An isolated low-cost communication module

Abstract

The invention discloses an isolated low-cost communication module, comprising a CM485 main module and a CM485 slave module. The CM485 main module comprises a USB to UART circuit, a communication isolation circuit, a power isolation circuit, a conversion circuit, a first protection circuit and an indicator light circuit. The CM485 slave module comprises a second protection circuit, a rectifier circuit, an optical coupling circuit and a level shaping circuit. The invention relates to the technical field of communication modules. The circuit of the CM485 slave module in the invention is extremely simple, requiring only 10 components, and the cost is as low as about 0.5 yuan. Compared with 5 yuan required for an RS485 isolated power supply, the cost can be saved by more than 90%, so the production cost is greatly reduced. The production configuration directly replaces the RS485 communication module with the CM485 main module of the invention, and not only the CM485 slave module device but also the RS485 device can be debugged.

Description

Technical Field

[0001] The present invention relates to the technical field of communication modules, in particular to an isolated low-cost communication module. Background Art

[0002] Currently, the existing 2-wire isolated communication buses for computer and device communication mainly include CAN, RS485, and M-Bus, among which RS485 is the most widely used and the lowest cost.

[0003] For example, the patent with announcement number CN 219875713 U discloses a low-cost RS485 communication isolation circuit, including a DC power access module, an RS485 interface circuit and an optocoupler circuit, wherein the DC power access module input end is connected to a DC power supply and a PWM signal source, and the output end outputs an isolated power supply and is connected to the RS485 interface circuit input end, the RS485 interface circuit is connected to the optocoupler circuit and is connected to the outside through an interface, and the output end of the optocoupler circuit performs serial communication; another example is the patent with announcement number CN 217445370 U discloses an RS485 interface circuit with communication control and power supply monitoring and isolation, including a communication interface chip and a 5 volt power supply chip, the RS485 signal end of the communication interface chip is connected to the RS485 communication network, the RS485 interface circuit also includes a dual-channel digital isolation chip and two optocoupler isolation chips, the 3.3 volt side input and output ends of the isolation channel of the dual-channel digital isolation chip are connected to the local motor controller communication module, and the 5 volt side input and output ends of the isolation channel of the dual-channel digital isolation chip are connected to the data receiving and sending signal ends of the communication interface chip.

[0004] However, the above devices all power the RS485 chip by setting an isolated power module on one side of the RS485 chip, but the cost of the isolated power module is at least 5 yuan, and the cost of the RS485 chip is at least 2-3 yuan, so the overall cost is about 7-8 yuan. Therefore, for some devices that only need an isolated debugging interface but do not need networking communication, this setting method greatly increases the cost.

[0005] To this end, the present invention provides an isolated low-cost communication module to solve the above problems. Summary of the invention

[0006] In view of the deficiencies of the prior art, the present invention provides an isolated low-cost communication module to solve the above problems.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solutions: an isolated low-cost communication module, comprising:

[0008] CM485 main module;

[0009] A CM485 slave module, electrically connected to the CM485 master module, and the CM485 slave module is used to receive and send data signals;

[0010] The CM485 master module is electrically connected to an external device through the CM485 slave module, and the CM485 master module is electrically connected to a computer;

[0011] The CM485 main module includes a USB to UART circuit, a communication isolation circuit, a power isolation circuit, a conversion circuit, a first protection circuit and an indicator light circuit, wherein the USB to UART circuit is electrically connected to the communication isolation circuit and the power isolation circuit, the power isolation circuit is electrically connected to the communication isolation circuit and the conversion circuit, the communication isolation circuit is electrically connected to the conversion circuit, the conversion circuit is electrically connected to the first protection circuit, and the indicator light circuit is electrically connected to the conversion circuit;

[0012] The CM485 slave module includes a second protection circuit, a rectifier circuit, an optocoupler circuit and a level shaping circuit, wherein the second protection circuit is electrically connected to the rectifier circuit, the rectifier circuit is electrically connected to the optocoupler circuit, and the optocoupler circuit is electrically connected to the level shaping circuit.

[0013] Preferably, the USB to UART circuit comprises:

[0014] USB connector USB1 connected to the USB port of the computer; and

[0015] USB to UART chip U1, the USB to UART chip U1 converts the USB connector USB1 signal into a TTL level signal;

[0016] The signal of pin 2 of the USB connector USB1 is connected to pin 2 of the USB to UART chip U1, the signal of pin 3 of the USB connector USB1 is connected to pin 1 of the USB to UART chip U1, pin 5 of the USB connector USB1 and pin 3 of the USB to UART chip U1 are both grounded, and capacitors C5 and C3 are connected in series between pin 7 and pin 10 of the USB to UART chip U1 in sequence.

[0017] Preferably, the communication isolation circuit comprises:

[0018] A digital isolation chip U2 and a digital isolation chip U3, wherein the digital isolation chip U2 and the digital isolation chip U3 electrically isolate the TTL level signal converted by the USB to UART chip U1;

[0019] The pin 2 signal of the digital isolation chip U2 is connected to the pin 9 of the USB to UART chip U1, the pin 3 signal of the digital isolation chip U2 is connected to the pin 8 of the USB to UART chip U1, and the pin 3 signal of the digital isolation chip U3 is connected to the pin 6 of the USB to UART chip U1.

[0020] Preferably, the power isolation circuit comprises a DC-DC power isolation module M1, and the DC-DC power isolation module M1 isolates the power of the USB connector USB1 and then supplies power to the conversion circuit;

[0021] Pin No. 1 and pin No. 2 of the DC-DC power isolation module M1 are grounded, capacitors C2 and C4 are connected in parallel between pin No. 9 and pin No. 10 of the DC-DC power isolation module M1, capacitors C6 and C7 are connected in parallel between pin No. 11 and pin No. 12 of the DC-DC power isolation module M1, and a rectifier diode D1 is connected in series between pin No. 11 of the DC-DC power isolation module M1 and capacitor C6.

[0022] Preferably, the conversion circuit comprises:

[0023] RS485 chip U8, the RS485 chip U8 converts the TTL level signal converted by the USB to UART chip U1 into an RS485 level signal;

[0024] A digital analog switch U6, wherein the digital analog switch U6 is used to disconnect the A line of the RS485 chip U8 in a receiving state;

[0025] an operational amplifier U5, wherein the operational amplifier U5 amplifies the received voltage signal; and

[0026] A photocoupler U11, wherein the photocoupler U11 pulls the voltage level down to a negative voltage under the control of the amplified signal output by the operational amplifier U5;

[0027] Pin 1 of the RS485 chip U8 is connected to pin 7 of the digital isolation chip U2 by signal, pins 2 and 3 of the RS485 chip U8 are connected to pin 6 of the digital isolation chip U3 by signal, pin 4 of the RS485 chip U8 is connected to pin 6 of the digital isolation chip U2 by signal, a resistor R7 is connected in series between pins 6 and 8 of the RS485 chip U8, and a resistor R17 is connected in series between pins 5 and 7 of the RS485 chip U8;

[0028] The signal of pin 1 of the digital analog switch U6 is connected to pin 6 of the RS485 chip U8, the signal of pin 2 of the digital analog switch U6 is connected to pin 8 of the RS485 chip U8 after being connected in series with resistor R16, and the signal of pin 4 of the digital analog switch U6 is connected to pin 6 of the digital isolation chip U3;

[0029] Pin 4 of the photocoupler U11 is connected in series with resistor R18 and then connected to pin 6 of the RS485 chip U8, and pin 3 of the photocoupler U11 is grounded;

[0030] A resistor R10 is connected in series between pin 1 and pin 2 of the operational amplifier U5, a resistor R11 is connected in series between pin 3 and pin 4 of the operational amplifier U5, a resistor R12 is connected in series with pin 4 of the operational amplifier U5, and the signal is then connected to pin 2 of the photocoupler U11, a resistor R6 is connected in series with pin 1 of the operational amplifier U5, and the signal is then connected to pin 2 of the digital analog switch U6, and a resistor R9 is connected in series with pin 2 of the operational amplifier U5, and the signal is then connected to pin 7 of the RS485 chip U8.

[0031] Preferably, the first protection circuit comprises:

[0032] Transient suppression diode DZ1, transient suppression diode DZ2, lightning arrester PTC1 and connector JP3;

[0033] The transient suppression diode DZ1, the transient suppression diode DZ2 and the lightning arrester PTC1 are connected in series in sequence, and the signal is connected to pin 1 and pin 2 of the connector JP3. The two ends of the transient suppression diode DZ1 are connected in series with capacitor F1, and the two ends of the transient suppression diode DZ2 are connected in series with capacitor F2. After pin 1 of the connector JP3 is connected in series with the lightning arrester PTC1, the signal is connected to pin 7 of the RS485 chip U8. The signal of pin 2 of the connector JP3 is connected to pin 2 of the digital analog switch U6.

[0034] Preferably, the indicator light circuit comprises:

[0035] Indicator light LED2, indicator light LED3 and indicator light LED4, the cathode of the indicator light LED2 is connected in series with resistor R2 and then grounded, the anode of the indicator light LED3 is connected in series with resistor R3 and then the signal is connected to the anode of the indicator light LED2, the anode of the indicator light LED4 is connected in series with resistor R4 and then the signal is connected to the anode of the indicator light LED2, the cathode signal of the indicator light LED3 is connected to pin 1 of the RS485 chip U8, and the cathode signal of the indicator light LED4 is connected to pin 4 of the RS485 chip U8.

[0036] Preferably, the second protection circuit comprises:

[0037] A transient suppression diode DZ4, two ends of which are respectively connected in series with a port JP8 and a port JP7, and the port JP8 and the port JP7 cooperate with the connector JP3.

[0038] Preferably, the rectifier circuit comprises:

[0039] The rectifier diode D2 and the rectifier diode D3, the cathode signal of the rectifier diode D2 is connected to the anode of the rectifier diode D3, and the anode signal of the rectifier diode D3 is connected to one end of the transient voltage suppression diode DZ4.

[0040] Preferably, the optocoupler circuit comprises:

[0041] Optocoupler U4 and optocoupler U7;

[0042] Pin 1 of the photocoupler U4 is connected in series with resistors R14 and R19, and then the signal is connected to interface JP4; Pin 2 of the photocoupler U4 is connected in series with interface JP5; Pin 3 of the photocoupler U4 is connected in series with resistor R15, and then the signal is connected to pin 1 of the photocoupler U7; Pin 4 of the photocoupler U4 is connected in series with the cathode of the rectifier diode D3;

[0043] The pin 2 of the photocoupler U7 is connected to the positive electrode of the rectifier diode D2;

[0044] The level shaping circuit comprises:

[0045] Transistor Q1, the base of the transistor Q1 is connected in series with resistor R20 and then the signal is connected to pin 3 of the photocoupler U7, the base of the transistor Q1 is connected in series with resistor R20 and resistor R13 and then the signal is connected to the emitter of the transistor Q1, the emitter of the transistor Q1 is grounded, and the collector signal of the transistor Q1 is connected to interface JP4.

[0046] Beneficial Effects

[0047] The present invention provides an isolated low-cost communication module. Compared with the prior art, it has the following beneficial effects:

[0048] (1) The circuit of the CM485 slave module in the isolated low-cost communication module is extremely simple, requiring only 10 components and costing as low as RMB 0.5. Compared with the RMB 5 required for the RS485 isolated power supply, it can save more than 90% of the cost, thus greatly reducing the production cost.

[0049] (2) The CM485 master module and the CM485 slave module in the isolated low-cost communication module have been tested in large quantities, and their communication is stable with few faults. The communication baud rate between the CM485 master module and the CM485 slave module can reach 38400bps, and the communication baud rate between the CM485 master module and the RS485 slave device can reach 115200bps. The production configuration directly replaces the RS485 communication module with the CM485 master module of the present invention, which can not only debug the CM485 slave module device but also debug the RS485 device. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 It is the structural block diagram of the CM485 main module of the present invention;

[0051] Figure 2 It is the structural block diagram of CM485 slave module of the present invention;

[0052] Figure 3 It is a circuit diagram of the USB to UART circuit of the present invention;

[0053] Figure 4 is a circuit diagram of a communication isolation circuit of the present invention;

[0054] Figure 5 is a circuit diagram of a power isolation circuit of the present invention;

[0055] Figure 6 is a circuit diagram of a conversion circuit of the present invention;

[0056] Figure 7 is a circuit diagram of a first protection circuit of the present invention;

[0057] Figure 8 is a circuit diagram of an indicator light circuit of the present invention;

[0058] Fig. 9 It is the overall circuit diagram of the CM485 slave module of the present invention.

[0059] In the figure, 1, USB to UART circuit; 2, communication isolation circuit; 3, power isolation circuit; 4, conversion circuit; 5, first protection circuit; 6, indicator light circuit; 7, second protection circuit; 8, rectification circuit; 9, optocoupler circuit; 10, level shaping circuit. DETAILED DESCRIPTION

[0060] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0061] Embodiment 1:

[0062] See also Figure 1-2 , an isolated low-cost communication module, comprising:

[0063] CM485 main module;

[0064] The CM485 slave module is electrically connected to the CM485 master module, and the CM485 slave module is used to receive and send data signals;

[0065] The CM485 master module is electrically connected to the external device through the CM485 slave module, and the CM485 master module is electrically connected to the computer;

[0066] The CM485 main module includes a USB to UART circuit 1, a communication isolation circuit 2, a power isolation circuit 3, a conversion circuit 4, a first protection circuit 5 and an indicator light circuit 6. The USB to UART circuit 1 is electrically connected to the communication isolation circuit 2 and the power isolation circuit 3, the power isolation circuit 3 is electrically connected to the communication isolation circuit 2 and the conversion circuit 4, the communication isolation circuit 2 is electrically connected to the conversion circuit 4, the conversion circuit 4 is electrically connected to the first protection circuit 5, and the indicator light circuit 6 is electrically connected to the conversion circuit 4.

[0067] In this embodiment, the USB to UART circuit 1 set in the CM485 main module is used to convert the USB signal into a TTL level signal, the communication isolation circuit 2 is set to isolate the converted TTL level signal, the power isolation circuit 3 is set to isolate the USB power supply and then supply power to the conversion circuit 4, the conversion circuit 4 is set to convert the TTL level signal into an RS485 level signal and process the signal, the first protection circuit 5 is configured with a transient suppression diode and a lightning arrester to protect internal components, and the indicator light circuit 6 is set to display the status of the power supply and communication signal.

[0068] The CM485 slave module includes a second protection circuit 7 , a rectifier circuit 8 , an optocoupler circuit 9 and a level shaping circuit 10 . The second protection circuit 7 is electrically connected to the rectifier circuit 8 , the rectifier circuit 8 is electrically connected to the optocoupler circuit 9 , and the optocoupler circuit 9 is electrically connected to the level shaping circuit 10 .

[0069] In this embodiment, the second protection circuit 7 set in the CM485 slave module is used to protect internal components, the rectifier circuit 8 is used to rectify the received and transmitted signals, the optocoupler circuit 9 is used to realize data reception and transmission and electrical isolation, and the level shaping circuit 10 is used to shape the waveform of the received signal.

[0070] Embodiment 2:

[0071] See also Figure 3-8This embodiment provides a technical solution based on the first embodiment:

[0072] USB to UART circuit 1 includes:

[0073] USB connector USB1 connected to the USB port of the computer; and

[0074] USB to UART chip U1, USB to UART chip U1 converts the USB connector USB1 signal into a TTL level signal;

[0075] The signal of pin 2 of USB connector USB1 is connected to pin 2 of USB to UART chip U1, the signal of pin 3 of USB connector USB1 is connected to pin 1 of USB to UART chip U1, pin 5 of USB connector USB1 and pin 3 of USB to UART chip U1 are both grounded, and capacitors C5 and C3 are connected in series between pin 7 and pin 10 of USB to UART chip U1 respectively.

[0076] The communication isolation circuit 2 comprises:

[0077] Digital isolation chip U2 and digital isolation chip U3, digital isolation chip U2 and digital isolation chip U3 electrically isolate the TTL level signal converted by USB to UART chip U1;

[0078] The signal of pin 2 of the digital isolation chip U2 is connected to pin 9 of the USB to UART chip U1, the signal of pin 3 of the digital isolation chip U2 is connected to pin 8 of the USB to UART chip U1, and the signal of pin 3 of the digital isolation chip U3 is connected to pin 6 of the USB to UART chip U1.

[0079] The power isolation circuit 3 includes a DC-DC power isolation module M1, which isolates the power of the USB connector USB1 and supplies power to the conversion circuit 4;

[0080] Pin No. 1 and pin No. 2 of the DC-DC power isolation module M1 are grounded, capacitors C2 and C4 are connected in parallel between pin No. 9 and pin No. 10 of the DC-DC power isolation module M1, capacitors C6 and C7 are connected in parallel between pin No. 11 and pin No. 12 of the DC-DC power isolation module M1, and a rectifier diode D1 is connected in series between pin No. 11 of the DC-DC power isolation module M1 and capacitor C6.

[0081] The conversion circuit 4 comprises:

[0082] RS485 chip U8, RS485 chip U8 converts the TTL level signal converted by USB to UART chip U1 into RS485 level signal;

[0083] Digital analog switch U6, digital analog switch U6 is used to disconnect the A line of RS485 chip U8 in the receiving state;

[0084] An operational amplifier U5, the operational amplifier U5 amplifies the received voltage signal; and

[0085] Photocoupler U11, which pulls the level down to a negative voltage under the control of the amplified signal output by the operational amplifier U5;

[0086] The signal of pin 1 of RS485 chip U8 is connected to pin 7 of digital isolation chip U2, the signal of pins 2 and 3 of RS485 chip U8 is connected to pin 6 of digital isolation chip U3, the signal of pin 4 of RS485 chip U8 is connected to pin 6 of digital isolation chip U2, a resistor R7 is connected in series between pins 6 and 8 of RS485 chip U8, and a resistor R17 is connected in series between pins 5 and 7 of RS485 chip U8;

[0087] The signal of pin 1 of the digital analog switch U6 is connected to pin 6 of the RS485 chip U8. The signal of pin 2 of the digital analog switch U6 is connected to pin 8 of the RS485 chip U8 after being connected in series with resistor R16. The signal of pin 4 of the digital analog switch U6 is connected to pin 6 of the digital isolation chip U3.

[0088] Pin 4 of the photocoupler U11 is connected in series with resistor R18 and then the signal is connected to pin 6 of the RS485 chip U8, and pin 3 of the photocoupler U11 is grounded;

[0089] A resistor R10 is connected in series between pin 1 and pin 2 of the operational amplifier U5, a resistor R11 is connected in series between pin 3 and pin 4 of the operational amplifier U5, a resistor R12 is connected in series to pin 4 of the operational amplifier U5, and its signal is then connected to pin 2 of the optocoupler U11, a resistor R6 is connected in series to pin 1 of the operational amplifier U5, and its signal is then connected to pin 2 of the digital analog switch U6, a resistor R9 is connected in series to pin 2 of the RS485 chip U8, and its signal is then connected to pin 7 of the RS485 chip U8.

[0090] The first protection circuit 5 comprises:

[0091] Transient suppression diode DZ1, transient suppression diode DZ2, lightning arrester PTC1 and connector JP3;

[0092] After the transient suppression diode DZ1, the transient suppression diode DZ2 and the lightning arrester PTC1 are connected in series in sequence, the signal is connected to pins 1 and 2 of the connector JP3. The two ends of the transient suppression diode DZ1 are connected in series with capacitor F1, and the two ends of the transient suppression diode DZ2 are connected in series with capacitor F2. After pin 1 of the connector JP3 is connected in series with the lightning arrester PTC1, the signal is connected to pin 7 of the RS485 chip U8, and the signal of pin 2 of the connector JP3 is connected to pin 2 of the digital analog switch U6.

[0093] The indicator light circuit 6 comprises:

[0094] Indicator light LED2, indicator light LED3 and indicator light LED4, the negative pole of indicator light LED2 is connected in series with resistor R2 and then grounded, the positive pole of indicator light LED3 is connected in series with resistor R3 and then the signal is connected to the positive pole of indicator light LED2, the positive pole of indicator light LED4 is connected in series with resistor R4 and then the signal is connected to the positive pole of indicator light LED2, the negative pole signal of indicator light LED3 is connected to pin 1 of RS485 chip U8, and the negative pole signal of indicator light LED4 is connected to pin 4 of RS485 chip U8.

[0095] In this embodiment, the CM485 main module is connected to the computer via the USB connector USB1. The CM485 main module has a built-in USB to UART chip U1. The USB to UART chip U1 is connected to the RS485 chip U8 through a high-speed digital isolation device (i.e., a digital isolation chip U2 and a digital isolation chip U3). At the same time, the DC-DC power isolation module M1 outputs the power of the USB connector USB1 into two sets of isolated power supplies, one of which is used to power the RS485 chip U8.

[0096] When the CM485 master module sends data to the CM485 slave module, it can be sent directly through the RS485 chip U8. The level logic of the RS485 chip U8 when sending (A=H, B=L when data=0, A=L, B=H when data=1) corresponds to the receiving mode of the CM485 slave module. When current B flows to A, the slave module can receive data 1. Therefore, the CM485 master module signal can be directly sent using the RS485 chip.

[0097] When the CM485 slave module sends data to the CM485 master module, since the CM485 slave module has no power supply, it is impossible to make AB greater than the receiving judgment threshold of the RS485 chip U8 (generally around -200mV), and can only make A close to B. Therefore, an operational amplifier (i.e., operational amplifier U5) needs to be added to the CM485 master module side to amplify the differential voltage of AB, and then control the optocoupler U11 to pull A down to the negative pole of another group of power supply of the DC-DC power isolation module M1. The positive pole of this group of power supply is connected to B. The AB level received by the RS485 chip can be detected by the RS485 chip U8, and then transmitted to the USB to UART chip U1 through the high-speed digital isolation device, and then transmitted to the computer.

[0098] Through the above two points, data transmission between the CM485 master module and the CM485 slave module can be realized, and the CM485 master module of the present invention can also be directly compatible with RS485 communication. At the same time, the DC-DC power isolation module M1 in the present invention only needs about 0.2 yuan, and the other components are also ordinary components with extremely low cost, so the overall cost of the CM485 master module is not much different from that of the ordinary RS485 module.

[0099] Embodiment three:

[0100] See also Fig. 9 This embodiment provides a technical solution based on the first embodiment:

[0101] The second protection circuit 7 comprises:

[0102] Transient suppression diode DZ4, two ends of transient suppression diode DZ4 are respectively connected in series with interface JP8 and interface JP7, and interface JP8 and interface JP7 cooperate with connector JP3.

[0103] The rectifier circuit 8 comprises:

[0104] The rectifier diode D2 and the rectifier diode D3, the cathode signal of the rectifier diode D2 is connected to the anode of the rectifier diode D3, and the anode signal of the rectifier diode D3 is connected to one end of the transient suppression diode DZ4.

[0105] The optocoupler circuit 9 comprises:

[0106] Optocoupler U4 and optocoupler U7;

[0107] Pin 1 of the photocoupler U4 is connected in series with resistors R14 and R19, and then the signal is connected to interface JP4. Pin 2 of the photocoupler U4 is connected to interface JP5. Pin 3 of the photocoupler U4 is connected in series with resistor R15, and then the signal is connected to pin 1 of the photocoupler U7. Pin 4 of the photocoupler U4 is connected to the cathode of the rectifier diode D3.

[0108] The signal of pin 2 of the photocoupler U7 is connected to the positive electrode of the rectifier diode D2;

[0109] The level shaping circuit 10 comprises:

[0110] Transistor Q1, the base of transistor Q1 is connected in series with resistor R20, and then the signal is connected to pin 3 of optocoupler U7. The base of transistor Q1 is connected in series with resistor R20 and resistor R13, and then the signal is connected to the emitter of transistor Q1. The emitter of transistor Q1 is grounded, and the collector signal of transistor Q1 is connected to interface JP4.

[0111] In this embodiment, the UART debugging interface of the external device is connected to the interface JP4 (receiving end) and the interface JP5 (transmitting end), wherein the interface JP4 and the interface JP5 can also be a group arrangement of multiple interfaces, which can be selected according to actual conditions. The interface JP4 and the interface JP5 are respectively connected to two optical couplers, namely, the photoelectric coupler U4 (transmitting photocoupler of the TX signal) and the photoelectric coupler U7 (receiving photocoupler of the RX signal). The directions of the photoelectric coupler U4 and the photoelectric coupler U7 are opposite. The data transmission and reception and electrical isolation are realized by the set photoelectric coupler U4 and the photoelectric coupler U7. The electrical coupler U4 and the photoelectric coupler U7 are connected in parallel after passing through the rectifier diode D2 and the rectifier diode D3, wherein the rectifier diode D2 and the rectifier diode D3 play the role of rectifying the current direction. In this embodiment, data reception or transmission is realized by changing the current direction on two communication buses. The serial numbers of the two communication buses are A and B (the corresponding circuits are marked with ZF-A and ZF-B). When the CM485 slave module sends data, the current flows from A to B. When the current flows from B to A, after being rectified by the rectifier diode and passing through the receiving optical coupler, the CM485 slave module can correctly receive the data. At the same time, a transient suppression diode DZ4 is added between the A line and the B line to prevent the high voltage from burning the internal components. The circuit of the CM485 slave module in the present invention is extremely simple, requiring only 10 components, and the cost is as low as about 0.5 yuan. Compared with the 5 yuan required for the RS485 isolation power supply, it can save more than 90% of the cost.

[0112] Meanwhile, the contents not described in detail in this specification belong to the prior art known to those skilled in the art.

[0113] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0114] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An isolated low-cost communication module, characterized in that: include: CM485 main module; A CM485 slave module, electrically connected to the CM485 master module, and the CM485 slave module is used to receive and send data signals; The CM485 master module is electrically connected to an external device through the CM485 slave module, and the CM485 master module is electrically connected to a computer; The CM485 main module comprises a USB to UART circuit (1), a communication isolation circuit (2), a power isolation circuit (3), a conversion circuit (4), a first protection circuit (5) and an indicator light circuit (6), wherein the USB to UART circuit (1) is electrically connected to the communication isolation circuit (2) and the power isolation circuit (3), the power isolation circuit (3) is electrically connected to the communication isolation circuit (2) and the conversion circuit (4), the communication isolation circuit (2) is electrically connected to the conversion circuit (4), the conversion circuit (4) is electrically connected to the first protection circuit (5), and the indicator light circuit (6) is electrically connected to the conversion circuit (4); The CM485 slave module comprises a second protection circuit (7), a rectifier circuit (8), an optocoupler circuit (9) and a level shaping circuit (10), wherein the second protection circuit (7) is electrically connected to the rectifier circuit (8), the rectifier circuit (8) is electrically connected to the optocoupler circuit (9), and the optocoupler circuit (9) is electrically connected to the level shaping circuit (10).

2. An isolated low-cost communication module according to claim 1, characterized in that: The USB to UART circuit (1) comprises: USB connector USB1 connected to the USB port of the computer; and USB to UART chip U1, the USB to UART chip U1 converts the USB connector USB1 signal into a TTL level signal; The signal of pin 2 of the USB connector USB1 is connected to pin 2 of the USB to UART chip U1, the signal of pin 3 of the USB connector USB1 is connected to pin 1 of the USB to UART chip U1, pin 5 of the USB connector USB1 and pin 3 of the USB to UART chip U1 are both grounded, and capacitors C5 and C3 are connected in series between pin 7 and pin 10 of the USB to UART chip U1 in sequence.

3. An isolated low-cost communication module according to claim 2, characterized in that: The communication isolation circuit (2) comprises: A digital isolation chip U2 and a digital isolation chip U3, wherein the digital isolation chip U2 and the digital isolation chip U3 electrically isolate the TTL level signal converted by the USB to UART chip U1; The pin 2 signal of the digital isolation chip U2 is connected to the pin 9 of the USB to UART chip U1, the pin 3 signal of the digital isolation chip U2 is connected to the pin 8 of the USB to UART chip U1, and the pin 3 signal of the digital isolation chip U3 is connected to the pin 6 of the USB to UART chip U1.

4. The isolated low-cost communication module according to claim 3, characterized in that: The power isolation circuit (3) comprises a DC-DC power isolation module M1, and the DC-DC power isolation module M1 isolates the power of the USB connector USB1 and then supplies power to the conversion circuit (4); Pin No. 1 and pin No. 2 of the DC-DC power isolation module M1 are grounded, capacitors C2 and C4 are connected in parallel between pin No. 9 and pin No. 10 of the DC-DC power isolation module M1, capacitors C6 and C7 are connected in parallel between pin No. 11 and pin No. 12 of the DC-DC power isolation module M1, and a rectifier diode D1 is connected in series between pin No. 11 of the DC-DC power isolation module M1 and capacitor C6.

5. The isolated low-cost communication module according to claim 4, characterized in that: The conversion circuit (4) comprises: RS485 chip U8, the RS485 chip U8 converts the TTL level signal converted by the USB to UART chip U1 into an RS485 level signal; A digital analog switch U6, wherein the digital analog switch U6 is used to disconnect the A line of the RS485 chip U8 in a receiving state; an operational amplifier U5, wherein the operational amplifier U5 amplifies the received voltage signal; and A photocoupler U11, wherein the photocoupler U11 pulls the voltage level down to a negative voltage under the control of the amplified signal output by the operational amplifier U5; Pin 1 of the RS485 chip U8 is connected to pin 7 of the digital isolation chip U2 by signal, pins 2 and 3 of the RS485 chip U8 are connected to pin 6 of the digital isolation chip U3 by signal, pin 4 of the RS485 chip U8 is connected to pin 6 of the digital isolation chip U2 by signal, a resistor R7 is connected in series between pins 6 and 8 of the RS485 chip U8, and a resistor R17 is connected in series between pins 5 and 7 of the RS485 chip U8; The signal of pin 1 of the digital analog switch U6 is connected to pin 6 of the RS485 chip U8, the signal of pin 2 of the digital analog switch U6 is connected to pin 8 of the RS485 chip U8 after being connected in series with resistor R16, and the signal of pin 4 of the digital analog switch U6 is connected to pin 6 of the digital isolation chip U3; Pin 4 of the photocoupler U11 is connected in series with resistor R18 and then connected to pin 6 of the RS485 chip U8, and pin 3 of the photocoupler U11 is grounded; A resistor R10 is connected in series between pin 1 and pin 2 of the operational amplifier U5, a resistor R11 is connected in series between pin 3 and pin 4 of the operational amplifier U5, a resistor R12 is connected in series with pin 4 of the operational amplifier U5, and the signal is then connected to pin 2 of the photocoupler U11, a resistor R6 is connected in series with pin 1 of the operational amplifier U5, and the signal is then connected to pin 2 of the digital analog switch U6, and a resistor R9 is connected in series with pin 2 of the operational amplifier U5, and the signal is then connected to pin 7 of the RS485 chip U8.

6. The isolated low-cost communication module according to claim 5, characterized in that: The first protection circuit (5) comprises: Transient suppression diode DZ1, transient suppression diode DZ2, lightning arrester PTC1 and connector JP3; The transient suppression diode DZ1, the transient suppression diode DZ2 and the lightning arrester PTC1 are connected in series in sequence, and the signal is connected to pin 1 and pin 2 of the connector JP3. The two ends of the transient suppression diode DZ1 are connected in series with capacitor F1, and the two ends of the transient suppression diode DZ2 are connected in series with capacitor F2. After pin 1 of the connector JP3 is connected in series with the lightning arrester PTC1, the signal is connected to pin 7 of the RS485 chip U8. The signal of pin 2 of the connector JP3 is connected to pin 2 of the digital analog switch U6.

7. The isolated low-cost communication module according to claim 6, characterized in that: The indicator light circuit (6) comprises: Indicator light LED2, indicator light LED3 and indicator light LED4, the cathode of the indicator light LED2 is connected in series with resistor R2 and then grounded, the anode of the indicator light LED3 is connected in series with resistor R3 and then the signal is connected to the anode of the indicator light LED2, the anode of the indicator light LED4 is connected in series with resistor R4 and then the signal is connected to the anode of the indicator light LED2, the cathode signal of the indicator light LED3 is connected to pin 1 of the RS485 chip U8, and the cathode signal of the indicator light LED4 is connected to pin 4 of the RS485 chip U8.

8. The isolated low-cost communication module according to claim 7, characterized in that: The second protection circuit (7) comprises: A transient suppression diode DZ4, two ends of which are respectively connected in series with a port JP8 and a port JP7, and the port JP8 and the port JP7 cooperate with the connector JP3.

9. The isolated low-cost communication module according to claim 8, characterized in that: The rectifier circuit (8) comprises: The rectifier diode D2 and the rectifier diode D3, the cathode signal of the rectifier diode D2 is connected to the anode of the rectifier diode D3, and the anode signal of the rectifier diode D3 is connected to one end of the transient voltage suppression diode DZ4.

10. The isolated low-cost communication module according to claim 9, characterized in that: The optical coupler circuit (9) comprises: Optocoupler U4 and optocoupler U7; Pin 1 of the photocoupler U4 is connected in series with resistors R14 and R19, and then the signal is connected to interface JP4; Pin 2 of the photocoupler U4 is connected in series with interface JP5; Pin 3 of the photocoupler U4 is connected in series with resistor R15, and then the signal is connected to pin 1 of the photocoupler U7; Pin 4 of the photocoupler U4 is connected in series with the cathode of the rectifier diode D3; The pin 2 of the photocoupler U7 is connected to the positive electrode of the rectifier diode D2; The level shaping circuit (10) comprises: Transistor Q1, the base of the transistor Q1 is connected in series with resistor R20 and then the signal is connected to pin 3 of the photocoupler U7, the base of the transistor Q1 is connected in series with resistor R20 and resistor R13 and then the signal is connected to the emitter of the transistor Q1, the emitter of the transistor Q1 is grounded, and the collector signal of the transistor Q1 is connected to interface JP4.

Images