CN108880826B

CN108880826B - RS232 and RS485 combined interface

Info

Publication number: CN108880826B
Application number: CN201810620128.6A
Authority: CN
Inventors: 冯军伟; 张连忠
Original assignee: Baoding Better Electric Equipment Manufacturing Co ltd
Current assignee: Baoding Better Electric Equipment Manufacturing Co ltd
Priority date: 2018-06-15
Filing date: 2018-06-15
Publication date: 2020-07-14
Anticipated expiration: 2038-06-15
Also published as: CN108880826A

Abstract

The invention discloses an RS232 and RS485 combined interface which comprises an interface and an external input protection module, wherein the interface and the external input protection module are used for providing interfaces of an RS232 mode and an RS485 mode and inhibiting an overvoltage signal and an overcurrent signal from entering a rear-stage circuit, a differential pressure comparison analysis and RS485 protection module is used for controlling the on-off of the RS485 circuit according to the output of a voltage comparator and realizing the protection of the RS485 circuit, the RS232 and RS485 main circuit and a TT L isolation conversion module are used for signal communication of the RS232 and the RS485 and introducing an interference signal and an abnormal voltage current signal to the external communication, a power supply module is used for providing a 5V isolation power supply for the RS232 main circuit and the RS485 main circuit, and an MCU control unit is in communication connection with the RS232 and RS485 main circuit and the TT L isolation conversion module and is used for receiving and transmitting a rear-stage control instruction.

Description

RS232 and RS485 combined interface

Technical Field

The invention relates to a communication interface, in particular to an RS232 and RS485 combined interface.

Background

With the acceleration of industrialization and information degree, various electronic communication devices rely on RS232 and RS485 interfaces to be more and more extensive, and are used as two most widely applied interface standards of RS232 and RS 485. The RS232 is used as full duplex, but the transmission distance is short, the interference is easy to occur, the RS232 is in a single-point communication mode, the RS485 communication interface is used for replacing the RS232 communication interface, and the RS485 is in a half-duplex transmission mode, so that two most common communication modes of the RS232 and the RS485 exist. Therefore, developing a combined interface which can meet the RS232 communication requirement and is compatible with an RS485 interface becomes a problem to be solved urgently in the field.

Disclosure of Invention

The technical problem to be solved by the invention is to provide an RS232 and RS485 combined interface, which can solve the defects of the prior art, realize the compatible communication of the RS232 and RS485 interfaces, greatly simplify the program design and solve the problem of hardware incompatibility, and is beneficial to better maintenance and communication interconnection of equipment.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows.

An RS232 and RS485 combined interface comprises,

the interface and external input protection module is used for providing interfaces of RS232 and RS485 modes and inhibiting overvoltage signals and overcurrent signals from entering a rear-stage circuit;

a differential pressure comparison analysis and RS485 protection module used for controlling the on-off of the RS485 circuit according to the output of the voltage comparator to realize the protection of the RS485 circuit,

the RS232 and RS485 main circuit and the TT L isolation conversion module are used for signal communication of the RS232 and RS485 and introducing an interference signal and an abnormal voltage and current signal to external communication;

the power supply module is used for providing a 5V isolation power supply for the RS232 main circuit and the RS485 main circuit;

and the MCU control unit is in communication connection with the RS232 and RS485 main circuit and the TT L isolation conversion module and is used for receiving and transmitting a post-stage control instruction.

Preferably, the interface and external input protection module comprises a three-terminal connection port, a self-recovery fuse and a two-terminal regulator which are connected in series.

Preferably, the differential pressure comparison analysis and RS485 protection module comprises an RS232 signal positive-negative conversion module, an L M324 voltage comparator, a T L P521 photoelectric coupler and an RS485 power supply control module which are arranged in series.

Preferably, the RS232 and RS485 main circuits and the TT L isolation conversion module include a port module, a TT L communication isolation module and a TT L communication isolation module which are arranged in series and are respectively connected with the RS485 main circuit and the RS232 main circuit in parallel.

Preferably, the power supply module comprises an internal connection port and an L7805 CV voltage stabilizer which are arranged in series, and the output end of the L7805 CV voltage stabilizer is connected with an ASM1117 voltage stabilizer, an RS485 circuit power supply output module and an RS232 circuit power supply output module in parallel respectively.

Adopt the beneficial effect that above-mentioned technical scheme brought to lie in: the invention can solve the problems of communication mismatching caused by a single interface, equipment development difficulty increase caused by multiple interfaces and resource waste design in the prior art. The method can meet the requirements of different interface standards, greatly simplify port resources, integrate a connection method and simplify operation and maintenance.

Drawings

FIG. 1 is a schematic diagram of one embodiment of the present invention.

Fig. 2 is a block diagram of an interface and external input protection module according to an embodiment of the present invention.

Fig. 3 is a block diagram of a differential pressure comparison analysis and RS485 protection module according to an embodiment of the present invention.

Fig. 4 is a structural diagram of an RS232 and RS485 main circuit and a TT L isolation conversion module according to an embodiment of the present invention.

Fig. 5 is a block diagram of a power module in accordance with an embodiment of the present invention.

Detailed Description

Referring to fig. 1-5, one embodiment of the present invention includes,

the interface and external input protection module 1 is used for providing interfaces of RS232 and RS485 modes and inhibiting overvoltage signals and overcurrent signals from entering a rear-stage circuit;

a differential pressure comparison analysis and RS485 protection module 2, which is used for controlling the on-off of the RS485 circuit according to the output of the voltage comparator to realize the protection of the RS485 circuit,

the RS232 and RS485 main circuit and the TT L isolation conversion module 3 are used for signal communication of the RS232 and RS485 and introducing interference signals and abnormal voltage and current signals to external communication;

the power supply module 4 is used for providing a 5V isolation power supply for the RS232 main circuit and the RS485 main circuit;

and the MCU control unit 5 is in communication connection with the RS232 and RS485 main circuit and the TT L isolation conversion module 3 and is used for receiving and transmitting a post-stage control instruction.

The interface and external input protection module 1 comprises a three-terminal connection port 11, a self-recovery fuse 12 and a two-terminal voltage stabilizer 13 which are arranged in series.

The differential pressure comparison analysis and RS485 protection module 2 comprises an RS232 signal positive-negative conversion module 21, an L M324 voltage comparator 22, a T L P521 photoelectric coupler 23 and an RS485 power supply control module 24 which are arranged in series.

The RS232 and RS485 main circuits and the TT L isolation conversion module 3 comprise a port module 31, a TT L communication isolation module 32 and a TT L communication isolation module 32 which are arranged in series, and the RS485 main circuit 33 and the RS232 main circuit 34 are connected in parallel respectively.

The power module 4 comprises an internal connection port 41 and an L7805 CV voltage stabilizer 42 which are arranged in series, and the output end of the L7805 CV voltage stabilizer 42 is respectively connected with an ASM1117 voltage stabilizer 43, an RS485 circuit power output module 44 and an RS232 circuit power output module 45 in parallel.

The working principle is as follows: the power module 4 provides a required 5V isolation power supply for the RS485 circuit and the RS232 circuit. The interface and external input protection module 1 can be respectively accessed to an RS485 interface mode and an RS232 interface mode; after the communication signal enters the three-terminal connection port 11, in order to protect the damage influence of abnormal overcurrent and overvoltage on the rear-end circuit, the self-recovery fuse 12 and the two-terminal voltage stabilizer 13 are respectively connected, so that the abnormal overcurrent and overvoltage signals can be effectively inhibited from entering the rear-end circuit at the front end. Because the RS232 signal transmission is the signal transceiving mode between RXD and logic ground and between TXD and logic ground, overvoltage protection is respectively carried out between RXD and logic ground, between TXD and logic ground and between RXD and TXD. The protection parameters mainly take RS232 maximum voltage parameters as main parameters, and voltage and current signals in two different modes can pass through the protection parameters.

The interface device has the following three operation modes.

The working mode is as follows: after the MCU control unit 5 sends signals to the circuit, the signals are respectively and simultaneously transmitted to the RS485 and RS232 signals through the isolation circuit, the RS485 and the RS232 can simultaneously generate an A, B differential RS485 mode sending signal and a TXD and logic ground voltage sending signal, and because the RS485 and the RS232 are respectively independent of a power supply, a single line does not form loop pressure difference, so that the signal sending tasks under two modes can be completed due to complementary influence of the two signals.

The second working mode is that when an RS485 mode A, B differential signal is introduced into the external interface or the RXD of the RS232 and a voltage receiving signal of a logic ground are approximately the same as the first working mode, and the signals do not influence respective independent circuits mutually, namely the RS485 signal can be converted into a TT L level by the RS485 circuit and input through an internal port, or the RS232 signal can be converted into a TT L level by the RS232 circuit and input into the MCU control unit 5 or other control acquisition ends through the internal port.

The working mode is three: because RS485 is in A, B differential signal transceiving mode, it is not possible to perform transceiving simultaneously, i.e. half-duplex mode, and RS232 is in transceiving mode between RXD and logic ground, TXD and logic ground, it is possible to perform transceiving simultaneously, i.e. full-duplex mode. Although an independent power supply is arranged between the RXD and the TXD, when data is transmitted and received simultaneously in an RS232 mode, a differential pressure signal of about 30V is generated between the RXD and the TXD, namely an A, B end of the RS485, so that interference can be caused on the RS485 signal, and even the RS485 chip can be damaged. Particularly, a differential pressure comparison analysis and RS485 protection module 2 is designed for the purpose.

When the RS232 interface receives and transmits data independently in a first working mode or a second working mode, namely, a logic 1 is-3-15V, a logic 0 is + 3-15V and noise margin is 2V data, after the RS232 signal positive-negative conversion module 21, a common ground positive signal is generated due to the fact that different power sources are adopted, namely, the conditions of logic 0 and logic 1 are changed into the conditions of logic 0(+3- +15V) for voltage comparison and judgment, after two paths generate voltage signals respectively, after the voltage signals are subjected to more than 3V voltage signals set by L M324, the L M324 voltage comparator 22 generates a low-level signal which is output to the T L P521 photoelectric coupler 23, a rear-level control triode 9013 reference signal is cut off, the RS485 is received and transmitted by control signals at two ends, when the RS 90232 is used for receiving and transmitting data independently, the RS485 protection module does not cut off the data when the RS 90232 is used for receiving and transmitting data independently, the RS485 protection circuit can be switched into a single working mode, and the RS485 protection circuit can be switched into a single receiving and transmitting and receiving and transmitting signals can be switched into a single mode when the RS232 is switched on the RS485 protection circuit.

In the description of the present invention, it is to be understood that the terms "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on those shown in the drawings, are merely for convenience of description of the present invention, and do not indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and thus, are not to be construed as limiting the present invention.

The foregoing shows and describes the general principles and broad features of the present invention and advantages thereof. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims

1. The utility model provides a RS232 and RS485 combination formula interface which characterized in that: comprises the steps of (a) preparing a mixture of a plurality of raw materials,

the interface and external input protection module (1) is used for providing interfaces of RS232 and RS485 modes and inhibiting overvoltage signals and overcurrent signals from entering a rear-stage circuit;

a differential pressure comparison analysis and RS485 protection module (2) for controlling the on-off of the RS485 circuit according to the output of the voltage comparator to realize the protection of the RS485 circuit,

the RS232 and RS485 main circuit and the TT L isolation conversion module (3) are used for signal communication of the RS232 and RS485 and preventing external communication from introducing interference signals and abnormal voltage and current signals;

the power supply module (4) is used for providing a 5V isolation power supply for the RS232 main circuit and the RS485 main circuit;

the MCU control unit (5) is in communication connection with the RS232 and RS485 main circuits and the TT L isolation conversion module (3) and is used for receiving and transmitting a post-stage control instruction;

the output end of the interface and external input protection module (1) is in communication connection with the input end of the differential pressure comparison analysis and RS485 protection module (2), the output end of the differential pressure comparison analysis and RS485 protection module (2) is in communication connection with the input ends of the RS232 and RS485 main circuits and the TT L isolation conversion module (3), and the output ends of the RS232 and RS485 main circuits and the TT L isolation conversion module (3) are in communication connection with the input end of the MCU control unit (5);

the differential pressure comparison analysis and RS485 protection module (2) comprises an RS232 signal positive-negative conversion module (21), an L M324 voltage comparator (22), a T L P521 photoelectric coupler (23) and an RS485 power supply control module (24) which are arranged in series, the output end of the RS232 signal positive-negative conversion module (21) is connected with the input end of the L M324 voltage comparator (22), the output end of the L M324 voltage comparator (22) is connected with the input end of the T L P521 photoelectric coupler (23), and the output end of the T L P521 photoelectric coupler (23) is connected with the input end of the RS485 power supply control module (24);

when the RS232 interface receives and transmits data independently, after the RS232 signal passes through the RS232 signal positive-negative conversion module (21), a common-ground positive signal is generated due to the fact that different power sources are used for sharing the ground, namely, the situation of logic 0 and logic 1 is changed into the situation of logic 0 to carry out voltage comparison and judgment, after two paths of the two paths generate a low-level signal to be output to the T L P521 photoelectric coupler (23), a reference signal of a rear-level control triode is cut-in, and the RS485 circuit cannot be powered and controlled by the RS485 when the RS232 receives and transmits and receives data independently, and only when the RS485 is in a half-duplex working mode and the RS485 and the RS232 is a full-duplex.

2. The RS232 and RS485 combo interface of claim 1, wherein: the interface and external input protection module (1) comprises a three-terminal connection port (11), a self-recovery fuse (12) and a double-terminal voltage stabilizer (13) which are arranged in series; the output end of the three-end connecting port (11) is connected with the input end of the self-recovery fuse (12), and the output end of the self-recovery fuse (12) is connected with the input end of the double-end voltage stabilizer (13).

3. The RS232 and RS485 combined interface as claimed in claim 1, wherein the RS232 and RS485 main circuit and the TT L isolation conversion module (3) comprise a port module (31) and a TT L communication isolation module (32) which are serially connected, and the TT L communication isolation module (32) is respectively connected with the RS485 main circuit (33) and the RS232 main circuit (34) in parallel.

4. The RS232 and RS485 combined interface as claimed in claim 1, wherein the power module (4) comprises an internal connection port (41) and an L7805 CV voltage stabilizer (42) connected in series, and the output end of the L7805 CV voltage stabilizer (42) is connected in parallel with an ASM1117 voltage stabilizer (43), an RS485 circuit power output module (44) and an RS232 circuit power output module (45), respectively.