Communication device and communication system

Abstract

The utility model discloses a kind of communication device and communication system, it is related to communication technical field.Communication device includes: USB conversion chip, first RS485 chip, second RS485 chip, second RS485 chip is connected with first RS485 chip by RS485 communication line;USB conversion chip is adapted to connect host computer, is configured as receiving the USB signal of host computer output and conversion into UART signal, and receiving the UART signal of first RS485 chip output and conversion into USB signal;First RS485 chip is connected with USB conversion chip, is configured as receiving the UART signal of USB conversion chip output and conversion into RS485 signal, and receiving the RS485 signal of second RS485 chip output and conversion into UART signal;Second RS485 chip is adapted to connect the concentrator box of well logging system, is configured as receiving the RS485 signal of first RS485 chip output and conversion into UART signal, and receiving the UART signal of concentrator box output and conversion into RS485 signal. Thus, long-distance communication between host computer and concentrator box can be realized, and the anti-interference ability is strong.

Description

Technical Field

[0001] This utility model relates to the field of communication technology, and in particular to a communication device and a communication system. Background Technology

[0002] When the instrument is operating downhole, signals are transmitted to the surface via drilling mud. Mud sensors (such as riser pressure sensors) connected to a junction box collect these mud signals. The junction box processes the collected mud signals and uploads the processed data to a PC. However, because the mud sensors and junction box are located near the derrick, while the operators are in the instrument room, the distance between the two locations is considerable. Furthermore, various interferences exist at the well site, which can affect data communication. Utility Model Content

[0003] The purpose of this invention is to provide a communication device and system that enables long-distance communication and has strong anti-interference capabilities.

[0004] In a first aspect, this utility model proposes a communication device, the device comprising: a USB conversion chip, a first RS485 chip, and a second RS485 chip, the second RS485 chip being connected to the first RS485 chip via an RS485 communication line; the USB conversion chip being adapted to connect to a host computer and configured to receive USB signals output by the host computer and convert them into UART signals, and to receive UART signals output by the first RS485 chip and convert them into USB signals; the first RS485 chip being connected to the USB conversion chip and configured to receive UART signals output by the USB conversion chip and convert them into RS485 signals, and to receive RS485 signals output by the second RS485 chip and convert them into UART signals; the second RS485 chip being adapted to connect to a hub of a logging system and configured to receive RS485 signals output by the first RS485 chip and convert them into UART signals, and to receive UART signals output by the hub and convert them into RS485 signals.

[0005] In some examples, the device further includes: a first decoupling capacitor, a second decoupling capacitor, and a third decoupling capacitor; wherein the first decoupling capacitor is connected between the power supply terminal of the USB conversion chip and ground; the second decoupling capacitor is connected between the power supply terminal of the first RS485 chip and ground; and the third decoupling capacitor is connected between the power supply terminal of the second RS485 chip and ground.

[0006] In some examples, the device further includes: a first pull-up resistor, a second pull-up resistor, a third pull-up resistor, and a fourth pull-up resistor; wherein, one end of the first pull-up resistor is connected to a first preset power supply, and the other end of the first pull-up resistor is connected to a first UART port of the first RS485 chip; one end of the second pull-up resistor is connected to the first preset power supply, and the other end of the second pull-up resistor is connected to a shutdown mode port and a receive enable port of the first RS485 chip, respectively; one end of the third pull-up resistor is connected to a second preset power supply, and the other end of the second pull-up resistor is connected to a first UART port of the second RS485 chip; one end of the fourth pull-up resistor is connected to the second preset power supply, and the other end of the fourth pull-up resistor is connected to a shutdown mode port and a receive enable port of the second RS485 chip, respectively.

[0007] In some examples, the device further includes: a first bias resistor, a second bias resistor, a third bias resistor (R8), and a fourth bias resistor; wherein, One end of the first bias resistor is connected to the first RS485 port of the first RS485 chip, and the other end of the first bias resistor is grounded; one end of the second bias resistor is connected to the second RS485 port of the first RS485 chip, and the other end of the second bias resistor is connected to a first preset power supply; one end of the third bias resistor is connected to the first RS485 port of the second RS485 chip, and the other end of the third bias resistor is grounded; one end of the fourth bias resistor is connected to the second RS485 port of the second RS485 chip, and the other end of the fourth bias resistor is connected to a second preset power supply.

[0008] In some examples, the resistance values ​​of the first bias resistor and the second bias resistor are smaller than the resistance values ​​of the third bias resistor and the fourth bias resistor.

[0009] In some examples, the device further includes: a first current-limiting resistor, a second current-limiting resistor, a third current-limiting resistor, and a fourth current-limiting resistor; wherein the first current-limiting resistor is connected between a first RS485 port of the first RS485 chip and a first terminal of the RS485 communication line, the second current-limiting resistor is connected between a second RS485 port of the first RS485 chip and a second terminal of the RS485 communication line, the third current-limiting resistor is connected between a first RS485 port of the second RS485 chip and a third terminal of the RS485 communication line, and the fourth current-limiting resistor is connected between a second RS485 port of the second RS485 chip and a fourth terminal of the RS485 communication line.

[0010] In some examples, the device further includes: a first TVS diode and a second TVS diode; wherein, a first end of the first TVS diode is connected to a first RS485 port of the first RS485 chip and a first terminal of the RS485 communication line, a second end of the first TVS diode is connected to a second RS485 port of the first RS485 chip and a second terminal of the RS485 communication line, and a third end of the first TVS diode is grounded; a first end of the second TVS diode is connected to a first RS485 port of the second RS485 chip and a third terminal of the RS485 communication line, a second end of the second TVS diode is connected to a second RS485 port of the second RS485 chip and a fourth terminal of the RS485 communication line, and a third end of the second TVS diode is grounded.

[0011] In some examples, the USB conversion chip is model CH340N, with an operating voltage of 3.3V or 5V; the first RS485 chip and the second RS485 chip (U3) are model THVD1406DR, with an operating voltage of 3V~5.5V; or, the first RS485 chip and the second RS485 chip are model MAX13487EESA+, with an operating voltage of 4.75V~5.25V.

[0012] In some examples, the RS485 communication cable is a twisted-pair shielded cable with a length greater than 40 meters.

[0013] Secondly, this utility model proposes a communication system, including: a host computer, a hub box, and the communication device described in the first aspect.

[0014] The communication device and communication system of this utility model embodiment, by sequentially connecting a USB conversion chip, a first RS485 chip and a second RS485 chip between the host computer and the hub box of the logging system, and connecting the second RS485 chip and the first RS485 chip through an RS485 communication cable, can realize long-distance communication between the host computer and the hub box, and has strong anti-interference ability. Attached Figure Description

[0015] Figure 1 This is a structural block diagram of the communication device according to an embodiment of the present utility model; Figure 2 This is a circuit topology diagram of the communication device of the first example of this utility model; Figure 3 This is a circuit topology diagram of the communication device of the second example of this utility model; Figure 4 This is a circuit topology diagram of the communication device of the third example of this utility model; Figure 5This is a circuit topology diagram of the communication device of the fourth example of this utility model; Figure 6 This is a circuit topology diagram of the communication device of the fifth example of this utility model; Figure 7 This is a structural block diagram of the communication system according to an embodiment of the present utility model. Detailed Implementation

[0016] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this utility model, and should not be construed as limiting this utility model.

[0017] The communication device and communication system of the present invention are described below with reference to the accompanying drawings.

[0018] Figure 1 This is a structural block diagram of the communication device according to an embodiment of the present utility model.

[0019] like Figure 1 As shown, the communication device 10 includes: a USB conversion chip U1, a first RS485 chip U2, and a second RS485 chip U3. The second RS485 chip U3 is connected to the first RS485 chip U2 via an RS485 communication line 1.

[0020] See Figure 1 The USB conversion chip U1 is adapted to connect to the host computer 20 and is configured to receive the USB signal output by the host computer 20 and convert it into a UART signal, and to receive the UART signal output by the first RS485 chip U2 and convert it into a USB signal; the first RS485 chip U2 is connected to the USB conversion chip U1 and is configured to receive the UART signal output by the USB conversion chip U1 and convert it into an RS485 signal, and to receive the RS485 signal output by the second RS485 chip U3 and convert it into a UART signal; the second RS485 chip U3 is adapted to connect to the hub box 30 of the logging system and is configured to receive the RS485 signal output by the first RS485 chip U2 and convert it into a UART signal, and to receive the UART signal output by the hub box 30 and convert it into an RS485 signal.

[0021] In this embodiment, the host computer 20 can sequentially send commands to the hub box 30 via the USB conversion chip U1, the first RS485 chip U2, the RS485 communication line 1, and the second RS485 chip U3. Upon receiving the command, the hub box can sequentially reply via the second RS485 chip U3, the RS485 communication line 1, the first RS485 chip U2, and the USB conversion chip U1, such as uploading data processed from the mud signal to the PC. For example,... Figures 2-6 As shown, the USB conversion chip U1 and the first RS485 chip U2 are installed at the host computer 20 (referred to as the host end) in the instrument room, such as inside the ground box in the instrument room; the second RS485 chip U3 is installed at the hub box 30 near the derrick (referred to as the slave end). The RS485 communication cable 1 is connected between the 485_A and 485_B interfaces on the host end and the 485_A and 485_B interfaces on the slave end, and its length is greater than the distance between the hub box 30 and the host computer 20, such as 100 meters. Therefore, long-distance signal transmission between the hub box 30 and the host computer 20 can be achieved through the communication device 10, with stable communication and strong anti-interference capability.

[0022] For example, the USB converter chip U1 is model CH340N, and its operating voltage is 3.3V or 5V. The first RS485 chip U2 and the second RS485 chip U3 are model THVD1406DR, and their operating voltage is 3V~5.5V; or, the first RS485 chip U2 and the second RS485 chip U3 are model MAX13487EESA+, and their operating voltage is 4.75V~5.25V.

[0023] The THVD1406DR features automatic transmission and reception capabilities, automatically switching between sending and receiving data modes. It does not require a main control chip, such as an MCU (Micro Control Unit), which simplifies circuit design.

[0024] For example, RS485 communication line 1 is a twisted-pair shielded cable with a length greater than 40 meters, such as 50 meters or 100 meters. This enables long-distance signal transmission with strong anti-interference capabilities.

[0025] In some examples of this utility model, such as Figure 2 As shown, the communication device 10 also includes: a first decoupling capacitor C1, a second decoupling capacitor C2, and a third decoupling capacitor C3.

[0026] The first decoupling capacitor C1 is connected between the power supply terminal of the USB conversion chip U1 and ground; the second decoupling capacitor C2 is connected between the power supply terminal of the first RS485 chip U2 and ground; and the third decoupling capacitor C3 is connected between the power supply terminal of the second RS485 chip U3 and ground.

[0027] The decoupling capacitor can be selected according to the needs, such as a capacitance of 100nF.

[0028] By setting decoupling capacitors, local, instantaneous current can be provided to the corresponding chip to maintain the stability of the power supply voltage and filter out high-frequency noise generated during communication.

[0029] In some examples of this utility model, such as Figure 3 As shown, the communication device 10 also includes: a first pull-up resistor R1, a second pull-up resistor R3, a third pull-up resistor R7, and a fourth pull-up resistor R9.

[0030] Specifically, one end of the first pull-up resistor R1 is connected to the first preset power supply, and the other end of the first pull-up resistor R1 is connected to the first UART port of the first RS485 chip U2; one end of the second pull-up resistor R3 is connected to the first preset power supply, and the other end of the second pull-up resistor R3 is connected to the shutdown mode port and the receive enable port of the first RS485 chip U2, respectively; one end of the third pull-up resistor R7 is connected to the second preset power supply, and the other end of the second pull-up resistor R1 is connected to the first UART port of the second RS485 chip U3; one end of the fourth pull-up resistor R9 is connected to the second preset power supply, and the other end of the fourth pull-up resistor R9 is connected to the shutdown mode port and the receive enable port of the second RS485 chip U3, respectively.

[0031] Taking the first RS485 chip U2 and the second RS485 chip U3 as examples (model THVD1406DR), the voltage of the first and second preset power supplies can be +3.3V. Pull-up resistors can be selected as needed, such as 10KΩ.

[0032] By setting pull-up resistors R3 and R9, the corresponding RS485 chip can be ensured to automatically enter a clear, safe, and low-power default state when the main control chip is not initialized, reset, or encounters an error, thereby enhancing the reliability and stability of the system. By setting pull-up resistors R1 and R7, the line can be pulled to a definite and stable high level when no device actively drives the corresponding communication line, thereby preventing unpredictable behavior caused by floating signals.

[0033] In some examples of this utility model, such as Figure 4 As shown, the communication device 10 also includes: a first bias resistor R2, a second bias resistor R6, a third bias resistor R8, and a fourth bias resistor R12.

[0034] Specifically, one end of the first bias resistor R2 is connected to the first RS485 port of the first RS485 chip U2, and the other end of the first bias resistor R2 is grounded; one end of the second bias resistor R6 is connected to the second RS485 port of the first RS485 chip U2, and the other end of the second bias resistor R6 is connected to the first preset power supply; one end of the third bias resistor R8 is connected to the first RS485 port of the second RS485 chip U3, and the other end of the third bias resistor R8 is grounded; one end of the fourth bias resistor R12 is connected to the second RS485 port of the second RS485 chip U3, and the other end of the fourth bias resistor R12 is connected to the second preset power supply.

[0035] By setting the bias resistor, a stable voltage difference can be forced between the two transmission lines of RS485 communication line 1 when no device actively drives RS485 communication line 1. This allows RS485 communication line 1 to enter a definite and unambiguous idle state, avoiding false triggering of the "0" state, thereby preventing RS485 communication line 1 from floating and suppressing noise.

[0036] For example, the resistance values ​​of the first bias resistor R2 and the second bias resistor R6 (e.g., 1KΩ) are less than the resistance values ​​of the third bias resistor R8 and the fourth bias resistor R12 (e.g., 4.7KΩ).

[0037] This ensures that the strong bias of the host side dominates the idle state of RS485 communication line 1, thereby solving the problem of power failure / inconsistency on the slave side.

[0038] In some examples of this utility model, such as Figure 5 As shown, the communication device 10 also includes: a first current-limiting resistor R4, a second current-limiting resistor R5, a third current-limiting resistor R10, and a fourth current-limiting resistor R11.

[0039] Specifically, the first current-limiting resistor R4 is connected between the first RS485 port of the first RS485 chip U2 and the first terminal of the RS485 communication line 1; the second current-limiting resistor R5 is connected between the second RS485 port of the first RS485 chip U2 and the second terminal of the RS485 communication line 1; the third current-limiting resistor R10 is connected between the first RS485 port of the second RS485 chip U3 and the third terminal of the RS485 communication line 1; and the fourth current-limiting resistor R11 is connected between the second RS485 port of the second RS485 chip U3 and the fourth terminal of the RS485 communication line 1.

[0040] The current-limiting resistor can be selected according to needs, such as 10Ω. By setting the current-limiting resistor, the corresponding RS485 chip pins can be protected.

[0041] In some examples of this utility model, such as Figure 6As shown, the communication device 10 also includes: a first TVS tube D1 and a second TVS tube D2.

[0042] The first end of the first TVS diode D1 is connected to the first RS485 port of the first RS485 chip U2 and the first terminal of the RS485 communication line 1, respectively. The second end of the first TVS diode D1 is connected to the second RS485 port of the first RS485 chip U2 and the second terminal of the RS485 communication line 1, respectively. The third end of the first TVS diode D1 is grounded. The first end of the second TVS diode D2 is connected to the first RS485 port of the second RS485 chip U3 and the third terminal of the RS485 communication line 1, respectively. The second end of the second TVS diode D2 is connected to the second RS485 port of the second RS485 chip U3 and the fourth terminal of the RS485 communication line 1, respectively. The third end of the second TVS diode D2 is grounded.

[0043] By using a TVS diode, electrostatic discharge and electrical surges can be protected, thus protecting the RS485 chip from damage caused by transient overvoltage.

[0044] Figure 7 This is a structural block diagram of the communication system according to an embodiment of the present utility model.

[0045] like Figure 7 As shown, the communication system 100 includes: a host computer 20, a hub box 30, and the communication device 10 described in the above embodiment.

[0046] The host computer 20 can be located in the instrument room, and the junction box 30 can be located near the derrick of the logging system, with a considerable distance between them, such as 100 meters. Long-distance stable communication between the host computer 20 and the junction box 30 can be achieved by connecting them via the communication device 10.

[0047] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0048] In the description of this utility model, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model.

[0049] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this utility model, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0050] In this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0051] In this utility model, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0052] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A communication device (10), characterized in that, The device (10) includes: a USB conversion chip (U1), a first RS485 chip (U2), and a second RS485 chip (U3). The second RS485 chip (U3) is connected to the first RS485 chip (U2) via an RS485 communication line (1). The USB conversion chip (U1) is adapted to connect to a host computer (20) and is configured to receive the USB signal output by the host computer (20) and convert it into a UART signal, and to receive the UART signal output by the first RS485 chip (U2) and convert it into a USB signal. The first RS485 chip (U2) is connected to the USB conversion chip (U1) and is configured to receive the UART signal output by the USB conversion chip (U1) and convert it into an RS485 signal, and to receive the RS485 signal output by the second RS485 chip (U3) and convert it into a UART signal. The second RS485 chip (U3), adapted to connect to the hub box (30) of the logging system, is configured to receive the RS485 signal output by the first RS485 chip (U2) and convert it into a UART signal, and to receive the UART signal output by the hub box (30) and convert it into an RS485 signal.

2. The communication device (10) according to claim 1, characterized in that, The device (10) further includes: a first decoupling capacitor (C1), a second decoupling capacitor (C2), and a third decoupling capacitor (C3); wherein, The first decoupling capacitor (C1) is connected between the power supply terminal of the USB conversion chip (U1) and ground; The second decoupling capacitor (C2) is connected between the power supply terminal of the first RS485 chip (U2) and ground; The third decoupling capacitor (C3) is connected between the power supply terminal of the second RS485 chip (U3) and ground.

3. The communication device (10) according to claim 1, characterized in that, The device (10) further includes: a first pull-up resistor (R1), a second pull-up resistor (R3), a third pull-up resistor (R7), and a fourth pull-up resistor (R9); wherein One end of the first pull-up resistor (R1) is connected to the first preset power supply, and the other end of the first pull-up resistor (R1) is connected to the first UART port of the first RS485 chip (U2). One end of the second pull-up resistor (R3) is connected to the first preset power supply, and the other end of the second pull-up resistor (R3) is connected to the shutdown mode port and the receive enable port of the first RS485 chip (U2) respectively. One end of the third pull-up resistor (R7) is connected to the second preset power supply, and the other end of the second pull-up resistor (R1) is connected to the first UART port of the second RS485 chip (U3). One end of the fourth pull-up resistor (R9) is connected to the second preset power supply, and the other end of the fourth pull-up resistor (R9) is connected to the shutdown mode port and the receive enable port of the second RS485 chip (U3) respectively.

4. The communication device (10) according to claim 1, characterized in that, The device (10) further includes: a first bias resistor (R2), a second bias resistor (R6), a third bias resistor (R8), and a fourth bias resistor (R12); wherein, One end of the first bias resistor (R2) is connected to the first RS485 port of the first RS485 chip (U2), and the other end of the first bias resistor (R2) is grounded. One end of the second bias resistor (R6) is connected to the second RS485 port of the first RS485 chip (U2), and the other end of the second bias resistor (R6) is connected to the first preset power supply. One end of the third bias resistor (R8) is connected to the first RS485 port of the second RS485 chip (U3), and the other end of the third bias resistor (R8) is grounded. One end of the fourth bias resistor (R12) is connected to the second RS485 port of the second RS485 chip (U3), and the other end of the fourth bias resistor (R12) is connected to the second preset power supply.

5. The communication device (10) according to claim 4, characterized in that, The resistance values ​​of the first bias resistor (R2) and the second bias resistor (R6) are less than the resistance values ​​of the third bias resistor (R8) and the fourth bias resistor (R12).

6. The communication device (10) according to claim 1, characterized in that, The device (10) further includes: a first current-limiting resistor (R4), a second current-limiting resistor (R5), a third current-limiting resistor (R10), and a fourth current-limiting resistor (R11); The first current-limiting resistor (R4) is connected between the first RS485 port of the first RS485 chip (U2) and the first terminal of the RS485 communication line (1); the second current-limiting resistor (R5) is connected between the second RS485 port of the first RS485 chip (U2) and the second terminal of the RS485 communication line (1); the third current-limiting resistor (R10) is connected between the first RS485 port of the second RS485 chip (U3) and the third terminal of the RS485 communication line (1); and the fourth current-limiting resistor (R11) is connected between the second RS485 port of the second RS485 chip (U3) and the fourth terminal of the RS485 communication line (1).

7. The communication device (10) according to claim 1, characterized in that, The device (10) further includes: a first TVS tube (D1) and a second TVS tube (D2); wherein, The first end of the first TVS diode (D1) is connected to the first RS485 port of the first RS485 chip (U2) and the first terminal of the RS485 communication line (1), respectively. The second end of the first TVS diode (D1) is connected to the second RS485 port of the first RS485 chip (U2) and the second terminal of the RS485 communication line (1), respectively. The third end of the first TVS diode (D1) is grounded. The first end of the second TVS diode (D2) is connected to the first RS485 port of the second RS485 chip (U3) and the third terminal of the RS485 communication line (1), respectively. The second end of the second TVS diode (D2) is connected to the second RS485 port of the second RS485 chip (U3) and the fourth terminal of the RS485 communication line (1), respectively. The third end of the second TVS diode (D2) is grounded.

8. The communication device (10) according to claim 1, characterized in that, The USB conversion chip (U1) is model CH340N and operates at 3.3V or 5V. The first RS485 chip (U2) and the second RS485 chip (U3) are model THVD1406DR, with an operating voltage of 3V~5.5V; or, the first RS485 chip (U2) and the second RS485 chip (U3) are model MAX13487EESA+, with an operating voltage of 4.75V~5.25V.

9. The communication device (10) according to claim 1, characterized in that, The RS485 communication line (1) is a twisted-pair shielded cable with a length greater than 40 meters.

10. A communication system (100), characterized in that, include: The host computer (20), the hub box (30), and the communication device (10) as claimed in any one of claims 1-9.

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