CN104243256A - RS485 bus star-shaped extension device and method - Google Patents
RS485 bus star-shaped extension device and method Download PDFInfo
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- CN104243256A CN104243256A CN201410463782.2A CN201410463782A CN104243256A CN 104243256 A CN104243256 A CN 104243256A CN 201410463782 A CN201410463782 A CN 201410463782A CN 104243256 A CN104243256 A CN 104243256A
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Abstract
The invention discloses an RS485 bus star-shaped extension device and method. The device comprises a power source, an RS485 master interface circuit and RS485 slave interface circuits. The RS485 master interface circuit is connected with the RS485 slave interface circuits, the RS485 slave interface circuits are connected with RS485 devices, the number of the RS485 slave interface circuits is at least two, the RS485 devices are grouped, one group of RS485 devices is connected to one of the RS485 slave interface circuits, the other groups of RS485 devices are sequentially connected with the corresponding RS485 slave interface circuits respectively, RS485 slave interfaces are connected with the other RS485 slave interface circuits, and an RS485 master interface is connected with the RS485 slave interfaces. The RS485 bus star-shaped extension device and method solve the problem that when a plurality of RS485 devices are connected together in parallel, communication cannot be realized due to the fact that the load of an RS485bus is too heavy, can extend the structure of the RS485 bus into a star-shaped or tree-shaped structure and meet the standard requirements of the RS485 bus.
Description
technical field:
The present invention relates to a kind of expanding unit, particularly relate to a kind of RS485 bus star expanding unit and method.
background technology:
RS485 communication has a wide range of applications in fields such as industry, electric power, and the common multifunction electric meter etc. as electric power system, is generally all equipped with RS485 communication interface.When carrying out automatic data logging, if the ammeter equipment connection of multiple RS485 interface together time, can realize easily wiring and communicate with ammeter.According to the requirement of RS485 specification, reduce signal reflex on the impact of RS485 bus, when connect multiple RS485 ammeter equipment time, need to connect into hand-in-hand daisy-chain fashion, can not star, tree structure.Simultaneously when on too much RS485 equipment connection to RS485 bus, because the overload in bus causes kilowatt meter recorder can not read data normal through RS485 bus from ammeter.
summary of the invention:
Technical problem to be solved by this invention is: overcome the deficiencies in the prior art, there is provided a kind of structure simple, solve multiple RS485 equipment, the overload of RS485 bus is caused and cannot the RS485 bus star expanding unit of communication issue when being connected in parallel, there is provided a kind of reasonable in design simultaneously, good stability, ensures that RS485 bus has the RS485 bus star extended method of steady operation performance.
Technical scheme of the present invention is:
A kind of RS485 bus star expanding unit, comprise power supply, RS485 master interface circuit, RS485 from interface circuit, described RS485 master interface circuit is connected from interface circuit with RS485, described RS485 is from interface circuit and RS485 equipment connection, described RS485 is at least two from interface circuit, and described RS485 equipment is at least one and no more than 32.
Described RS485 master interface circuit comprises RS485 change-over circuit and main RS485 interface, and described RS485 comprises RS485 change-over circuit and from RS485 interface from interface circuit.
Described RS485 change-over circuit comprises MAX485, resistance, thyristor.
A kind of RS485 bus star extended method, it is characterized in that: RS485 equipment is divided into groups, often group is no more than 32, the RS485 interface of one group of RS485 equipment is connected to one of them from RS485 interface circuit, down arrange successively, connect from RS485 and be connected from RS485 interface circuit with other, main RS485 interface is connected with from RS485 interface as the communication interface of RS485 equipment, the data that main RS485 interface receives are by sending from RS485 interface, and the data received from RS485 interface are sent by main RS485 interface.
Described RS485 master interface circuit is connected by SN7408J element from interface circuit with RS485.
The invention has the beneficial effects as follows:
1, the invention solves multiple RS485 equipment, cause the overload of RS485 bus when being connected in parallel and the problem that cannot communicate.
2, the present invention can expand the structure of RS485 bus is star or tree structure, and meets the requirement of RS485 specification, has ensured signaling rate.
accompanying drawing illustrates:
Fig. 1 is RS485 bus star expanding unit structured flowchart.
Fig. 2 is RS485 change-over circuit circuit diagram.
embodiment:
Embodiment: see Fig. 1 and Fig. 2.
RS485 bus star expanding unit: comprise power supply, RS485 master interface circuit, RS485 from interface circuit, RS485 master interface circuit is connected from interface circuit with RS485, RS485 is from interface circuit and RS485 equipment connection, RS485 is at least two from interface circuit, and RS485 equipment is at least one and no more than 32.
RS485 master interface circuit comprises RS485 change-over circuit and main RS485 interface, and RS485 comprises RS485 change-over circuit and from RS485 interface from interface circuit.
RS485 change-over circuit comprises MAX485, resistance, thyristor.
A kind of RS485 bus star extended method, it is characterized in that: RS485 equipment is divided into groups, often group is no more than 32, the RS485 interface of one group of RS485 equipment is connected to one of them from RS485 interface circuit, down arrange successively, be connected from RS485 interface circuit from RS485 interface with other, main RS485 interface is connected with from RS485 interface as the communication interface of RS485 equipment, the data that main RS485 interface receives are by sending from RS485 interface, and the data received from RS485 interface are sent by main RS485 interface.
RS485 master interface circuit is connected by SN7408J element from interface circuit with RS485.
Operation principle: when numeral 1 needs to be sent to A2, B2 from A1, B1, Txd1 is high level, Q1 conducting, and Dir1 is low level, therefore Rxd1(Txd2) be high level.Txd2 is high level, Q2 conducting, and Dir2 is low level, so now U2 is in accepting state.And the pull-up of R8 and the drop-down of R9, so A2>B2, so now the state of the RS485 bus of A2, B2 is numeral 1.When numeral 0 needs to be sent to A2, B2 from A1, B1, Txd1 is high level, Q1 conducting, and Dir1 is low level, therefore Rxd1(Txd2) be low level, Txd2 is low level, Q2 by, Dir2 is high level, and now U2 is in transmission state.Txd2 is low level, so now the RS485 bus state of A2, B2 is numeral 0, because circuit is symmetrical, when data send A1, B1 from A2, B2, performs similar process.
The above, it is only preferred embodiment of the present invention, not any pro forma restriction is done to the present invention, every above embodiment is done according to technical spirit of the present invention any simple modification, equivalent variations and modification, all still belong in the scope of technical solution of the present invention.
Claims (5)
1. a RS485 bus star expanding unit, comprise power supply, RS485 master interface circuit, RS485 from interface circuit, it is characterized in that: described RS485 master interface circuit is connected from interface circuit with RS485, described RS485 is from interface circuit and RS485 equipment connection, described RS485 is at least two from interface circuit, and described RS485 equipment is at least one and no more than 32.
2. RS485 bus star expanding unit according to claim 1, is characterized in that: described RS485 master interface circuit comprises RS485 change-over circuit and main RS485 interface, and described RS485 comprises RS485 change-over circuit and from RS485 interface from interface circuit.
3. RS485 bus star expanding unit according to claim 2, is characterized in that: described RS485 change-over circuit comprises MAX485, resistance, thyristor.
4. a RS485 bus star extended method, it is characterized in that: RS485 equipment is divided into groups, often group is no more than 32, the RS485 interface of one group of RS485 equipment is connected to one of them from RS485 interface circuit, down arrange successively, be connected from RS485 interface circuit from RS485 interface with other, main RS485 interface is connected with from RS485 interface as the communication interface of RS485 equipment, the data that main RS485 interface receives are by sending from RS485 interface, and the data received from RS485 interface are sent by main RS485 interface.
5. RS485 bus star extended method according to claim 4, is characterized in that: described RS485 master interface circuit is connected by SN7408J element from interface circuit with RS485.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201410463782.2A CN104243256A (en) | 2014-09-13 | 2014-09-13 | RS485 bus star-shaped extension device and method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201410463782.2A CN104243256A (en) | 2014-09-13 | 2014-09-13 | RS485 bus star-shaped extension device and method |
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| Publication Number | Publication Date |
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| CN104243256A true CN104243256A (en) | 2014-12-24 |
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| CN201410463782.2A Pending CN104243256A (en) | 2014-09-13 | 2014-09-13 | RS485 bus star-shaped extension device and method |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103941700A (en) * | 2014-04-28 | 2014-07-23 | 张晓华 | Automation process safety monitoring system based on Modbus protocol |
| US11585835B2 (en) | 2021-01-15 | 2023-02-21 | Red Lion Controls, Inc. | System of determining the sequence and positioning of pluggable modules |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103941700A (en) * | 2014-04-28 | 2014-07-23 | 张晓华 | Automation process safety monitoring system based on Modbus protocol |
| CN103941700B (en) * | 2014-04-28 | 2019-04-30 | 张晓华 | A kind of automation process safety monitoring system based on Modbus agreement |
| US11585835B2 (en) | 2021-01-15 | 2023-02-21 | Red Lion Controls, Inc. | System of determining the sequence and positioning of pluggable modules |
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Application publication date: 20141224 |
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