CN105629832B - It is a kind of to automatically switch isolation circuit and method without transmitting-receiving control terminal RS485 transmitting-receiving - Google Patents
It is a kind of to automatically switch isolation circuit and method without transmitting-receiving control terminal RS485 transmitting-receiving Download PDFInfo
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- CN105629832B CN105629832B CN201510994349.6A CN201510994349A CN105629832B CN 105629832 B CN105629832 B CN 105629832B CN 201510994349 A CN201510994349 A CN 201510994349A CN 105629832 B CN105629832 B CN 105629832B
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B19/00—Programme-control systems
- G05B19/02—Programme-control systems electric
- G05B19/04—Programme control other than numerical control, i.e. in sequence controllers or logic controllers
- G05B19/042—Programme control other than numerical control, i.e. in sequence controllers or logic controllers using digital processors
- G05B19/0423—Input/output
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B2219/00—Program-control systems
- G05B2219/20—Pc systems
- G05B2219/25—Pc structure of the system
- G05B2219/25458—Opto isolation, optical separation
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- General Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Automation & Control Theory (AREA)
- Optical Communication System (AREA)
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Abstract
Automatically switch isolation circuit and method without transmitting-receiving control terminal RS485 transmitting-receiving the invention discloses a kind of, the automatic switchover isolation circuit includes MCU, RXD, TXD, ISO1, ISO2, U1, send control terminal and U2, the MCU is equipped with UART, RXD on the UART is connected to the RXD automatically switched in isolation circuit, TXD on the UART is connected to the TXD automatically switched in isolation circuit, after the ISO1 and ISO2 carries out signal isolation, it is connected to the end TXD and the end RXD automatically switched in isolation circuit, signal of the TXD after isolation in the automatic switchover isolation circuit is exported by 5 feet of ISO2, it is connected to the transmission control terminal of part under U1, RS485 is partially received on the U1 Signal in bus exports from 1 foot, is connected to 3 feet of ISO1, is sent on the RXD automatically switched in isolation circuit after optical isolation.The method transmission of switching isolation circuit of the invention is simple, by being suitble to promote this process simplify hardware connection and programming.
Description
Technical field
The present invention relates to automatically switch isolation circuit technical field more particularly to it is a kind of without transmitting-receiving control terminal RS485 transmitting-receiving
Automatically switch isolation circuit and method.
Background technique
With the development of digital technology, system consisting of a single chip microcomputer is also increasingly complicated, and single single-chip microcontroller is often difficult to full
Foot requires, and at this moment often to use multiple singlechip groups at a distributed system, can use between multiple single-chip microcontrollers
RS485 bus is attached communication.
In hardware realization, RS485 only uses two lines, is transmitted using differential signal, and compared with RS232, RS485 is total
The transmission range of line is longer, and anti-interference ability is stronger, and hardware interface is at low cost, and the link cost between each equipment is also low, these
Characteristic is also the main reason for using RS485 bus in industrial system.
In software realization, since RS485 bus is substantially compatible with RS232 bus in software design, communication software
Design is simple, and all single-chip microcontrollers have UART (UART Universal Asynchronous Receiver Transmitter) function, can be easily carried out the design of software.
RS458 industrial application is mature, and largely existing industrial equipment is provided which RS485 interface, thus even to this day,
Also there is highly important status in the application of RS485 bus industrial.
Traditional RS485 bus connection connects multiple equipment by two lines with bus mode, realizes half between each equipment
Duplex communication.It is driven using the serially-transmitted data end TXD connection RS485 of UART Universal Asynchronous Receiver Transmitter UART in microcontroller
Sending data end DI, serial received data terminal RXD connection RS485 driving reception data terminal RO.Because RS485 is half-duplex side
Formula work, so it to be driven to transmission state to control RS485 by setting high direction controlling end TXEN when needing to send data,
When needing to receive data, control RSS485 is controlled by setting low direction controlling end TXEN and is driven to reception state.MCU with
The conventional coupling arrangement of RS485 drive part be using three lines (TXD, RXD, TXEN) connect, MCU will according to be send data,
Or receive data, it is necessary to which data direction control terminal TXEN when suitable just can guarantee and reliably communicate, in software programming
When, direction control terminal TXEN is controlled, with program to determine being to send data or receive data, and transmission is required to terminate
After could modify TXEN be reception state.And when generally serial line interface programs, the data of transmission and received data are not one
Byte, but data one by one, data are generally put into queue, are fetched from transmit queue according to transmission by interrupting, or
It is put into receiving queue by interrupting reception data, and at this moment upper level applications need to know that a frame data have been sent
At reception state could be converted to by direction controlling end TXEN, it is desirable that upper layer application checks whether low layer queue is empty shape
State, alternatively, low-level communication library just checks the function of queue without providing sometimes.So the method for delay is usually used to solve
This problem, it is believed that after a certain period of time, a frame has been sent completely, and is at this moment converted to just direction controlling end TXEN and is connect for delay
Receipts state.And when being delayed too long, other side may send reply data, may not receive data.So when other side sends
Quarter will also carry out delay adjustment according to sender, adjust bad, may make to communicate unstable, communication is good or bad.
So adjustment control TXEN carries out direction switch instant when tradition RS485 is communicated, it is that a system communication that influences is stablized
Factor, to be adjusted according to traffic rate, line length and equipment response time is realized, otherwise system communication will can not
It leans on.In this mode, it is also contemplated that how long to become reception state after sending in program, this delay is logical according to realizing
Letter rate, line length and equipment response time are adjusted, very inconvenient.
Summary of the invention
Technical problems based on background technology, it is automatic without transmitting-receiving control terminal RS485 transmitting-receiving that the invention proposes a kind of
Switch isolation circuit and method.
A kind of receive and dispatch without transmitting-receiving control terminal RS485 proposed by the present invention automatically switches isolation circuit, including MCU, RXD,
TXD, ISO1, ISO2, U1, transmission control terminal and U2, the MCU are equipped with UART, and the RXD on the UART is connected to be cut automatically
The RXD in isolation circuit is changed, the TXD on the UART is connected to the TXD, the ISO1 and ISO2 automatically switched in isolation circuit
After carrying out signal isolation, it is connected to the end TXD and the end RXD automatically switched in isolation circuit, in the automatic switchover isolation circuit
TXD by isolation after signal by ISO2 5 feet export, be connected to the transmission control terminal of part under U1, the U1's is upper
The signal being partially received in RS485 bus exports from 1 foot, is connected to 3 feet of ISO1, is sent to after optical isolation and cuts automatically
It changes on the RXD in isolation circuit, is connected on the right side of the U1 in external RS485 bus, the U2 is that 5V/5V isolated from power turns
It changes, is isolated for power supply internal/external power.
Preferably, the U1 is RS485 driving element.
The invention also provides it is a kind of without transmitting-receiving control terminal RS485 transmitting-receiving automatically switch isolation circuit method, it is described from
The method of dynamic switching isolation circuit includes sending data TXD and receiving data RXD, and specific step is as follows by the transmission data TXD:
When TXD does not send data, TXD is high level, and when sending data, it may be possible to 1 is also likely to be 0；When TXD sends 1, ISO2
Light emitting diode be not turned on, the cut-off of phototriode in ISO2,5 feet in ISO2 are low level, make the transmission that U1 is following
Part output is forbidden, and output is high-impedance state, by two resistance of R3 and R6, RS485 is made to transmit 1；When TXD sends 0, ISO2
LEDs ON, the phototriode conducting in ISO2,5 feet in ISO2 are high level, make the transmission unit that U1 is following
Dividing allows, and exports 4 feet by connecting to determine, and 4 feet of U1 are grounded, so U1 following transmitting portion output is 0, that is,
Make RS485 transmission differential signal transmission 0；
The reception data RXD controls and receives mode including receiving mode and TXD always, and the mode that receives always is to work as
In the 0 Ohmic resistance welding of R4, and when R5 is not welded, that is, the 2 feet ground connection of U1, allow the top U1 receiving portion always,
Then the data in RS485 bus can receive always, and the data oneself sent also can receive, and can be used in software oneself examining
It looks into；The TXD control and receive mode be when R4 is not welded, and when in the welding of 0 Ohmic resistance of R5, the receiving portion of the top U1 by
TXD control after optical isolation makes when TXD sends data, and RXD always 1 does not receive data, and RS485 bus carrys out data
When, RXD can receive data.
Preferably, when TXD output 1, when RS485 driving output is 1, TXD output 0, RS485 driving output 0；When
When TXD does not send data, TXD output is that 1, RS485 output is 1.
Preferably, when TXD sends 1,5 feet of ISO2 are low level, and the control top U1 receiving portion, which receives, to be allowed,
RS485 bus signals are 1, so the 1 foot output of U1 is high level, then the Light-Emitting Diode of ISO1 is not turned on, then corresponding light
Electric triode cut-off, R1 pull-up resistor make RXD 1；When TXD sends 0,5 feet of ISO2 are high level, and the control top U1 connects
Receiving portions reception is forbidden, and the 1 foot output of U1 is high-impedance state, then the Light-Emitting Diode of ISO1 is also not turned on, then corresponding photoelectricity
Triode is also switched off, and R1 pull-up resistor makes RXD 1.
Preferably, when external RS485 bus carrys out data 1, TXD does not send data, TXD 1, the reception of the top U1 at this time
Device is allowed, and RXD is made to be received as 1, and when external RS485 bus carrys out data 0, the receiver of the top U1 is allowed, and the 1 of U1
Foot output is low level, then the Light-Emitting Diode conducting of ISO1, and corresponding phototriode conducting makes RXD 0.
In the present invention, by using this method, eliminates in traditional RS485 bus communication and transmit and receive direction controlling end
TXEN pin does not have to consider that TXEN turns to moment problem in programming, and the present invention may be implemented after a frame data are sent completely,
It is automatically converted to reception state.Improve programming and debugging efficiency, time and the programming time of general debugging routine be it is comparable,
So nearly 50% or more efficiency can be improved.The reliability of system communication is improved simultaneously.
By removing the end TXEN, a part of hardware resource is also saved, PCB design is simplified.
The interference of system is inevitable in industrial environment, by the way that Phototube Coupling and isolated from power is added, is also increased
The reliability of system communication.By being suitble to promote this process simplify hardware connection and programming.
Detailed description of the invention
Fig. 1 is a kind of circuit diagram for automatically switching isolation circuit without transmitting-receiving control terminal RS485 transmitting-receiving proposed by the present invention.
Specific embodiment
Combined with specific embodiments below the present invention is made further to explain.
A kind of receive and dispatch without transmitting-receiving control terminal RS485 proposed by the present invention automatically switches isolation circuit, including MCU, RXD,
TXD, ISO1, ISO2, U1, transmission control terminal and U2, the MCU are equipped with UART, and the RXD on the UART is connected to be cut automatically
Change the RXD in isolation circuit, the TXD on the UART is connected to the TXD automatically switched in isolation circuit, the ISO1 and
After ISO2 carries out signal isolation, it is connected to the end TXD and the end RXD automatically switched in isolation circuit, the automatic switchover isolation electricity
Signal of the TXD of road after isolation is exported by 5 feet of ISO2, is connected to the transmission control terminal of part under U1, the U1
On be partially received signal in RS485 bus, exported from 1 foot, be connected to 3 feet of ISO1, be sent to after optical isolation from
On RXD in dynamic switching isolation circuit, be connected on the right side of the U1 in external RS485 bus, the U2 be 5V/5V power supply every
From conversion, it is isolated for power supply internal/external power.
The invention also provides it is a kind of without transmitting-receiving control terminal RS485 transmitting-receiving automatically switch isolation circuit method, it is described from
The method of dynamic switching isolation circuit includes sending data TXD and receiving data RXD, and specific step is as follows by the transmission data TXD:
When TXD does not send data, TXD is high level, and when sending data, it may be possible to 1 is also likely to be 0；When TXD sends 1, ISO2
Light emitting diode be not turned on, the cut-off of phototriode in ISO2,5 feet in ISO2 are low level, make the transmission that U1 is following
Part output is forbidden, and output is high-impedance state, by two resistance of R3 and R6, RS485 is made to transmit 1；When TXD sends 0, ISO2
LEDs ON, the phototriode conducting in ISO2,5 feet in ISO2 are high level, make the transmission unit that U1 is following
Dividing allows, and exports 4 feet by connecting to determine, and 4 feet of U1 are grounded, so U1 following transmitting portion output is 0, that is,
Make RS485 transmission differential signal transmission 0；
The reception data RXD controls and receives mode including receiving mode and TXD always, and the mode that receives always is to work as
In the 0 Ohmic resistance welding of R4, and when R5 is not welded, that is, the 2 feet ground connection of U1, allow the top U1 receiving portion always,
Then the data in RS485 bus can receive always, and the data oneself sent also can receive, and can be used in software oneself examining
It looks into；The TXD control and receive mode be when R4 is not welded, and when in the welding of 0 Ohmic resistance of R5, the receiving portion of the top U1 by
TXD control after optical isolation makes when TXD sends data, and RXD always 1 does not receive data, and RS485 bus carrys out data
When, RXD can receive data.
In the present invention, when the TXD exports 1, when RS485 driving output is 1, TXD output 0, RS485 drives output 0；When
When TXD does not send data, TXD output is that 1, RS485 output is 1.When TXD sends 1,5 feet of ISO2 are low level, control U1
Top receiving portion receive allow, RS485 bus signals be 1, so U1 1 foot output be high level, then ISO1 shine two
Grade pipe is not turned on, then corresponding phototriode cut-off, R1 pull-up resistor make RXD 1；When TXD sends 0,5 feet of ISO2
It for high level, controls the reception of the top U1 receiving portion and forbids, the 1 foot output of U1 is high-impedance state, then the Light-Emitting Diode of ISO1
Also it is not turned on, then corresponding phototriode is also switched off, and R1 pull-up resistor makes RXD 1.When external RS485 bus carrys out data 1
When, TXD does not send data at this time, and the receiver of TXD 1, the top U1 are allowed, and so that RXD is received as 1, when external RS485 is total
When line carrys out data 0, the receiver of the top U1 is allowed, and the 1 foot output of U1 is low level, then the Light-Emitting Diode of ISO1 is led
Logical, corresponding phototriode conducting makes RXD 0.
In the present invention, RS485 is industry standard communication bus, can connect multiple devices with bus connecting mode, in fact
It is existing at low cost, it is widely used in industrial control equipment.The present invention realize it is a kind of do not need transmitting-receiving control terminal, automatic transceiving turn
To RS485 bus communication circuitry.
The foregoing is only a preferred embodiment of the present invention, but protection scope of the present invention be not limited to
This, anyone skilled in the art in the technical scope disclosed by the present invention, according to the technique and scheme of the present invention
And its inventive concept is subject to equivalent substitution or change, should be covered by the protection scope of the present invention.
Claims (3)
1. a kind of method for automatically switching isolation circuit without transmitting-receiving control terminal RS485 transmitting-receiving, is characterized in that,
Using without transmitting-receiving control terminal RS485 transmitting-receiving automatically switch isolation circuit comprising MCU, RXD, TXD, ISO1, ISO2, U1,
It sends control terminal and U2, the MCU is equipped with UART, the RXD on the UART, which is connected to, to automatically switch in isolation circuit
TXD on RXD, the UART is connected to the TXD, the ISO1 and ISO2 automatically switched in isolation circuit and carries out signal isolation
Afterwards, it is connected to the end TXD and the end RXD automatically switched in isolation circuit, the TXD automatically switched in isolation circuit is by isolation
Signal afterwards is exported by 5 feet of ISO2, is connected to the transmission control terminal of part under U1, is partially received on the U1
Signal in RS485 bus exports from 1 foot, is connected to 3 feet of ISO1, automatic switchover isolation circuit is sent to after optical isolation
On RXD on, be connected on the right side of the U1 in external RS485 bus, the U2 is the conversion of 5V/5V isolated from power, for electricity
The isolation of source internal/external power；U1 is RS485 driving element；
The method for automatically switching isolation circuit includes sending data TXD and reception data RXD, the transmission data TXD tool
Steps are as follows for body: when TXD does not send data, TXD is 1, and when sending data, TXD is 1 or 0；When TXD sends 1, ISO2
Light emitting diode be not turned on, the cut-off of phototriode in ISO2,5 feet in ISO2 are low level, make the transmission that U1 is following
Part output is forbidden, and output is high-impedance state, by two resistance of R3 and R6, RS485 is made to transmit differential signal 1；When TXD is sent
When 0, the LEDs ON of ISO2, the phototriode conducting in ISO2,5 feet in ISO2 are high level, keep U1 following
Transmitting portion allow, 4 feet by connecting are exported to determine, and 4 feet of U1 are grounded, so U1 following transmitting portion output is
0, that is, RS485 is made to transmit differential signal 0；
The reception data RXD controls and receives mode including receiving mode and TXD always, and the mode that receives always is when R4's
In the welding of 0 Ohmic resistance, and when R5 is not welded, that is, the 2 feet ground connection of U1, allow the top U1 receiving portion always, then one
It directly can receive the data in RS485 bus and the data oneself sent；The TXD control and receive mode be when R4 is not welded,
And when in the 0 Ohmic resistance welding of R5, TXD of the receiving portion of the top U1 after by optical isolation is controlled, and makes to send data in TXD
When, always 1, RXD does not receive the data of MCU oneself transmission to RXD, and can receive the data that external RS485 bus is come；
Wherein, 2 pins of ISO1 are the anodes of light emitting diode in chip, are connected to positive pole V5E after isolation；The 3 of ISO1
Pin is the cathode of light emitting diode in chip, connects one end of resistance R2, while being connected to one end of capacitor C1；The 5 of ISO1
Pin is the earth signal end in chip, is connected to the earth signal of power supply before being isolated；6 pins of ISO1 are defeated after chip optical isolation
Signal out is connected to one end of pull-up resistor R1, while the asynchronous serial of microprocessor is input to as serial received signal RXD
The receiving end of transceiver；7 pins of ISO1 are chip signal output enable ends, are connected to positive pole VCC before isolation；ISO1's
8 pins are chip interior power supply signal ends, are connected to positive pole VCC before isolation；2 pins of ISO2 are light-emitting diodes in chip
The anode of pipe is connected to positive pole VCC before isolation；3 pins of ISO2 are the cathode of light emitting diode in chip, connect resistance
One end of R7, the other end of R7 are serial signal transmitting terminals, are connected to the transmitting terminal of the asynchronous serial transceiver of microprocessor；
5 pins of ISO2 are the earth signal ends in chip, are connected to one end of pull down resistor R8, power cathode after another termination isolation of R8
EGND；6 pins of ISO2 are the output signals after chip optical isolation, are connected to the positive V5E of power supply after isolation；Draw the 7 of ISO2
Foot is chip signal output enable end, is connected to the positive V5E of power supply after isolation；8 pins of ISO2 are chip interior power supply letters
Number end, be connected to isolation after positive pole V5E；6 feet of one end connection U1 of R3；Positive pole after the other end connection isolation of R3
V5E；2 feet of one end connection U1 of R4；Power cathode EGND after the other end connection isolation of R4；2 feet of one end connection U1 of R5；
3 feet of the other end connection U1 of R5, while connecting 5 feet of ISO2；7 feet of one end connection U1 of R6；R6 the other end connection every
Cathode EGND from rear power supply.
2. a kind of method for automatically switching isolation circuit without transmitting-receiving control terminal RS485 transmitting-receiving according to claim 1, special
Sign is, when the TXD exports 1, when the output of RS485 driving element is 1, TXD output 0, and RS485 driving element output 0；When
When TXD does not send data, TXD output is that the output of 1, RS485 driving element is 1.
3. a kind of method for automatically switching isolation circuit without transmitting-receiving control terminal RS485 transmitting-receiving according to claim 1, special
Sign is, when TXD sends 1,5 feet of ISO2 are low level, and the control top U1 receiving portion, which receives, to be allowed, RS485 bus letter
Number be 1, so U1 1 foot output be high level, then the Light-Emitting Diode of ISO1 is not turned on, then corresponding phototriode cut
Only, R1 pull-up resistor makes RXD 1；When TXD sends 0,5 feet of ISO2 are high level, and the control top U1 receiving portion receives
Forbid, the 1 foot output of U1 is high-impedance state, then the Light-Emitting Diode of ISO1 is also not turned on, then corresponding phototriode is also cut
Only, R1 pull-up resistor makes RXD 1.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201510994349.6A CN105629832B (en) | 2015-12-25 | 2015-12-25 | It is a kind of to automatically switch isolation circuit and method without transmitting-receiving control terminal RS485 transmitting-receiving |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201510994349.6A CN105629832B (en) | 2015-12-25 | 2015-12-25 | It is a kind of to automatically switch isolation circuit and method without transmitting-receiving control terminal RS485 transmitting-receiving |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN105629832A CN105629832A (en) | 2016-06-01 |
| CN105629832B true CN105629832B (en) | 2018-12-21 |
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| CN201510994349.6A Expired - Fee Related CN105629832B (en) | 2015-12-25 | 2015-12-25 | It is a kind of to automatically switch isolation circuit and method without transmitting-receiving control terminal RS485 transmitting-receiving |
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Families Citing this family (2)
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| CN109597783A (en) * | 2018-11-30 | 2019-04-09 | 中国电子科技集团公司第四十八研究所 | A kind of double light-coupled isolation type RS485 circuits |
| CN113934673B (en) * | 2021-12-16 | 2022-03-08 | 知迪汽车技术(北京)有限公司 | Data transmission isolation circuit and data transmission equipment |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0122218A3 (en) * | 1983-04-09 | 1986-09-10 | Bellheimer Metallwerk Gmbh | Control device for circulating shelves |
| EP0825503A2 (en) * | 1996-08-23 | 1998-02-25 | Bosch-Siemens HausgerÀ¤te GmbH | Circuit and procedure for the connection of an electrical household appliance with a control system |
| CN101188488A (en) * | 2007-07-30 | 2008-05-28 | 郑州春泉暖通节能设备有限公司 | Control method and device for half duplex communication receiving/transmission |
| CN201467234U (en) * | 2009-05-04 | 2010-05-12 | 河南新天科技有限公司 | 485 communication circuit capable of automatically controlling transmitting and receiving |
| CN204089768U (en) * | 2014-08-29 | 2015-01-07 | 天津天地伟业数码科技有限公司 | RS485 automatic reversing circuit |
-
2015
- 2015-12-25 CN CN201510994349.6A patent/CN105629832B/en not_active Expired - Fee Related
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0122218A3 (en) * | 1983-04-09 | 1986-09-10 | Bellheimer Metallwerk Gmbh | Control device for circulating shelves |
| EP0825503A2 (en) * | 1996-08-23 | 1998-02-25 | Bosch-Siemens HausgerÀ¤te GmbH | Circuit and procedure for the connection of an electrical household appliance with a control system |
| CN101188488A (en) * | 2007-07-30 | 2008-05-28 | 郑州春泉暖通节能设备有限公司 | Control method and device for half duplex communication receiving/transmission |
| CN201467234U (en) * | 2009-05-04 | 2010-05-12 | 河南新天科技有限公司 | 485 communication circuit capable of automatically controlling transmitting and receiving |
| CN204089768U (en) * | 2014-08-29 | 2015-01-07 | 天津天地伟业数码科技有限公司 | RS485 automatic reversing circuit |
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| CN105629832A (en) | 2016-06-01 |
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Granted publication date: 20181221 Termination date: 20191225 |