WO2021213194A1

WO2021213194A1 - Touch sensing method and circuit, and electronic device

Info

Publication number: WO2021213194A1
Application number: PCT/CN2021/086413
Authority: WO
Inventors: 弓殷强; 杨洋
Original assignee: 深圳光峰科技股份有限公司
Priority date: 2020-04-22
Filing date: 2021-04-12
Publication date: 2021-10-28
Also published as: CN113541668A

Abstract

Embodiments of the present application provide a touch sensing method and circuit, and an electronic device. The method is applied to a control unit, and the control unit is connected to a touch key by means of a pin. The method comprises: first switching the pin between a first configuration and a second configuration by means of time division multiplexing, wherein in the first configuration, a parasitic capacitor of the touch key is charged to a preset voltage by means of the pin, and when the parasitic capacitor is charged to the preset voltage, the pin is switched to the second configuration; and in the second configuration, the parasitic capacitor is discharged by means of the pin, and when a preset time arrives, the current voltage of the parasitic capacitor is measured; and then determining the sensing state of the touch key according to the current voltage. The hardware cost required by the touch sensing method provided by the present application is lower.

Description

Touch sensing method, circuit and electronic equipment

Technical field

This application relates to the field of touch sensing, and in particular to a touch sensing method, circuit and electronic equipment.

Background technique

Because of the advantages of small size, good dustproof effect, and beautiful appearance, touch keys are widely used in household smart appliances. Common touch buttons include piezoelectric film buttons, resistive touch buttons, and capacitive touch buttons. Capacitive touch buttons are usually conductive electrodes with a certain shape. When a finger touches or approaches the electrodes, the distributed capacitance of the human body causes the capacitance of the electrodes to change. The chip detects the change in capacitance to determine whether the button is pressed.

However, the detection of the traditional capacitive touch button requires the use of a dedicated capacitance detection IC (Integrated Circuit, integrated circuit) chip, and the principle of the capacitance detection IC chip is complicated and the cost is relatively high. Therefore, those skilled in the art urgently need to improve the capacitive touch button.

Summary of the invention

In view of the above problems, embodiments of the present application provide a touch sensing method, circuit, and electronic device to solve the above technical problems.

The embodiments of this application are implemented using the following technical solutions:

In the first aspect, an embodiment of the present application provides a touch sensing method, which is applied to a control unit, and the control unit is connected to a touch button through a pin. The method includes: using time division multiplexing to place the pin between the first configuration and the second configuration Among them, in the first configuration, the parasitic capacitance formed by the touch button and the ground network is charged to a preset voltage through the pin, and when the parasitic capacitance is charged to the preset voltage, the pin is converted to the second configuration; In the second configuration, the parasitic capacitance is discharged through the pin, and when the preset time is reached, the current voltage of the parasitic capacitance is measured; and

Judge the sensing state of the touch button according to the current voltage.

In some embodiments, judging the sensing state of the touch button according to the current voltage includes calculating the difference between the current voltage and a reference voltage, where the reference voltage is a reference measurement value of the current voltage in the second configuration when the touch button is in an untouched state. ; And the difference is compared with the preset threshold, and the sensing state of the touch button is judged according to the comparison result.

In some embodiments, before calculating the difference between the current voltage and the reference voltage, it further includes filtering the current voltage; and calibrating the filtered current voltage.

In some embodiments, filtering the current voltage includes filtering the current voltage by any one or more of the average method, median method, recursive average method, recursive median method, and Kalman filter method. The voltage is filtered.

In some embodiments, calibrating the filtered current voltage includes using any one or more of the average method, the median method, the recursive average method, the recursive median method, and the Kalman filter method. The algorithm filters the reference voltage; performs multiple measurement experiments on the filtered reference voltage, and obtains the average value and standard deviation of the multiple measurement experiments; and normalizes the current voltage through the average value and standard deviation of the reference voltage.

In some embodiments, after performing multiple measurement tests on the filtered reference voltage, and obtaining the average value and standard deviation of the multiple measurement tests, it also includes performing multiple touch tests on the touch buttons and passing the average value of the reference voltage. And the standard deviation normalizes the voltage measurement value of each touch test; calculates the average value and standard deviation of multiple voltage measurement values after normalization; and determines according to the average value and standard deviation of multiple voltage measurement values Preset threshold.

In a second aspect, an embodiment of the present application also provides a touch sensing circuit, which includes a touch button, and a grounding network is arranged around the touch button, so that parasitic capacitance is generated between the touch button and the grounding network; The discharge circuit is connected to the touch button; and the control circuit includes pins, the pins are connected to the charge and discharge circuit, and the control circuit is configured to switch the pins between the first configuration and the second configuration through time division multiplexing; In the first configuration, the charging and discharging circuit is used to charge the parasitic capacitance of the touch button to a preset voltage through the pin, and when the parasitic capacitance is charged to the preset voltage, the pin is converted to the second configuration; in the second configuration, The charging and discharging circuit discharges the parasitic capacitance through the pin, and when the preset time is reached, the current voltage of the parasitic capacitance is measured; and the sensing state of the touch button is judged according to the current voltage.

In some embodiments, the ground network includes a bottom ground wire and a top ground wire, and the top ground wire is arranged around the touch button.

In some embodiments, the charging and discharging circuit includes a first diode, a second diode, a third diode, a fourth diode, a first resistor, a second resistor, and a first capacitor. The anode of the tube is connected to the cathode of the second diode, the cathode of the first diode is connected to one end of the first resistor, the anode of the second diode is connected to one end of the second resistor, and the other end of the first resistor is connected to the The other end of the second resistor is connected; the anode of the third diode is connected to the cathode of the fourth diode, the cathode of the third diode is connected between the second diode and the second resistor, the fourth diode The anode of the tube is connected between the first diode and the first resistor; the first capacitor is connected in parallel to both ends of the first resistor; the connection node of the first diode and the second diode is connected to the touch button, the third and second The connection node of the pole tube and the fourth diode is connected to the control circuit, and the connection node of the first resistor and the second resistor is grounded.

In a third aspect, an embodiment of the present application also provides an electronic device, which includes a device main body and the above-mentioned touch sensing circuit provided in the device main body.

The touch sensing method, circuit, and electronic equipment provided in the present application are applied to a control unit, and the control unit is connected to a touch button through a pin. Among them, in the first configuration, the parasitic capacitance of the touch button is charged to the preset voltage through the pin, and when the parasitic capacitance is charged to the preset voltage, the pin is converted to the second configuration; in the second configuration Under the configuration, the parasitic capacitance is discharged by the pin, and when the preset time is reached, the current voltage of the parasitic capacitance is measured; and then the sensing state of the touch button is judged according to the current voltage. In the above process, the implementation of this method does not need to rely on a dedicated capacitance detection IC chip, but uses the time-division multiplexing function in the control unit. Therefore, compared with the traditional touch detection scheme that requires a dedicated capacitance detection IC chip, The touch sensing method provided in this application requires a lower hardware cost.

These and other aspects of the application will be more concise and understandable in the description of the following embodiments.

Description of the drawings

In order to more clearly describe the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings that need to be used in the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

FIG. 1 shows a schematic flowchart of a touch sensing method provided by an embodiment of the present application.

Figure 2 shows a schematic diagram of the flow of step S110 in Figure 1

FIG. 3 shows a schematic flowchart of another touch sensing method provided by an embodiment of the present application.

FIG. 4 shows a schematic flowchart of step S220 in FIG. 3.

Figure 5 shows a schematic diagram of a sliding window.

FIG. 6 shows a schematic flowchart of step S230 in FIG. 3.

FIG. 7 shows a schematic flowchart of steps S260 to S280 provided in an embodiment of the present application.

FIG. 8 shows a schematic structural diagram of a touch sensing circuit provided by an embodiment of the present application.

FIG. 9 shows a schematic diagram of a ground network of a touch sensing circuit provided by an embodiment of the present application.

FIG. 10 shows a schematic diagram of one of the circuit structures of the charging and discharging circuit in FIG. 8.

FIG. 11 shows a schematic structural diagram of another touch sensing circuit provided by an embodiment of the present application.

Detailed ways

The embodiments of the present application are described in detail below. Examples of the embodiments are shown in the accompanying drawings, in which the same or similar reference numerals indicate the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary, and are only used to explain the present application, and cannot be understood as a limitation to the present application.

The buttons currently on the market are divided into traditional mechanical buttons and touch buttons. Mechanical keys are gradually abandoned due to shortcomings such as easy wear, complex installation, and environmental influences, while touch keys are gradually widely used in household smart appliances due to their small size, good dust-proof effect, and beautiful appearance.

Common touch buttons are divided into piezoelectric film touch buttons, resistive touch buttons, and capacitive touch buttons. Among them, the capacitive touch button is usually a conductive electrode of a certain shape. When a finger touches or approaches the electrode, the distributed capacitance of the human body causes the capacitance of the electrode to change. The chip detects the change in capacitance to determine whether the button is pressed. .

In order to solve the above technical problems, the inventors have proposed the touch sensing method, circuit and electronic device in the embodiments of the present application after long-term research. The touch sensing method is applied to the control unit, and the control unit is connected to the touch button through the pin. The method first switches the pin between the first configuration and the second configuration through time-division multiplexing; wherein, in the first configuration, through the lead The pin charges the parasitic capacitance formed by the touch button and the ground network to a preset voltage, and when the parasitic capacitance is charged to the preset voltage, the pin is converted to the second configuration; in the second configuration, the pin is connected to the parasitic capacitance Discharge, and when the preset time arrives, measure the current voltage of the parasitic capacitance; finally, judge the sensing state of the touch button based on the current voltage. In the above process, the implementation of this method does not need to rely on a dedicated capacitance detection IC chip, but uses the time-division multiplexing function in the control unit. Therefore, compared with the traditional touch detection scheme that requires a dedicated capacitance detection IC chip, The touch sensing method provided in this application requires a lower hardware cost.

In order to enable those skilled in the art to better understand the solutions of the present application, the technical solutions in the embodiments of the present application will be described clearly and completely in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative work shall fall within the protection scope of this application.

As shown in FIG. 1, FIG. 1 shows a schematic flowchart of a touch sensing method provided by an embodiment of the present application. The method can be applied to a control unit, and the control unit is connected to a touch button through a pin. The control unit is a microprocessor with pins with time division multiplexing function. In the embodiment of the present application, the control unit may be an MCU (Microcontroller Unit, Microcontroller Unit), and the MCU is connected to the touch button through an external pin. The touch sensing method may include the following steps:

S110: Switch the pin between the first configuration and the second configuration through time division multiplexing.

Time division multiplexing is an inherent function of the control unit. Its basic principle is to control multiple switches through the configuration register to connect the off-chip pins to different on-chip pins at different times, so that the off-chip pins have multiple functions, but Only one of these functions can be used at the same time. In this embodiment, the time division multiplexing function of the control unit is used to switch the off-chip pin connected to the touch button between the first configuration and the second configuration, so that the off-chip pin has two functions, so it can Save pin resources of the control unit.

Further, as shown in FIG. 2, step S110 may include the following steps S111 to S112.

Step S111: In the first configuration, the parasitic capacitance formed by the touch button and the ground network is charged to a preset voltage through the pin, and when the parasitic capacitance is charged to the preset voltage, the pin is converted to the second configuration.

In this embodiment, when the pins of the control unit are multiplexed to the first configuration, the off-chip pins connected to the touch buttons are connected to the on-chip GPIO (General-purpose input/output, general-purpose input/output) pins . The touch button has a parasitic capacitance to the ground. At this time, the parasitic capacitance of the touch button is charged through the GPIO pin until the voltage of the parasitic capacitance is charged to a preset voltage. When the voltage of the parasitic capacitor reaches the preset voltage, the off-chip pin is converted to the second configuration, that is, the off-chip pin is connected to another on-chip pin.

Step S112: In the second configuration, the parasitic capacitance is discharged through the pin, and when the preset time is reached, the current voltage of the parasitic capacitance is measured.

In this embodiment, when the pins of the control unit are multiplexed to the second configuration, the off-chip pins connected to the touch buttons are connected to the on-chip ADC (Analog-to-Digital Converter) pins. At this time, the parasitic capacitance of the touch button is discharged through the ADC pin, and the timing is started at the same time. When the preset time is reached, the current voltage of the parasitic capacitance is measured through the ADC pin on the chip. In the embodiment of the present application, the current voltage refers to the voltage to which the parasitic capacitance starts to discharge from the preset voltage and the discharge drops to after the preset time has elapsed. In this embodiment, the preset time can be flexibly designed according to specific working conditions and requirements, and its typical value can be set between tens of microseconds to hundreds of microseconds.

It is understandable that after the current voltage measurement is completed, the pins will be multiplexed into the first configuration to charge the parasitic capacitance in a new round. Specifically, the pin can be multiplexed into the first configuration after the voltage of the parasitic capacitance is discharged to zero; or the pin can be multiplexed into the first configuration when the voltage of the parasitic capacitance is not discharged to zero. In this embodiment, the pins are multiplexed between the first configuration and the second configuration at a certain frequency, and the frequency can be set freely.

S120: Determine the sensing state of the touch button according to the current voltage.

Due to the distributed capacitance of the human body, when the finger approaches or touches the touch button, the parasitic capacitance of the touch button will change, and the discharge speed of the parasitic capacitance will change. Then within the same preset time, the voltage discharged by the parasitic capacitance It also changes accordingly, so that the voltage dropped to after a preset period of time after the preset voltage starts to discharge is changed. Therefore, by measuring the current voltage of the parasitic capacitance when the preset time is reached, the current voltage change can be obtained, and then the sensing state of the touch button can be judged by the current voltage change.

The above-mentioned touch sensing method utilizes the time division multiplexing function of the control unit to realize the detection of the touch capacitance. It does not need to rely on the traditional capacitance detection dedicated chip, has a wide range of applicability, and can greatly reduce the hardware cost of capacitance detection.

In the touch sensing method provided by the embodiment of the application, the pin is first converted between the first configuration and the second configuration through time division multiplexing; wherein, in the first configuration, the parasitic capacitance of the touch button is charged to When the parasitic capacitance is charged to the preset voltage, the pin is converted to the second configuration; in the second configuration, the parasitic capacitance is discharged by the pin, and the parasitic capacitance is measured when the preset time is reached. The current voltage of the capacitor; finally, the sensing state of the touch button is judged according to the current voltage. In the above process, the implementation of this method does not need to rely on a dedicated capacitance detection IC chip, but uses the time-division multiplexing function in the control unit. Therefore, compared with the traditional touch detection scheme that requires a dedicated capacitance detection IC chip, The touch sensing method provided in this application requires a lower hardware cost.

As shown in FIG. 3, the present application also provides another touch sensing method 200. The touch sensing method 200 may include the following steps S210 to S250.

Step S210: Switch the pins between the first configuration and the second configuration through time division multiplexing.

The principle of step S210 is the same as the principle of step 110 described above, and will not be repeated here. Step S210 may also include the following steps S211 and S212. The principles of step S211 and step S212 are consistent with the principles of step S111 and step S112 described above.

Step S211: In the first configuration, the parasitic capacitance formed by the touch button and the ground network is charged to a preset voltage through the pin, and when the parasitic capacitance is charged to the preset voltage, the pin is converted to the second configuration.

Step S212: In the second configuration, the parasitic capacitance is discharged through the pin, and when the preset time is reached, the current voltage of the parasitic capacitance is measured.

In this embodiment, after obtaining the measured value of the current voltage, the following steps can be continued.

Step S220: Filter the current voltage.

In this embodiment, by filtering the current voltage, the system noise can be reduced and the measurement error can be reduced. The filtering algorithm used in this embodiment may be any of the average value method, the median method, the recursive median method, and the Kalman filter method. In fact, any filtering algorithm can be used as long as it can improve the signal-to-noise ratio of the system. Hereinafter, the present embodiment takes the recursive average method of m consecutive numbers as an example to explain the filtering of the current voltage. As shown in Fig. 4, Fig. 4 is a schematic flowchart of the recursive average filtering method. It includes steps S221 to S222:

Step S221: Set a sliding window, and calculate the arithmetic average of a fixed number of measurement data in the sliding window to output a piece of data.

As shown in Figure 5, Figure 5 is a schematic diagram of a sliding window. V1 to Vn represent voltage values sequentially measured through the ADC pins, and the sliding window can cover consecutive m measured voltage values. In this embodiment, the typical value of m can be 2-5. Further, the arithmetic mean value of m consecutive measured voltage values in the sliding window is used as one output data. Assuming that m is 3, the ADC pin continuously measures 3 measured voltage values V1～V3. At this time, calculate the arithmetic average value X1 of V1～V3. The arithmetic average value X1 is equivalent to the output result of one measurement.

Step S222: The sliding window is sequentially covered with the new measurement data, and the arithmetic average of the measurement data in the sliding window is sequentially calculated to output multiple data in sequence.

As shown in Figure 5, X1 to Xn represent data output in sequence, and each output data is the arithmetic average of m continuous measured voltage values during the sliding process of the sliding window. Specifically, as the new measured voltage value is generated, the sliding window slides forward in turn to cover the new measurement data. Since the amount of data contained in the sliding window is fixed, the new measurement data is added to the window at the same time as the old one. The measurement data exits the window. For example, the sliding window covers the measured voltage values V1～V3, and a data X1 is output at this time; as a new measured voltage value V4 is generated, the sliding window slides forward, so that the measured voltage value V4 is added to the window and the measured voltage value V1 exits the window At this time, the sliding window covers the measured voltage values V2 to V4 and outputs a data X2; as new measured voltage values are continuously generated, the sliding window slides and covers the new measured voltage values in turn, and sequentially outputs data X1 to Xn. Filtering the current voltage measurement value through the filtering algorithm can improve the stability of the system and the current voltage measurement accuracy.

Step S230: Calibrate the filtered current voltage.

In this embodiment, by calibrating the filtered current voltage, the measurement accuracy can be further improved. As shown in FIG. 6, FIG. 6 is a schematic diagram of the calibration process, which includes steps S231 to S233.

Step S231: filtering the reference voltage.

The reference voltage is the reference measurement value of the current voltage in the second configuration when the touch button is in the untouched state. When the touch button is not touched, measure the voltage of the touch button after the parasitic capacitance is discharged for a preset period of time in the second configuration by the method of the above steps S211 to S212. This voltage is also the reference voltage, and the reference voltage is also Indicates the reference value of the above current voltage when the touch button is not touched. In the actual measurement phase, the reference voltage can be used as a reference to make a judgment on the touch state of the touch button.

In this embodiment, the filtering algorithm of this embodiment can also be used to filter the reference voltage, that is, any one of the average value method, the median method, the recursive median method, and the Kalman filter method. And as long as the system signal-to-noise ratio can be improved, any filtering algorithm can be used. In some embodiments, the filtering algorithm used for the current voltage in step S220 may be the same as the filtering algorithm used for the reference voltage to ensure the accuracy of the measurement data.

Step S232: Perform multiple measurement experiments on the filtered reference voltage, and obtain the average value and standard deviation of the multiple measurement experiments.

In this implementation, multiple measurement tests are performed on the reference voltage, and after the above-mentioned filtering, N1 reference measurement data are obtained, and then the average μ and standard deviation σ of the N1 reference measurement data are calculated. The value of N1 can be flexibly selected according to the use scene and measurement speed, and its typical value can be between 10 and 10,000.

Step S233: normalize the current voltage according to the average value and standard deviation of the reference voltage.

In this embodiment, through the average μ and standard deviation μ of the N1 benchmark measurement data, the actual measurement data can be normalized in the subsequent actual measurement:

Among them, X is the measurement data of the current voltage during actual measurement.

Step S240: Calculate the difference between the current voltage and the reference voltage.

As mentioned above, the reference voltage represents the reference value of the current voltage when the touch button is not touched. The touch detection of the touch button is divided into two phases. One is the reference measurement phase, in which a reference value is obtained during the reference measurement phase; the other is the actual measurement phase, in which an actual value is obtained during the actual measurement phase. The amount of change can then determine whether the touch button is currently touched.

In this embodiment, the current voltage is also the actual measured value, and the difference between the current voltage and the reference voltage also represents the amount of change between the actual value and the reference value, and whether the touch button is currently touched is determined by the amount of change. Specifically, due to the distributed capacitance of the human body, when the touch button is touched, the distributed capacitance of the human body is equivalent to the parasitic capacitance of the touch button in parallel, so that the measured value of the parasitic capacitance increases. It is worth noting that the distributed capacitance of the human body is usually 30pF～50pF, and the design of the parasitic capacitance of the touch button should be equivalent to it. Since the charging and discharging speed of the capacitor is affected by the size of the capacitor, when the measured value of the parasitic capacitance increases, the discharge speed of the parasitic capacitance becomes slower, and the preset time is fixed, so when the preset time arrives, the parasitic capacitance The voltage will be higher than the voltage in the untouched state of the reference, and the measured voltage value will be greater at this time. Therefore, based on the difference between the current voltage and the reference voltage, it can be determined whether the touch button is currently touched.

It is worth mentioning that the size of the distributed capacitance connected in parallel to the parasitic capacitance in different human body or working conditions is different, which makes the charging and discharging speed of the parasitic capacitance in different working conditions inconsistent, which will generally bring about the system software control. Negative Effects. However, in this embodiment, since the parasitic capacitor is charged to a preset voltage during the charging phase, and the voltage value after the preset discharge time is measured during the discharge phase, the charging and discharging speed of the parasitic capacitor may be inconsistent even under each working condition. , Will not affect the measurement results, and will not affect the system software control required by this application.

Step S250: The difference is compared with a preset threshold, and the sensing state of the touch button is judged according to the comparison result.

The preset threshold is the touch activation threshold of the touch button. In this embodiment, the difference is compared with the preset threshold. If the difference is greater than the preset threshold, it indicates the amount of change between the current actual measurement value and the reference measurement value. The touch activation window was exceeded, and a valid touch occurred on the touch button. The amount of change within the preset threshold is the allowable range of error, and the error within this range may be caused by factors such as measurement and environment.

As shown in FIG. 7, in some embodiments, after step S233, the following steps S260 to S280 may be further included.

Step S260: Perform multiple touch tests on the touch button, and normalize the voltage measurement of each touch test by the average value and standard deviation of the reference voltage.

In this embodiment, after obtaining the average value μ and the standard deviation μ of the reference measurement data, the touch test can be continued on the touch button. After multiple touch tests, N2 test touch data can be obtained by measuring the voltage of the parasitic capacitance. Normalize the touch data for each test:

X1 is the test touch data. The value of N2 can be flexibly selected according to the use scenario and measurement speed, and its typical value can be between 10 and 10,000.

Step S270: Calculate the average value and standard deviation of the multiple voltage measurement values after normalization.

In this embodiment, the multiple measured values are the aforementioned test touch data, and the average value μ'and the standard deviation σ'of the N2 test touch data after the normalization process are calculated.

Step S280: Determine a preset threshold according to the average value and standard deviation of the multiple voltage measurement values.

In this embodiment, the average value μ'and standard deviation σ'of the N2 test touch data obtained from the touch test can reflect the stability of the actual measurement data in the actual measurement phase. The smaller the standard deviation σ', the actual measurement. The higher the stability of the data and the higher the stability of the measurement data, the greater the value of the preset threshold can be set.

Further, the preset threshold may affect the sensitivity of the touch button touch and the probability of false touch. The smaller the preset threshold, the higher the sensitivity of the touch and the greater the probability of false touch; the larger the preset threshold, the higher the stability of the touch. The typical value of the preset threshold is between 2～μ'-2σ'. The value range of the preset threshold can also evaluate the stability of the device, that is, the larger the value of μ'-2σ'-2, the stability of the device The better.

In the touch sensing method provided in this embodiment, the pins are first converted between the first configuration and the second configuration through time division multiplexing; wherein, in the first configuration, the parasitic formed by the touch button and the ground network is connected through the pins. The capacitor is charged to the preset voltage, and when the parasitic capacitance is charged to the preset voltage, the pin is converted to the second configuration; in the second configuration, the parasitic capacitance is discharged by the pin, and when the preset time arrives , Measure the current voltage of the parasitic capacitance; finally judge the sensing state of the touch button based on the current voltage. In the above process, the implementation of this method does not need to rely on a dedicated capacitance detection IC chip, but uses the time-division multiplexing function in the control unit. Therefore, compared with the traditional touch detection scheme that requires a dedicated capacitance detection IC chip, The touch sensing method provided in this application requires a lower hardware cost. And by filtering and calibrating the measured voltage, the accuracy of the measured data is higher.

As shown in FIG. 8, the present application also provides a touch sensing circuit 300, the touch sensing circuit 300 includes a touch button 310, a charging and discharging circuit 320 and a control circuit 330. Wherein, a grounding network is arranged around the touch button 310 to generate parasitic capacitance between the touch button and the grounding network. The control circuit 330 is connected to the touch button 310 through the charge and discharge circuit 320. The control circuit 330 includes a pin TK, the control circuit 330 is connected to the charging and discharging circuit 320 through the off-chip pin TK, and the control circuit 330 is configured to place the pin TK between the first configuration and the second configuration through time division multiplexing Conversion; wherein, in the first configuration, the charging and discharging circuit 320 charges the parasitic capacitance C0 of the touch button 310 to a preset voltage through the pin TK, and when the parasitic capacitance C0 is charged to the preset voltage, the pin TK is converted It is the second configuration; in the second configuration, the charging and discharging circuit 320 discharges the parasitic capacitance C0 through the pin TK, and when the preset time is reached, the current voltage of the parasitic capacitance C0 is measured; and the touch button is judged according to the current voltage 310's sensing state.

The touch button 310 can be a conductive electrode of any shape, and there is a parasitic capacitance C0 between the conductive electrode and the ground. The control circuit 130 is a Microcontroller Unit (MCU). Time division multiplexing is the original function of the MCU. Its basic principle is to control the multiplexer through the configuration register to connect the off-chip pins to different on-chip pins at different times, so that the off-chip pins have multiple functions. Only one of these functions can be used at the same time. In this embodiment, the time division multiplexing function of the MCU is used to switch the pin TK connected to the touch button 310 between the first configuration and the second configuration. The pin has two functions, so it can save the pin resources of the MCU.

When multiplexing to the first configuration, the control circuit 330 connects the pin TK to the on-chip GPIO (General-purpose input/output, general-purpose input/output) pin. There is a parasitic capacitance C0 between the pair of touch buttons 310 and the ground. At this time, the GPIO pin charges the parasitic capacitance C0 of the touch button 310 through the charging and discharging circuit until the voltage of the parasitic capacitance C0 is charged to a preset voltage. When the voltage of the parasitic capacitor C0 reaches the preset voltage, the TK pin is converted to the second configuration, that is, the pin TK is connected to another on-chip pin.

When multiplexing to the second configuration, the control circuit connects the pin TK to the on-chip ADC (Analog-to-Digital Converter) pin. At this time, the ADC pin discharges the parasitic capacitance C0 of the touch button 310 through the charging and discharging circuit 320, and starts timing. When the preset time is reached, the current voltage of the parasitic capacitance C0 is measured through the on-chip ADC pin. Due to the distributed capacitance of the human body, when a finger approaches or touches the touch button 310, the parasitic capacitance C0 of the touch button 310 will change, which in turn causes the discharge speed of the parasitic capacitance C0 to change. Then within the same preset time, the parasitic capacitance C0 The discharged voltage also changes accordingly, so that the voltage dropped to after a preset period of time after the preset voltage starts to discharge is changed. Therefore, the current voltage change of the parasitic capacitance C0 can be obtained by measuring the current voltage of the parasitic capacitance C0 when the preset time is reached, and then the sensing state of the touch button 310 can be judged by the current voltage change.

Specifically, a grounding network can be set around the touch button 310 to generate a parasitic capacitance C0 between the touch button 310 and the grounding network. The pin TK of the control circuit 330 is connected to the charging and discharging circuit 320 to charge and discharge the parasitic capacitance C0 through the charging and discharging circuit 320.

It is worth mentioning that in this embodiment, since the touch button 310 is surrounded by a grounding network, a parasitic capacitance C0 is generated between the touch button 310 and the grounding network, so that the touch sensing circuit 300 has a parasitic capacitance even under each operating condition. When the charging and discharging speeds of the system may be inconsistent, it will not affect the overall measurement result, thereby avoiding affecting the system software control required by this application.

As shown in FIG. 9, the ground network of the touch sensing circuit 300 includes a bottom bottom line 311 and a top bottom line 312. The bottom line 311 is laid on the back of the touch button, and the top ground line 312 is arranged around the touch button. With this configuration, sufficient parasitic capacitance can be generated between the touch button and the ground to meet the requirements of the touch sensing circuit 300, and the bottom ground 311 and the top ground 312 can shield EMI (Electromagnetic Interference) and enhance The stability of the system.

As shown in FIG. 10, FIG. 10 shows a schematic diagram of one structure of the charging and discharging circuit 120. The charging and discharging circuit 320 includes a first diode D1, a second diode D2, a third diode D3, a fourth diode D4, a first resistor R1, a second resistor R2, and a first capacitor C1. The anode of the diode D1 is connected to the cathode of the second diode D2, the cathode of the first diode D1 is connected to one end of the first resistor R1, and the anode of the second diode D2 is connected to one end of the second resistor R2 , The other end of the first resistor R1 is connected to the other end of the second resistor R2; the anode of the third diode D3 is connected to the cathode of the fourth diode D4, and the cathode of the third diode D3 is connected to the second diode. Between the pole tube D2 and the second resistor R2, the anode of the fourth diode D4 is connected between the first diode D1 and the first resistor R1; the first capacitor C1 is connected in parallel to both ends of the first resistor R1; The connection node of the diode D1 and the second diode D2 is connected to the touch button 310, the connection node of the third diode D3 and the fourth diode D4 is connected to the control circuit 330, the first resistor R1 and the second resistor The connection node of R2 is grounded. The touch sensing circuit provided by the embodiment of the present application is provided with a touch button; a charging and discharging circuit connected to the touch button; and a control circuit, including pins, which are connected to the charging and discharging circuit, and the control circuit is configured to: Use the pin to switch between the first configuration and the second configuration; among them, in the first configuration, the charge and discharge circuit is used to charge the parasitic capacitance of the touch button to a preset voltage through the pin, and the parasitic capacitance is charged to the preset voltage. When setting the voltage, the pin is converted to the second configuration; in the second configuration, the charging and discharging circuit discharges the parasitic capacitance through the pin, and when the preset time is reached, the current voltage of the parasitic capacitance is measured; and according to the current The voltage judges the sensing state of the touch button. The touch sensing circuit provided by the embodiments of the present application only uses the time division multiplexing function of the control circuit to realize the touch state sensing, and the circuit structure is simple, low in cost, and can be widely used.

As shown in FIG. 11, the embodiment of the present application also provides another touch sensing circuit 400, the touch sensing circuit 400 includes a circuit board 410 and the above-mentioned touch sensing circuit 300, the touch sensing circuit 300 is disposed on the circuit board 410 on.

The touch sensing circuit provided by the embodiments of the present application is provided with a touch button; a charging and discharging circuit connected to the touch button; and a control circuit including pins, which are connected to the charging and discharging circuit, and the control circuit is configured to: The pin is switched between the first configuration and the second configuration; wherein, in the first configuration, the charge and discharge circuit is used to charge the parasitic capacitance of the touch button to a preset voltage through the pin, and the parasitic capacitance is charged to the preset voltage When the time, the pin is converted to the second configuration; in the second configuration, the charging and discharging circuit is used to discharge the parasitic capacitance through the pin, and when the preset time is reached, the current voltage of the parasitic capacitance is measured; and the current voltage is judged The sensing state of the touch button. The touch sensing circuit provided by the embodiments of the present application only uses the time-division multiplexing function of the control circuit to realize the sensing of the touch state, and has a simple circuit structure, low cost, wide range of use, and can prevent electromagnetic interference.

An embodiment of the present application also provides an electronic device, which includes a device main body and the above-mentioned touch sensing circuit, wherein the touch sensing circuit is provided in the device main body.

In this embodiment, the electronic device may be, but is not limited to, a projector, a micro-projector, a smart TV, a smart phone, a tablet computer, an electronic paper book reader, and other smart home appliances.

The electronic device provided by the embodiment of the present application is provided with a touch button; a charging and discharging circuit connected to the touch button; and a control circuit, including pins, which are connected to the charging and discharging circuit, and the control circuit is configured to: Switch between the first configuration and the second configuration; wherein, in the first configuration, the charging and discharging circuit charges the parasitic capacitance of the touch button to a preset voltage through the pin, and when the parasitic capacitance is charged to the preset voltage, Convert the pin to the second configuration; in the second configuration, the charging and discharging circuit discharges the parasitic capacitance through the pin, and when the preset time is reached, the current voltage of the parasitic capacitance is measured; and the touch button is judged according to the current voltage The sensing state. The touch sensing circuit of the electronic device provided by the embodiments of the present application only uses the time-division multiplexing function of the control circuit to realize the touch state sensing. The circuit structure is simple, the cost is low, the use range is wide, and electromagnetic interference can be prevented.

The above are only the preferred embodiments of the application, and do not limit the application in any form. Although the application has been disclosed as above in the preferred embodiments, it is not intended to limit the application. Anyone skilled in the art, Without departing from the scope of the technical solution of the present application, when the technical content disclosed above can be used to make slight changes or modification into equivalent embodiments with equivalent changes, provided that the content of the technical solution of the present application is not deviated from the technical content of the present application, the technical essence of the present application Any introduction modifications, equivalent changes and modifications made in the above embodiments still fall within the scope of the technical solution of the present application.

Claims

A touch sensing method, applied to a control unit, the control unit is connected to a touch button through a pin, and is characterized in that it includes:

Switching the pin between the first configuration and the second configuration through time division multiplexing;

Wherein, in the first configuration, the parasitic capacitance formed by the touch button and the ground network is charged to a preset voltage through the pin, and when the parasitic capacitance is charged to the preset voltage, the lead The feet are converted to the second configuration;

In the second configuration, discharge the parasitic capacitance through the pin, and measure the current voltage of the parasitic capacitance when a preset time is reached; and

The sensing state of the touch button is determined according to the current voltage.
5. The touch sensing method of claim 1, wherein the judging the sensing state of the touch button according to the current voltage comprises:

Calculating the difference between the current voltage and a reference voltage, where the reference voltage is a reference measurement value of the current voltage in the second configuration when the touch button is in an untouched state; and

The difference value is compared with a preset threshold value, and the sensing state of the touch button is judged according to the comparison result.
3. The touch sensing method of claim 2, wherein before calculating the difference between the current voltage and the reference voltage, the method further comprises:

Filtering the current voltage; and

Calibrate the filtered current voltage.
The touch sensing method of claim 3, wherein the filtering the current voltage comprises:

The current voltage is filtered by any one or more of the average method, the median method, the recursive average method, the recursive median method, and the Kalman filter method.
8. The touch sensing method of claim 3, wherein the calibrating the filtered current voltage comprises:

Filtering the reference voltage by any one or more of an average value method, a median method, a recursive average method, a recursive median method, and a Kalman filter method;

Perform multiple measurement tests on the filtered reference voltage, and obtain the average value and standard deviation of the multiple measurement tests; and

The current voltage is normalized by the average value and standard deviation of the reference voltage.
7. The touch sensing method of claim 5, wherein after performing multiple measurement experiments on the filtered reference voltage and obtaining the average value and standard deviation of the multiple measurement experiments, the method further comprises:

Performing multiple touch tests on the touch button, and normalizing the voltage measurement value of each touch test by the average value and standard deviation of the reference voltage;

Calculate the average value and standard deviation of multiple voltage measurements after normalization; and

The preset threshold value is determined according to the average value and standard deviation of a plurality of voltage measurement values.
A touch sensing circuit, characterized in that it comprises:

A touch button, a grounding network is arranged around the touch button, so that a parasitic capacitance is generated between the touch button and the grounding network;

A charging and discharging circuit, connected to the touch button; and

The control circuit includes a pin connected to the charging and discharging circuit, and the control circuit is configured to:

Switching the pin between the first configuration and the second configuration through time division multiplexing;

Wherein, in the first configuration, the charging and discharging circuit is used to charge the parasitic capacitance of the touch button to a preset voltage through the pin, and when the parasitic capacitance is charged to the preset voltage, the charge and discharge circuit is charged to the preset voltage. The pin is converted to the second configuration;

In the second configuration, the charging and discharging circuit is used to discharge the parasitic capacitance through the pin, and when a preset time is reached, the current voltage of the parasitic capacitance is measured; and

The sensing state of the touch button is determined according to the current voltage.
8. The touch sensing circuit of claim 7, wherein the ground network comprises a bottom ground wire and a top ground wire, and the top ground wire is arranged around the touch button.
The touch sensing circuit of claim 7, wherein the charging and discharging circuit comprises a first diode, a second diode, a third diode, a fourth diode, a first resistor, A second resistor and a first capacitor, the anode of the first diode is connected to the cathode of the second diode, the cathode of the first diode is connected to one end of the first resistor, the The anode of the second diode is connected to one end of the second resistor, the other end of the first resistor is connected to the other end of the second resistor; the anode of the third diode is connected to the first resistor The cathode of the four diodes, the cathode of the third diode is connected between the second diode and the second resistor, and the anode of the fourth diode is connected to the first and second resistors. Between the pole tube and the first resistor; the first capacitor is connected in parallel across the first resistor; the connection node of the first diode and the second diode is connected to the touch button A connection node of the third diode and the fourth diode is connected to the control circuit, and a connection node of the first resistor and the second resistor is grounded.
An electronic device, characterized by comprising a device main body and the touch sensing circuit according to any one of claims 7 to 9 provided in the device main body.