A touch signal conversion and reading circuit

Abstract

This utility model discloses a touch signal conversion and reading circuit, including an MCU. The PWM signal output terminal of the MCU is connected to the MCU's ADC signal detection terminal via resistor R1, capacitor C1, and resistor R2 in sequence. A touch electrode A1 is also connected between capacitor C1 and resistor R2. The MCU's ADC signal detection terminal is equipped with a signal processing module, which includes a resistor R3 and a capacitor C2 connected in parallel. One end of each resistor R3 and capacitor C2 is connected to the MCU's ADC signal detection terminal, and the other end is connected and grounded. This utility model replaces a dedicated chip with "capacitive coupling waveform distortion detection" and combines a hardware hardening design of "diode reverse protection + voltage divider filtering," reducing hardware costs and improving reliability and compatibility.

Description

Technical Field

[0001] This utility model relates to a touch signal conversion and reading circuit. Background Technology

[0002] Currently, capacitive touch buttons mostly rely on dedicated touch chips for signal detection, which has the following drawbacks: 1. Poor compatibility: They require matching specific chips and cannot be adapted to general-purpose MCUs; 2. High cost: Dedicated chips are expensive, increasing hardware costs; 3. Weak anti-interference: Static electricity from the human body can easily damage circuit components.

[0003] Therefore, there is an urgent need for a low-cost, highly compatible touch signal detection solution. Utility Model Content

[0004] To address the aforementioned problems, this utility model provides a touch signal conversion and reading circuit, which effectively solves the problems mentioned in the background art.

[0005] The technical solution adopted in this utility model is:

[0006] A touch signal conversion and reading circuit includes an MCU. The PWM signal output terminal of the MCU is connected to the ADC signal detection terminal of the MCU through a resistor R1, a capacitor C1, and a resistor R2 in sequence. A touch electrode A1 is also connected between the capacitor C1 and the resistor R2. The ADC signal detection terminal of the MCU is provided with a signal processing module. The signal processing module includes a resistor R3 and a capacitor C2 connected in parallel. One end of the resistor R3 and the capacitor C2 are both connected to the ADC signal detection terminal of the MCU, and the other end is connected and grounded.

[0007] Preferably, a diode D1 is provided between the touch electrode A1 and the resistor R2, with the positive terminal of the diode D1 grounded and the negative terminal connected to the node between the touch electrode A1 and the resistor R2.

[0008] Preferably, the touch electrode A1 is a pressing spring.

[0009] Preferably, the MCU has multiple PWM signal output terminals and multiple ADC signal detection terminals that match the multiple PWM signal output terminals.

[0010] The innovative points of this utility model are as follows:

[0011] 1. Circuit structure innovation that eliminates reliance on dedicated chips:

[0012] Traditional solution: Requires the use of a dedicated touch chip (such as a capacitive sensing chip) to process the signal;

[0013] This invention is innovative in that it achieves touch recognition solely through the PWM output and ADC detection of a general-purpose MCU; it utilizes capacitive coupling and the capacitance change of the touch electrode A1 to induce PWM waveform distortion (such as changes in pulse width / amplitude); the MCU directly analyzes the waveform distortion through an algorithm (without requiring a dedicated signal processing module); and it is the first time that a complete integration of capacitive touch detection has been achieved on a general-purpose MCU.

[0014] 2. Hardware protection design against electrostatic interference:

[0015] Traditional drawback: Static electricity from the human body can easily damage the MCU pins connected to the touch electrode A1;

[0016] This utility model innovates by connecting a diode D1 (positive terminal grounded, negative terminal connected to touch electrode A1) in reverse parallel between the touch electrode A1 and ground. When subjected to electrostatic high voltage, diode D1 conducts to discharge reverse current, protecting the ADC pin of the MCU. Combined with current-limiting resistors R1 and R2, it further suppresses surge current, solves industry pain points, and extends circuit life.

[0017] 3. Optimized design of the signal processing link:

[0018] Resistor R1, capacitor C1 and resistor R2 form a coupling module that couples the PWM pulse to touch electrode A1 while limiting current.

[0019] Resistor R3 and capacitor C2 are connected in parallel to ground, so that the ADC signal detection terminal of the MCU can obtain the sampling voltage and filter out noise;

[0020] The touch electrode A1 uses a metal pressing spring to increase the contact area and improve sensitivity;

[0021] 4. Multi-channel expansion compatibility innovation:

[0022] Supports multiple PWM output terminals connected in parallel with ADC detection terminals (e.g., MCU P31 / P32 pins correspond to AD2 / AD3).

[0023] Each channel operates independently, and multi-button detection is achieved by time-division multiplexing MCU resources. A single MCU can replace multiple dedicated touch chips, which greatly reduces costs.

[0024] The beneficial effects of this utility model are as follows:

[0025] I. Significantly reduce hardware costs:

[0026] 1. The main control chip uses a general-purpose MCU, eliminating the need for a dedicated touch chip, reducing costs by more than 60%;

[0027] 2. A single MCU supports multiple detection channels, which greatly reduces system costs;

[0028] II. Breakthrough improvement in anti-interference capability:

[0029] 1. Electrostatic protection performance:

[0030] Innovative design: Diode D1 is connected in reverse parallel (negative terminal connected to electrode, positive terminal grounded).

[0031] Protection mechanism: Static electricity from the human body (>8kV) → diode D1 conducts forward to discharge current, reverse voltage in the circuit → diode D1 reverse to block the path;

[0032] 2. Signal interference immunity design:

[0033] Resistors R1 and R2 are connected in series to form current limiting protection, suppressing surge current and preventing MCU pins from burning out;

[0034] Capacitor C2 is connected in parallel to ground to filter out high-frequency noise;

[0035] Resistor R3 enables voltage divider sampling, reduces signal fluctuation sensitivity, and prevents false triggering;

[0036] III. Compatibility and Flexibility:

[0037] A general-purpose MCU can be used to achieve this, and it supports multi-channel detection. In practical applications, a suitable MCU can be selected according to the needs.

[0038] This invention replaces a dedicated chip with "capacitive coupling waveform distortion detection" and combines it with a hardware reinforcement design of "diode reverse protection + voltage divider filtering", which reduces hardware costs and improves reliability and compatibility. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the MCU structure;

[0040] Figure 2 This is the circuit diagram between the P32 pin of the MCU and AD3. Detailed Implementation

[0041] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0042] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0043] Furthermore, in the description of this utility model, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0044] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, unless otherwise stated, "a plurality of" means two or more, unless otherwise expressly defined.

[0045] In this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0046] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0047] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings.

[0048] like Figure 1-2As shown, a touch signal conversion and reading circuit includes an MCU. The PWM signal output terminal of the MCU is connected to the signal detection terminal of the MCU after passing through resistor R1, capacitor C1, and resistor R2 in sequence. A touch electrode A1, which is a pressing spring, is also connected between capacitor C1 and resistor R2. The ADC signal detection terminal of the MCU is equipped with a signal processing module. The signal processing module includes a resistor R3 and a capacitor C2 connected in parallel. One end of resistor R3 and capacitor C2 is connected to the ADC signal detection terminal of the MCU, and the other end is connected and grounded. A diode D1 is provided between the touch electrode A1 and resistor R2. The positive terminal of the diode D1 is grounded, and the negative terminal is connected to the node between the touch electrode A1 and resistor R2.

[0049] The MCU has multiple PWM signal output terminals ( Figure 1 Pins T5F P30, P31, P32, P33, P34, P35, P36, P37, and multiple ADC signal detection terminals matched with multiple PWM signal output terminals. Figure 1 The pins T5FAD1, AD2, AD3, AD4, AD5, AD6, AD7, AD8, and pins P30, P31, P32, P33, P34, P35, P36, P37 correspond one-to-one with AD1, AD2, AD3, AD4, AD5, AD6, AD7, AD8.

[0050] This invention generates PWM pulses via an MCU, which are then capacitively coupled to the touch electrode A1. Human touch changes the electrode capacitance, causing distortion in the coupled waveform. The MCU detects the waveform distortion parameters and determines the touch state. This invention requires no dedicated touch chip and relies solely on the PWM output and ADC detection capabilities of a general-purpose MCU.

[0051] by Figure 2 Taking the circuit diagram between pin P32 and AD3 as an example, its working principle will be described in detail:

[0052] Step 1: PWM pulse generation and coupling (untouched state): The MCU sends a PWM pulse through the P32 pin, which is coupled by capacitor C1, divided by resistor R3, filtered by capacitor C2, and the standard waveform is output at the AD1 terminal;

[0053] Step 2: Capacitance change triggered by touch: When a finger touches the spring, the human body's capacitance is connected, forming a capacitance network with capacitor C1;

[0054] Step 3: Waveform distortion mechanism: The human body capacitance changes the coupling characteristics of capacitor C1 → waveform distortion at AD1 terminal (such as pulse width / amplitude change) → MCU determines it as a valid touch.

[0055] Diode D1 serves as electrostatic discharge protection. The protection mechanism is as follows: when a person comes into contact with the electrode with high electrostatic discharge, diode D1 conducts in the forward direction, the current is discharged to GND, the circuit generates a negative voltage transient, diode D1 cuts off in the reverse direction, blocking the current from flowing into the MCU pin and controlling the ADC pin voltage within a safe range.

[0056] Capacitor C2 acts as a filter, removing high-frequency interference.

[0057] Resistor R3 acts as a voltage divider, dividing the coupled signal to the ADC input range of the MCU.

[0058] The MCU has a built-in comparison program that can determine a valid touch based on conditions such as:

[0059] 1. Pulse amplitude attenuation > set value;

[0060] 2. Waveform distortion rate > set value.

[0061] The fundamental difference from traditional solutions: dedicated touch chips rely on charge transfer or frequency detection, while this invention directly analyzes PWM waveform distortion to achieve lower latency and higher anti-interference capability.

[0062] Because the circuit diagrams between pins P30 and AD1, P31 and AD2, P33 and AD4, P34 and AD5, P35 and AD6, P36 and AD7, and P37 and AD8 are... Figure 2 Consistent with the present invention, these circuit diagrams are not shown.

[0063] Finally, it should be noted that the above examples are merely specific embodiments of this utility model. Obviously, this utility model is not limited to the above embodiments and can have many variations. All variations that can be directly derived or conceived by those skilled in the art from the disclosure of this utility model should be considered within the protection scope of this utility model.

Claims

1. A touch signal conversion and reading circuit, characterized in that, The system includes an MCU. The PWM signal output terminal of the MCU is connected to the signal detection terminal of the MCU via resistor R1, capacitor C1, and resistor R2 in sequence. A touch electrode A1 is also connected between capacitor C1 and resistor R2. The ADC signal detection terminal of the MCU is equipped with a signal processing module. The signal processing module includes a resistor R3 and a capacitor C2 connected in parallel. One end of resistor R3 and capacitor C2 is connected to the ADC signal detection terminal of the MCU, and the other end is connected and grounded.

2. The touch signal conversion reading circuit according to claim 1, wherein, A diode D1 is provided between the touch electrode A1 and the resistor R2. The positive terminal of the diode D1 is grounded, and the negative terminal is connected to the node between the touch electrode A1 and the resistor R2.

3. The touch signal conversion reading circuit according to claim 2, wherein, The touch electrode A1 is a pressing spring.

4. The touch signal conversion reading circuit according to claim 3, wherein, The MCU has multiple PWM signal output terminals and multiple ADC signal detection terminals that are matched with the multiple PWM signal output terminals.

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