CN212180969U - Key detection circuit - Google Patents

Abstract

The utility model provides a key detection circuit, comprising a first key switch unit, at least one second key switch unit and at least one auxiliary detection circuit; the first key switch unit includes a first key switch and a first resistor connected in series; The first terminal of a key switch unit is connected to the first voltage terminal through a third resistor, and the second terminal of the first key switch unit is connected to the reference voltage terminal; the second key switch unit includes a second key switch and a second resistor connected in series; The first end of the second key switch unit is connected to the first voltage end through the third resistor, and the second end of the second key switch unit is connected to the auxiliary detection circuit; the auxiliary detection circuit is used for according to the voltage of the second end of the second key switch unit signal to determine whether the second key switch in the second key switch unit is pressed; wherein, the first end of the first key switch unit and the first end of the second key switch unit are both connected to the analog-to-digital conversion interface of the key detection circuit .

Description

key detection circuit

technical field

The utility model relates to the technical field of detection, in particular to a key detection circuit.

Background technique

Common key detection circuits include matrix scanning and voltage detection. Among them, the matrix scanning method requires many I/O interfaces, which is not suitable for occasions with many buttons and limited I/O resources; the voltage detection method uses the principle of resistance division, and different buttons correspond to different voltages after being pressed. A single analog-to-digital conversion interface (ADC) is implemented to detect multiple buttons, but as the number of buttons increases, the difference between the voltage divider values between adjacent buttons must become smaller, and external interference can easily cause fluctuations in the detection voltage, resulting in false button detection. .

Utility model content

In view of this, one of the purposes of the embodiments of the present invention is to provide a key detection circuit to solve the above problems.

Based on the above purpose, an embodiment of the present invention provides a key detection circuit, including a first key switch unit, at least one second key switch unit, and at least one auxiliary detection circuit;

The first key switch unit includes a first key switch and a first resistor connected in series; the first end of the first key switch unit is connected to the first voltage terminal through the third resistor, and the first key switch unit of the first key switch unit is connected to the first voltage terminal. The two terminals are connected to the reference voltage terminal;

The second key switch unit includes a second key switch and a second resistor connected in series; the first end of the second key switch unit is connected to the first voltage terminal through the third resistor, and the first end of the second key switch unit is connected to the first voltage terminal. The two ends are connected to the auxiliary detection circuit;

The auxiliary detection circuit is configured to determine whether the second key switch in the second key switch unit is pressed according to the voltage signal of the second terminal of the second key switch unit;

Wherein, the first end of the first key switch unit and the first end of the second key switch unit are both connected to the analog-to-digital conversion interface of the key detection circuit.

Optionally, the first key switch unit includes several first key switches and several first resistors; the first key switches and the first resistors are connected in series in one-to-one correspondence to form several first series branches; A plurality of the first series branches are arranged in parallel, and the resistance values of the plurality of the first resistors are different from each other.

Optionally, the second key switch unit includes several second key switches and several second resistors; the second key switches and the second resistors are connected in series in one-to-one correspondence to form several second series branches; A plurality of the second series branches are arranged in parallel, and the resistance values of the plurality of the second resistors are different from each other.

Optionally, the resistance value of the first resistor is equal to the resistance value of the second resistor.

Optionally, the first key switch unit includes several first key switches and several first resistors; the first key switches and the first resistors are connected in series in one-to-one correspondence to form several first series branches; A plurality of the first series branches are arranged in parallel, and the resistance values of the plurality of the first resistors are different;

The second key switch unit includes several second key switches and several second resistors; the second key switches and the second resistors are connected in series in one-to-one correspondence to form several second series branches; several of the first Two series branches are arranged in parallel, and the resistance values of the plurality of second resistors are different;

Wherein, the resistance values of the first resistors are equal to the resistance values of the second resistors in a one-to-one correspondence.

Optionally, the auxiliary detection circuit includes a first control unit and a transistor, the second end of the second key switch unit is connected to the control electrode of the transistor, and the first electrode of the transistor is connected to the first control unit The I/O interface of the transistor, the second pole of the transistor is connected to the reference voltage terminal, and the first pole of the transistor is connected to the second voltage terminal through a fourth resistor.

Optionally, the button detection circuit further includes a second control unit, the second control unit includes an analog-to-digital conversion module, and the analog-to-digital conversion interface is connected to the analog-to-digital conversion module;

The analog-to-digital conversion module is used to convert the voltage signal of the analog-to-digital conversion interface into a digital signal, and the second control unit is used to determine the Whether a key switch is pressed in the first key switch unit and the second key switch unit is determined, or it is determined that the key switch in the first key switch unit and the second key switch unit is pressed.

Optionally, at least one of the first control unit and the second control unit is an MCU chip or an SOC chip.

Optionally, the first control unit and the second control unit are multiplexed into one control chip.

Optionally, the number of the second key switch unit and the auxiliary detection circuit is multiple; the first control units in the multiple auxiliary detection circuits are multiplexed into one control chip.

It can be seen from the above that in the key detection circuit provided by the embodiment of the present invention, the first key switch unit and the second key switch unit are designed, and the auxiliary detection circuit detects whether there is a key in the second key switch unit. The switch is pressed, so that when the analog-to-digital conversion interface ADC of the button detection circuit detects a corresponding voltage signal, combined with the detection result of the auxiliary detection circuit, it can be obtained whether the first button switch unit or the second button switch unit exists. The pressed key switch, so as to determine the specific pressed key switch, and then complete the key detection. By adopting the button detection circuit of this structure, the detection result of the auxiliary detection circuit can be used to realize the block and time-sharing detection of the button to be detected, thereby improving the stability and detection accuracy of the detection circuit.

Description of drawings

In order to more clearly illustrate the embodiments of the present utility model or the technical solutions in the prior art, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description These are just some embodiments of the present invention, and for those of ordinary skill in the art, other drawings can also be obtained from these drawings without creative effort.

1 is a schematic diagram of a circuit structure of an embodiment provided by the present invention;

2 is a schematic diagram of a circuit structure of another embodiment provided by the present invention;

FIG. 3 is a schematic diagram of a circuit structure of another embodiment provided by the present invention.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present utility model more clearly understood, the present utility model will be further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the embodiments of the present invention shall have the usual meanings understood by those with ordinary skill in the art to which the present disclosure belongs. As used in this disclosure, "first," "second," and similar terms do not denote any order, quantity, or importance, but are merely used to distinguish the various components. "Comprises" or "comprising" and similar words mean that the elements or things appearing before the word encompass the elements or things recited after the word and their equivalents, but do not exclude other elements or things. Words like "connected" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "Down", "Left", "Right", etc. are only used to represent the relative positional relationship, and when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

Referring to FIG. 1 , the key detection circuit includes a first key switch unit 101 , a second key switch unit 102 and an auxiliary detection circuit 103 ;

The first key switch unit 101 includes first key switches (K1a-K1e) and first resistors (R1a-R1e) connected in series; the first end of the first key switch unit 101 is connected to the first key switch unit 101 through a third resistor R3 a voltage terminal VCC, the second terminal of the first key switch unit 101 is connected to the reference voltage terminal GND;

The second key switch unit 102 includes second key switches (K2a-K2e) and second resistors (R2a-R2e) connected in series; the first end of the second key switch unit 102 is connected to the second key switch via the third resistor R3. a voltage terminal VCC, the second terminal of the second key switch unit 102 is connected to the auxiliary detection circuit 103;

The auxiliary detection circuit 103 is configured to determine whether the second key switches (K2a-K2e) in the second key switch unit 102 are pressed according to the voltage signal of the second terminal of the second key switch unit 102;

The first end of the first key switch unit 101 and the first end of the second key switch unit 102 are both connected to the analog-to-digital conversion interface ADC of the key detection circuit.

In this embodiment, in the key detection circuit, the first key switch unit and the second key switch unit are designed, and the auxiliary detection circuit detects whether a key switch is pressed in the second key switch unit, so that when all the When the analog-to-digital conversion interface ADC of the key detection circuit detects the corresponding voltage signal, combined with the detection result of the auxiliary detection circuit (whether the second key switch is pressed), it can be obtained whether the first key switch unit or the second key switch unit is the first key switch unit or the second key switch unit. There is a pressed key switch in the device, so as to determine the specific pressed key switch, and then complete the key detection. With the case detection circuit of this structure, the detection results of the auxiliary detection circuit can be used to realize the block and time-division detection of the keys to be detected, thereby improving the stability and detection accuracy of the detection circuit.

Optionally, the resistance value of the first resistor and the resistance value of the second resistor may be equal. Because the detection of whether there is a key switch in the second key switch unit has been realized through the auxiliary detection circuit, even if the analog-to-digital conversion interface ADC detects that the magnitude of the corresponding voltage signal remains unchanged, it can be known that the voltage signal is generated in the first key switch unit. The key switch unit is also a second key switch unit. In this way, when the resistance value of the first resistor is equal to the resistance value of the second resistor, resistors of the same type can be purchased during circuit design, thereby saving costs.

As an optional embodiment, as shown in FIG. 1, the first key switch unit 101 includes a plurality of first key switches K1a-K1e and a plurality of first resistors R1a-R1e; the first key switch and the first key switch A resistor is connected in series in a one-to-one correspondence to form several first series branches. For example, taking FIG. 1 as an example, the first key switch K1a is connected in series with the first resistor R1a, the first key switch K1b is connected in series with the first resistor R1b, and the first key switch K1a is connected in series with the first resistor R1b The switch K1c is connected in series with the first resistor R1c, the first key switch K1d is connected in series with the first resistor R1d, and the first key switch K1e is connected in series with the first resistor R1e, thereby forming five branches; a plurality of the first series branches are arranged in parallel , the resistance values of several of the first resistors R1a to R1e are different from each other. Through such a structural design, when the key switch in any branch is pressed, the voltage signal of the corresponding branch will be different due to the difference in resistance value, and then it is known which branch corresponding key switch is pressed. Press to complete key detection.

Optionally, the resistance values of the several first resistors can be sequentially increased, and the increasing rule can be an arithmetic progression or an arithmetic progression. 10Ω, 100Ω, 1000Ω, 10000Ω, etc.

As an optional embodiment, as shown in FIG. 1, the second key switch unit 102 includes a plurality of second key switches K2a-K2e and a plurality of second resistors R2a-R2e; the second key switch and the first key switch The two resistors are connected in series in one-to-one correspondence to form a number of second series branches. For example, taking FIG. 1 as an example, the second key switch K2a is connected in series with the second resistor R2a, the second key switch K2b is connected in series with the second resistor R2b, and the second key switch K2a is connected in series with the second resistor R2b. The switch K2c is connected in series with the second resistor R2c, the second key switch K2d is connected in series with the second resistor R2d, and the second key switch K2e is connected in series with the second resistor R2e, thereby forming five branches; a number of the second series branches are arranged in parallel , the resistance values of several of the second resistors are different. Through such a structural design, when the key switch in any branch is pressed, the voltage signal of the corresponding branch will be different due to the difference in resistance value, and then it is known which branch corresponding key switch is pressed. Press to complete key detection.

Optionally, the resistance values of the plurality of second resistors can be sequentially increased, and the increasing rule can be an arithmetic progression or an arithmetic progression. 10Ω, 100Ω, 1000Ω, 10000Ω, etc.

As an optional embodiment, as shown in FIG. 1 , the first key switch unit 101 and the second key switch unit 102 each include several key switches and resistors; wherein, the several first resistors R1a to R1e The resistance values are equal to the resistance values of the plurality of second resistors R2a-R2e in a one-to-one correspondence.

Taking FIG. 1 as an example, the resistance value of the first resistor R1a may be equal to the resistance value of the second resistor R2a, the resistance value of the first resistor R1b may be equal to the resistance value of the second resistor R2b, and the resistance value of the first resistor R1c may be equal to the resistance value of the first resistor R1c. The resistance of the two resistors R2c, the resistance of the first resistor R1d may be equal to the resistance of the second resistor R2d, and the resistance of the first resistor R1e may be equal to the resistance of the second resistor R2e.

The button detection circuit can realize the detection of whether there is a button switch in the second button switch unit through the auxiliary detection circuit. It is known whether the voltage signal is generated by the first key switch unit or the second key switch unit. In this way, in the case where the resistance values of the first resistors R1a-R1e and the resistance values of the second resistors R2a-R2e are equal to one-to-one correspondence, for the resistors with the same resistance value, the same type of resistor can be purchased , thereby saving costs.

The key detection circuit, because the key switch is divided into two parts (the first key switch unit 101 and the second key switch unit 102), makes it possible to increase the key detection voltage under the premise of using fewer interfaces (because the number of key switches in the same switch unit is less), thereby improving the detection accuracy. In this embodiment, the voltage interval between two adjacent keys can be doubled, thereby improving the anti-interference ability of the detection circuit and improving the detection accuracy. At the same time, resistors with the same resistance value can be reused in the circuit design, and the purchase cost of the resistors is reduced in the detection of the same number of buttons. In addition, when the number of keys is the same, the key detection circuit of this embodiment can greatly save the number of I/O interfaces compared to the key detection circuit of the matrix scanning method or the binary encoding method.

As an optional embodiment, as shown in FIG. 1 , the auxiliary detection circuit 103 includes a first control unit and a transistor Q1, and the second end of the second key switch unit 102 is connected to the control electrode of the transistor Q1, so The first pole of the transistor Q1 is connected to the I/O interface of the first control unit, the second pole of the transistor Q1 is connected to the reference voltage terminal GND, and the first pole of the transistor Q1 is connected to the second pole through the fourth resistor R4. Voltage terminal VDD. In this way, when any second key switch in the second key switch unit 102 is pressed, the control pole of the transistor Q1 will be connected to a high-level signal, so that the transistor Q1 is turned on, so that the first control unit The I/O interface is connected to the signal of the reference voltage terminal GND (if the reference voltage terminal is grounded, the voltage is 0), so that the first control unit can determine that there is a pressed second key switch in the second key switch unit 102 . This design is simple and effective, and only needs to occupy one I/O interface of the first control unit.

Optionally, the first control unit may be an MCU chip (microprocessor) or an SOC chip (system-on-chip or system-on-chip).

As an optional embodiment, the key detection circuit further includes a second control unit, the second control unit includes an analog-to-digital conversion module, and the analog-to-digital conversion interface is connected to the analog-to-digital conversion module;

The analog-to-digital conversion module is used to convert the voltage signal of the analog-to-digital conversion interface into a digital signal, and the second control unit is used to determine the Whether a key switch is pressed in the first key switch unit and the second key switch unit is determined, or it is determined that the key switch in the first key switch unit and the second key switch unit is pressed.

For example, at the beginning, when all the key switches are not pressed, the second control unit detects that there is a voltage signal (which can be used as a reference voltage) in the analog-to-digital conversion interface ADC. When the second control unit detects that the voltage signal of the analog-to-digital conversion interface ADC changes, if the auxiliary detection circuit detects and determines that a key switch is pressed in the second key switch unit (for example, the I/O of the first control unit If the interface detects a low-level signal), the pressed key switch in the second key switch unit can be determined according to the changed voltage signal (feedback voltage) of the analog-to-digital conversion interface ADC. The specific calculation method is calculated according to the divided voltage between the third resistor R3 and the second resistor. When the second control unit detects that the voltage signal of the analog-to-digital conversion interface ADC changes, if the auxiliary detection circuit detects and determines that no key switch is pressed in the second key switch unit (for example, the I/O of the first control unit O interface detects a high-level signal), it means that there is a key switch in the first key switch unit that is pressed, and then it can be determined according to the changed voltage signal of the analog-to-digital conversion interface ADC. Pressed key switch. The specific calculation method is calculated according to the divided voltage between the third resistor R3 and the first resistor. When the second control unit does not detect that the voltage signal of the analog-to-digital conversion interface ADC changes, it means that no key switch is pressed.

Optionally, in the judgment method, the voltage of the I/O interface can be judged first, the switch unit to which the pressed key switch belongs, and the exact key switch is located according to the voltage fed back by the analog-to-digital conversion interface ADC. Therefore, the voltage detected by the ADC will be divided from the original 10 resistors to 5 resistors, the voltage difference between adjacent buttons will increase, and the degree of influence by interference will decrease.

Optionally, the second control unit may be an MCU chip or an SOC chip.

Optionally, the first control unit and the second control unit are multiplexed into one control chip. Taking FIG. 3 as an example, when the control unit itself has an ADC module, the analog-to-digital conversion interface of the control unit itself can be directly used, thereby multiplexing a control chip and simultaneously realizing the functions of the first control unit and the second control unit.

As an optional embodiment, referring to FIG. 2 or FIG. 3 , the number of the second key switch unit 102/102' and the auxiliary detection circuit is multiple, so as to realize the detection of more keys.

Optionally, as shown in FIG. 2 or FIG. 3 , the first control units in the plurality of auxiliary detection circuits are multiplexed into one control chip, and there are usually more than one I/O interface in one control chip, which is controlled by multiplexing. The chip can save cost and simplify circuit wiring.

In this embodiment, the key detection circuit has strong scalability, and can flexibly divide the number of key modules and the number of keys in each module according to the number of idle I/O interfaces of the control chip. In this way, under the condition of limited I/O interface, it can meet the needs of different button detection numbers.

It should be understood by those of ordinary skill in the art that: the above are only specific embodiments of the present utility model, and are not intended to limit the present utility model. All within the spirit and principle of the present utility model, any modifications made, equivalent to Replacement, improvement, etc., should be included within the protection scope of the present invention.

Claims (10)

1. A key detection circuit is characterized by comprising a first key switch unit, at least one second key switch unit and at least one auxiliary detection circuit;

the first key switch unit comprises a first key switch and a first resistor which are connected in series; the first end of the first key switch unit is connected with a first voltage end through a third resistor, and the second end of the first key switch unit is connected with a reference voltage end;

the second key switch unit comprises a second key switch and a second resistor which are connected in series; the first end of the second key switch unit is connected with a first voltage end through a third resistor, and the second end of the second key switch unit is connected with the auxiliary detection circuit;

the auxiliary detection circuit is used for determining whether a second key switch in the second key switch unit is pressed down or not according to the voltage signal of the second end of the second key switch unit;

the first end of the first key switch unit and the first end of the second key switch unit are both connected with the analog-to-digital conversion interface of the key detection circuit.

2. The key detection circuit of claim 1, wherein the first key switch unit comprises a plurality of first key switches and a plurality of first resistors; the first key switches and the first resistors are connected in series in a one-to-one correspondence mode to form a plurality of first series branches; the first series branches are arranged in parallel, and the resistance values of the first resistors are different.

3. The key detection circuit of claim 1, wherein the second key switch unit comprises a plurality of second key switches and a plurality of second resistors; the second key switches and the second resistors are connected in series in a one-to-one correspondence mode to form a plurality of second series branches; the plurality of second series branches are arranged in parallel, and the resistance values of the plurality of second resistors are different.

4. The key detection circuit of claim 1, wherein the first resistor has a resistance equal to the second resistor.

5. The key detection circuit of claim 1, wherein the first key switch unit comprises a plurality of first key switches and a plurality of first resistors; the first key switches and the first resistors are connected in series in a one-to-one correspondence mode to form a plurality of first series branches; the first series branches are arranged in parallel, and the resistance values of the first resistors are different;

the second key switch unit comprises a plurality of second key switches and a plurality of second resistors; the second key switches and the second resistors are connected in series in a one-to-one correspondence mode to form a plurality of second series branches; the plurality of second series branches are arranged in parallel, and the resistance values of the plurality of second resistors are different;

the resistance values of the first resistors are equal to the resistance values of the second resistors in a one-to-one correspondence manner.

6. The key detection circuit of claim 1, wherein the auxiliary detection circuit comprises a first control unit and a transistor, the second terminal of the second key switch unit is connected to the control electrode of the transistor, the first electrode of the transistor is connected to the I/O interface of the first control unit, the second electrode of the transistor is connected to the reference voltage terminal, and the first electrode of the transistor is connected to the second voltage terminal through a fourth resistor.

7. The key detection circuit of claim 6, further comprising a second control unit, wherein the second control unit comprises an analog-to-digital conversion module, and the analog-to-digital conversion interface is connected to the analog-to-digital conversion module;

the analog-to-digital conversion module is used for converting a voltage signal of the analog-to-digital conversion interface into a digital signal, and the second control unit is used for determining whether a key switch is pressed down in the first key switch unit and the second key switch unit or determining the pressed key switch in the first key switch unit and the second key switch unit according to the digital signal and by combining a detection result of the auxiliary detection circuit.

8. The key detection circuit of claim 7, wherein at least one of the first control unit and the second control unit is an MCU chip or an SOC chip.

9. The key detection circuit of claim 7, wherein the first control unit and the second control unit are multiplexed into one control chip.

10. The key detection circuit of claim 6, wherein the number of the second key switch unit and the auxiliary detection circuit is plural; and the first control units in the auxiliary detection circuits are multiplexed into one control chip.

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