CN118694355B - Multichannel touch detection system and detection method - Google Patents

一种多通道触摸检测系统和检测方法，所述检测方法包括如下步骤：步骤1.构建电容值检测输出函数,步骤2.对各个时间片设置采样频点和充电电流，对外部电容变化进行检测，得到输出频点；步骤3.将输出频点和对应的充电电流输入电容值检测输出函数，得到电容检测原始值，并对每个检测循环周期中的全部电容检测原始值进行筛选，得到优选电容值；步骤4.根据优选电容值进行判断是否发生触摸。本发明通过模式设置调节采样频点和检测频点，并预先获取电容值检测输出函数，能够有效避免外界电磁信号对电容检测干扰，并通过直接调用电容值检测输出函数提高了检测速度。

A multi-channel touch detection system and detection method, the detection method comprising the following steps: step 1. constructing a capacitance value detection output function, step 2. setting a sampling frequency and a charging current for each time slice, detecting changes in external capacitance, and obtaining an output frequency; step 3. inputting the output frequency and the corresponding charging current into the capacitance value detection output function to obtain a capacitance detection original value, and screening all capacitance detection original values in each detection cycle to obtain a preferred capacitance value; step 4. judging whether a touch occurs according to the preferred capacitance value. The present invention adjusts the sampling frequency and the detection frequency through mode setting, and obtains the capacitance value detection output function in advance, which can effectively avoid interference of external electromagnetic signals on capacitance detection, and improves the detection speed by directly calling the capacitance value detection output function.

Multichannel touch detection system and detection method

Technical Field

The invention belongs to the technical field of electronic circuits, relates to a capacitive touch detection circuit, and in particular relates to a multichannel touch detection system and a multichannel touch detection method.

Background

In the trend of popularization of intelligent electrical appliances, a capacitive touch key is an excellent choice for a scheme with quick response and low cost. The principle of capacitive touch is that when a finger approaches a sensing electrode, the capacitance of the sensing electrode is increased, the capacitance is positively correlated with the dielectric constant of a charge conduction medium, the touch area of the finger and the like, and whether a touch action exists is judged by detecting the change of a capacitance value through a circuit. Common capacitance detection circuits include charge transfer capacitance acquisition circuits, relaxation oscillation circuits, sigma-delta capacitance detection circuits, and the like.

Capacitive touch detection is easily affected by factors such as electricity, magnetism, heat and the like, so that stable operation of touch response under different working conditions becomes difficult. The charge transfer capacitor acquisition circuit has a complex structure, can accurately control the charge transfer process and obtain higher capacitor detection precision, but has relatively higher cost and complex control. Sigma-delta modulation technology is adopted in the Sigma-delta detection circuit, signals with high signal to noise ratio are output, the structure is complex, and the cost is high. The relaxation oscillation circuit is a self-oscillation circuit, has the advantages of simple structure, high precision and cost, but the signal processing is complex. The relaxation oscillation circuit has the circuit characteristic that the output frequency point is reduced along with the increase of the detection capacitance. By detecting the change of the capacitance value of the finger approaching the capacitive touch device, whether the finger has a series of behaviors such as approaching the detection device or touching the detection device can be judged.

In the chinese patent application No. 201511020533.7, entitled "a method for improving electromagnetic interference resistance of capacitive touch key", it is proposed to use multiple switching frequency points, determine whether the slope of a key value under a key judgment frequency point exceeds a set range to determine whether electromagnetic interference is received, and perform key judgment by using other undisturbed frequency points to make touch detection more stable. However, this method only processes data after multi-frequency sampling at the acquisition end, which has limited interference suppression capability.

In the chinese patent application No. 201410283861.5, entitled "anti-interference method and apparatus for capacitive touch sensor" is provided, in which whether there is a touch is determined by determining whether there is noise in the collected capacitive raw data, and using the capacitive raw data without noise as a reference value of the capacitor, but only the noise-filtered signal cannot suppress periodic interference, and once there is a strong interference signal, the touch behavior cannot be identified.

Disclosure of Invention

Aiming at the defects in the prior art, the invention discloses a multichannel touch detection system and a multichannel touch detection method.

The invention discloses a multi-channel touch detection method, which comprises the following steps:

Step 1, constructing a capacitance value detection output function, which specifically comprises the following steps:

step 11, configuring detection cycle periods, wherein each detection cycle period comprises a plurality of time slices, and different charging currents are set for each time slice through a mode driving controller so that a multi-driving relaxation oscillation circuit outputs detection frequency points with different frequencies;

Step 12, the data sampler configures different detection frequencies for different time slices in the detection cycle period;

Step 13, setting different detection frequency points and sampling frequency points for each time slice in the detection cycle period in step 11 and step 12, and repeating the detection cycle period to perform continuous capacitance detection;

detecting each time slice by adopting different sampling frequency points to obtain different capacitance detection original values and corresponding output frequency points;

Step 14, replacing the detected capacitor, repeating the step 13, and constructing a capacitor value detection output function F (k 1, k 2) by using the output frequency points of each time slice and the capacitor detection original value obtained in the step 13 and the charging current corresponding to the time slice, wherein k1 represents the charging current, k2 represents the output frequency point, and F represents the corresponding capacitor detection original value;

Step 2, after obtaining a capacitance value detection output function F (k 1, k 2), setting sampling frequency points and charging current for each time slice according to the step 11 and the step 12, and detecting external capacitance changes to obtain output frequency points;

Step 3, inputting the output frequency point and the corresponding charging current into a capacitance value detection output function F (k 1, k 2) to obtain a capacitance detection original value, and screening all capacitance detection original values in each detection cycle period to obtain a preferred capacitance value;

and step 4, judging whether touch occurs or not according to the optimal capacitance value.

Preferably, the screening method in step 3 specifically includes the following steps:

step 31, screening out the interfered capacitance values by a preferential filter from a plurality of capacitance detection original values in the same detection cycle period, and outputting a primary screening capacitance value, wherein the preferential filter is a variance filter or a multi-order median filter;

step 32, taking the primary screening capacitance value X _n as an excitation input IIR filter for further smoothing treatment so as to inhibit periodic interference, wherein the subscript n represents different primary screening capacitance values;

an IIR filter is implemented as follows:

Y _n=(1-L)* Y_n-1+L*X_n (equation 1)

Y _n is a preferred capacitance value of the preliminary screening capacitance value X _n after being input into the IIR filter, when n=1, Y ₀ takes an electrical constant value, and L is a filter parameter;

step 33, performing second-order differential error calculation on the optimal capacitance value output by the IIR filter;

The formula for calculating the preferred capacitance value second order differential value FD is:

Fd=y _j+k+Y_j-k-2*Y_j (formula 2)

And solving a second-order differential value FD, wherein k is a set second-order differential offset length, and Y _j+k、Y_j-k、Y_j respectively represents the optimal capacitance values of the j+k, the j-k and the j-th primary screening capacitance values after being input into an IIR filter.

An error detection threshold is set, and when FD is greater than the error detection threshold, the corresponding preferred capacitance value is discarded.

Preferably, in the step 33, the preferred capacitance values output by the IIR filter are stored in the large-bit-width data memory in such a manner that the preferred capacitance values are sequentially stored from the least significant bit of the first channel of the memory in time sequence, the data already stored at each time of storage is shifted from the least significant bit to the most significant bit, the preferred capacitance value is divided from the most significant bit when the channel is full, and the number of stored preferred capacitance values of each channel is 2k+1, k is the set second-order differential offset length.

Preferably, the capacitance detection output function F (k 1, k 2) obtained in the step 1 is a capacitance lookup table, an index one of the capacitance lookup table is a charging current of the relaxation oscillator, an index two is an output frequency point in a circuit detection range, and a lookup result is a capacitance detection original value.

Preferably, in the step 4,

When the difference value between the optimal capacitance value and the baseline value serving as a comparison reference is larger than a target finger threshold value and the duration time is larger than a time threshold value T1, touch is considered to be generated, otherwise no touch is considered to be generated;

if the touch is judged not to occur, the obtained optimal capacitance value is utilized to update the baseline;

the modes of the baseline updating include a normal following mode and an abnormal following mode;

If the capacitance changes but the capacitance value is not increased, performing an abnormal following mode, otherwise, entering a common following mode;

in normal following mode, if:

Pre-update baseline value + target finger threshold > preferred capacitance value > pre-update baseline value,

Then update is performed in the following way

Post-update baseline value = pre-update baseline value + baseline value update step size,

If:

preferred capacitance value < baseline before update value:

Post-update baseline value = pre-update baseline value-baseline value update step size;

otherwise not updated;

In the anomaly following mode, if:

preferably the capacitance value < pre-update baseline value-baseline anomaly threshold value,

The initial baseline value is re-adopted, otherwise not updated.

Preferably, in the step 4, when the difference between the preferred capacitance value and the baseline value as the reference of comparison is greater than the target finger threshold value and the duration is greater than the time threshold T1, a touch is considered to occur, otherwise no touch is considered to occur;

If a touch occurs, a sensitivity adjustment is performed, specifically:

Setting a high activity sensitivity threshold VTH and a low activity sensitivity threshold VTL, wherein an interval between the high activity sensitivity threshold VTH and the low activity sensitivity threshold VTL is defined as an activity sensitivity threshold interval;

when touching occurs, the preferred capacitance value is higher than the high activity sensitivity threshold VTH, and the set target finger threshold is not in the activity sensitivity threshold interval, and the target finger threshold is automatically adjusted to be in the activity sensitivity threshold interval;

The magnitude of the capacitance value is preferably above the low activity sensitivity threshold VTL, but below the high activity sensitivity threshold VTH, and the target finger threshold is in the activity sensitivity threshold interval, at which time the target finger threshold is adjusted to be less than the low activity sensitivity threshold VTL.

Preferably, the target finger threshold is adjusted by adjusting an active finger threshold adjustment step length in each detection cycle according to the set active finger threshold adjustment step length until the adjustment target is reached.

The multi-channel touch detection system comprises a configuration register, a clock frequency divider, a mode driving controller, a data sampler, a data preprocessor, a base line follower and a touch judgment device, wherein the configuration register, the clock frequency divider, the mode driving controller, the data sampler, the base line follower and the touch judgment device are used for executing the multi-channel touch detection method;

The configuration register is used for receiving an external command and configuring other modules of the detection system;

The clock divider provides a corresponding clock for the detection system;

The mode driving controller is connected with the multi-channel relaxation oscillator and used for adjusting the charging current and the detection frequency point of the multi-channel relaxation oscillator;

The data sampler is connected with the multi-channel relaxation oscillator and is used for setting different sampling frequencies;

the data preprocessor is used for processing the sampling signals output by the multi-channel relaxation oscillator and screening out the optimal capacitance value;

the baseline follower is used for setting and adjusting a baseline;

and the touch judgment device is used for adjusting the sensitivity and outputting a judgment touch result.

Preferably, the data preprocessor comprises a preferred filter, an IIR filter and a second-order differential difference calculator which are sequentially connected, wherein the preferred filter is a variance filter or a multi-order median filter.

Preferably, the data preprocessor further comprises a multi-channel large bit width data memory connected between the IIR filter and the second order differential difference calculator.

According to the invention, the sampling frequency point and the detection frequency point are adjusted through mode setting, and the capacitance value detection output function is obtained in advance, so that the interference of external electromagnetic signals on capacitance detection can be effectively avoided, and the detection speed is improved by directly calling the capacitance value detection output function.

Drawings

FIG. 1 is a schematic diagram of a multi-channel touch detection system according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of an embodiment of a multi-channel touch detection method according to the present invention in which charging current, sampling frequency points, and detection frequency points are set;

FIG. 3 is a schematic diagram of a data preprocessor according to an embodiment of the invention;

FIG. 4 is a schematic diagram of a specific data storage mode of the large bit width data memory according to the present invention;

FIG. 5 is a schematic diagram of an embodiment of the sensitivity adjustment according to the present invention.

Detailed Description

In order to overcome the defects of the scheme when a capacitive touch circuit is interfered by various interference sources in a complex environment, including but not limited to circuit noise floor, external conduction or radio frequency interference, electric fast transient and alternating current power supply interference, the invention discloses a multichannel touch detection system and a multichannel touch detection method.

For a more intuitive and clear description of the technical solution of the present invention, the following detailed description will be given with reference to specific embodiments and example drawings.

The multi-channel touch detection system comprises a configuration register, a clock frequency divider, a mode driving controller, a data sampler, a data preprocessor, a base line follower and a touch judgment device aiming at a multi-channel relaxation oscillator with adjustable sampling frequency and detection frequency, wherein the configuration register is connected with an external bus matrix, and provides software configuration for the system through the bus matrix, as shown in figure 1.

The clock divider provides corresponding clocks for the system to meet different sampling clock requirements and low power consumption clock requirements.

The mode driving controller is connected with the multi-channel relaxation oscillator and used for adjusting the charging current and the detection frequency point of the multi-channel relaxation oscillator. The mode driving controller inputs different digital signals to the multi-channel relaxation oscillator to realize the adjustment of charging current and detection frequency point.

The data sampler is connected with the multi-channel relaxation oscillator and is used for setting different sampling frequencies. The data preprocessor processes the sampling signals output by the multichannel relaxation oscillator, and preferably screens out the capacitance value after interference is removed;

one specific implementation mode of the data preprocessing comprises a preferential filter, an IIR filter and a second-order differential difference calculator which are connected in sequence;

one specific workflow of the data preprocessor includes:

1. A plurality of sets of capacitance measurement original values are input,

2. Obtaining a capacitance detection output function f (n) according to the output characteristics of the relaxation oscillator

3. Multiple groups of capacitance measurement original values are used as excitation input capacitance detection output functions to obtain multiple detection capacitance values of the current capacitance

4. Multiple detection capacitance values are input into the preferential filter to obtain a preferential capacitance value without distortion

5. Preferably, the capacitance value is input into an IIR filter for IIR filtering;

6. And selecting a plurality of groups of optimal capacitance data of each channel to input the optimal capacitance data into a second-order differential difference calculator for second-order differential detection so as to judge errors. And if errors exist, the driving strategy in the mode driver and the sampling strategy in the data sampler are changed, and if errors exist, the errors are output to the baseline follower.

And the touch judgment device is used for adjusting the sensitivity and outputting a judgment touch result. The two sensitivity configuration modes of fixed sensitivity and movable sensitivity can be adopted, namely, the sensitivity adjustment in the environment change is increased, the touch sensitivity can be improved, and the response is stable.

Before detection, a capacitance detection output function is firstly constructed, and output detection frequency points under different conductors and different charging currents are obtained. The specific steps for constructing the capacitance value detection output function are as follows:

step 11, configuring detection cycle periods, wherein each detection cycle period comprises a plurality of time slices, and different charging currents are set for each time slice through a mode driving controller so that a multi-driving relaxation oscillation circuit outputs detection frequency points with different frequencies;

In the detection of the capacitor, when the charge current I1 is configured by the mode driving controller for the same input capacitance value, the relaxation oscillation circuit outputs detection current through an internal constant current source, controls the corresponding output detection frequency point f1, outputs the detection frequency point f2 when the charge current I2 is configured, and the like, and corresponds to the output detection frequency point fn when the charge current In is configured by the mode driving controller. After the capacitors with the same size are applied, the multi-drive relaxation oscillation circuit correspondingly outputs detection frequency points with different frequencies under different charging currents.

For single-channel detection of the multi-drive relaxation oscillation circuit, a finger contacts and leaves the touch detection circuit in a millisecond time range, at this time, the mode drive controller sets the time length of time slices, and changes in capacitance values are detected by configuring different detection modes in each time slice.

As shown In fig. 2, a charging current I1 is configured In a time slice t1 to obtain a detection frequency point f1 of the finger capacitance detection output, a charging current I3 is configured In a time slice t5 to obtain an output detection frequency point f3 of the same capacitance under different driving forces, and similarly, a charging current In is configured In a time slice tx to obtain a detection frequency point fn.

Research shows that if the frequency of an external electromagnetic input interference source (usually 150 KHz-80 MHz) is near a detection frequency point, serious interference can be generated on an output signal. However, since the multi-driven relaxation oscillator outputs detection frequency points with different characteristics to the current detection capacitance value according to different charging currents, other detection frequency points which are not near the frequency point of the interference source are greatly reduced in the degree of being influenced by the interference source. Furthermore, the data sampling circuit is also affected by interference when sampling the detection frequency points, so that the suppression effect of sampling the detection frequency points by implementing various sampling strategies on interference is obvious in the divided capacitance detection time slices.

Step 12, the data sampler configures different detection frequencies for different time slices in the detection cycle period;

As shown in fig. 2, in the time slices t1 and t2, the set charging currents are the same, so that the same detection frequency point fs1 is sampled;

However, the sampling frequency points of different time slices are different, the sampling frequency point fs1 is used for data sampling in the time slice t1 to obtain a capacitance detection original value c1, the sampling frequency point fs2 is used for data sampling in the time slice t2 to obtain a capacitance detection original value c2, and the like, the sampling frequency point fsm can be used for detecting the different frequency points of the same capacitor in the time slice tx to obtain the capacitance detection original value cm, so that the influence of an interference source on signals in the transmission process is further reduced.

The setting of the sampling frequency point is based on a general sampling rule, so that the interference to the sampling frequency point is minimized on the premise of meeting the over-sampling requirement.

Setting a sampling cycle period, wherein the cycle period comprises a plurality of time slices, the detection frequency point and the sampling frequency point of each time slice are set according to the requirement,

When a conductor such as a finger approaches to and leaves from the touch detection circuit, the capacitance value detected by the touch detection circuit can be continuously changed due to the induction action of the conductor, and the detection of the relatively slowly-changed capacitance at different detection frequency points and sampling frequency points can be realized in a cycle period by setting the length of a time slice, for example, 5 to 10 microseconds for the normal millisecond-level human body touch time.

Step 13, setting different detection frequency points and sampling frequency points for each time slice in the detection cycle period in step 11 and step 12, and repeating the detection cycle period to perform continuous capacitance detection;

detecting each time slice by adopting different sampling frequency points to obtain different capacitance detection original values and corresponding output frequency points;

Step 14, replacing the detected capacitor, repeating the step 13, and constructing a capacitor value detection output function F (k 1, k 2) by using the output frequency points and the capacitor detection original values of each time slice obtained in the step 13 and the charging current corresponding to the time slice, wherein k1 represents the charging current, k2 represents the output frequency points, F represents the corresponding capacitor detection original values, and the capacitor value detection output function F (k 1, k 2) outputs the corresponding capacitor detection original values according to the input values of k1 and k 2;

The present invention has obtained sets of capacitance detection raw values at nearly the same capacitance value, including both disturbed and undisturbed capacitance detection raw values, through different combinations of strategies during the entire time period that a finger touches the touch sensor.

The accurate capacitance of the variable capacitance value in the detection range is applied to the multi-drive relaxation oscillation circuit, capacitance detection is carried out, and the output frequency point characteristic data of the accurate capacitance of the circuit with the known capacitance value under different detection currents can be obtained after different detection currents are traversed.

One specific implementation of the capacitance detection output function F (k 1, k 2) is to construct a capacitance lookup table limited in the detection range by using the feature data, wherein the first index of the capacitance lookup table is the charging current of the relaxation oscillator, the second index is the output frequency point in the circuit detection range, and the lookup result is the original capacitance detection value.

The capacitance lookup table can be used as the capacitance detection output function F (k 1, k 2).

Step 2, after obtaining a capacitance value detection output function F (k 1, k 2), setting sampling frequency points and charging current for each time slice according to the step 11 and the step 12, and detecting external capacitance changes to obtain output frequency points;

step 3, inputting the output frequency point and the corresponding charging current into a capacitance value detection output function F (k 1, k 2) to obtain a capacitance detection original value;

the sampled data may be further processed in step 3 using a data preprocessor. Sample data processing in a data preprocessor involves the following process, as shown in fig. 3:

step 31, screening out the interfered capacitance values by a preferential filter which can be a device for effectively filtering interference, such as a variance filter or a multi-order median filter, and outputting a primary screening capacitance value;

The filtering strategy in the step can be variance filtering, calculating variances of all capacitance detection original values in the same detection cycle period, and reserving one with the smallest variance value as a preferred capacitance value, or adopting median filtering, traversing data through a detection window, and taking the intermediate value in the detection window as output data.

Step 32, the primary screening capacitance value X _n is used as an excitation input IIR (infinite impulse response Infinite Impulse Response) filter to be further processed in a smoothing mode so as to inhibit periodic interference, the subscript n represents different primary screening capacitance values, and n actually represents preferred capacitance values obtained in different cycle detection periods;

an IIR filter is implemented as follows.

Y _n=(1-L)* Y_n-1+L*X_n (equation 1)

Y _n is the output of the initial screening capacitance value X _n after input to the IIR filter, and for n=1, Y ₀ is any constant value, and L is the filter parameter.

Step 33, storing the data Y output by the IIR filter in a large bit width data memory in a mode of fig. 4 so as to perform IIR filtering and second-order differential error detection calculation;

In the embodiment shown in fig. 4, the large-bit-width data memory is a 9-window data storage space, the first detected preferred capacitance value Y ₁ is stored from the least significant bit LSB of the channel 0 address, when the second detection data Y ₂ is valid, Y ₁ is shifted to the left by a corresponding data bit width of the preferred capacitance value, so that a data bit width corresponding to the preferred capacitance value is left from the least significant bit, then the second detected preferred capacitance Y ₂ is stored in the least significant bit LSB, and similarly, when all the significant bits of the channel 0 address store the capacitance values, the 9 detected preferred capacitance values are stored in the memory. The preferred capacitance value for the first detection near the MSB of the most significant bit and the preferred capacitance value for the 9 th detection near the LSB of the least significant bit. When the new data of the tenth input preferred capacitance value continues to be valid, the first preferred capacitance value is shifted out of the data in the MSB of the most significant bit, the new data is shifted in from the LSB of the least significant bit, and 9 preferred capacitance values, Y _j、Y_j+1、…Y_j+8, are stored in time sequence for channel j.

The large bit width data memory can realize simultaneous detection of multiple groups of priority capacitance values by arranging multiple channels, namely, each channel corresponds to a touch scene with different time or space, each group of priority capacitance values can aim at a multi-channel relaxation oscillator of one touch point, or the multiple channels detect the same multi-channel relaxation oscillator which outputs multiple groups of capacitance values in a time division multiplexing mode, so that the application scene of the invention is widened.

In order to further detect whether the capacitance value has errors, the invention adopts a second-order differentiator to detect the errors, if no errors occur, the strategy of the mode driving controller and the data sampler is not changed, and if errors occur, the output control signals of the mode driving controller and the data sampler are changed, and the detection frequency and the sampling frequency are changed to stagger the interference interval so as to acquire more accurate capacitance data. The second order difference formula is:

Fd=y _j+k+Y_j-k-2*Y_j (formula 2)

In the formula 2, inputting the preferential capacitance value into the formula 2 to solve the two-order differential value FD, k= (WD-1)/2, wherein WD is the number of windows of the large-bit-width data memory;

For example, for nine preferred capacitance values Y ₁ to Y ₉ of channel 1 in the data of FIG. 4, the data to the left of the Y ₅ point is left offset data with gradually increasing offset values, and the data to the right of the Y ₅ point is right offset data with gradually increasing offset values, with the center Y ₅ as the center point position for the second order differential detection. And selecting an offset point of the second-order differential detection through a formula 2 and a configuration register, and calculating to obtain an error detection value which is used for representing the disturbed degree of the capacitor. When the value is larger than the set error detection threshold value, whether the error exists in the current preferred capacitor can be judged.

And finally, sending the optimal capacitance value with the second-order difference value not larger than the error detection threshold value to the baseline follower of each channel.

And step 4, judging whether touch occurs or not according to the optimal capacitance value, and updating the base line if no touch occurs.

Judging whether touching occurs is a prior art in the field, and not described in detail herein, for example, a target finger threshold may be set, when the difference between the preferred capacitance value and the baseline value as the comparison reference is greater than the target finger threshold and the set period of time is continued, the touching is considered to occur, otherwise, the preferred capacitance value when the touching does not occur is considered to be still changed relative to the baseline value, and generally considered to be a slow change caused by environmental reasons such as temperature, humidity, noise, and the like, and the baseline updating is required.

The data after passing through the data preprocessor needs to identify the detection capacitance when no touch exists, so as to construct a baseline.

The baseline follower is mainly used for constructing a capacitance baseline of each channel when no touch exists, and the updating mode of the baseline follower is divided into 3 modes of initializing baseline updating, waking up updating baseline and continuously updating baseline.

Mode 1. A baseline update mode is initialized,

Post-update baseline value = 3/4 preferred capacitance value +1/4 pre-update baseline value for initial state, the pre-update baseline value is the set baseline default value, and the post-initialization baseline can be quickly followed from the reset default value to the current preferred capacitance value.

And 2, waking up to update the baseline mode, namely, waking up all enabled channels to scan after waiting for the end of the timed wake-up counting to update the baseline when the module is in the sleep mode through a low-power switch in a configuration register and timed wake-up configuration. Waiting for a period of time, and if no touch occurs, going to sleep again.

Mode 3. Continuously updating the baseline mode, in which the baseline is continuously updated as long as no touch action is generated. At this time, the baseline updating mode is further divided into a normal following mode and an abnormal following mode.

The normal following mode and the abnormal following mode are used for judging whether the preferred capacitance value input at this time meets the characteristic that the capacitance can be increased by touching with a finger, if the capacitance changes but the capacitance value is not increased, the abnormal following mode is carried out, otherwise, the normal following is carried out.

The normal following mode is if:

Pre-update baseline value + target finger threshold > preferred capacitance value > pre-update baseline value,

Then update is performed in the following way

Post-update baseline value = pre-update baseline value + baseline value update step size,

The baseline value update step size is set according to the current environmental change and experience.

If:

preferred capacitance value < baseline before update value:

post-update baseline value = pre-update baseline value-baseline value update step size;

otherwise not updated;

In the anomaly following mode, if:

preferably the capacitance value < pre-update baseline value-baseline anomaly threshold value,

The abnormal following mode indicates that the detected preferred capacitance value does not change according to the characteristic of the increase in capacitance value after the finger touch, for example, the detected preferred capacitance value decreases after the finger touch due to unknown factors, and the abnormal detection capacitance increases in characteristic, so the baseline abnormal threshold is generally set closer to the initial value or the current baseline value.

At this point, it is shown that the preferred capacitance value is much less than the baseline, which follows the anomaly, and returns to the initialized state.

And 5, selecting base line values of different channels by the touch judger according to the configured channels, and performing touch judgment by using the sensitivity threshold value set by the configuration register.

In the normal use process of the capacitive touch detection system, after the signal amplitude is changed due to environmental changes such as water drops, oil drops and deformation of a touch panel, the touch signal is affected to not meet the sensitivity threshold set in the stable environment, the problems of touch unrecognization, reduction in recognition rate and the like are likely to be caused, and the user experience is affected. This situation can be improved by the sensitivity threshold setting.

The sensitivity control mode of the touch judger is divided into two modes of active sensitivity configuration and fixed sensitivity configuration. The sensitivity can be adjusted according to the change of the actual signal quantity without software intervention, so that the recognition rate is improved.

In the active sensitivity configuration mode, a double-threshold method is used for sensitivity limitation of the target finger threshold of the configuration register. As shown in fig. 5, first, 3 sensitivity values, namely, a low activity sensitivity threshold VTL, a high activity sensitivity threshold VTH, and a target finger threshold VTF, are configured. The values of the low activity sensitivity threshold VTL and the high activity sensitivity threshold VTH are set based on the actual capacitance judgment optimal sensitivity threshold measured for each channel a plurality of times in a stable environment.

In the fixed sensitivity configuration mode, the judgment logic of the module directly uses the target finger threshold VTF configured by the configuration register as a threshold for judging the touch response. And judging that touch occurs at the moment after the detection capacitance value is larger than the target finger threshold value for a certain number of times, or else, judging that no touch occurs.

Scenario 1 in fig. 5 shows that the magnitude of the preferred capacitance value detected upon occurrence of a touch in a stable environment is greater than the high activity sensitivity threshold VTH, and if the set target finger threshold is not in the activity sensitivity threshold interval, i.e., is higher than the high activity sensitivity threshold VTH or lower than the low activity sensitivity threshold VTH, it may result in excessive sensitivity or insensitivity, affecting the stable operation of the system.

The active sensitivity configuration mode automatically adjusts the target finger threshold to be between the two active sensitivity thresholds VTL and VTH according to the active finger threshold adjustment step set by the configuration register. If the target finger threshold is in the interval between VTL and VTH, the target finger threshold is not adjusted.

Scene 2 in fig. 5 shows that the detected preferred capacitance value amplitude of the same detection circuit output at the time of one touch after an environmental change is higher than the low activity sensitivity threshold VTL but lower than the high activity sensitivity threshold VTH, at which point it is explained that the capacitance change amount at the time of finger touch is reduced due to the environmental change, at which point the target finger threshold setting needs to be reduced, thereby improving the detection accuracy.

The target finger threshold is in the interval between VTL and VTH due to the current register configuration. The target finger threshold is then subtracted by the active finger threshold adjustment step until the target finger threshold VTF is less than the low activity sensitivity threshold VTL. To ensure minimal impact on sensitivity after environmental changes. When the target finger threshold set by the configuration register is less than the low activity sensitivity threshold VTL, there is no need to adjust the target finger threshold.

And (3) judging that touch occurs when the optimal capacitance value output in the step (3) is larger than the adjusted target finger threshold value for a certain number of times, or else, judging that no touch occurs.

The invention can comprehensively improve the anti-interference capability of the system, and the detection system can obtain stable and reliable performance with high identification precision and high cost performance while achieving cost advantage.

It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.

These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.

The foregoing description of the preferred embodiments of the present invention is not obvious contradiction or on the premise of a certain preferred embodiment, but all the preferred embodiments can be used in any overlapped combination, and the embodiments and specific parameters in the embodiments are only for clearly describing the invention verification process of the inventor and are not intended to limit the scope of the invention, and the scope of the invention is still subject to the claims, and all equivalent structural changes made by applying the specification and the content of the drawings of the present invention are included in the scope of the invention.