CN207968522U - A kind of RS485 bus driving circuits for realizing multi-host communication mode - Google Patents
A kind of RS485 bus driving circuits for realizing multi-host communication mode Download PDFInfo
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Abstract
The RXD pins of a kind of RS485 bus driving circuits for realizing multi-host communication mode, MCU controller chips are connected to the RXD pins of Bus Interface Chip, and the TXD pins of MCU controller chips are connected to the TXD pins of Bus Interface Chip；Signal wire A, the CANL pin that the CANH pins of Bus Interface Chip are connected to RS485 communication lines is connected to the signal wire B of RS485 communication lines.The Bus Interface Chip that the circuit uses can generate and meet the transmission characteristic that RS485 bus specifications and performance are better than RS485 bus specifications.On the basis of the interface circuit, is coordinated by the software of MCU controller chips, the RS485 bus systems of multi-host communication may be implemented.The RS485 bus real-times that the RS485 bus systems of multi-host communication overcome traditional standard are poor, and the low deficiency of network utilization ratio can be used widely in practical applications.
Description
Technical field
The utility model is related to electronic circuit field, especially a kind of RS485 bus drivers for realizing multi-host communication mode
Circuit.
Background technology
RS485 buses are a kind of common serial bus standards, by the way of balance transmission and differential received, therefore are had
There is the ability that suppression common mode is interfered.Some require communication distance be tens meters to upper km when, RS485 buses are a kind of
The bus being most widely used.RS485 system bus is because the advantages that hardware design is simple, easy to control, of low cost, is automatic
Change monitoring, security protection, access control and attendance and industrial automation system to be popularized and applied.
The RS485 communication modes of the prior art are master-slave modes, that is, are connected in all nodes in one network, only
One is host node, remaining is all subordinate computer node.Host node can be from host actively to slave transmission data, and slave section
It, could be passively to another slave transmission data after point only receives the querying command of host node.
This communication mode is in the presence of there are three insufficient：(1) it needs host node to traverse poll one by one to subordinate computer node, works as institute
Having subordinate computer node poll one to enclose will take a long time；(2) subordinate computer node can not active transmission data in time, if main
Machine node is not polled to it, it just can not transmission data, the timely and effective property of subordinate computer node data is largely effected on, to drop
The low timeliness of whole system；(3) network bandwidth utilization factor is relatively low, and host node does not know which subordinate computer node has data to
Send, can only constantly poll, inquire whether each all subordinate computer nodes want transmission data one by one, network bandwidth is greatly
Space is queried packet and consumes, and causes to waste network bandwidth, reduces the smoothness of network and the communication work efficiency of host and slave.
The deficiency for aiming to overcome that the above-mentioned prior art of RS485 buses of this patent scheme, connects only with a piece of bus
Mouth chip, and coordinate the communication software interface of each node, it constitutes using multi-host communication mode, and transmission performance is better than tradition
Standard RS485 buses, compatible RS485 buses；The RS485 bus real-times for overcoming traditional standard described above are poor, network profit
With the low deficiency of efficiency, can widely use in practical applications.
Utility model content
In order to solve above-mentioned problems of the prior art, the utility model provides a kind of multi-host communication mode of realizing
RS485 bus driving circuits.
Technical solution adopted by the utility model to solve its technical problems is：A kind of multi-host communication mode realized
RS485 bus driving circuits, include the MCU controller chips with UART asynchronous communication mouths, and device model PCA82C250's is total
Line interface chip and the RS485 communication lines for meeting RS485 bus specifications；The RXD pins of MCU controller chips are connected to always
The TXD pins of the RXD pins of line interface chip, MCU controller chips are connected to the TXD pins of Bus Interface Chip；Bus connects
Signal wire A, the CANL pin that the CANH pins of mouthful chip are connected to RS485 communication lines is connected to the letters of RS485 communication lines
Number line B.
Compared to the prior art the utility model, the advantage is that：
(1) Bus Interface Chip that the circuit uses, can generate that meet RS485 bus specifications and performance total better than RS485
The transmission characteristic of line gauge model.
(2) compared with the RS485 bus interface devices using other standards, the Bus Interface Chip 2 which uses does not have
There is transmitting-receiving control terminal, circuit connection is simpler and succinct, more convenient to use.
(3) the UART interface end that the interface circuit has MCU controller chips can realize that data synchronize internal loopback
Characteristic is the most basic and indispensable hardware circuit condition that multi-host communication mode is realized in RS485 buses.
(4) interface circuit is compatible with traditional standard RS485 buses, and the software of MCU controller chips can be still with original
The master-slave mode of traditional standard RS485 buses exchanges data, and original code is slightly changed, and is directly used even without change.
(5) on the basis of the interface circuit, coordinated by the software of MCU controller chips, multi-host communication may be implemented
RS485 bus systems.The RS485 bus real-times that the RS485 bus systems of multi-host communication overcome traditional standard are poor, network
The low deficiency of utilization ratio can be used widely in practical applications.
(6) physical layer interface circuit of this interface circuit compatibility CAN bus.
The additional aspect and advantage of the utility model will be set forth in part in the description, partly will be from following description
In become apparent, or recognized by the practice of the utility model.
Description of the drawings
In order to illustrate the embodiment of the utility model or the technical proposal in the existing technology more clearly, below will be to embodiment
Or attached drawing needed to be used in the description of the prior art is briefly described, it should be apparent that, the accompanying drawings in the following description is only
It is some embodiments of the utility model, for those of ordinary skill in the art, in the premise not made the creative labor
Under, other drawings may also be obtained based on these drawings.
Fig. 1 is the interface circuit structure schematic diagram of one node of RS485 buses for realizing multi-host communication mode；
Fig. 2 is the RS485 bus system structural schematic diagrams being made of 3 nodes；
Reference sign：
MCU controller chips 1；Bus Interface Chip 2；RS485 communication lines 3.
Specific implementation mode
The exemplary embodiment of the disclosure is more fully described below with reference to accompanying drawings.Although showing the disclosure in attached drawing
Exemplary embodiment, it being understood, however, that may be realized in various forms the disclosure without should be by embodiments set forth here
It is limited.On the contrary, these embodiments are provided to facilitate a more thoroughly understanding of the present invention, and can be by the scope of the present disclosure
Completely it is communicated to those skilled in the art.
In the description of the present invention, it should be understood that term " longitudinal direction ", " transverse direction ", "upper", "lower", " preceding ",
The orientation or positional relationship of the instructions such as " rear ", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outside" be based on
Orientation or positional relationship shown in the drawings is merely for convenience of description the utility model, does not indicate or imply the indicated dress
It sets or element must have a particular orientation, with specific azimuth configuration and operation, therefore should not be understood as to the utility model
Limitation.
A kind of RS485 bus driving circuits for realizing multi-host communication mode include the MCU controls with UART asynchronous communication mouths
Device chip 1, the Bus Interface Chip 2 of device model PCA82C250 and the RS485 communication lines for meeting RS485 bus specifications
Road 3；The RXD pins of the MCU controller chips 1 are connected to the RXD pins of Bus Interface Chip 2, MCU controller chips 1
TXD pins are connected to the TXD pins of Bus Interface Chip 2；The CANH pins of Bus Interface Chip 2 are connected to RS485 communication lines
Signal wire A, the CANL pin on road 3 is connected to the signal wire B of RS485 communication lines 3.
The MCU controller chips 1 are RS485 bus node controllers, pass through the RXD pins of the UART ports of chip
Receive the data that node is sent in its RS485 bus, and other nodes by the TXD of UART ports in RS485 buses
Transmission data；The transmission mode of UART communication interfaces is standard asynchronous transmission character data frame format.
The Bus Interface Chip 2 is the physical layer conversion device of communication protocol, and the UART of MCU controller chips 1 is connect
After mouth transmitting terminal TXD is converted by the signal that standard asynchronous transmission character data frame format is sent out, with RS485 bus standards
Balance transmission mode is sent on RS485 signal wire A and RS485 signal wires B；And the RS485 of RS485 buses is received in a differential manner
Signal on signal wire A and RS485 signal wire B, and the signal for being converted into meeting asynchronous transmission character data frame format is transmitted to
The receiving terminal RXD of the UART interface of MCU controller chips 1.
The conversion of the Bus Interface Chip 2 sent and received is full duplex, when the MCU controller cores of a node
The UART transmitting terminals TXD of piece 1 sends number by Bus Interface Chip 2 to the RS485 communication lines 3 for meeting RS485 bus specifications
According to while, the UART receiving terminals RXD of the MCU controller chips 1 of the node will receive Bus Interface Chip 2 from meeting RS485
The data transmitted on the RS485 communication lines 3 of bus specification；The RS485 interface electricity being made up of the Bus Interface Chip 2
Lu Hou realizes the synchronization internal loopback of data at the UART interface end of MCU controller chips 1.
The RS485 communication lines 3 using the twisted-pair feeder for meeting RS485 specifications by being constituted, respectively RS485 signal wires A
With RS485 signal wires B；Several communication nodes are connected on RS485 communication lines 3；The each node being connected in RS485 buses
Intercommunication and transmission data；The communication mode of RS485 buses is half-duplex mode.The RS485 signal wires A and
It is connected with resistance R1 and resistance R2 between the both ends of RS485 signal wires B；The resistance value of the resistance R1 and resistance R2 is 120 Ω.
Embodiment 1
Fig. 1 is the interface circuit figure that can realize a node in the RS485 buses of multi-host communication mode, it includes band UART
MCU controller chips 1, Bus Interface Chip 2 and the RS485 communication lines 3 for meeting RS485 bus specifications of asynchronous communication mouth.
Specifically optimize as this programme, MCU controller chips 1 are a RS485 bus node controllers.It is in inside
Under the cooperation of program, the data that node is sent in other RS485 buses are received by the RXD pins of the UART ports of chip,
And other node transmission datas by the TXD of UART ports in RS485 buses.The transmission mode of UART communication interfaces is
Standard asynchronous transmission character data frame format.In the market most of MCU chip be equipped with meet the standard UART it is asynchronous logical
Believe interface.
Specifically optimize as this programme, the RS485 communication lines 3 for meeting RS485 bus specifications meet RS485 by using
The twisted-pair feeder of specification is constituted.Twisted-pair feeder wherein one is RS485 signal wire A, and wherein other one of twisted-pair feeder is RS485 signal wires
B.The RS485 buses for meeting RS485 bus standards are to transmit signal by the way of balance transmission and differential received, have and inhibit
The ability of common mode interference, communication distance can be to upper kms.It can connect on the RS485 communication lines 3 for meet RS485 bus specifications
Up to 100 or more communication nodes are connect, the connection type of each communication node is all made of structure as shown in Figure 1.Using this
Mode, which is connected between each node in RS485 buses, can be in communication with each other simultaneously transmission data.The characteristic of RS485 buses determines
The communication mode of the bus is half-duplex mode；It can only allow there are one nodes to be sent out to RS485 buses in any one time
Send data；All nodes can receive data from RS485 buses at any time.
Specifically optimize as this programme, one end of Bus Interface Chip 2 is controlled with the MCU with UART asynchronous communication interfaces
The UART ports of device chip 1 dock, wherein：RXD pins are connect with the RXD of MCU controller chips 1；TXD pins are controlled with MCU
The TXD connections of device chip 1 processed.The other end of chip 2 is docked with the RS485 communication lines 3 for meeting RS485 bus specifications, wherein：
CANH pins are connect with the signal wire A for the RS485 communication lines 3 for meeting RS485 bus specifications, CANL pins and meet RS485
The signal wire B connections of the RS485 communication lines 3 of bus specification.
Specifically optimize as this programme, Bus Interface Chip 2 is the physical layer conversion device of a piece of communication protocol, it will
The UART interface transmitting terminal TXD of MCU controller chips 1 is turned by the signal that standard asynchronous transmission character data frame format is sent out
After changing, be sent into a manner of the balance transmission of RS485 bus standards RS485 buses A on B signal line；And it receives in a differential manner
The A of RS485 buses signal on B signal line, and the signal for being converted into meeting asynchronous transmission character data frame format is transmitted to
The receiving terminal RXD of the UART interface of MCU controller chips 1.
Specifically optimize as this programme, the conversion of Bus Interface Chip 2 sent and received is full duplex, is not needed
Switch the transmission direction sent and received as conventional use of RS485 interface chips.Both when the MCU controllers of a node
The UART transmitting terminals TXD of chip 1 is sent by Bus Interface Chip 2 to the RS485 communication lines 3 for meeting RS485 bus specifications
While data, the UART receiving terminals RXD of the MCU controller chips 1 of the node will receive Bus Interface Chip 2 from meeting
The data transmitted on the RS485 communication lines 3 of RS485 bus specifications.It simply says, is exactly by the Bus Interface Chip
After the 2 RS485 interface circuits constituted, the synchronization internal loopback of data is realized at the UART interface end of MCU controller chips 1.
Specifically optimize as this programme, the UART interface end that interface circuit has MCU controller chips 1 can realize number
It is the most basic and indispensable hardware circuit that multi-host communication mode is realized in RS485 buses according to the characteristic of synchronous internal loopback
Condition.
Embodiment 2
Fig. 2 shows a RS485 bus system figure being made of 3 nodes.Each node is according to Fig. 1 in figure
Mode is docked at the signal wire A for meeting the RS485 communication lines 3 of RS485 bus specifications using the twisted-pair feeder for meeting RS485 specifications
On signal wire B.Bus both ends resistance R1 and resistance R2 are the bus termination for meeting 120 ohm of RS485 bus specifications requirement
With resistance.
Feature a：In any one of this RS485 bus system node, can (but cannot be simultaneously) pass through RS485
Bus and an any other node realize communication, exchange data.
Feature b：In this RS485 bus system, only a node is allowed to send number to RS485 buses in any time
According to.If having more than 2 and 2 or more nodes in the same time to RS485 bus transmission datas simultaneously, in RS485 buses
Data will clash.
Feature c：It can simultaneously be received in RS485 buses in any one of this RS485 bus system node
The data of transmission.
Features above a and feature b are the communication specifications of standard RS485 buses, and that crucial is not both feature c.In standard
In RS485 buses, any one node (but do not include node oneself) to RS485 bus transmission datas can receive simultaneously
The data transmitted on to RS485 buses.And in the RS485 buses using this patent forecast scheme configuration, any one node (including
To the node oneself of RS485 bus transmission datas) data transmitted in RS485 buses can be received simultaneously.
This last electric circuit characteristic is to carry out bus snooping, collision detection for MCU communications control softwares, random to avoid,
Realize the hardware foundation of multi-host communication.
According to the docking mode in Fig. 2, more nodes can be docked in RS485 buses, just constitute more nodes
RS485 bus systems.It, can actively (but cannot at this point, any one of system node, is all a host node
Simultaneously) by RS485 buses and to an any other node transmission data so that multi-host communication mechanism is in RS485 buses
It is carried out.
Shown in Fig. 2, all nodes are formed according to the RS485 interface circuits of this patent description in RS485 buses
RS485 bus systems be constitute multi-host communication mode hardware on necessary and sufficient conditions.Realize that multi-host communication also needs to MCU
Software coordinates.
Embodiment 3
Realize that the concrete operation method of the RS485 systems communications softwares of multi-host communication mechanism is as follows：
(1) communication software of MCU uses identical algorithm in all communication nodes.
(2) according to the actual conditions of application, a time initial value tidle is determined, unit is millisecond.The value one of the initial value
As should be greater than the UART of communication node MCU and send required for a byte five to ten times of the time.For example, the UART of MCU is used
9600bps baud rate transmission datas, then it is about 1ms to send a byte required time, the initial value of tidel can at this time
To be set as 10ms.
(3) counting that subtracts one of oneself special Millisecond is each provided in all communication nodes in the communication software of MCU
Device T485.After node powers on, counter T485 initial value designs are tidel, then every millisecond of automatic counting that subtracts one, until counting
The value of device T485 is zero.T485 is the duration that final stage no data communicates in zero expression RS485 buses to be more than 10ms, table
No data transmission at this time in RS485 buses is levied, is in standby.
(4) the MCU communication controlers of all nodes allow UART to receive interruption, receive in (intercepting) RS485 buses at any time
The data of transmission.The MCU communication controlers of all nodes are Yi Dan after the data that RS485 buses receive a byte, by itself
Millisecond subtracts one counter T485 is reset to initial value tidel, then counter T485 every millisecond of automatic meter that subtracts one again
Number, until the value for the counter T485 that subtracts one is zero；Or a new data is received again, will subtracting one, counter T485 is reset
Initial value tidel.
(5) the MCU communication controlers of all nodes allow UART to receive interruption, receive in (intercepting) RS485 buses at any time
The data of transmission, and be sent into the reception buffer of MCU communication controlers and preserve.After completely receiving a data packet, give
Upper-layer user's layer software processing.
(6) it is with reference to Ethernet media access control when RS485 some node is needed to other node transmission datas
The principle of the mechanism of technology CSMA/CD, " first listen and send out afterwards, sent out when listening, conflict stops, and delay is retransmitted " is sent to RS485 buses
Data are described in detail below：
1) sending node MCU is ready to the data packet being sent in RS485 buses, and this example hypothesis is made of i byte；
2) it checks and subtracts one by the special Millisecond of this node whether counter T485 is zero.It is indicated if being not zero current
RS485 buses are occupied by other host, are had other node transmission data in bus, are needed to wait until that T485 is zero ability always herein
It (first listens and sends out afterwards) into next step transmission data；
3) sending node MCU sends a byte data by UART port to RS485, and receives simultaneously in RS485 buses
Data (sent out when listening, it is can realizing it is crucial that the RS485 interfaces that the bus that is designed by this patent is constituted have internal loopback
Function).Then the byte data that this node MCU has just sent oneself does ratio with the byte data just received
Compared with, it as a result differing, illustrates there be other hosts transmission data (conflict stops) simultaneously in RS485 buses, bus clashes, this
When random delay for a period of time, go to (2) and again attempt to send from the beginning (delay is retransmitted).If this node MCU by oneself
The byte data just sent is compared with the byte data just received, as a result identical, is illustrated in RS485 buses only
There is the machine in transmission data, no conflict occurred, then repeats this process 3), continues next byte in transmission data packet, always
I byte of entire data packet is recycled to all to be sent completely.
Although the various embodiments described above are described, once a person skilled in the art knows basic wounds
The property made concept, then additional changes and modifications can be made to these embodiments, so the foregoing is merely the realities of the utility model
Example is applied, the scope of patent protection of the utility model is not intended to limit, it is every to utilize the utility model specification and accompanying drawing content
Made by equivalent structure or equivalent flow shift, be applied directly or indirectly in other relevant technical fields, and include similarly
Within the scope of patent protection of the utility model.
Claims (3)
1. a kind of RS485 bus driving circuits for realizing multi-host communication mode, which is characterized in that including band UART asynchronous communication mouths
MCU controller chips (1), the Bus Interface Chip (2) of device model PCA82C250 and meet RS485 bus specifications
RS485 communication lines (3)；The RXD that the RXD pins of the MCU controller chips (1) are connected to Bus Interface Chip (2) draws
Foot, the TXD pins of MCU controller chips (1) are connected to the TXD pins of Bus Interface Chip (2)；Bus Interface Chip (2)
Signal wire A, the CANL pin that CANH pins are connected to RS485 communication lines (3) is connected to the signals of RS485 communication lines (3)
Line B；
The MCU controller chips (1) are RS485 bus node controllers, are connect by the RXD pins of the UART ports of chip
The data that node is sent in its RS485 bus are received, and are sent out by other nodes of the TXD of UART ports in RS485 buses
Send data；The transmission mode of UART communication interfaces is standard asynchronous transmission character data frame format；
The Bus Interface Chip (2) is the physical layer conversion device of communication protocol, and the UART of MCU controller chips (1) is connect
After mouth transmitting terminal TXD is converted by the signal that standard asynchronous transmission character data frame format is sent out, with RS485 bus standards
Balance transmission mode is sent on RS485 signal wire A and RS485 signal wires B；And the RS485 of RS485 buses is received in a differential manner
Signal on signal wire A and RS485 signal wire B, and the signal for being converted into meeting asynchronous transmission character data frame format is transmitted to
The receiving terminal RXD of the UART interface of MCU controller chips (1)；
The RS485 communication lines (3) by being constituted using the twisted-pair feeder for meeting RS485 specifications, respectively RS485 signal wires A and
RS485 signal wires B；RS485 communication lines connect several communication nodes on (3)；The each node being connected in RS485 buses
Intercommunication and transmission data；The communication mode of RS485 buses is half-duplex mode.
2. the RS485 bus driving circuits according to claim 1 for realizing multi-host communication mode, which is characterized in that described
The conversion of Bus Interface Chip (2) sent and received is full duplex, when the MCU controller chips (1) of node
UART transmitting terminals TXD is by Bus Interface Chip (2) to RS485 communication lines (3) transmission data for meeting RS485 bus specifications
While, the UART receiving terminals RXD of the MCU controller chips (1) of the node will receive Bus Interface Chip (2) from meeting
The data transmitted on the RS485 communication lines (3) of RS485 bus specifications；It is made up of the Bus Interface Chip (2)
After RS485 interface circuits, the synchronization internal loopback of data is realized at the UART interface end of MCU controller chips (1).
3. the RS485 bus driving circuits according to claim 1 for realizing multi-host communication mode, which is characterized in that described
It is connected with resistance R1 and resistance R2 between the both ends of RS485 signal wire A and RS485 signal wires B；The resistance R1's and resistance R2
Resistance value is 120 Ω.
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| CN201721652568.7U CN207968522U (en) | 2017-12-01 | 2017-12-01 | A kind of RS485 bus driving circuits for realizing multi-host communication mode |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110069437A (en) * | 2019-04-24 | 2019-07-30 | 大连理工大学 | RS-485 polarity of bus adaptive approach based on response frame validity |
| CN110224911A (en) * | 2019-06-28 | 2019-09-10 | 贵州航天林泉电机有限公司 | One kind being based on MODBUS-RS485 multichannel integrated system and its high-speed traffic method |
| CN112597084A (en) * | 2020-12-31 | 2021-04-02 | 杭州拓深科技有限公司 | System for two-wire system solves many main arbitration of RS485 and collides |
-
2017
- 2017-12-01 CN CN201721652568.7U patent/CN207968522U/en active Active
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110069437A (en) * | 2019-04-24 | 2019-07-30 | 大连理工大学 | RS-485 polarity of bus adaptive approach based on response frame validity |
| CN110069437B (en) * | 2019-04-24 | 2023-03-14 | 大连理工大学 | RS-485 bus polarity self-adaption method based on response frame validity |
| CN110224911A (en) * | 2019-06-28 | 2019-09-10 | 贵州航天林泉电机有限公司 | One kind being based on MODBUS-RS485 multichannel integrated system and its high-speed traffic method |
| CN110224911B (en) * | 2019-06-28 | 2021-07-09 | 贵州航天林泉电机有限公司 | Rapid communication method based on MODBUS-RS485 multi-path integrated system |
| CN112597084A (en) * | 2020-12-31 | 2021-04-02 | 杭州拓深科技有限公司 | System for two-wire system solves many main arbitration of RS485 and collides |
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