Communication Circuit between a Monitor Keyboard and a Host Terminal

Abstract

The present invention relates to the technical field of keyboard systems, and in particular to a communication circuit for a keyboard with a display and a host terminal, which includes a controller, a power supply module, a display control module, a key control module, and a data communication module. The controller includes a single-chip microcomputer chip U1, and the data communication module includes a CDC chip U2. The ADC9 terminal, ADC10 terminal, ADC11 terminal, and ADC12 terminal of the single-chip microcomputer chip U1 are all electrically connected to the V3 terminal of the CDC chip U2; the key control module includes a power conversion chip U3, an electrical connection row CON1 electrically connected to the single-chip microcomputer chip, and an electrical connection row CON2 electrically connected to the power conversion chip U3. The 2nd terminal and the 3rd terminal of the electrical connection row CON2 are respectively electrically connected to the UD- terminal and the UD+ terminal of the CDC chip U2. The present invention realizes the compatibility of the keyboard with the mainstream USB interface of the host terminal through the USB-to-CDC communication method, and at the same time, the communication can be directly carried out by the serial port method considering the cost.

Description

Technical Field

[0001] The present invention relates to the technical field of keyboard systems, and in particular to a communication circuit between a keyboard with a display and a host terminal. Background Art

[0002] The keyboard is the most commonly used and main input device. Through the keyboard, English letters, numbers, punctuation marks, etc. can be input into the host, so as to send commands to the host, input data, etc.

[0003] Currently, host keyboards, especially keyboards with a display screen, all use the USB HID method for communication. Such keyboards generally only input information to the host. If information needs to be displayed on the keyboard, usually only the local information of the keyboard itself can be displayed, and the information echo of the host cannot be realized. Moreover, there are a wide variety of current hosts, and not all hosts can provide a USB interface, but only provide ordinary serial interfaces (such as TTL, RS232, etc.). The USB interface keyboard cannot be used. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a communication circuit between a keyboard with a display and a host terminal. The present invention realizes the compatibility of the keyboard with the mainstream USB interface of the host terminal through the USB to CDC communication method, and at the same time, the communication can be directly carried out by the serial port method considering the cost. Moreover, the device requirements of the present invention are low, the program development difficulty is low, the compatibility is good, and the product function is flexibly realized.

[0005] To solve the above technical problem, the present invention adopts the following technical scheme: A communication circuit between a keyboard with a display and a host terminal, including a controller, a power supply module, a display control module, and a key control module. The controller includes a single-chip microcomputer chip U1; it also includes a data communication module, and this data communication module includes a CDC chip U2. The ADC9 terminal, ADC10 terminal, ADC11 terminal, and ADC12 terminal of the single-chip microcomputer chip U1 are all electrically connected to the V3 terminal of the CDC chip U2; the key control module includes an electrical connection row CON1, a power conversion chip U3, and an electrical connection row CON2 electrically connected to the power conversion chip U3. The 2nd terminal and the 3rd terminal of this electrical connection row CON2 are respectively electrically connected to the UD- terminal and the UD+ terminal of the CDC chip U2. The 1st terminal, 2nd terminal, 3rd terminal, 5th terminal, 6th terminal, 7th terminal, 8th terminal, 10th terminal, 11th terminal, and 12th terminal of the electrical connection row CON1 are respectively electrically connected to the P00 terminal, P01 terminal, P02 terminal, ADC9 terminal, ADC10 terminal, ADC11 terminal, ADC12 terminal, XMO terminal, XMI terminal, and P03 terminal of the single-chip microcomputer chip U1.

[0006] Preferably, a resistor R3 is connected in series between the ADC9 terminal of the single-chip microcomputer chip U1 and the V3 terminal of the CDC chip U2, a resistor R4 is connected in series between the ADC10 terminal of the single-chip microcomputer chip U1 and the V3 terminal of the CDC chip U2, a resistor R5 is connected in series between the ADC11 terminal of the single-chip microcomputer chip U1 and the V3 terminal of the CDC chip U2, and a resistor R9 is connected in series between the ADC12 terminal of the single-chip microcomputer chip U1 and the V3 terminal of the CDC chip U2.

[0007] Preferably, the RXD terminal of the CDC chip U2 is connected in series with a resistor R1 and then electrically connected to the TX1 terminal of the single-chip microcomputer chip U1, and the RXD terminal of the CDC chip U2 is also connected in series with a resistor R6 and then electrically connected to the UD+ terminal of the CDC chip U2; the TXD terminal of the CDC chip U2 is connected in series with a diode D1 and then electrically connected to the RX1 terminal of the single-chip microcomputer chip U1, and the TXD terminal of the CDC chip U2 is also connected in series with a resistor R7 and then electrically connected to the UD- terminal of the CDC chip U2.

[0008] Preferably, both the V3 terminal and the VCC terminal of the CDC chip U2 are electrically connected to the power supply voltage VDD, and the VCC terminal of the CDC chip U2 is also connected in series with a capacitor C2 and then grounded; the GND terminal of the CDC chip U2 is grounded.

[0009] Preferably, the OUT terminal of the power conversion chip U3 is connected in series with a capacitor C5 and then grounded, and this capacitor C5 is connected in parallel with a capacitor C6, and the OUT terminal of the power conversion chip U3 is electrically connected to the power supply voltage VDD.

[0010] Preferably, the 1st terminal of the electrical connection row CON2 is electrically connected to the IN terminal of the power conversion chip U3, and the 1st terminal of the electrical connection row CON2 is also electrically connected to the USB power supply voltage VBUS; the 4th terminal of the electrical connection row CON2 is connected in series with a capacitor C3 and then electrically connected to the EN terminal of the power conversion chip U3, the 5th terminal of the electrical connection row CON2 is electrically connected to the 4th terminal of the electrical connection row CON2 and then grounded; the GND terminal of the power conversion chip U3 is grounded; the capacitor C3 is connected in parallel with a capacitor C7.

[0011] Preferably, a resistor R8 is electrically connected between the IN terminal of the power conversion chip U3 and the OUT terminal of the processor, and this resistor R8 is also electrically connected to the EN terminal of the power conversion chip U3.

[0012] Preferably, the display control module includes an electrical connection row CON3, and the COM0 terminal to the COM3 terminal of this electrical connection row CON3 are respectively and electrically connected to the BCOM0 to BCOM3 of the single-chip microcomputer chip U1 in correspondence, and the SEG0 terminal to the SEG17 terminal of the electrical connection row CON3 are respectively and electrically connected to the BSEG0 to BSEG17 of the single-chip microcomputer chip U1 in correspondence.

[0013] Preferably, the power supply circuit includes a buzzer BUZZ and a MOS transistor. The negative pole of the buzzer is electrically connected to the 2-terminal of the MOS transistor. The 3-terminal of the MOS transistor is grounded. A resistor R14 is connected in series to the 1-terminal of the MOS transistor and then electrically connected to the XSO terminal of the single-chip microcomputer chip U1. The positive pole of the buzzer is sequentially connected in series with an LED lamp LD1 and a resistor R13 and then electrically connected to the PWM1 terminal of the single-chip microcomputer chip U1.

[0014] Preferably, the positive pole of the buzzer and the LED lamp LD1 are both electrically connected to the VDD terminal of the single-chip microcomputer chip U1. The VDD terminal of the single-chip microcomputer chip U1 is electrically connected to the power supply voltage VDD. The VSS terminal of the single-chip microcomputer chip U1 is grounded. And a capacitor C1 is electrically connected between the VDD terminal and the VSS terminal of the single-chip microcomputer chip U1. The NRST / SWUT terminal of the single-chip microcomputer chip U1 is electrically connected to a jumper JP1. This jumper JP1 is electrically connected to a resistor R2 and then to the VDD terminal of the single-chip microcomputer chip U1. The jumper JP1 is also electrically connected to a capacitor C4 and then grounded.

[0015] Preferably, the data communication module further includes a socket CN1 adopting the SWD debugging method. The 1-terminal of this socket CN1 is connected in series with a resistor R48 and then electrically connected to the power supply voltage VDD. The 2-terminal of the socket CN1 is connected in series with a resistor R51 and then electrically connected to the NRST / SWUT terminal of the single-chip microcomputer chip U1. The 3-terminal of the socket CN1 is grounded.

[0016] The beneficial effects of the present invention are as follows: The present invention provides a communication circuit for a display keyboard and a host terminal. The present invention realizes the compatibility of the keyboard with the mainstream USB interface of the host terminal through the USB to CDC communication method. At the same time, it can directly use the serial port method for communication considering cost. Moreover, the device requirements of the present invention are low, the program development difficulty is low, the compatibility is good, and the product function is flexibly realized. Description of the Drawings

[0017] Figure 1 It is the circuit principle block diagram of the communication circuit for the display keyboard and the host terminal of the present invention.

[0018] Figure 2 It is the circuit principle block diagram of the single-chip microcomputer chip U1 in the communication circuit for the display keyboard and the host terminal of the present invention.

[0019] Figure 3 It is the circuit principle block diagram of the power supply module in the communication circuit for the display keyboard and the host terminal of the present invention.

[0020] Figure 4 It is the circuit principle block diagram of the display control module in the communication circuit for the display keyboard and the host terminal of the present invention.

[0021] Figure 5This is the circuit principle block diagram of the key control module in the communication circuit of the display keyboard and the host terminal of the present invention.

[0022] Figure 6 This is the circuit principle block diagram of the data communication module in the communication circuit of the display keyboard and the host terminal of the present invention.

[0023] Figure 7 This is the system principle block diagram of the communication circuit of the display keyboard and the host terminal of the present invention. Detailed implementation manners

[0024] For the convenience of those skilled in the art to understand, the present invention will be further described below in conjunction with embodiments. The content mentioned in the implementation manners does not limit the present invention.

[0025] As Figures 1 to 7 shown, the communication circuit of the display keyboard and the host terminal includes a controller 1, a power supply module 2, a display control module 3, and a key control module 4. The controller 1 includes a single-chip microcomputer chip U1;

[0026] It further includes a data communication module 5. The data communication module 5 includes a CDC chip U2. The ADC9 terminal, ADC10 terminal, ADC11 terminal, and ADC12 terminal of the single-chip microcomputer chip U1 are all electrically connected to the V3 terminal of the CDC chip U2;

[0027] The key control module 4 includes an electrical connection row CON1, a power conversion chip U3, and an electrical connection row CON2 electrically connected to the power conversion chip U3. The 2nd terminal and 3rd terminal of the electrical connection row CON2 are respectively electrically connected to the UD- terminal and UD+ terminal of the CDC chip U2. The 1st terminal, 2nd terminal, 3rd terminal, 5th terminal, 6th terminal, 7th terminal, 8th terminal, 10th terminal, 11th terminal, and 12th terminal of the electrical connection row CON1 are respectively electrically connected to the P00 terminal, P01 terminal, P02 terminal, ADC9 terminal, ADC10 terminal, ADC11 terminal, ADC12 terminal, XMO terminal, XMI terminal, and P03 terminal of the single-chip microcomputer chip U1.

[0028] Preferably, the single-chip microcomputer chip U1 is an LQFP44 single-chip microcomputer, and the CDC chip U2 is a chip CH340E.

[0029] The data communication module 5 is a USB to CDC serial port module / serial port direct bridge, which allows users to select different interfaces for matching communication according to the interface resource situation of the host;

[0030] The single-chip microcomputer chip U1 is the main controller, which is the core controller of the keyboard. It is configured to receive the data from the data communication module 5, decode the data to separate the payload, and then send the payload data to the display control module 3. It also receives the key information from the key control module 4, encodes and packages it into standard serial port data and sends it out.

[0031] The display control module 3 is configured to receive the display data sent by the single-chip microcomputer chip U1 and generate corresponding control signals to drive the display for display.

[0032] The key control module 4 continuously sends out electrical signals for key monitoring. Once a key is pressed, the key control module 4 encodes the currently input key into key value data, and then the key control module 4 transmits the key value to the single-chip microcomputer chip U1.

[0033] In this embodiment, a resistor R3 is connected in series between the ADC9 terminal of the single-chip microcomputer chip U1 and the V3 terminal of the CDC chip U2, a resistor R4 is connected in series between the ADC10 terminal of the single-chip microcomputer chip U1 and the V3 terminal of the CDC chip U2, a resistor R5 is connected in series between the ADC11 terminal of the single-chip microcomputer chip U1 and the V3 terminal of the CDC chip U2, and a resistor R9 is connected in series between the ADC12 terminal of the single-chip microcomputer chip U1 and the V3 terminal of the CDC chip U2.

[0034] In this embodiment, the RXD terminal of the CDC chip U2 is connected in series with a resistor R1 and then electrically connected to the TX1 terminal of the single-chip microcomputer chip U1, and the RXD terminal of the CDC chip U2 is also connected in series with a resistor R6 and then electrically connected to the UD+ terminal of the CDC chip U2; the TXD terminal of the CDC chip U2 is connected in series with a diode D1 and then electrically connected to the RX1 terminal of the single-chip microcomputer chip U1, and the TXD terminal of the CDC chip U2 is also connected in series with a resistor R7 and then electrically connected to the UD- terminal of the CDC chip U2.

[0035] In this embodiment, the V3 terminal and the VCC terminal of the CDC chip U2 are both electrically connected to the power supply voltage VDD, and the VCC terminal of the CDC chip U2 is also connected in series with a capacitor C2 and then grounded; the GND terminal of the CDC chip U2 is grounded.

[0036] In this embodiment, the OUT terminal of the power conversion chip U3 is connected in series with a capacitor C5 and then grounded, and this capacitor C5 is connected in parallel with a capacitor C6. The OUT terminal of the power conversion chip U3 is electrically connected to the power supply voltage VDD.

[0037] In this embodiment, the 1st terminal of the electrical connection row CON2 is electrically connected to the IN terminal of the power conversion chip U3, and the 1st terminal of the electrical connection row CON2 is also electrically connected to the USB power supply voltage VBUS; the 4th terminal of the electrical connection row CON2 is connected in series with a capacitor C3 and then electrically connected to the EN terminal of the power conversion chip U3, and the 5th terminal of the electrical connection row CON2 is electrically connected to the 4th terminal of the electrical connection row CON2 and then grounded; the GND terminal of the power conversion chip U3 is grounded; the capacitor C3 is connected in parallel with a capacitor C7.

[0038] In this embodiment, a resistor R8 is electrically connected between the IN terminal of the power conversion chip U3 and the OUT terminal of the processor, and the resistor R8 is also electrically connected to the EN terminal of the power conversion chip U3.

[0039] In this embodiment, the display control module 3 includes an electrical connection row CON3. The COM0 terminal to the COM3 terminal of the electrical connection row CON3 are respectively and electrically connected to the BCOM0 to BCOM3 of the single-chip microcomputer chip U1 in correspondence, and the SEG0 terminal to the SEG17 terminal of the electrical connection row CON3 are respectively and electrically connected to the BSEG0 to BSEG17 of the single-chip microcomputer chip U1 in correspondence.

[0040] In this embodiment, the power supply circuit includes a buzzer BUZZ and a MOS transistor. The negative electrode of the buzzer is electrically connected to the 2nd terminal of the MOS transistor. The 3rd terminal of the MOS transistor is grounded. The 1st terminal of the MOS transistor is connected in series with a resistor R14 and then electrically connected to the XSO terminal of the single-chip microcomputer chip U1. The positive electrode of the buzzer is connected in series with an LED lamp LD1 and a resistor R13 in sequence and then electrically connected to the PWM1 terminal of the single-chip microcomputer chip U1. Preferably, the model of the MOS transistor is SI2301.

[0041] In this embodiment, both the positive electrode of the buzzer and the LED lamp LD1 are electrically connected to the VDD terminal of the single-chip microcomputer chip U1. The VDD terminal of the single-chip microcomputer chip U1 is electrically connected to the power supply voltage VDD. The VSS terminal of the single-chip microcomputer chip U1 is grounded, and a capacitor C1 is electrically connected between the VDD terminal and the VSS terminal of the single-chip microcomputer chip U1; a jumper JP1 is electrically connected to the NRST / SWUT terminal of the single-chip microcomputer chip U1. The jumper JP1 is electrically connected to a resistor R2 and then to the VDD terminal of the single-chip microcomputer chip U1, and the jumper JP1 is also electrically connected to a capacitor C4 and then grounded.

[0042] In this embodiment, the data communication module 5 further includes a socket CN1 adopting the SWD debugging method. The 1st terminal of the socket CN1 is connected in series with a resistor R48 and then electrically connected to the power supply voltage VDD. The 2nd terminal of the socket CN1 is connected in series with a resistor R51 and then electrically connected to the NRST / SWUT terminal of the single-chip microcomputer chip U1. The 3rd terminal of the socket CN1 is grounded. Preferably, the power supply voltage VDD is 3.3V.

[0043] The present invention realizes the compatibility of the keyboard with the mainstream USB interface of the host terminal through the USB-to-CDC communication method. At the same time, the communication can be directly carried out in the serial port mode considering the cost. Moreover, the device requirements of the present invention are low, the program development difficulty is low, the compatibility is good, and the product function can be realized flexibly.

[0044] In the description of the present invention, it should be noted that for the orientation terms, such as the terms "center", "horizontal (X)", "vertical (Y)", "vertical (Z)", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc., the indicated orientation and position relationship are based on the orientation or position relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and should not be construed as limiting the specific protection scope of the present invention.

[0045] In addition, such terms as "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, the meaning of "several" is two or more, unless otherwise specifically defined.

[0046] In the present invention, unless otherwise clearly specified and defined, such terms as "assembled", "connected", and "joined" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may also be a mechanical connection; it can be directly connected or connected through an intermediate medium, and it can be the internal connection and communication of two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0047] The above-described embodiments only represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as limiting the scope of the patent of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention should be subject to the appended claims.

Claims

1. The communication circuit of a keyboard with a display and a host terminal, comprising a controller (1), a power supply module (2), a display control module (3), and a key control module (4). It is characterized in that: The controller (1) includes a single-chip microcomputer chip U1; It further includes a data communication module (5), and this data communication module (5) includes a CDC chip U2. The ADC9 terminal, ADC10 terminal, ADC11 terminal, and ADC12 terminal of the single-chip microcomputer chip U1 are all electrically connected to the V3 terminal of the CDC chip U2; The key control module (4) includes an electrical connection row CON1, a power conversion chip U3, and an electrical connection row CON2 electrically connected to the power conversion chip U3. The 2nd terminal and the 3rd terminal of this electrical connection row CON2 are respectively electrically connected to the UD- terminal and the UD+ terminal of the CDC chip U2. The 1st terminal, 2nd terminal, 3rd terminal, 5th terminal, 6th terminal, 7th terminal, 8th terminal, 10th terminal, 11th terminal, and 12th terminal of the electrical connection row CON1 are respectively electrically connected to the P00 terminal, P01 terminal, P02 terminal, ADC9 terminal, ADC10 terminal, ADC11 terminal, ADC12 terminal, XMO terminal, XMI terminal, and P03 terminal of the single-chip microcomputer chip U1; The display control module includes an electrical connection row CON3. The COM0 terminal to the COM3 terminal of this electrical connection row CON3 are respectively electrically connected to the BCOM0 to BCOM3 of the single-chip microcomputer chip U1 correspondingly. The SEG0 terminal to the SEG17 terminal of the electrical connection row CON3 are respectively electrically connected to the BSEG0 to BSEG17 of the single-chip microcomputer chip U1 correspondingly; The display control module (3) is configured to receive the display data sent by the single-chip microcomputer chip U1 and generate corresponding control signals to drive the display for display.

2. The communication circuit of a keyboard with a display and a host terminal according to claim 1, It is characterized in that: A resistor R3 is connected in series between the ADC9 terminal of the single-chip microcomputer chip U1 and the V3 terminal of the CDC chip U2. A resistor R4 is connected in series between the ADC10 terminal of the single-chip microcomputer chip U1 and the V3 terminal of the CDC chip U2. A resistor R5 is connected in series between the ADC11 terminal of the single-chip microcomputer chip U1 and the V3 terminal of the CDC chip U2. A resistor R9 is connected in series between the ADC12 terminal of the single-chip microcomputer chip U1 and the V3 terminal of the CDC chip U2.

3. The communication circuit of a keyboard with a display and a host terminal according to claim 1, It is characterized in that: A resistor R1 is connected in series to the RXD terminal of the CDC chip U2 and then electrically connected to the TX1 terminal of the single-chip microcomputer chip U1, and a resistor R6 is also connected in series to the RXD terminal of the CDC chip U2 and then electrically connected to the UD+ terminal of the CDC chip U2. A diode D1 is connected in series to the TXD terminal of the CDC chip U2 and then electrically connected to the RX1 terminal of the single-chip microcomputer chip U1, and a resistor R7 is also connected in series to the TXD terminal of the CDC chip U2 and then electrically connected to the UD- terminal of the CDC chip U2.

4. The communication circuit of a keyboard with a display and a host terminal according to claim 1, It is characterized in that: The V3 terminal and the VCC terminal of the CDC chip U2 are both electrically connected to the power supply voltage VDD, and a capacitor C2 is also connected in series to the VCC terminal of the CDC chip U2 and then grounded; the GND terminal of the CDC chip U2 is grounded.

5. The communication circuit between the display keyboard and the host terminal according to claim 1, characterized in that: A capacitor C5 is connected in series to the OUT terminal of the power conversion chip U3 and then grounded, and a capacitor C6 is connected in parallel with this capacitor C5. The OUT terminal of the power conversion chip U3 is electrically connected to the power supply voltage VDD.

6. The communication circuit between the display keyboard and the host terminal according to claim 5, characterized in that: The 1st terminal of the electrical connection row CON2 is electrically connected to the IN terminal of the power conversion chip U3, and the 1st terminal of the electrical connection row CON2 is also electrically connected to the USB power supply voltage VBUS; a capacitor C3 is connected in series to the 4th terminal of the electrical connection row CON2 and then electrically connected to the EN terminal of the power conversion chip U3. The 5th terminal of the electrical connection row CON2 is electrically connected to the 4th terminal of the electrical connection row CON2 and then grounded; the GND terminal of the power conversion chip U3 is grounded; the capacitor C3 is connected in parallel with a capacitor C7.

7. The communication circuit between the display keyboard and the host terminal according to claim 6, characterized in that: A resistor R8 is electrically connected between the IN terminal of the power conversion chip U3 and the OUT terminal of the processor, and this resistor R8 is also electrically connected to the EN terminal of the power conversion chip U3.

8. The communication circuit between the display keyboard and the host terminal according to claim 1, characterized in that: The communication circuit includes a buzzer BUZZ and a MOS transistor. The negative pole of the buzzer is electrically connected to the 2nd terminal of the MOS transistor. The 3rd terminal of the MOS transistor is grounded. A resistor R14 is connected in series to the 1st terminal of the MOS transistor and then electrically connected to the XSO terminal of the single-chip microcomputer chip U1. The positive pole of the buzzer is sequentially connected in series with an LED lamp LD1 and a resistor R13 and then electrically connected to the PWM1 terminal of the single-chip microcomputer chip U1.

9. The communication circuit between the display keyboard and the host terminal according to claim 8, characterized in that: The positive pole of the buzzer and the LED lamp LD1 are both electrically connected to the VDD terminal of the single-chip microcomputer chip U1. The VDD terminal of the single-chip microcomputer chip U1 is electrically connected to the power supply voltage VDD. The VSS terminal of the single-chip microcomputer chip U1 is grounded, and a capacitor C1 is electrically connected between the VDD terminal and the VSS terminal of the single-chip microcomputer chip U1; a jumper JP1 is electrically connected to the NRST / SWUT terminal of the single-chip microcomputer chip U1. This jumper JP1 is electrically connected to a resistor R2 and then to the VDD terminal of the single-chip microcomputer chip U1. The jumper JP1 is also electrically connected to a capacitor C4 and then grounded.

10. The communication circuit between the display keyboard and the host terminal according to claim 1, characterized in that: The data communication module (5) further includes a socket CN1 adopting the SWD debugging method. The 1st terminal of this socket CN1 is connected in series with a resistor R48 and then electrically connected to the power supply voltage VDD. The 2nd terminal of the socket CN1 is connected in series with a resistor R51 and then electrically connected to the NRST / SWUT terminal of the single-chip microcomputer chip U1. The 3rd terminal of the socket CN1 is grounded.

Images