CN111813277A - Double-layer pressure touch signal acquisition method of capacitive touch switch - Google Patents
Double-layer pressure touch signal acquisition method of capacitive touch switch Download PDFInfo
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- CN111813277A CN111813277A CN202010661716.1A CN202010661716A CN111813277A CN 111813277 A CN111813277 A CN 111813277A CN 202010661716 A CN202010661716 A CN 202010661716A CN 111813277 A CN111813277 A CN 111813277A
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- 238000000034 method Methods 0.000 title claims abstract description 16
- 238000005070 sampling Methods 0.000 claims abstract description 40
- 239000003990 capacitor Substances 0.000 claims abstract description 36
- 230000005611 electricity Effects 0.000 claims 1
- 230000036632 reaction speed Effects 0.000 abstract 1
- 238000004364 calculation method Methods 0.000 description 7
- 238000010586 diagram Methods 0.000 description 7
- 230000003321 amplification Effects 0.000 description 5
- 238000001514 detection method Methods 0.000 description 5
- 238000003199 nucleic acid amplification method Methods 0.000 description 5
- 238000009795 derivation Methods 0.000 description 3
- 241000218691 Cupressaceae Species 0.000 description 2
- 230000006978 adaptation Effects 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000000356 contaminant Substances 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000005684 electric field Effects 0.000 description 1
- 230000005669 field effect Effects 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000001960 triggered effect Effects 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
- G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
- G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
- G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
- G06F3/044—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means by capacitive means
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
- G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
- G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
- G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
- G06F3/0414—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means using force sensing means to determine a position
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F2203/00—Indexing scheme relating to G06F3/00 - G06F3/048
- G06F2203/041—Indexing scheme relating to G06F3/041 - G06F3/045
- G06F2203/04105—Pressure sensors for measuring the pressure or force exerted on the touch surface without providing the touch position
Abstract
The invention discloses a double-layer pressure touch signal acquisition method of a capacitive touch switch, which comprises the following steps of acquiring an upper layer touch SENSOR signal and a lower layer pressure SENSOR signal, wherein the acquisition of the upper layer touch SENSOR signal and the lower layer pressure SENSOR signal comprises the following steps: a primary charging step: the charging power supply charges the internal capacitor, and the charging power supply is cut off after the charging is finished; a primary charge sharing step: the internal capacitance charges the sensor capacitance; a primary sampling step: performing first AD sampling after charging is completed to obtain a first sampling voltage value; a secondary charging step: the sensor capacitor is charged by the charging power supply, and the charging power supply is cut off after the charging is finished; a secondary charge sharing step: the sensor capacitor charges the internal capacitor; secondary sampling: and performing second AD sampling after the charging is finished to obtain a second AD sampling voltage value. The touch signal acquisition method can increase the reaction speed of the touch key and improve the anti-interference capability of the touch key.
Description
Technical Field
The invention relates to the technical field of touch detection of touch screens, in particular to a double-layer pressure touch signal acquisition method of a capacitive touch switch.
Background
At present, there are two common touch detection methods for a capacitive touch screen: one is to use the RC oscillator as a time constant, and different periods or frequencies correspond to different capacitance values, taking cypress as an example, as shown in fig. 1, the output of the comparator is fed into a clock input circuit of a Pulse Width Modulator (PWM), the PWM is responsible for gating a counter, and a finger on a sensor increases the capacitance, thereby increasing the count value, and achieving the purpose of detection based on the principle; the other is to convert a capacitor into a resistor by using the characteristic of equivalent resistance of a switched capacitor, and the change of the detection voltage is caused by the change of impedance due to the change of the capacitor, taking a freescale electric field sensor as an example, as shown in fig. 2, the switched capacitor forms an impedance to form a partial voltage for an input sinusoidal signal through a load resistor, and the detector detects the partial voltage signal. Magnitude of impedance
The larger C, the smaller the impedance, the smaller the divided voltage level, and thus the detected signal level decreases with the increase in capacitance.
The two detection methods adopt single signal acquisition, and have the problems of poor anti-interference capability, poor reliability and the like. Meanwhile, the field effect of capacitive touch brings some limitations: 1. standard capacitive touch systems are generally not capable of functioning through metal surfaces; 2. special software is required to operate in environments with radiated and/or conducted noise; 3. buttons are difficult to read in the presence of water or other contaminants; 4. visually impaired users relying on braille may encounter problems; 5. it is difficult to detect a touch through the glove.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a double-layer pressure touch signal acquisition method of a capacitive touch switch, which has strong anti-interference capability and good reliability.
In order to achieve the purpose, the invention provides the following technical scheme:
a double-layer pressure touch signal acquisition method of a capacitive touch switch comprises an internal capacitor, a sensor capacitor, a charging power supply, a selection switch and an AD acquisition device, wherein the selection switch is respectively electrically connected with the internal capacitor, the sensor capacitor and the charging power supply, and the touch signal acquisition method comprises the following steps:
the acquisition of the upper touch SENSOR signal is started:
the first step is as follows: the charging power supply charges the internal capacitor, the charging power supply is cut off after the charging is finished, the internal capacitor charges the sensor capacitor, and the first AD sampling is carried out after the charging is finished to obtain a first AD sampling voltage value;
the second step is that: the charging power supply charges the sensor capacitor, the charging power supply is cut off after the charging is finished, the sensor capacitor charges the internal capacitor, and the second AD sampling is carried out after the charging is finished to obtain a second AD sampling voltage value;
and taking the difference value of the first AD sampling voltage value and the second AD sampling voltage value as final acquisition data.
The next is the acquisition of the lower layer pressure SENSOR signal:
the third step: the charging power supply charges the internal capacitor, the charging power supply is cut off after the charging is finished, the internal capacitor charges the sensor capacitor, and the third AD sampling is carried out after the charging is finished to obtain a third AD sampling voltage value;
the fourth step: the charging power supply charges the SENSOR capacitor (at the moment, the capacitance value not only has the capacitance value of the lower layer SENSOR, but also has the capacitance value generated by the upper layer pressure deformation), after the charging is finished, the charging power supply is cut off, the SENSOR capacitor charges the internal capacitor, and after the charging is finished, the fourth AD sampling is carried out to obtain the fourth AD sampling voltage value;
and taking the difference value of the third AD sampling voltage value and the fourth AD sampling voltage value as final acquisition data.
The internal capacitance is generally a capacitance on a control chip of the capacitive touch switch, and the sensor capacitance is a sensor capacitance of a touch sensor of the capacitive touch switch (i.e., a total capacitance outside a port of the control chip).
The invention has the beneficial effects that:
the touch signal acquisition method can increase the response speed of the touch key and improve the anti-interference capability of the touch key.
Drawings
FIG. 1 is a schematic diagram of a prior art cypress capacitive touch concept;
FIG. 2 is a schematic diagram of a freescale capacitive touch principle of the prior art;
FIG. 3 is a schematic diagram of the charging power supply of the present invention charging the internal capacitor;
FIG. 4 is a schematic diagram of charge sharing according to the present invention;
FIG. 5 is a schematic diagram of sampling after stable capacitance power sharing;
FIG. 6 is a graph of voltage versus time for a collection point of the present invention;
FIG. 7 is a schematic diagram showing the relationship between the voltage of the product measured actually and the time when the product is not triggered;
FIG. 8 is a schematic diagram showing the relationship between the voltage of the product and the time under trigger condition.
Detailed Description
The present invention is described in detail below by way of examples, which are intended to be illustrative only and not to be construed as limiting the scope of the invention, and those skilled in the art can make insubstantial modifications and adaptations of the invention based on the above disclosure.
As shown in fig. 3 to 8, the method for acquiring a double-layer pressure touch signal of a capacitive touch switch according to the present invention can be specifically divided into processing of an upper layer touch SENSOR and a lower layer pressure SENSOR:the method comprises the steps of primary charging, primary charge sharing, primary sampling, secondary charging, secondary charge sharing and secondary sampling. The following VcholdVoltage, V, representing internal capacitancerefRepresenting the voltage of the charging source, Q representing the total charge after charging is complete, CholdA capacitance representing an internal capacitance; csensorRepresenting the equivalent capacitance of the sensor part, VcsensorRepresenting the voltage of the sensor capacitance. The method comprises the following specific steps:
the first step, a primary charging step: as shown in FIG. 3, the charging power supply charges the internal capacitor, and after the charging is completed, V ischold=Vref；Q= Vref*Chold。
Second, a charge sharing step, as shown in FIG. 4, CholdCharge sharing to CsensorAccording to conservation of charge, Vcsensor*(Csensor+Chold)= Vref*CholdI.e. Vcsensor= Vref*Chold/(Csensor+Chold)。
Thirdly, a sampling step, as shown in fig. 5, is performed, after the capacitance and the electric quantity are shared stably, the AD value is sampled, and V is obtainedcsensorThe value is obtained.
Fourthly, secondary charging, namely charging the sensor capacitor by the power supply, and after charging is finished, charging by Vcsensor=Vref；Q= Vref* Csensor。
The fifth step, the second charge sharing step, the step CsensorCharge sharing to CholdAccording to conservation of charge, Vchold*(Csensor+Chold)= Vref*CsensorI.e. Vchold=Vref*Csensor/(Csensor+Chold)。
Sixthly, performing secondary sampling, namely performing AD value sampling after the electric quantity of the capacitor is shared stably to obtain VcholdThe value is obtained. According to the above step, VcsensorCan be represented by the waveform shown in fig. 6. After the AD sampling value is obtained, numerical calculation is carried out, specifically, the numerical calculation comprises the steps of numerical difference calculation and difference calculation, and A is carried out for the second timeD sampling obtained value VcholdMinus the first sampled value Vcsensor。
From the above analysis, it can be seen that: sampling voltage value and sampling capacitor CsensorIs related to the size of Vchold-Vcsensor=Vref*Csensor/(Csensor+Chold)- Vref*Chold/(Csensor+Chold)= Vref*(1-2* Chold/(Csensor+Chold) C is shown by the above formulasensorThe larger the difference is; and a single sampling value Vcsensor= Vref*Chold/(Csensor+Chold) In contrast, V is knownrefAnd CholdD (V) is obtained by derivation calculation under the condition of constantchold-Vcsensor)/d(csensor) =2Vref*Chold/2 (Csensor+Chold). Comparing single sampling: vchold=Vref*Csensor/(Csensor+Chold) D (V) is obtained by derivation calculationchold)/ d(csensor)= -Vref* Chold/2 (Csensor+Chold) From this derivation conclusion: the ratio of the value of the two-sample calculation to the change in capacitance is twice that of the single sample. Therefore, the touch signal acquisition method can increase the response speed of the touch keys and improve the anti-interference capability of the touch keys. Here, two charging voltage signals, i.e., two input signals equivalent to a differential circuit: setting the voltage obtained by AD sampling after the first charging as Vi1And for the second time is Vi2The difference modulus of the two signals is: vid=Vi1–Vi2The common mode value is: vsc= 1/2 (Vs1+ Vs2) Then the input voltage value signal is represented by differential and common mode inputs as: vs1=1/2Vid + Vsc，Vs2= -1/2Vid+ Vsc(ii) a Output signal Vo=Aod*Vid+Aoc*VicWhere A isodFor differential mode amplification, AocIs common mode amplification factor, and under the condition of ideal differential amplification circuit, the common mode amplification factor is 0, so that it can obtain high amplification efficiencyV in the ideal stateo=Aod*Vid+Aoc*Vic= Aod*Vid= Aod*（Vi1- Vi2) And here the differential mode magnification is 1, thus Vo=Vi1- Vi2. Assuming that the capacitor is disturbed during charging, the noise value is VxThe voltage after the first charging is Vi1=Vi+VxHere ViThe voltage value after the capacitor is charged is set to be not interfered, and the voltage value of the second charging is V when the interference is still existed during the second chargingi2=5-Vi+VxOutput V of the differential circuito=Vi1- Vi2=5+2 ViAs can be seen from the above equation, the process removes noise interference when the capacitor is charged.
Claims (1)
1. The utility model provides a capacitive touch switch's double-deck pressure touch signal acquisition method, this capacitive touch switch includes internal capacitance, SENSOR capacitance, charging source, select switch and AD collector, select switch is connected with internal capacitance, SENSOR capacitance and charging source electricity respectively, characterized in that, this touch signal acquisition method includes the collection to upper strata touch SENSOR signal and lower floor pressure SENSOR signal, and the collection to upper strata touch SENSOR signal and lower floor pressure SENSOR signal all includes the following step:
s1, primary charging step: the charging power supply charges the internal capacitor, and the charging power supply is cut off after the charging is finished;
s2, a charge sharing step: the internal capacitance charges the sensor capacitance;
s3, primary sampling step: performing first AD sampling after charging is completed to obtain a first sampling voltage value;
s4, secondary charging step: the sensor capacitor is charged by the charging power supply, and the charging power supply is cut off after the charging is finished;
s5, secondary charge sharing: the sensor capacitor charges the internal capacitor;
s6, secondary sampling: performing second AD sampling after charging is completed to obtain a second AD sampling voltage value; and the difference value of the first AD sampling voltage value and the second AD sampling voltage value is the final sampling data.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010661716.1A CN111813277A (en) | 2020-07-10 | 2020-07-10 | Double-layer pressure touch signal acquisition method of capacitive touch switch |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202010661716.1A CN111813277A (en) | 2020-07-10 | 2020-07-10 | Double-layer pressure touch signal acquisition method of capacitive touch switch |
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN201956996U (en) * | 2011-01-14 | 2011-08-31 | 苏州路之遥科技股份有限公司 | Capacitive sensing key |
| CN102902435A (en) * | 2011-07-26 | 2013-01-30 | 比亚迪股份有限公司 | Touch detection method and touch device |
| CN103049154A (en) * | 2012-11-21 | 2013-04-17 | 温州长江汽车电子有限公司 | Touch signal acquisition method for capacitive touch switch |
| US20150077389A1 (en) * | 2013-09-13 | 2015-03-19 | Apex Material Technology Corp. | Touch recognition method and system for a capacitive touch apparatus |
| US20190391704A1 (en) * | 2018-06-21 | 2019-12-26 | Shenzhen GOODIX Technology Co., Ltd. | Capacitance detection circuit, touch apparatus and terminal device |
-
2020
- 2020-07-10 CN CN202010661716.1A patent/CN111813277A/en not_active Withdrawn
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN201956996U (en) * | 2011-01-14 | 2011-08-31 | 苏州路之遥科技股份有限公司 | Capacitive sensing key |
| CN102902435A (en) * | 2011-07-26 | 2013-01-30 | 比亚迪股份有限公司 | Touch detection method and touch device |
| CN102902432A (en) * | 2011-07-26 | 2013-01-30 | 比亚迪股份有限公司 | Touch detection method and touch device |
| CN102902433A (en) * | 2011-07-26 | 2013-01-30 | 比亚迪股份有限公司 | Touch detection method and touch control device |
| CN103049154A (en) * | 2012-11-21 | 2013-04-17 | 温州长江汽车电子有限公司 | Touch signal acquisition method for capacitive touch switch |
| US20150077389A1 (en) * | 2013-09-13 | 2015-03-19 | Apex Material Technology Corp. | Touch recognition method and system for a capacitive touch apparatus |
| US20190391704A1 (en) * | 2018-06-21 | 2019-12-26 | Shenzhen GOODIX Technology Co., Ltd. | Capacitance detection circuit, touch apparatus and terminal device |
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Address after: No. 289 and 291, Binhai Second Road, Wenzhou Economic and Technological Development Zone, Wenzhou, Zhejiang 325000 Applicant after: Zhejiang Changjiang Automobile Electronics Co.,Ltd. Address before: No.289, Binhai 2nd Road, Wenzhou Economic and Technological Development Zone, Wenzhou City, Zhejiang Province 325000 Applicant before: WENZHOU CHANGJIANG AUTOMOBILE ELECTRONIC SYSTEM Co.,Ltd. |
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Application publication date: 20201023 |