CN112052212A

CN112052212A - RS485 communication flow control isolation circuit

Info

Publication number: CN112052212A
Application number: CN202010870672.3A
Authority: CN
Inventors: 刘炳山
Original assignee: Tianjin Jinhang Computing Technology Research Institute
Current assignee: Tianjin Jinhang Computing Technology Research Institute
Priority date: 2020-08-26
Filing date: 2020-08-26
Publication date: 2020-12-08
Anticipated expiration: 2040-08-26
Also published as: CN112052212B

Abstract

The invention relates to an RS485 communication flow control isolation circuit, and belongs to the technical field of aviation data communication. The invention provides an RS485 communication flow control isolation circuit, which can automatically adjust the level of a receiving and transmitting enabling port of an RS485 receiving and transmitting chip by utilizing the characteristics of a bus and transmitting port data in the receiving and transmitting process of RS485 communication data, can switch the receiving and transmitting states of an RS485 protocol chip in time, realizes the receiving and transmitting control of an RS485 communication circuit, saves pin resources of a main control chip, has simple circuit, is easy to realize, and can effectively ensure the stability and reliability of bus data communication.

Description

RS485 communication flow control isolation circuit

Technical Field

The invention belongs to the technical field of aviation data communication, and particularly relates to an RS485 communication flow control isolation circuit.

Background

RS485 has the characteristics of strong anti-noise anti-interference capability, long transmission distance and support of multi-point communication, and is a half-duplex multi-point communication mode widely used in the field of aviation. RS485 adopts two-wire differential signal transmission data, has the ability of resisting common mode interference, is widely applied to some airborne equipment with complex environment, supports multi-node communication, and is very suitable for the application occasions of communication between a multi-node slave machine and a host machine. However, due to the adoption of multi-node communication, the receiving and sending directions of the RS485 protocol chip need to be controlled, extra IO port resources of the processor need to be occupied to realize the switching of the data receiving and sending states, and the logic sequence of the receiving enable/RE and the sending enable DE control end also needs to be additionally processed on the driving software. When multi-node RS485 communication is adopted, due to the fact that electromagnetic environments of a multi-node slave machine and a host machine are complex, interference such as electrostatic discharge, electric fast transient pulse groups or surge exists in an interconnected electric link.

Disclosure of Invention

Technical problem to be solved

The technical problem to be solved by the invention is as follows: how to realize the automatic receiving and transmitting control of RS485 communication and the electric isolation of the circuit.

(II) technical scheme

In order to solve the above technical problem, the present invention provides an RS485 communication flow control isolation circuit, including: the isolation power circuit and the RS485 communication circuit are two parts of circuits; the isolation power supply circuit is used for providing an isolated power supply for the RS485 communication circuit.

Preferably, the isolated power supply circuit includes: an isolation power supply module N1, capacitors C1, C2, C3 and C4;

in the isolation power supply circuit, capacitors C1 and C2 are respectively connected in parallel between the input positive end and the input negative end of an isolation power supply module N1, capacitors C3 and C4 are respectively connected in parallel between the output positive end and the output negative end of an isolation power supply module N1, the input positive end of an isolation power supply module N1 is connected with an internal input power supply +5Vcc, and the input negative end of an isolation power supply module N1 is connected with an internal ground GND; the output positive terminal of the isolation power supply module N1 is connected with the output isolation power supply VCC _485, and the output negative terminal of N1 is connected with the isolation ground GND _485 terminal.

Preferably, the RS485 communication circuit comprises an isolation device magnetic coupling B1, an inverting buffer D1, an RS485 protocol chip D2, resistors R1, R2, R3, R4 and R5; the first pin of the isolation device magnetic coupling B1 is connected with +5Vcc of an input power supply, the second pin is connected with an internal ground GND, VCC1 of the isolation device magnetic coupling B1 is connected with an isolation power supply VCC _485, GND1 is connected with the isolation ground GND _485, INB of the isolation device magnetic coupling B1 is connected with an RO port of an RS485 protocol chip D2 and is connected with the isolation power supply VCC _485 through a resistor R1, and OUTA of the isolation device magnetic coupling B1 is respectively connected with DI of the RS485 protocol chip D2 and input of an inverting buffer D1; the power supply of the inverting buffer D1 is connected with an isolation power supply VCC _485, the power supply ground is connected with an isolation ground GND _485, the output of the inverting buffer D1 is respectively connected with a transmitting enable DE and a receiving enable DE of an RS485 protocol chip D2, and is connected with the isolation power supply VCC _485 through a resistor R2; the power VCC of the RS485 chip D2 is connected with an isolation power VCC _485, the power ground is connected with an isolation ground GND _485, wherein the RS485 communication differential pair positive terminal A of the RS485 protocol chip D2 is connected with the isolation power VCC _485 through a resistor R3, the RS485 communication differential pair negative terminal pin B of the RS485 protocol chip D2 is connected with the isolation ground GND _485 through a resistor R4, and the RS485 communication differential pair positive terminal A of the RS485 protocol chip D2 is connected with the RS485 protocol chip D2 differential pair negative terminal pin B through a resistor R5.

Preferably, the isolation power supply circuit isolates the input power supply +5Vcc from the internal ground GND, and outputs the isolation power supply Vcc _485 and the isolation ground GND _485, wherein the input power supply +5Vcc and the internal ground GND are used for supplying power to the main control chip, the isolation power supply Vcc _485 and the isolation ground GND _485 supply power to the RS485 communication circuit, the isolation power supply circuit filters and stabilizes the input power supply +5Vcc through capacitors C1 and C2, and the capacitors C3 and C4 filter and stabilize the isolation power supply Vcc _ 485.

Preferably, the isolation power supply circuit realizes the complete isolation of the power supply and the ground between the RS485 communication circuit and the internal main control chip; OUTB and INA of the magnetic coupling B1 of the isolation device are connected with an internal main control chip, and an RS485 communication differential pair positive terminal A and a differential pair negative terminal pin B of an RS485 protocol chip D2 are connected with an external RS485 node.

Preferably, the RS485 protocol chip D2 adopts a communication protocol chip with a receive enable/RE and a transmit enable DE, and uses the inverting buffer D1 to control the transceiving switching.

The invention also provides a method for realizing transceiving control by using the RS485 communication flow control isolation circuit, wherein a control signal is input from the input end of the inverting buffer D1, and is output to the receiving enable and sending enable DE of the RS485 protocol chip D2 from the output end to control transceiving enable switching, the RO port of the RS485 chip D2 is a signal receiving port, a differential signal received by the RS485 communication differential pair positive terminal A of the RS485 protocol chip D2 and the differential pair negative terminal pin B port is converted into a single-ended signal by the RS485 protocol chip D2, the single-ended signal enters the INB port of the isolation device magnetic coupling B1 through the RO port and then enters the main control chip through the OUTB port, and the main control chip receives and processes the signal; the main control chip sends signals to enter a DI port of an RS485 protocol chip D2 through an OUTA port after being isolated by an INA port of an isolation device magnetic coupling B1, the signals are converted into differential signals through an RS485 protocol chip D2, and the differential signals are sent out through an A port and a B port.

Preferably, the data receiving process is that the data is received by an RS485 communication differential pair positive terminal A and a differential pair negative terminal pin B of an RS485 protocol chip D2, and the data enters the processor through an OUTB port of a magnetic coupling B1 after the RS485 protocol chip D2 and the magnetic coupling B1, so that the receiving process is completed; the data sending process is sent by the main control chip, after entering the magnetic coupling B1 and the RS485 protocol chip D2 from the INA port of B1, the data is sent by the RS485 communication differential pair positive terminal A and the differential pair negative terminal pin B of the RS485 protocol chip D2, and the sending process is completed.

Preferably, the specific data reception control procedure is as follows:

when no data is sent, the INA port defaults to high level, the low level is output through the inverter D1 after being isolated by the magnetic coupling B1, the RE low level of the RS485 chip D2 is enabled, and the RO receives data to be enabled, at the moment, the data received from the A, B port of the RS485 protocol chip D2 is transmitted to the magnetic coupling B1 through an RO channel, and the data is transmitted to the main control chip after being isolated by the magnetic coupling B1, so that the data receiving process is completed.

Preferably, the specific data transmission and reception control procedure is as follows: when data is transmitted, the INA port has a pull-down level which indicates that data transmission is started, the data is isolated by the magnetic coupling B1 and then output a high level through the inverter D1, DE of the RS485 protocol chip D2 is a high level, and transmission is enabled, when data '0' is transmitted, the DI port of the RS485 protocol chip D2 is a low level, at the moment, the data '0' is transmitted to the A, B port of the RS485 protocol chip D2, the '0' is transmitted, the low-level transmission is completed, when the '1' is transmitted, RE and DE of the RS485 protocol chip D2 are both low levels, but at the moment, because the data is still transmitted, the RS485 chip D2 is in a high-resistance state, the state is determined by the pull-up resistor R3 of the A port and the pull-down resistor R4 of the B port, and at the moment, the '1' is transmitted, and the high-level transmission. And finishing the data sending process according to the rule.

(III) advantageous effects

The invention provides an RS485 communication flow control isolation circuit, which can automatically adjust the level of a receiving and transmitting enabling port of an RS485 receiving and transmitting chip by utilizing the characteristics of a bus and transmitting port data in the receiving and transmitting process of RS485 communication data, can switch the receiving and transmitting states of an RS485 protocol chip in time, realizes the receiving and transmitting control of an RS485 communication circuit, saves pin resources of a main control chip, has simple circuit, is easy to realize, and can effectively ensure the stability and reliability of bus data communication.

Drawings

FIG. 1 is a schematic diagram of an isolated power supply circuit of the present invention;

fig. 2 is a schematic diagram of an RS485 communication flow control isolation circuit in the invention.

Detailed Description

In order to make the objects, contents, and advantages of the present invention clearer, the following detailed description of the embodiments of the present invention will be made in conjunction with the accompanying drawings and examples.

In order to solve the problems of automatic receiving and transmitting control and circuit electrical isolation of RS485 communication, the invention provides an automatic flow control method, in the process of receiving and transmitting RS485 communication data, the level of a receiving and transmitting enabling port of an RS485 receiving and transmitting chip is automatically adjusted by utilizing the characteristics of a bus and transmitting port data, the receiving and transmitting state of the RS485 protocol chip can be timely switched, the receiving and transmitting control of the RS485 communication circuit is realized, the circuit saves pin resources of a main control chip, is simple and easy to realize, and can effectively ensure the stability and reliability of bus data communication.

The circuit of the invention consists of an isolation power circuit and an RS485 communication circuit. The method can be realized by the following technical scheme:

as shown in fig. 1, the isolated power supply circuit includes: an isolation power supply module N1, capacitors C1, C2, C3 and C4;

in the isolation power supply circuit, capacitors C1 and C2 are respectively connected in parallel between an input positive terminal (pin 2) and an input negative terminal (pin 1) of an isolation power supply module N1, capacitors C3 and C4 are respectively connected in parallel between an output positive terminal (pin 4) and an output negative terminal (pin 3) of an isolation power supply module N1, the input positive terminal (pin 2) of the isolation power supply module N1 is connected with an internal input power supply +5Vcc, and the input negative terminal (pin 1) of the isolation power supply module N1 is connected with an internal ground GND; keep apart power module N1's the positive end of output (pin 4) and output isolation power VCC _485 and connect, N1's output negative terminal (pin 3) and the end connection of isolation GND _485, keep apart power supply circuit and be used for providing the power of isolation for RS485 communication circuit, realize that the complete isolation of power and ground between RS485 communication circuit and the inside main control chip (main control chip does not contain in this circuit).

This keep apart power supply circuit keeps apart input power +5Vcc and inside ground GND, and output isolation power VCC _485 and isolation ground GND _485, wherein input power +5Vcc and inside ground GND are used for supplying power for main control chip, and isolation power VCC _485 and isolation ground GND _485 are the RS485 communication circuit power supply, keep apart power supply circuit and carry out the filtering steady voltage to input power +5Vcc through electric capacity C1, C2, electric capacity C3, C4 carry out the filtering steady voltage to isolation power VCC _485, guarantee the reliability of mains operated.

As shown in fig. 2, the RS485 communication circuit includes an isolation device, a magnetic coupling B1, an inverting buffer D1, an RS485 protocol chip D2, and resistors R1, R2, R3, R4, and R5; pin 8 of the isolation device magnetic coupling B1 is connected with +5Vcc of an input power supply, pin 5 is connected with an internal ground GND, OUTB (pin 6) and INA (pin 7) of the isolation device magnetic coupling B1 are connected with an internal main control chip, VCC1 (pin 1) of the isolation device magnetic coupling B1 is connected with an isolation power supply VCC _485, GND1 (pin 4) is connected with the isolation GND _485, INB (pin 3) of the isolation device magnetic coupling B1 is connected with an RO port (pin 1) of an RS485 protocol chip D2 and is connected with the isolation power supply VCC _485 through a resistor R1, OUTA (pin 2) of the isolation device magnetic coupling B1 is respectively connected with DI (pin 4) of an RS485 protocol chip D2 and an input (pin 2) of an inverting buffer D1; a power supply (pin 5) of the inverting buffer D1 is connected with an isolation power supply VCC _485, a power supply ground (pin 3) is connected with an isolation GND _485, and an output (pin 4) of the inverting buffer D1 is respectively connected with a transmitting enable DE (pin 3) and a receiving enable (pin 2) of an RS485 protocol chip D2 and is connected with the isolation power supply VCC _485 through a resistor R2; the power VCC (pin 8) of the RS485 chip D2 is connected with the isolation power VCC _485, the power ground (pin 5) is connected with the isolation GND _485, the RS485 communication differential pair positive terminal A (pin 6) of the RS485 protocol chip D2, the differential pair negative terminal pin B (pin 7) is connected with the external RS485 node (the external RS485 node is not contained in the circuit), wherein the RS485 communication differential pair positive terminal A (pin 6) of the RS485 protocol chip D2 is connected with the isolation power VCC _485 through a resistor R3, the RS485 communication differential pair negative terminal pin B (pin 7) of the RS485 protocol chip D2 is connected with the isolation ground GND _ through a resistor R4, and the RS485 communication differential pair positive terminal A (pin 6) of the RS485 protocol chip D2 is connected with the RS485 differential pair negative terminal pin B (pin 7) of the RS485 protocol chip D2 through a resistor R5.

The RS485 protocol chip D2 adopts a communication protocol chip with a receiving enable/RE and a sending enable DE, and the circuit uses an inverting buffer D1 to control the receiving and sending switching. The control signal is input from the input end (pin 2) of the D1, is output from the output end (pin 4) to the receiving enable/RE and the sending enable DE, controls the switching of the receiving and sending enable, and the R2 is used as a pull-up resistor to ensure the stability of the output signal. The RS485 protocol chip D2 has a differential signal positive terminal A connected with a pull-up resistor R3, a differential signal negative terminal B connected with a pull-down resistor R4, and a resistor R5 connected between A and B for impedance matching. The RO port of the RS485 chip D2 is a signal receiving port, differential signals received by the A and B ports are converted into single-ended signals through the RS485 protocol chip D2, the single-ended signals enter the INB port of the magnetic coupling B1 of the isolation device through the RO port and are isolated, then the single-ended signals enter the main control chip through the OUTB port, the main control chip receives and processes the signals, and the R1 is used as a pull-up resistor to ensure that input signals are stable. The main control chip sends signals to enter a DI port of an RS485 protocol chip D2 through an OUTA port after being isolated by an INA port of an isolation device magnetic coupling B1, the signals are converted into differential signals through an RS485 protocol chip D2, and the differential signals are sent out through an A port and a B port. The data receiving process is that the data is received by an RS485+ and RS 485-differential pair, and the RS485 protocol chip D2 and the magnetic coupling B1 enter a processor through a UART3_ RX to complete the receiving process; the data sending process is sent by the main control chip, enters the magnetic coupling B1 and the RS485 protocol chip D2 from the UART3_ TX, and is sent by the RS485+ and RS 485-differential pair, so that the sending process is completed.

The specific transceiving control process is as follows:

data reception: when no data is sent, the UART3_ TX is defaulted to be high level, the low level is output through the inverter D1 after being isolated by the magnetic coupling B1, the RE low level of the RS485 chip D2 is enabled, and the RO receives data to be enabled, at this time, the data received from the A, B port of the RS485 protocol chip D2 is transmitted to the magnetic coupling B1 through an RO channel, and the data is transmitted to the main control chip after being isolated by the magnetic coupling B1, so that the data receiving process is completed.

Data transmission: when transmitting data, the UART3_ TX has a pull-down level indicating that data transmission is started, and outputs a high level through the inverter D1 after being isolated by the magnetic coupling B1, and the DE of the RS485 protocol chip D2 is a high level, and transmission is enabled. When data '0' is transmitted, the DI port of the RS485 protocol chip D2 is at low level, and then data '0' is transmitted to the A, B port, a-B <0, and '0' is transmitted, completing the low level transmission. When '1' is transmitted, both RE and DE of the RS485 protocol chip D2 are in low level, but at the moment, because the RS485 chip D2 is still in the data transmission state, the state is determined by the pull-up resistor R3 of the A port and the pull-down resistor R4 of the B port, at the moment, A-B is greater than 0, and '1' is transmitted, so that the high-level transmission is completed. And finishing the data sending process according to the rule.

The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.

Claims

1. The utility model provides a RS485 communication flow control isolation circuit which characterized in that includes: the isolation power circuit and the RS485 communication circuit are two parts of circuits; the isolation power supply circuit is used for providing an isolated power supply for the RS485 communication circuit.

2. The RS485 communication flow control isolation circuit of claim 1, wherein the isolated power supply circuit comprises: an isolation power supply module N1, capacitors C1, C2, C3 and C4;

3. The RS485 communication current control isolation circuit according to claim 2, wherein the RS485 communication circuit comprises an isolation device magnetic coupling B1, an inverting buffer D1, an RS485 protocol chip D2, resistors R1, R2, R3, R4 and R5; the first pin of the isolation device magnetic coupling B1 is connected with +5Vcc of an input power supply, the second pin is connected with an internal ground GND, VCC1 of the isolation device magnetic coupling B1 is connected with an isolation power supply VCC _485, GND1 is connected with the isolation ground GND _485, INB of the isolation device magnetic coupling B1 is connected with an RO port of an RS485 protocol chip D2 and is connected with the isolation power supply VCC _485 through a resistor R1, and OUTA of the isolation device magnetic coupling B1 is respectively connected with DI of the RS485 protocol chip D2 and input of an inverting buffer D1; the power supply of the inverting buffer D1 is connected with an isolation power supply VCC _485, the power supply ground is connected with an isolation ground GND _485, the output of the inverting buffer D1 is respectively connected with a transmitting enable DE and a receiving enable DE of an RS485 protocol chip D2, and is connected with the isolation power supply VCC _485 through a resistor R2; the power VCC of the RS485 chip D2 is connected with an isolation power VCC _485, the power ground is connected with an isolation ground GND _485, wherein the RS485 communication differential pair positive terminal A of the RS485 protocol chip D2 is connected with the isolation power VCC _485 through a resistor R3, the RS485 communication differential pair negative terminal pin B of the RS485 protocol chip D2 is connected with the isolation ground GND _485 through a resistor R4, and the RS485 communication differential pair positive terminal A of the RS485 protocol chip D2 is connected with the RS485 protocol chip D2 differential pair negative terminal pin B through a resistor R5.

4. The RS485 communication flow control isolation circuit according to claim 3, wherein the isolation power supply circuit isolates an input power supply +5Vcc from an internal ground GND, outputs an isolation power supply VCC-485 and an isolation ground GND-485, wherein the input power supply +5Vcc and the internal ground GND are used for supplying power to the main control chip, the isolation power supply VCC-485 and the isolation ground GND-485 supply power to the RS485 communication circuit, the isolation power supply circuit filters and stabilizes the input power supply +5Vcc through capacitors C1 and C2, and the capacitors C3 and C4 filter and stabilize the isolation power supply VCC-485.

5. The RS485 communication flow control isolation circuit of claim 4, wherein the isolation power supply circuit realizes complete isolation of power supply and ground between the RS485 communication circuit and the internal main control chip; OUTB and INA of the magnetic coupling B1 of the isolation device are connected with an internal main control chip, and an RS485 communication differential pair positive terminal A and a differential pair negative terminal pin B of an RS485 protocol chip D2 are connected with an external RS485 node.

6. The RS485 communication flow control and isolation circuit as claimed in claim 5, wherein the RS485 protocol chip D2 adopts a communication protocol chip with a receiving enable/RE and a sending enable DE, and the inverting buffer D1 is used for controlling the receiving and sending switching.

7. A method for realizing transceiving control by using the RS485 communication flow control isolation circuit of any one of claims 1 to 7, wherein a control signal is input from the input end of the inverting buffer D1, and is output from the output end to the receiving enable DE and the sending enable DE of the RS485 protocol chip D2, so as to control transceiving enable switching, the RO port of the RS485 chip D2 is a signal receiving port, a differential signal received by the RS485 communication differential pair positive terminal A and the differential pair negative terminal pin B port of the RS485 protocol chip D2 is converted into a single-ended signal by the RS485 protocol chip D2, the single-ended signal enters the INB port of the isolation device magnetic coupling B1 through the RO port, and then enters the main control chip through the OUTB port, and the main control chip receives the signal; the main control chip sends signals to enter a DI port of an RS485 protocol chip D2 through an OUTA port after being isolated by an INA port of an isolation device magnetic coupling B1, the signals are converted into differential signals through an RS485 protocol chip D2, and the differential signals are sent out through an A port and a B port.

8. The method of claim 7, wherein the data receiving process is performed by RS485 communication differential pair positive terminal a and differential pair negative terminal pin B of RS485 protocol chip D2, and the RS485 protocol chip D2 and magnetic coupling B1 enter the processor through OUTB port of magnetic coupling B1 to complete the receiving process; the data sending process is sent by the main control chip, after entering the magnetic coupling B1 and the RS485 protocol chip D2 from the INA port of B1, the data is sent by the RS485 communication differential pair positive terminal A and the differential pair negative terminal pin B of the RS485 protocol chip D2, and the sending process is completed.

9. The method of claim 8, wherein the specific data reception control procedure is as follows:

10. The method of claim 9, wherein the specific data transmission and reception control procedure is as follows: when data is transmitted, the INA port has a pull-down level which indicates that data transmission is started, the data is isolated by the magnetic coupling B1 and then output a high level through the inverter D1, DE of the RS485 protocol chip D2 is a high level, and transmission is enabled, when data '0' is transmitted, the DI port of the RS485 protocol chip D2 is a low level, at the moment, the data '0' is transmitted to the A, B port of the RS485 protocol chip D2, the '0' is transmitted, the low-level transmission is completed, when the '1' is transmitted, RE and DE of the RS485 protocol chip D2 are both low levels, but at the moment, because the data is still transmitted, the RS485 chip D2 is in a high-resistance state, the state is determined by the pull-up resistor R3 of the A port and the pull-down resistor R4 of the B port, and at the moment, the '1' is transmitted, and the high-level transmission. And finishing the data sending process according to the rule.