Testing device for 485 circuit

Abstract

The utility model relates to the technical field of electronics, in particular to a testing device for a 485 circuit. The testing device comprises a control unit and a multi-slave unit, the multi-slave unit comprises a plurality of slave modules which are arranged in parallel; the control unit is respectively connected with the plurality of slave modules through a two-phase communication bus; wherein the slave module comprises a slave control chip and a 485 driving circuit, the slave driving chip is connected with the 485 driving circuit, and the 485 driving circuit comprises at least one load; the control unit is also connected with a test product through a two-phase communication bus. By adopting the test circuit provided by the invention, the feedback signal transmitted by the two-phase communication bus can be quickly acquired, and the working performance of the 485 circuit when the 485 circuit drives a plurality of slave devices at the same time can be tested by analyzing the feedback signal, so that the test efficiency of the 485 circuit is improved.

Description

Technical Field

[0001] The present application relates to the field of electronic technology, and in particular to a testing device for a 485 circuit. Background Art

[0002] 485 communication circuit is a commonly used communication circuit in industrial equipment. For example, digital display meters, electric energy meters and new energy vehicles often use 485 communication circuits for signal transmission.

[0003] Under most working conditions, multiple slave devices are connected to the host device through the two-phase communication bus in the 485 communication circuit, and the host device can communicate with one or more slave devices by polling or accessing according to the target address. In most cases, there can only be one slave device on the bus to communicate with the host device. For example, the host device performs read and write operations with the current slave device through the two-phase communication bus. During the communication process, the remaining multiple slave devices will also have certain interference with the signal transmitted by the two-phase communication bus, affecting the communication quality between the host device and the current slave device. In the related art, there is a lack of testing equipment for the communication function of the 485 circuit connected to multiple slave devices, so it is impossible to specifically determine the degree of impact on the communication function of the 485 circuit. Summary of the invention

[0004] The present application provides a testing device for a 485 circuit to perform a simulation test on the function of a 485 circuit connected to multiple slave devices.

[0005] In a first aspect, the present application provides a testing device for a 485 circuit, the testing device comprising: a control unit and a multi-slave unit;

[0006] The multi-slave unit comprises a plurality of slave modules arranged in parallel; the control unit is respectively connected to the plurality of slave modules via a two-phase communication bus;

[0007] Wherein, the slave module includes a slave control chip and a 485 drive circuit, the slave drive chip is connected to the 485 drive circuit, and the 485 drive circuit includes at least one load;

[0008] The control unit is also connected to the test product via the two-phase communication bus;

[0009] The control unit is used to send a test signal to the test product and receive a feedback signal corresponding to the test signal returned through the two-phase communication bus.

[0010] In one possible design, the control unit includes a main control chip and a plurality of communication expansion chips;

[0011] The master control chip is connected to the plurality of communication expansion chips via the two-phase communication bus; each of the communication expansion chips is connected to at least one of the slave control chips.

[0012] In one possible design, the testing device further includes an oscilloscope;

[0013] The signal acquisition end of the oscilloscope is connected to the two-phase communication bus to acquire the feedback signal transmitted on the two-phase communication bus and display the waveform of the feedback signal.

[0014] In one possible design, the 485 driving circuit includes at least two signal isolation circuits, a 485 chip and a protection circuit;

[0015] The slave control chip is connected to the 485 chip through the at least one signal isolation circuit, and the protection circuit is connected to the 485 chip.

[0016] In a possible design, the at least two signal isolation circuits include at least one first signal isolation circuit and at least one second signal isolation circuit; the first signal isolation circuit and the second signal isolation circuit have different response speeds.

[0017] In a possible design, the 485 driving circuit includes an isolation 485 chip and a protection circuit; the isolation 485 chip is connected to the slave control chip, and the protection circuit is connected to the isolation 485 chip.

[0018] In one possible design, the signal isolation circuit is an optocoupler isolation circuit.

[0019] In one possible design, the protection circuit includes a voltage protection circuit and / or a current protection circuit.

[0020] In a possible design, the testing device further includes a temperature regulating box, and the control unit and the multi-slave unit are arranged in a box body of the temperature regulating box;

[0021] The temperature regulating box comprises a temperature regulating mechanism, and the temperature regulating mechanism is used to regulate the temperature value in the box.

[0022] In a possible design, the slave unit includes 31 slave modules.

[0023] Through the test device provided in the first aspect above, the feedback signal transmitted by the two-phase communication bus can be quickly collected. By analyzing the feedback signal, the working performance of the 485 circuit when driving multiple slave devices at the same time can be tested, thereby improving the test efficiency of the 485 circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 One of the structural schematic diagrams of the testing device for 485 circuit provided in the embodiment of the present application;

[0025] Figure 2 The second structural schematic diagram of the testing device for 485 circuit provided in the embodiment of the present application;

[0026] Figure 3 One of the schematic diagrams of the 485 driving circuit structure provided in the embodiment of the present application;

[0027] Figure 4 The second schematic diagram of the 485 driving circuit structure provided in the embodiment of the present application;

[0028] Figure 5 The third schematic diagram of the 485 driving circuit structure provided in the embodiment of the present application;

[0029] Figure 6 The third structural schematic diagram of the testing device for 485 circuit provided in the embodiment of the present application.

[0030] Figure markings: 10-control unit, 20-multi-slave unit, 30-test product, 201-slave control chip, 202-485 drive circuit, 101-master control chip; 102-communication expansion chip, 41-first signal isolation circuit, 42-second signal isolation circuit, 43-first 485 chip, 44-first protection circuit, 51-third signal isolation circuit, 52-fourth signal isolation circuit, 53-fifth signal isolation circuit, 54-second 485 chip, 55-second protection circuit, 61-sixth signal isolation circuit, 62-seventh signal isolation circuit, 63-eighth signal isolation circuit, 64-third 485 chip, 65-third protection circuit, 70-oscilloscope. DETAILED DESCRIPTION

[0031] In this application, "at least one" means one or more, and "plurality" means two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone, where A and B can be singular or plural. The character " / " generally indicates that the associated objects before and after are in an "or" relationship. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, at least one of a, b, or c alone can represent: a, b, c, a and b, a and c, or a, b, and c, where a, b, and c can be single or multiple. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0032] The directions or positional relationships indicated by terms such as "center", "longitudinal", "lateral", "up", "down", "left", "right", "front", and "back" are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present application and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present application.

[0033] The terms "connected" and "connected" should be understood in a broad sense. For example, the "connected" or "connected" of a circuit structure can refer to not only physical connection, but also electrical connection or signal connection. For example, it can be directly connected, that is, physically connected, or indirectly connected through at least one intermediate element, as long as the circuit is connected, or it can be the internal connection of two elements; signal connection can refer to signal connection through a circuit or through a media medium, such as radio waves. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0034] In order to test the influence of multiple slave devices on the communication function between the host device and the target slave device in the actual working scene, the present application provides a test device for a 485 circuit, which includes: a control unit and a multi-slave unit; the multi-slave unit includes a plurality of slave modules arranged in parallel; the control unit is respectively connected to the plurality of slave modules through a two-phase communication bus. Among them, the slave module includes a slave control chip and a 485 drive circuit. The control unit is also connected to the test product through a two-phase communication bus; the control unit is used to send a test signal to the test product and receive a feedback signal corresponding to the test signal returned through the two-phase communication bus. This is equivalent to using a control unit to simulate a host device in an actual working scene, using multiple slave modules in the multi-slave unit to simulate multiple slave devices in an actual working scene, and using a test product to simulate a target slave device in multiple slave devices, and simulating the communication between the control unit and the test product to simulate the host device and a target slave device to communicate, so as to analyze the influence of multiple slave devices on the communication function according to the feedback signal.

[0035] Figure 1 One of the structural diagrams of the test device for 485 circuit provided in the embodiment of the present application is shown in FIG. Figure 1 As shown, the test device includes: a control unit 10 and a multi-slave unit 20. The multi-slave unit 20 includes a plurality of slave modules arranged in parallel; the control unit 10 is respectively connected to the plurality of slave modules through a two-phase communication bus. Each slave module includes a slave control chip 201 and a 485 drive circuit 202, and the slave drive chip 201 is connected to the 485 drive circuit 202, and the 485 drive circuit includes at least one load. The control unit 10 is also connected to the test product 30 through a two-phase communication bus; the control unit 10 is used to send a test signal to the test product 30, and receive a feedback signal corresponding to the test signal returned through the two-phase communication bus.

[0036] In some embodiments, the test product 30 may be a product suitable for 485 circuits, for example, a digital display meter or an electric energy meter. The two-phase communication bus may be line A and line B, respectively, and the test product 30 and the control unit 10 are connected by communication via line A and line B. The test product 30 is equivalent to any one of a plurality of slave devices, and can be understood as a target slave device.

[0037] It can be understood that the multi-slave unit with multiple slave modules in this embodiment is used to simulate multiple slave devices in an actual working scenario, and one slave module is equivalent to one slave device. In order to reduce the volume of the test device in this embodiment, multiple slave modules can be integrated into a multi-slave unit, for example, multiple slave modules are integrated into a chip, and a wiring terminal for connecting line A and line B is provided on the chip. Among them, multiple slave modules are connected in parallel, that is, each slave module can be connected to line A and line B through a wiring terminal. In this way, it is equivalent to simulating multiple slave devices hanging up and down on line A and line B in an actual application scenario.

[0038] It can be understood that in this embodiment, it is equivalent to using the control unit 10 to simulate the host device, host computer or PC (Personal Computer) in the actual working scenario. The host device can communicate with any slave device through polling or target address access method. In this embodiment, the control unit 10 and the test chip are used as examples for explanation.

[0039] Among them, the communication between the control unit 10 and the test product 30 is used to simulate the communication between the host device and a target slave device, for example, the host device is simulated to send a read instruction to the target slave device (such as a digital display) to read a certain signal of the digital display, such as the frequency, pulse, encoding and other signals of the digital display. After receiving the read instruction, the digital display obtains the corresponding signal according to the read instruction, that is, generates a corresponding feedback signal, and then sends the read feedback signal to the control unit 10 through the A line and the B line. At the same time, since the A line and the B line are connected to multiple slave modules at the same time, it is equivalent to sending the feedback signal to each slave module, so that the slave module also affects the feedback signal transmitted by the A line and the B line. According to the feedback signal, the communication quality between the control unit 10 and the test product 30 can be analyzed, which is equivalent to the function of testing the 485 circuit when driving multiple slave devices at the same time.

[0040] It can be seen that by using the test device provided in this embodiment, the feedback signals transmitted by the A line and the B line can be quickly collected. By analyzing the feedback signals, the working performance of the 485 circuit when driving multiple slave devices at the same time can be tested, thereby improving the test efficiency of the 485 circuit.

[0041] In some embodiments, based on the 485 circuit, the control unit 10 can use the modbus-RTU communication protocol, DLT645 communication protocol, DLT698 communication protocol and other communication protocols to communicate with multiple slave modules and the test product 30. Therefore, the control unit 10 in this embodiment can use a control unit 10 that supports multi-channel UART protocol to achieve the requirement of multi-channel UART output.

[0042] Figure 2The second structural diagram of the test device for the 485 circuit provided in the embodiment of the present application is shown in FIG. Figure 2 As shown, in one embodiment, the control unit 10 includes a main control chip 101 and multiple communication expansion chips 102; the main control chip 101 is connected to the multiple communication expansion chips 102 through a two-phase communication bus; each communication expansion chip 102 is connected to at least one slave control chip.

[0043] Generally, the conventional main control chip 101 does not have channels that support multiple UART protocols. Therefore, in this embodiment, multiple communication expansion chips 102 are set to expand the number of UART protocol channels of the main control chip 101, so that the main control chip 101 can communicate with multiple slave modules at the same time through communication protocols such as modbus-RTU communication protocol, DLT645 communication protocol, and DLT698 communication protocol.

[0044] Generally, one communication expansion chip 102 can communicate with at least one slave module at the same time. For example, one communication expansion chip 102 can communicate with four slave modules at the same time. Specifically, one communication expansion chip 102 is connected to the slave control chip 201 in at least one slave module to achieve mutual communication between the two. Therefore, the number of communication expansion chips 102 provided in this embodiment is less than the number of slave modules.

[0045] In one embodiment, the main control chip 101 can adopt an MCU (Microcontroller Unit) such as STM32F091RBT6 that supports the UART protocol, the communication expansion chip 102 can adopt a chip such as WK2114 that has an expanded UART protocol channel, and the slave control chip 201 can adopt a chip such as G80F942 that supports the UART protocol.

[0046] In this embodiment, taking 32 slave devices as an example, the test device includes 31 slave modules, that is, the test device includes 31 groups of slave driver chips 201 and 485 driver circuits 202, and the test product 30 is equivalent to a slave module. The test product 30 includes a group of slave driver chips 201 and 485 driver circuits 202.

[0047] Since the slave driver chip 201 and the 485 driver circuit 202 are used to simulate slave devices with different loads, it can be understood that in actual application scenarios, different slave devices have different loads. Therefore, in order to accurately simulate the actual application scenarios, the multiple 485 driver circuits 202 in this embodiment can respectively have multiple 485 driver circuits 202 with different loads.

[0048] In one embodiment, the 485 drive circuit 202 includes at least two signal isolation circuits, a 485 chip and a protection circuit; the slave control chip 201 is connected to the 485 chip through at least one signal isolation circuit, and the protection circuit is connected to the 485 chip. In the 485 drive circuit 202, different numbers of signal isolation circuits are connected in parallel between the slave control chip 201 and the 485 chip, so that the load of the 485 drive circuit 202 changes to simulate the 485 drive circuit 202 with different loads.

[0049] In some embodiments, the control unit 10 also includes a 485 drive circuit, and the main control chip 101 is connected to the A line and the B line through the 485 drive circuit.

[0050] In one embodiment, considering that different slave devices have different response speed requirements, signal isolation circuits with different response speeds can be set in this embodiment to simulate different slave devices. For example, the 485 drive circuit 202 includes at least two signal isolation circuits, and the at least two signal isolation circuits include at least one first signal isolation circuit and at least one second signal isolation circuit; the response speeds of the first signal isolation circuit and the second signal isolation circuit are different. For example, the first signal isolation circuit is a high-speed signal isolation circuit, and the second signal isolation circuit is an ordinary signal isolation circuit, so that the response speed of the first signal isolation circuit is greater than the response speed of the second signal isolation circuit.

[0051] In one embodiment, the 485 driving circuit 202 may include an isolation 485 chip and a protection circuit; the isolation 485 chip is connected to the slave control chip 201, and the protection circuit is connected to the isolation 485 chip. The isolation 485 chip has the functions of the above-mentioned optocoupler isolation circuit and the 485 chip.

[0052] In this embodiment, each of the above-mentioned signal isolation circuits can be an optocoupler isolation circuit. In this embodiment, each of the above-mentioned protection circuits includes a voltage protection circuit and a current protection circuit, which can protect each chip in the test device to prevent excessive current or voltage from damaging the chip device. In this embodiment, the voltage protection circuit and the current protection circuit can adopt a circuit structure commonly used in the circuit field, which will not be repeated in this embodiment.

[0053] Figure 3 One of the schematic diagrams of the 485 drive circuit structure provided in the embodiment of the present application is shown in FIG. Figure 3As shown, the 485 driving circuit includes a first signal isolation circuit 41, a second signal isolation circuit 42, a first 485 chip 43 and a first protection circuit 44. The slave control chip is connected to the first 485 chip 43 through the first signal isolation circuit 41 and the second signal isolation circuit 42, and the first protection circuit 44 is connected to the first 485 chip 43. The first signal isolation circuit 41 and the second signal isolation circuit 42 are optocoupler isolation circuits with the same response speed and load.

[0054] Figure 4 For the second schematic diagram of the 485 drive circuit structure provided in the embodiment of the present application, please refer to Figure 4 As shown, the 485 driving circuit includes a third signal isolation circuit 51, a fourth signal isolation circuit 52, a fifth signal isolation circuit 53, a second 485 chip 54 and a second protection circuit 55. The slave control chip is connected to the second 485 chip 54 through the third signal isolation circuit 51, the fourth signal isolation circuit 52 and the fifth signal isolation circuit 53, and the second protection circuit 55 is connected to the second 485 chip 54. The third signal isolation circuit 51, the fourth signal isolation circuit 52 and the fifth signal isolation circuit 53 are optocoupler isolation circuits with the same response speed and the same load.

[0055] Figure 5 For the third schematic diagram of the 485 drive circuit structure provided in the embodiment of the present application, please refer to Figure 5 As shown, the 485 driving circuit includes a sixth signal isolation circuit 61, a seventh signal isolation circuit 62, an eighth signal isolation circuit 63, a third 485 chip 64 and a third protection circuit 65. The slave control chip 201 is connected to the third 485 chip 64 through the sixth signal isolation circuit 61, the seventh signal isolation circuit 62 and the eighth signal isolation circuit 63, and the third protection circuit 65 is connected to the third 485 chip 64. Among them, the sixth signal isolation circuit 61 and the seventh signal isolation circuit 62 are high-speed signal isolation circuits, and the eighth signal isolation circuit 63 is a common signal isolation circuit.

[0056] Figure 6 The third structural diagram of the test device for the 485 circuit provided in the embodiment of the present application is shown in FIG. Figure 6 As shown, in one embodiment, the test device further includes an oscilloscope 70; the signal acquisition end of the oscilloscope 70 is connected to the A-line and B-line communication buses to acquire feedback signals transmitted on the A-line and B-line, and display the waveforms of the feedback signals. The difference between the A-line and B-line waveforms can be used to analyze information such as communication stability and communication quality.

[0057] Based on the test device provided in this embodiment, in one scenario, the power supply of the 485 circuit of any slave device is tested. The lowest baud rate allowed by the 485 circuit is used for communication, for example, 1200bps is used for communication. During low baud rate communication, the high and low level time in the circuit is prolonged, resulting in an increase in the continuous current per frame, which increases the power output current and power of the 485 circuit. When a long high level appears in the transmitted data, the power supply cannot respond quickly to the change in the output waveform, which may cause the power supply of the 485 circuit to oscillate, resulting in a decrease in the average voltage, and even causing the voltage difference between the AB lines of the 485 circuit output to be less than 200mV, resulting in abnormal communication. Therefore, the influence of the baud rate on the stability and quality of communication can be analyzed based on the voltage difference between the A line and the B line waveform.

[0058] Similarly, in the case of multiple slave devices, the feedback signal of the slave device will be sent to each slave device and the host device, resulting in an increase in the load resistance on the AB bus, further increasing the power consumption of the 485 circuit. Therefore, the test device of this embodiment can evaluate the communication performance of the 485 circuit under extreme power supply environments (such as multiple slave devices, minimum baud rate, and long data frames).

[0059] In one scenario, the above-mentioned test device is used to test the highest baud rate allowed by the 485 circuit (such as 19200bps). When communicating at the highest baud rate, according to the requirements of the communication protocol, the high / low level pulse width of the output waveform on the AB line needs to be within a reasonable error range with the theoretical value. For example, the high level pulse width corresponding to 19200bps is 52μs, and the deviation specified by the modbus-RTU protocol is ±1%. At the same time, the rising / falling edge time of the high and low level switching is also affected by the load of the remaining multiple slave devices. Therefore, the test device can be used to verify the performance of the 485 circuit under high baud rate conditions. Specifically, the performance test results of the 485 circuit can be obtained by analyzing the high level pulse width, rising / falling edge time and other information through the waveform of the oscilloscope.

[0060] When testing different baud rates, the baud rate can be modified by modifying the corresponding electrical parameters in the 485 circuit.

[0061] In one embodiment, the test device further includes a temperature regulating box, the control unit 10 and the multi-slave unit 20 are arranged in the box of the temperature regulating box; the temperature regulating box includes a temperature regulating mechanism, and the temperature regulating mechanism is used to adjust the temperature value in the box. In this way, the performance of the 485 circuit under different temperature environments can be tested.

[0062] In one scenario, taking the test object as an industrial product such as a digital display meter and an electric energy meter, the ambient temperature of the use environment is usually between -25°C and +55°C, and the communication of the 485 circuit is required to be normal. At different temperatures, the CTR (Current Transfer Ratio) of the optocoupler will change with the temperature. At 0°C, the CTR of the optocoupler is the largest. Changes in the CTR of the optocoupler will affect the rise and fall time when switching between high and low levels. Therefore, the rise / fall time information can be analyzed through the waveform of the oscilloscope to obtain the performance test results of the 485 circuit in different temperature environments.

[0063] In one scenario, taking the test object as an industrial product such as a digital display meter and an electric energy meter, since the working grid voltage is generally not the standard 220V voltage, there is actually a ±20% fluctuation, and the product is required to work normally. The low-voltage environment will cause the power supply of the 485 circuit to be lower than normal operation. The power supply of the 485 circuit is 220V when it works normally. At the same time, long-term communication will also cause the transformer and other devices in the slave device to heat up, resulting in lower working efficiency. The test device can be used to test the performance of the 485 circuit under high and low voltage conditions.

[0064] In one scenario, feedback signals on line A and line B can also be obtained, and the communication performance of the 485 circuit in various application scenarios can be analyzed by analyzing the packet loss rate of the feedback signal.

[0065] It can be seen that according to the test device provided in the present application, the feedback signals transmitted by the A line and the B line can be quickly collected. By analyzing the feedback signals, the working performance of the 485 circuit when driving multiple slave devices at the same time can be tested, thereby improving the test efficiency of the 485 circuit.

[0066] It should be noted that the above embodiments are only specific implementation methods of the present application, but the protection scope of the present application is not limited thereto, and any changes or substitutions within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A test device for 485 circuit, characterized in that: The test device comprises: a control unit and multiple slave units; The multi-slave unit comprises a plurality of slave modules arranged in parallel; the control unit is respectively connected to the plurality of slave modules via a two-phase communication bus; Wherein, the slave module includes a slave control chip and a 485 drive circuit, the slave control chip is connected to the 485 drive circuit, and the 485 drive circuit includes at least one load; The control unit is also connected to the test product via the two-phase communication bus; The control unit is used to send a test signal to the test product and receive a feedback signal corresponding to the test signal returned through the two-phase communication bus.

2. The test device for 485 circuit according to claim 1, characterized in that: The control unit includes a main control chip and a plurality of communication expansion chips; The master control chip is connected to the plurality of communication expansion chips via the two-phase communication bus; each of the communication expansion chips is connected to at least one of the slave control chips.

3. The test device for 485 circuit according to claim 1 or 2, characterized in that: The testing device also includes an oscilloscope; The signal acquisition end of the oscilloscope is connected to the two-phase communication bus to acquire the feedback signal transmitted on the two-phase communication bus and display the waveform of the feedback signal.

4. The test device for 485 circuit according to claim 1, characterized in that: The 485 driving circuit includes at least two signal isolation circuits, a 485 chip and a protection circuit; The slave control chip is connected to the 485 chip through the at least one signal isolation circuit, and the protection circuit is connected to the 485 chip.

5. The test device for 485 circuit according to claim 4, characterized in that: The at least two signal isolation circuits include at least one first signal isolation circuit and at least one second signal isolation circuit; the response speeds of the first signal isolation circuit and the second signal isolation circuit are different.

6. The test device for 485 circuit according to claim 1, characterized in that: The 485 driving circuit includes an isolation 485 chip and a protection circuit; the isolation 485 chip is connected to the slave control chip, and the protection circuit is connected to the isolation 485 chip.

7. The test device for 485 circuit according to claim 4 or 5, characterized in that: The signal isolation circuit is an optocoupler isolation circuit.

8. The test device for 485 circuit according to any one of claims 4 to 6, characterized in that: The protection circuit includes a voltage protection circuit and / or a current protection circuit.

9. The test device for 485 circuit according to claim 1 or 2, characterized in that: The testing device further comprises a temperature regulating box, wherein the control unit and the multi-slave unit are arranged in a box body of the temperature regulating box; The temperature regulating box comprises a temperature regulating mechanism, and the temperature regulating mechanism is used to regulate the temperature value in the box.

10. The test device for 485 circuit according to claim 1 or 2, characterized in that: The slave unit includes 31 slave modules.

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