detection port, an RC oscillation unit, a feedback waveform receiving and filtering unit, a reference clock and a key state detection unit, it is characterized in that the detection device also comprises a current reference unit, a modulation unit, a frequency calculator, a demodulation unit and a signal comparison unit, the current reference unit is respectively connected with a detection port and an RC oscillation unit, the detection port is connected with a feedback waveform receiving and filtering unit, the modulation unit is respectively connected with the RC oscillation unit, the signal comparison unit and the reference clock, the reference clock is respectively connected with the frequency calculator and the demodulation unit, the frequency calculator is respectively connected with the feedback waveform receiving and filtering unit, the demodulation unit and the key state detection unit, and the key state detection unit is connected with the signal comparison unit.
2. The apparatus according to claim 1, wherein the first output terminal of the reference clock is connected to the input terminal of the modulation unit, for controlling the modulation unit to output the modulation signal.
3. The apparatus according to claim 2, wherein the first output terminal of the modulation unit is connected to the input terminal of the RC oscillating unit, and is configured to control the RC oscillating unit to be enabled, and superimpose the modulation signal on the oscillating signal of the RC oscillating unit to generate the feedback signal.
4. The apparatus according to claim 3, wherein an output terminal of the RC oscillating unit is connected to an input terminal of the current reference unit, and configured to transmit the feedback signal to the current reference unit so as to control the current reference unit to output a corresponding current value.
5. The apparatus according to claim 1, wherein an output terminal of the current reference unit is connected to the detection port for charging and discharging the detection port to generate a feedback waveform at the detection port.
6. The device of claim 1, wherein an input terminal of the feedback waveform receiving and filtering unit is connected to the detection port, and is configured to receive the feedback waveform from the detection port and filter the feedback waveform.
7. The apparatus of claim 1, wherein the frequency calculator has a first input coupled to the output of the feedback waveform receiving and filtering unit, a second input coupled to the second output of the reference clock, and a first output coupled to the first input of the key state detecting unit, and is configured to calculate the frequency of the filtered feedback waveform and compare the frequency with the frequency of the reference clock to output a frequency fluctuation value to the key state detecting unit.
8. The apparatus of claim 4, wherein a first input of said demodulation element is coupled to a third output of said reference clock, and a second input of said demodulation element is coupled to a second output of said frequency calculator, for extracting a demodulated signal from the filtered feedback waveform.
9. The apparatus of claim 8, wherein a first input terminal of the signal comparing unit is connected to a second output terminal of the modulating unit, a second input terminal of the signal comparing unit is connected to an output terminal of the demodulating unit, and an output terminal of the signal comparing unit is connected to a second input terminal of the key state detecting unit, for comparing the modulated signal with the demodulated signal and outputting a signal comparison result to the key state detecting unit.
10. The device according to claim 1, wherein the current reference unit has configurable current stages, and the current stages respectively correspond to different external capacitance values of the detection port.
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| CN201920321732.9U CN210724736U (en) | 2019-03-14 | 2019-03-14 | Anti-interference detection device for capacitive touch keys |
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| CN201920321732.9U CN210724736U (en) | 2019-03-14 | 2019-03-14 | Anti-interference detection device for capacitive touch keys |
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