Keyboard circuit based on USB interface and keyboard

Abstract

The utility model relates to the technical field of electronic circuits, and discloses a keyboard circuit based on a USB interface and a keyboard. The circuit comprises a signal denoising module, a buffer input module, a signal processing module and an output protection module. The signal denoising module comprises a plurality of first filtering units; the first filtering unit is used for filtering each initial key signal of the key to obtain a filtered signal; the buffer input module is used for carrying out buffer processing on the filtering signal to obtain an effective signal; the signal processing module receives the effective signals and processes each effective signal to obtain a result signal; the input end of the output protection module is connected with the output end of the signal processing module, and the output end of the output protection module is connected with an upper computer through a USB interface; and the output protection module is used for transmitting the result signal to an upper computer. According to the invention, each key can be independently protected, and interference can be reduced through multiple protections, so that the accuracy of key signals is improved.

Description

Technical Field

[0001] The present application relates to the technical field of electronic circuits, and in particular to a keyboard circuit and a keyboard based on a USB interface. Background Art

[0002] Key circuits are widely used in the field of electronic circuits, such as Figure 1 The matrix keyboard design shown above is susceptible to interference from complex electromagnetic environments when used in industrial environments. This interference can even cause key combinations, long presses, or continuous presses to misrecognize key combinations, leading to overall malfunction and impacting normal use. Furthermore, traditional matrix keyboards are typically designed with a single, repetitive design that only works for the current scenario, thus limiting their application.

[0003] In order to filter out electromagnetic interference such as spikes in the external field environment, a matrix-coded keyboard circuit was designed. Although the production cost is low, the circuit function of the matrix keyboard may be affected because the design does not use relevant protection. Utility Model Content

[0004] In view of this, the embodiments of the present application provide a keyboard circuit and keyboard based on a USB interface, which can effectively solve the problem that the existing matrix keyboard is easily interfered with and causes malfunction.

[0005] In a first aspect, an embodiment of the present application provides a keyboard circuit based on a USB interface, comprising a signal denoising module, a buffer input module, a signal processing module, and an output protection module;

[0006] The signal denoising module includes a plurality of first filtering units; an input end of each first filtering unit is connected to a key of a keyboard, and the first filtering unit is used to filter the key signal of the key to obtain a filtered signal;

[0007] The input end of the buffer input module is connected to the output end of the first filtering unit; the buffer input module is used to buffer the filtered signal to obtain a valid signal;

[0008] The input end of the signal processing module is connected to the output end of the buffer input module; the signal processing module is used to receive the valid signals and process each of the valid signals to obtain a result signal;

[0009] The output protection module includes a USB interface, the input end of the output protection module is connected to the output end of the signal processing module, and the output end of the output protection module is connected to the host computer through the USB interface to transmit the result signal to the host computer.

[0010] In some embodiments, the signal denoising module further includes a plurality of second filtering units; each of the second filtering units is connected to an output end of each of the first filtering units in a one-to-one correspondence.

[0011] In some embodiments, the first filtering unit includes a filtering resistor and a filtering capacitor; a first end of the filtering resistor is connected to a power supply, and a second end of the filtering resistor is connected to the first pin of the button;

[0012] The first end of the filter capacitor is grounded, and the second end of the filter capacitor is connected to the second pin of the button; the third pin and the fourth pin of the button are grounded.

[0013] In some embodiments, the second filtering unit includes a transient voltage suppressor diode; a second end of the transient voltage suppressor diode is grounded, and a first end of the transient voltage suppressor diode is connected to the second end of the filtering resistor.

[0014] In some embodiments, the buffer input module includes multiple transmission channels, each of which is connected one-to-one with the output end of each first filtering unit; the buffer input module buffers the filtered signals corresponding to different keys through each transmission channel and outputs them to the signal processing module.

[0015] In some embodiments, the buffered input module further includes a direction enable pin and a module enable pin;

[0016] The direction enable pin is used to receive a direction control signal, and the direction control signal is used to control the transmission direction of all the transmission channels;

[0017] The module enable pin is used to receive a module control signal, and the module control signal is used to determine whether to enable the buffer output function of the buffer input module.

[0018] In some embodiments, the signal processing module includes a microcontroller unit;

[0019] The input end of the micro control unit is connected to the output end of the buffer input module, and is used to receive the valid signal corresponding to the corresponding key.

[0020] In some embodiments, the USB interface adopts the HID protocol, and the result signal is transmitted to the host computer based on the HID protocol.

[0021] In some embodiments, the output protection module includes an electrostatic discharge tube, which includes multiple electrostatic protection pins; each of the electrostatic protection pins is connected to the connection point between the signal processing module and the host computer; the static point discharge tube is used to perform electrostatic protection on the result signal.

[0022] In a second aspect, an embodiment of the present application provides a keyboard comprising a plurality of keys and the above-mentioned USB interface-based keyboard circuit; the keyboard circuit is used to independently control the transmission of the key signal of each key.

[0023] The embodiments of the present application have the following beneficial effects:

[0024] The keyboard circuit based on the USB interface of the present application filters the jitter interference signal in the key signal of each key through each first filtering unit of the signal denoising module, that is, it realizes independent denoising of each key, and then further improves the accuracy of the effective signal through the buffering processing of the buffer input module; in other words, it passes through multiple protections of the signal denoising module and the buffer input module, thereby improving the reliability and accuracy of the key signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0026] Figure 1 A schematic structural diagram of a matrix keyboard in the prior art is shown;

[0027] Figure 2 A schematic diagram of the principle structure of the keyboard circuit according to an embodiment of the present application is shown;

[0028] Figure 3 shows a first part of the circuit diagram of the keyboard circuit according to an embodiment of the present application;

[0029] Figure 4 A schematic diagram of the filtering principle of an embodiment of the present application is shown;

[0030] Figure 5 A schematic diagram of the circuit structure of the buffer input module according to an embodiment of the present application is shown;

[0031] Figure 6 A schematic diagram of a tri-state logic gate circuit of a buffer input module according to an embodiment of the present application is shown;

[0032] Figure 7 A schematic diagram of the circuit structure of the electrostatic discharge tube according to an embodiment of the present application is shown.

[0033] Description of main component symbols:

[0034] 10-Signal denoising module; 20-Buffer input module; 30-Signal processing module; 40-Output protection module. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments.

[0036] The components of the embodiments of the present application generally described and illustrated in the drawings herein may be arranged and designed in a variety of different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed application, but rather merely represents selected embodiments of the present application. All other embodiments obtained by those skilled in the art based on the embodiments of the present application without creative effort are within the scope of protection of the present application.

[0037] Hereinafter, the terms "including", "having" and their cognates used in various embodiments of the present application are intended only to indicate specific features, numbers, steps, operations, elements, components or combinations of the aforementioned items, and should not be understood as excluding the existence of one or more other features, numbers, steps, operations, elements, components or combinations of the aforementioned items or adding the possibility of one or more features, numbers, steps, operations, elements, components or combinations of the aforementioned items. In addition, the terms "first", "second", "third" and the like are only used to distinguish descriptions and should not be understood as indicating or implying relative importance.

[0038] Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by those skilled in the art to which the various embodiments of the present application belong. The terms (such as those defined in generally used dictionaries) will be interpreted as having the same meaning as in the context of the relevant technical field and will not be interpreted as having an idealized meaning or an overly formal meaning unless clearly defined in the various embodiments of the present application.

[0039] The following describes some embodiments of the present application in detail with reference to the accompanying drawings. In the absence of conflict, the following embodiments and features in the embodiments may be combined with each other.

[0040] Although the traditional matrix keyboard can realize the keyboard function under the optimal cost, its filtering effect on various interferences is extremely limited. Even if the key jitter itself can be filtered out by the single-chip microcomputer software, the key signal mixed with interference makes the software program writing more complicated; and after filtering, interference sources such as spikes may still penetrate through a certain link in the middle, causing the matrix keyboard to malfunction. It can be seen that most keyboards currently do not seriously examine the adverse effects of interference in the industrial field use environment on their circuits in order to optimize costs or based on the principle of being sufficient. As a result, the correctness and efficiency of the keyboard performance are affected, resulting in fewer usable working scenarios. In view of this, the present application proposes a keyboard circuit and keyboard based on a USB interface.

[0041] The keyboard circuit and keyboard based on the USB interface are described below with reference to some specific embodiments.

[0042] Figure 2 A schematic diagram of a USB-based keyboard circuit according to an embodiment of the present application is shown. Figure 3 A circuit diagram of a USB-based keyboard circuit according to an embodiment of the present application is shown. Exemplarily, the USB-based keyboard circuit includes a signal denoising module 10 , an input buffer module 20 , a signal processing module 30 , and an output protection module 40 .

[0043] The signal denoising module 10 includes a plurality of first filtering units; an input end of each first filtering unit is connected to a key of a keyboard, and the first filtering unit is used to filter the key signal of the key to obtain a filtered signal.

[0044] The input end of the buffer input module 20 is connected to the output end of the first filtering unit; the buffer input module is used to perform buffering processing on the filtered signal to obtain a valid signal.

[0045] The input end of the signal processing module 30 is connected to the output end of the buffer input module; the signal processing module receives valid signals and processes each valid signal to obtain a result signal.

[0046] The output protection module 40 includes a USB interface. The input end of the output protection module 40 is connected to the output end of the signal processing module. The output end of the output protection module is connected to the host computer through the USB interface to transmit the result signal to the host computer.

[0047] The key circuit of the present application filters the jitter interference signal in the initial key signal of each key through each first filtering unit of the signal denoising module, and then buffers it through the buffer input module, thereby improving the accuracy of the effective signal and thus improving the reliability of the result signal.

[0048] In some embodiments, the signal processing module includes a microcontroller unit; the input end of the microcontroller unit is connected to the output end of the buffer input module for receiving a valid signal corresponding to a corresponding key; and the input end of the microcontroller unit is an I / O interface.

[0049] In some embodiments, each first filtering unit includes a filter resistor R1 and a filter capacitor C1; the first end of the filter resistor R1 is connected to the power supply VCC, and the second end of the filter resistor R1 is connected to the first pin 1 of the button; the first end of the filter capacitor C1 is grounded, and the second end of the filter capacitor C1 is connected to the second pin 2 of the button, and the third pin 3 and the fourth pin 4 of the button SW are both grounded.

[0050] It can be understood that the first filtering unit filters and de-jitters part of the interference signal based on the RC filtering circuit composed of the filtering resistor R1 and the filtering capacitor C1. Figure 3 As shown, the filter resistor R1 is connected in parallel with the button SW and then connected to the first plate of the filter capacitor C1. The charge is transferred inside the filter capacitor to the second plate of the filter capacitor C1 and then input into the ground. Figure 4 The filtering principle of the first filtering unit shown is: when the button SW is pressed, the filter capacitor C1 discharges quickly, and the voltage at both ends is 0 after the discharge is completed; when the button is released, the power supply VCC flows along the filter resistor R1 and through the filter capacitor to the ground. At this time, the RC filter circuit charges the capacitor, and after the RC time constant, the capacitor voltage reaches the power supply voltage, preventing the level change of the button from making a large voltage mutation in a short time, so as to filter out the jitter interference level.

[0051] In this embodiment, the signal denoising module further includes a plurality of second filtering units; each second filtering unit is connected to each first filtering unit in a one-to-one correspondence; and the second filtering unit is used to further process interference in the filtered signal.

[0052] The signal denoising module of the present application effectively denoises various interference signals in the key signal through the first filtering unit and the second filtering unit, thereby improving the accuracy of the filtered signal.

[0053] In one embodiment, the second filtering unit includes a transient voltage suppressor diode D (TRANSIENT VOLTAGESUPPRESSOR, TVS tube); the second end of the transient voltage suppressor diode is grounded, and the first end of the transient voltage suppressor diode is connected to the second end of the filter resistor R1. The TVS tube can be bidirectional; it should be noted that the present application does not limit the specific model of the TVS tube, as long as it can withstand large current and high voltage. It can be understood that for interference signals, the TVS tube uses the principle of forward conduction and reverse cutoff of the clamping diode to provide a path for the release of static electricity, which can release an electrostatic surge voltage of more than ten kilovolts within a few microseconds. Therefore, the TVS tube has a very fast response capability and a strong surge absorption capability, and is mainly used at the power input end to absorb surges and protect the subsequent circuits.

[0054] In this embodiment, the buffered input module includes multiple transmission channels, each of which is connected to the output of each first filter unit in a one-to-one correspondence. The buffered input module buffers the filtered signals corresponding to different keys through each transmission channel and outputs them to the signal processing module. This buffered input module effectively prevents interference of a higher magnitude from burning out the second filter unit and then transmitting to the signal processing module, potentially burning out components within the signal processing module and affecting the normal function of the keyboard circuit.

[0055] In one embodiment, the buffer input module uses a three-state logic gate circuit and further includes a module enable pin. And direction enable pin DIR; the direction enable pin receives the direction control signal to control the transmission direction of all transmission channels, and the module enable pin receives the module control signal to decide whether to enable the buffer output function of the buffer input module.

[0056] Each key signal is input into the A port of the buffer input module after passing through the RC circuit of the first filtering unit, and then the filtered signal is output to the signal processing module through the B port of the buffer input module; it can also be input into the B port of the buffer input module first, and then the filtered signal is output to the signal processing module through the A port of the buffer input module.

[0057] Exemplarily, the buffer input module includes eight transmission channels, such as Figure 5 As shown, A1 and B1 are one transmission channel, A2 and B2 are one transmission channel, ..., A8 and B8 are one transmission channel. The first pin DIR is the direction enable pin. When the direction enable pin is pulled down to ground, Figure 3 As shown, the transmission direction of the transmission channel is from A to B, that is, end A is the input end and end B is the output end. Figure 6 As shown, pin 19 The module enable pin can be configured into three states: high active, low active, and disabled high impedance state, depending on whether the module enable pin is valid or not. The module enable pin is low active, that is, when the input is low level, the enable pin is in the valid state. Therefore, the buffering principle of the buffer input module in the embodiment of the present application is a three-state logic gate circuit with enable pin control. The logic diagram of the three-state logic gate circuit is shown in FIG. Figure 6 As shown, the module control signal received by the module enable pin is inverted and input into the AND gate together with the direction control signal received by the direction enable pin, and a first sub-control signal is output. The module control signal received by the module enable pin and the direction control signal received by the direction enable pin are respectively inverted and input into the AND gate together, and a second sub-control signal is output. According to the first sub-control signal and the second sub-control signal, the A end of each transmission channel is used as the input end and the B end is used as the output end. The filtered signal is input to the A end of the transmission channel and output through the B end.

[0058] The buffer input module of the present application includes but is not limited to a tri-state logic gate, an optocoupler, a capacitive coupled isolator, and the like.

[0059] The output protection module of this embodiment includes a USB interface, which connects the signal processing module and the host computer; the result signal is transmitted to the host computer via the USB interface. The USB interface hardware of the keyboard circuit of this application has its own NRZI encoding, which can effectively prevent interference from being transmitted to the host computer to a certain extent. It can achieve high conversion efficiency under certain interference, and the keyboard circuit itself has low operating loss. In addition, the USB interface adopts the HID protocol, which has cross-platform characteristics, which is beneficial to the scope of application and reusable design of the circuit.

[0060] The output protection module in this embodiment also includes an ESD (electrostatic discharge) diode (ESD). The ESD diode includes a power pin, a ground pin, and multiple ESD protection pins. Each ESD protection pin is connected to the connection point between the signal processing module and the host computer. The ESD diode provides ESD protection for the resulting signal. The ESD diode is primarily used to provide ESD protection on key pins, such as I / O ports and USB interfaces. It is suitable for applications requiring low-capacitance, high-speed signal transmission.

[0061] For example, Figure 7The electrostatic discharge tube shown includes a first clamping diode D1, a second clamping diode D2, a third clamping diode D3, a fourth clamping diode D4 and a voltage regulator WD; the anode of the first clamping diode D1 is connected to the cathode of the second clamping diode D2, the connection point of the first clamping diode D1 and the second clamping diode D2 is connected to the first I / O pin (I / O1), and the connection point of the first clamping diode D1 and the second clamping diode D2 is connected to the fourth I / O pin (I / O4) through the third resistor R3; the anode of the third clamping diode D3 is connected to the cathode of the fourth clamping diode D4. The cathode of the first clamping diode D1 and the cathode of the third clamping diode D3 are connected to the cathode of the Zener diode WD, and the anode of the second clamping diode D2 and the anode of the fourth clamping diode D4 are connected to the anode of the Zener diode WD; the anode of the Zener diode WD is grounded, and the cathode of the Zener diode WD is connected to the power supply.

[0062] The ESD tube uses the protection principle of forward conduction and reverse cutoff of the clamping diode to provide a discharge channel for static electricity. Whether the static electricity enters the signal line from the ESD protection pins (I / O1, I / O2) on the left side of the ESD tube or the ESD protection pins (I / O3, I / O4) on the right side, the signal enters between the two clamping diodes on the upper side when passing through the ESD tube. The positive voltage higher than the normal signal level is discharged to the left through the clamping diodes (D1, D3) on the left, while the negative voltage is discharged to GND through the clamping diodes (D2, D4) on the right, to ensure normal communication of the signal line.

[0063] The transmission control principle process of the key signal in the keyboard circuit of the present application is as follows: the interference signal is de-jittered and filtered by the first filtering unit and the second filtering unit; if the interference signal is too strong, the TVS protection tube in the second filtering unit is burned, and such strong interference is blocked by the buffer input module to prevent it from entering the signal processing module and burning the MCU microcontroller, affecting the overall normal function; even if the interference signal of a certain key signal is too strong, it will only cause the corresponding transmission channel in the buffer input module to be burned, so only one key function is affected, and the other keys can still work normally; and in the matrix-type keyboard design, as long as one key is interfered with, the entire row and column of this key will be affected in different situations. Therefore, the key circuit of the present application can ensure that each key signal is normally recognized, and can also prevent strong interference from burning the MCU (microcontroller); after all key input signals pass through these two layers of protection, they are recognized and integrated by the MCU in the signal processing module, converted into key information within the USBHID protocol and transmitted to the host computer for use. The output protection module between the signal processing module and the host computer can be used as a filter for interference in the front stage, and can also be used as an interference filter during the communication process between the back stage and the host computer, thereby improving the reliability of the key signal during the transmission process and further improving the reliability of the keyboard circuit based on the USB interface.

[0064] The present application also provides a keyboard. Exemplarily, the keyboard includes a plurality of keys and a keyboard circuit based on a USB interface; the keyboard circuit is configured to independently control the transmission of a key signal from each key.

[0065] It can be understood that the options in the above embodiment are also applicable to this embodiment, so they will not be described again here.

[0066] The keyboard of the present application corresponds each key one-to-one to the first filter unit and the second filter unit in the signal denoising module through the keyboard circuit; when strong electromagnetic interference is detected that may affect the signal reliability, the first filter unit and the second filter unit can filter out various common interferences outside the site; and then the residual interference signal that has not been filtered out is sent to the buffer input module to prevent the existence of interference; at the same time, the USB interface level coding in the output protection module can effectively prevent possible interference signals from being transmitted to the host computer, that is, the key signal of each key of the keyboard of the present application is independently transmitted and controlled, which can prevent the interference signal from entering and destroying the normal operation of all keys; it can achieve high conversion efficiency under certain interference, and the keyboard circuit has low working loss.

[0067] The above is only a specific implementation method of the present application, but the scope of protection of the present application is not limited thereto. Any technician familiar with this technical field can easily think of changes or replacements within the technical scope disclosed in this application, which should be covered by the scope of protection of the present application.

Claims

1. A keyboard circuit based on a USB interface, characterized in that: It includes signal denoising module, buffer input module, signal processing module and output protection module; The signal denoising module includes a plurality of first filtering units; an input end of each first filtering unit is connected to a key of a keyboard, and the first filtering unit is used to filter the key signal of the key to obtain a filtered signal; The input end of the buffer input module is connected to the output end of the first filtering unit; the buffer input module is used to buffer the filtered signal to obtain a valid signal; The input end of the signal processing module is connected to the output end of the buffer input module; the signal processing module is used to receive the valid signals and process each of the valid signals to obtain a result signal; The output protection module includes a USB interface, the input end of the output protection module is connected to the output end of the signal processing module, and the output end of the output protection module is connected to the host computer through the USB interface to transmit the result signal to the host computer.

2. The USB interface-based keyboard circuit according to claim 1, characterized in that: The signal denoising module further includes a plurality of second filtering units; each of the second filtering units is connected to an output end of each of the first filtering units in a one-to-one correspondence.

3. The USB interface-based keyboard circuit according to claim 2, characterized in that: The first filtering unit includes a filtering resistor and a filtering capacitor; The first end of the filter resistor is connected to the power supply, and the second end of the filter resistor is connected to the first pin of the button; The first end of the filter capacitor is grounded, and the second end of the filter capacitor is connected to the second pin of the button; the third pin and the fourth pin of the button are both grounded.

4. The USB interface-based keyboard circuit according to claim 3, characterized in that: The second filtering unit includes a transient voltage suppressor diode; a second end of the transient voltage suppressor diode is grounded, and a first end of the transient voltage suppressor diode is connected to the second end of the filtering resistor.

5. The USB interface-based keyboard circuit according to claim 1, characterized in that: The buffer input module includes multiple transmission channels, each of which is connected to the output end of each first filtering unit in a one-to-one correspondence; the buffer input module buffers the filtered signals corresponding to different keys through each transmission channel and outputs them to the signal processing module.

6. The USB interface-based keyboard circuit according to claim 5, characterized in that: The buffer input module also includes a direction enable pin and a module enable pin; The direction enable pin is used to receive a direction control signal, and the direction control signal is used to control the transmission direction of all the transmission channels; The module enable pin is used to receive a module control signal, and the module control signal is used to determine whether to enable the buffer output function of the buffer input module.

7. The USB interface-based keyboard circuit according to claim 1, characterized in that: The signal processing module includes a micro control unit; The input end of the micro control unit is connected to the output end of the buffer input module, and is used to receive the valid signal corresponding to the corresponding key.

8. The USB interface-based keyboard circuit according to claim 1, characterized in that: The USB interface adopts the HID protocol, and the result signal is transmitted to the host computer based on the HID protocol.

9. The USB interface-based keyboard circuit according to claim 1, characterized in that: The output protection module includes an electrostatic discharge tube, which includes multiple electrostatic protection pins; each of the electrostatic protection pins is connected to the connection point between the signal processing module and the host computer; the electrostatic discharge tube is used to perform electrostatic protection on the result signal.

10. A keyboard, characterized in that: The keyboard includes a plurality of keys and a USB interface-based keyboard circuit as described in any one of claims 1 to 9; the keyboard circuit is used to independently control the transmission of the key signal of each key.

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