CN105141491A - RS485 communication circuit capable of achieving self-sending and self-receiving and method - Google Patents

RS485 communication circuit capable of achieving self-sending and self-receiving and method Download PDF

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Publication number
CN105141491A
CN105141491A CN201510609888.3A CN201510609888A CN105141491A CN 105141491 A CN105141491 A CN 105141491A CN 201510609888 A CN201510609888 A CN 201510609888A CN 105141491 A CN105141491 A CN 105141491A
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pin
data
serial ports
photoelectric isolation
main control
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CN105141491B (en
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黄海宇
李帮家
赵国锋
王国安
王莉
马庆华
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HANGZHOU DECHENG ELECTRIC POWER TECHNOLOGY CO LTD
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HANGZHOU DECHENG ELECTRIC POWER TECHNOLOGY CO LTD
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    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02DCLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
    • Y02D10/00Energy efficient computing, e.g. low power processors, power management or thermal management

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Abstract

The invention discloses an RS485 communication circuit capable of achieving self-sending and self-receiving and a method. The RS485 communication circuit comprises a main control chip, a data sending and enabling photoelectric isolation module, a data receiving photoelectric isolation module and a data receiving and sending processing module. According to the invention, cost is quite low and self-receiving and self-sending can be achieved.

Description

A kind of RS485 communicating circuit and method realizing internal loopback
Technical field
The present invention relates to and the present invention relates to electronic applications, particularly relates to a kind of the RS485 communicating circuit and the method that realize internal loopback.
Background technology
Usually, in industrial automation, as in power industry reactive power compensation management system, Intelligent capacitor needs capacitor networking, data acquisition, control and management etc., is generally realized by fieldbus.Fieldbus kind is more, as RS485 bus, CAN, MBUS bus etc.Wherein RS485 bus hardware cost is low, easily realizes, the features such as good reliability, so be widely used in industrial automation.
RS485 is a kind of serial communication link layer protocol being widely used in industrial communication interface, transmitting based on differential signal.There is the advantages such as antijamming capability is strong, long transmission distance, belong to half-duplex operation.
Generally, for realizing RS485 communication, hardware circuit at least needs Master control chip (MCU) and RS485 communication module, main control chip (MCU) needs use three holding wires to be connected with communication interface chip, these three holding wires are data signal recipients (RXD), data-signal transmitting terminal (serial ports transmission pin), the data reception/transmission control end (CTR) of main control chip respectively, be connected with RS485 communication interface module respectively, as shown in Figure 1.Wherein the holding wire of data signal recipients (RXD) and data-signal transmitting terminal (serial ports transmission pin) generally uses the lead-in wire of the asynchronous serial communication mouth of main control chip (MCU), the I/O port that data reception/transmission control end (CTR) generally uses main control chip (MCU) common.These three holding wires are connected with RS485 communication interface chip, wherein data-signal transmitting terminal (serial ports transmission pin) is connected with the data input pin (DI) of RS485 communication interface chip, data flow is from main control chip (CPU) to RS485 communication interface module, as illustrated by the arrows in fig. 1, show that data that main control chip (MCU) sends are transferred to the data input pin (DI) of RS485 communication interface chip by signal sending end (serial ports transmission pin) lead-in wire; Data signal recipients (RXD) is connected with the data output end (RO) of RS485 communication interface module, data flow is from RS485 communication interface chip to main control chip (MCU), as illustrated by the arrows in fig. 1, show that number of buses that RS485 communication chip receives is transferred to the data signal recipients (RXD) of main control chip (MCU) from the data output end (RO) of RS485 communication interface chip; The data reception/transmission control end (CTR) of main control chip (MCU) is connected with the data reception/transmission Enable Pin (RE/DE) of RS485 communication interface chip, data flow is from main control chip (CPU) to RS485 communication interface chip, as illustrated by the arrows in fig. 1.Under current background technology, if consider electromagnetic compatibility (EMC) performance and the communication isolation needs of device, Phototube Coupling process can also be carried out respectively to three holding wires of above-mentioned main control chip (CPU), make communication interface part and main control part realize electrical isolation.
The weak point that current technology also exists is: first, because application of installation is in industrial occasions, a large amount of electromagnetic interference signals is there is around device, comprise the interference signal that some are introduced from RS485 bus, in addition the interference of device internal circuit, the bus communication ability actual performance of RS485 is reduced, as in communication distance shortening, bus, the quantity of connected node reduces.Secondly, data communication flows to be needed to control (CTR) separately, increases cost of hardware design.Again, because RS485 communication is half duplex communication, can not internal loopback be realized, in use bring a lot of inconvenience.Finally, in order to realize RS485 communication, independent RS485 communication module must be used, add very large hardware development cost.
Summary of the invention
Goal of the invention of the present invention is the limitation solving above-mentioned existing RS485 communicating circuit, the invention provides a kind of cost lower and can from receiving spontaneous RS485 communicating circuit and method.
The present invention includes main control chip, also comprise data and send and enable photoelectric isolation module, data receiver photoelectric isolation module and data transmit-receive processing module; Described main control chip comprises serial ports and sends pin, sends enable control pin and serial ports reception pin; Described data transmission and the input of enable photoelectric isolation module send pin with the serial ports of described main control chip and send enable control pin and be connected, and output is connected with data transmit-receive processing module; The input of described data receiver photoelectric isolation module is connected with described data transmit-receive processing module, and output receives pin with described main control chip serial ports and is connected; One end of described data transmit-receive processing module sends with data and enable photoelectric isolation module and data receiver photoelectric isolation module are connected, and the other end connects RS485 bus.
It is a kind of that to realize the implementation method of the RS485 communicating circuit of internal loopback based on a kind of described in any one of claim 1-4 as follows:
1) after starting working, the enable control pin of the transmission described in initial condition CTR is low level " 0 ", and RS485 communication is in accepting state;
2) RS485 bus occurs differential signal " 0 ", through described data transmit-receive processing module and the process of data receiver photoelectric isolation module, the serial ports of described main control chip MCU receives pin RXD and receives signal " 0 "; RS485 bus occurs differential signal " 1 ", through data transmit-receive processing module and the process of data receiver photoelectric isolation module, the serial ports of described main control chip MCU receives pin RXD and receives signal " 1 ";
3) the enable control pin CTR of the transmission described in output low level " 1 ", RS485 communication is in accepting state, the transmission pin serial ports of described main control chip MCU sends pin TXD and sends data-signal " 1 ", through described data receiver photoelectric isolation module and the process of data transmit-receive processing module, RS485 bus produces differential signal " 1 ", the serial ports of main control chip MCU sends pin TXD and sends data-signal " 0 ", through described data receiver photoelectric isolation module and data transmit-receive processing module, RS485 bus produces differential signal " 0 ";
4) the main control chip MCU described in sends out data-signal " 1 " or " 0 ", turns back to the serial ports reception pin RXD of main control chip MCU simultaneously, realize the internal loopback sending data through described data receiver photoelectric isolation module.
After adopting above structure, the present invention compared with prior art, has the following advantages:
A kind of RS485 communicating circuit realizing internal loopback of the present invention not only achieves the communication function of RS485, also achieve the control by sending optocoupler two input pin control realization transmissions, receiving function, thus decrease RS485 transceiver communication control pin isolation optocoupler, thus reduce design cost, the more important thing is, present invention eliminates standard RS485 communication chip, greatly reduce the cost of RS485 communication system, also achieve the internal loopback function that half-duplex RS 485 communicates, thus achieve RS485 communication single channel self-checking function.This distribution RS485 telecommunication circuit comprises signal photoelectric isolation module, the parts such as RS485 communication interface modules.
As improvement, described data transmit-receive processing module comprises triode, voltage stabilizing didoe, one-way conduction diode, current-limiting resistance, pull down resistor, the first divider resistance, the second divider resistance, pull-up resistor; The plus earth of described voltage stabilizing didoe, negative electrode is connected with described current-limiting resistance; One end ground connection of described pull down resistor; The node that described current-limiting resistance is connected with pull down resistor is connected with the base stage of described triode; The collector electrode of described triode connects power supply by described pull-up resistor; The emitter of described triode is connected with the anode of described one-way conduction diode; The first described divider resistance is connected with the negative electrode of the second divider resistance with described diode.
As improvement, described data send and enable photoelectric isolation module comprises the first Phototube Coupling optocoupler; 1 pin of the first described Phototube Coupling optocoupler is connected with the enable control pin of described transmission, and 2 pin and described serial ports receive pin and be connected, and 3 pin are by described pull down resistor R2 ground connection, and 4 pin connect insulating power supply.
As improvement, described data receiver photoelectric isolation module comprises the second Phototube Coupling optocoupler, and 1 pin of the second described Phototube Coupling optocoupler is connected with the second divider resistance with the first described divider resistance, 2 pin ground connection, 3 pin connect VSS end, and 4 pin connect serial ports and receive pin.
Accompanying drawing explanation
Fig. 1 is existing RS485 tri-light-coupled isolation communicating circuit structured flowchart.
Fig. 2 is circuit structure block diagram of the present invention.
Fig. 3 is circuit theory diagrams of the present invention.
Embodiment
Below in conjunction with the drawings and specific embodiments, the invention will be further described.
The present invention includes main control chip MCU as Figure 2-3, also comprise data and send and enable photoelectric isolation module, data receiver photoelectric isolation module and data transmit-receive processing module; Described main control chip MCU comprises serial ports and sends pin TXD, sends enable control pin CTR and serial ports reception pin RXD; Described data transmission and the input of enable photoelectric isolation module send pin TXD with the serial ports of described main control chip MCU and send enable control pin CTR and be connected, and output is connected with data transmit-receive processing module; The input of described data receiver photoelectric isolation module is connected with described data transmit-receive processing module, and output receives pin RXD with described main control chip MCU serial ports and is connected; One end of described data transmit-receive processing module sends with data and enable photoelectric isolation module and data receiver photoelectric isolation module are connected, and the other end connects RS485 bus.Described data transmit-receive processing module comprises triode Q1, voltage stabilizing didoe D1, one-way conduction diode D2, current-limiting resistance R1, pull down resistor R2, the first divider resistance R3, the second divider resistance R4, pull-up resistor R5; The plus earth of described voltage stabilizing didoe D1, negative electrode is connected with described current-limiting resistance R1; One end ground connection of described pull down resistor R2; The node that described current-limiting resistance R1 is connected with pull down resistor R2 is connected with the base stage of described triode Q1; The collector electrode of described triode Q1 connects power supply by described pull-up resistor R5; The emitter of described triode Q1 is connected with the anode of described one-way conduction diode D2; The first described divider resistance R3 is connected with the negative electrode of described diode D2 with the second divider resistance R4.Described data send and enable photoelectric isolation module comprises the first Phototube Coupling optocoupler; 1 pin of the first described Phototube Coupling optocoupler is connected with described transmission enable control pin CTR, and 2 pin and described serial ports receive pin RXD and be connected, and 3 pin are by described pull down resistor R2 ground connection, and 4 pin connect insulating power supply.Described data receiver photoelectric isolation module comprises the second Phototube Coupling optocoupler, and 1 pin of the second described Phototube Coupling optocoupler is connected with the second divider resistance R4 with the first described divider resistance R3,2 pin ground connection, and 3 pin connect VSS end, and 4 pin connect serial ports and receive pin RXD.
As shown in Figure 3, be compared to the existing RS485 tri-optocoupler communicating circuit structured flowchart shown in Fig. 1, first the present invention eliminates RS485 transmitting-receiving and controls isolation optocoupler, will receive and dispatch controlled loading and send on signal isolation optocoupler to data.Secondly, standard RS485 communication chip has been changed into data transmit-receive control circuit of the present invention.Again, be loaded into sending signal the internal loopback function receiving and data-signal realizes half-duplex RS 485 and communicate simultaneously.
Elaboration is made below, for helping the understanding of the present invention with regard to specific embodiment of the invention process.
Data transmission procedure, the transmission enable control pin CTR of described main control chip MCU is connected to 1 pin of the first Phototube Coupling optocoupler as RS485 communication transmission data enable control port, and the serial ports of main control chip MCU sends pin TXD and is connected to 2 pin of the first Phototube Coupling optocoupler as RS485 communication transmission FPDP.When enable control pin output low level " 0 ", no matter serial ports sends pin TXD exports high point flat " 1 " or output low level " 0 ", and the first Phototube Coupling optocoupler is all in cut-off state, and data can not send.When the enable control pin CTR of transmission exports high point flat " 1 " be, serial ports sends the flat 5V of pin TXD output signal " 1 " height point, first Phototube Coupling optocoupler cut-off, transistor base voltage is 0V, triode ends, RS485_B terminal voltage is-0.7V, then the voltage of RS485_A end is greater than more than the voltage 200mV of RS48_B, then RS485 bus produces differential signal " 1 "; Serial ports sends pin TXD and outputs signal " 0 " low level 0V, first Phototube Coupling optocoupler conducting, transistor base is high voltage 5V, triode ON, the flat 5V of the very high point of triode emission, one-way conduction diode current flow, RS485_B terminal voltage is 5V, then the voltage of RS485_A end is less than more than the voltage 200mV of RS48_B, then RS485 bus produces differential signal " 0 ", the transmission of this circuit realiration RS485 differential signal " 0 " and " 1 ".
DRP data reception process, the pin of described main control chip MCU is connected to 4 pin of the second Phototube Coupling optocoupler as RS485 communication reception FPDP.When enable control pin CTR port output low level " 0 " of transmission, RS485 communication is in system and sends state, when the total scene of RS485 produces differential signal " 1 ", then RS485_A port voltage is greater than RS485_B port voltage, then N2 Phototube Coupling optocoupler cut-off, it is signal one state that serial ports receives pin RXD port status; When the total scene of RS485 produces differential signal " 0 ", then RS485_A port voltage is less than RS485_B port voltage, then the second Phototube Coupling optocoupler conducting, RXD port status is signal " 0 " state, the reception of RS485 differential signal " 0 " and " 1 " of this circuit realiration.
Internal loopback process, when RS485 communication is in transmission state, serial ports sends pin TXD port and sends signal " 1 ", then RS485_B port is in low level, then the second Phototube Coupling optocoupler cut-off, when serial ports reception pin RXD ports port signal is " 1 "; Serial ports sends pin TXD port when sending signal " 0 ", to be then in high point flat for RS485_B port, then the second Phototube Coupling optocoupler conducting, and it be " 0 " that serial ports receives pin RXD ports port signal, the internal loopback function that this circuit realiration RS485 communicates.
Below only just most preferred embodiment of the present invention is described, but can not be interpreted as it is limitations on claims.The present invention is not limited only to above embodiment, and all various changes done in the protection range of independent claims of the present invention are all in protection scope of the present invention.

Claims (5)

1. realize a RS485 communicating circuit for internal loopback, comprise main control chip MCU, it is characterized in that: also comprise data and send and enable photoelectric isolation module, data receiver photoelectric isolation module and data transmit-receive processing module; Described main control chip MCU comprises serial ports and sends pin TXD, sends enable control pin CTR and serial ports reception pin RXD; Described data transmission and the input of enable photoelectric isolation module send pin TXD with the serial ports of described main control chip MCU and send enable control pin CTR and be connected, and output is connected with data transmit-receive processing module; The input of described data receiver photoelectric isolation module is connected with described data transmit-receive processing module, and output receives pin RXD with the serial ports of described main control chip MCU and is connected; One end of described data transmit-receive processing module sends with described data and enable photoelectric isolation module and data receiver photoelectric isolation module are connected, and the other end connects RS485 bus.
2. a kind of RS485 communicating circuit realizing internal loopback according to claim 1, is characterized in that: described data transmit-receive processing module comprises triode Q1, voltage stabilizing didoe D1, one-way conduction diode D2, current-limiting resistance R1, pull down resistor R2, the first divider resistance R3, the second divider resistance R4, pull-up resistor R5; The plus earth of described voltage stabilizing didoe D1, negative electrode is connected with described current-limiting resistance R1; One end ground connection of described pull down resistor R2; The node that described current-limiting resistance R1 is connected with pull down resistor R2 is connected with the base stage of described triode Q1; The collector electrode of described triode Q1 connects power supply by described pull-up resistor R5; The emitter of described triode Q1 is connected with the anode of described one-way conduction diode D2; The first described divider resistance R3 is connected with the negative electrode of described diode D2 with the second divider resistance R4.
3. a kind of RS485 communicating circuit realizing internal loopback according to claim 2, is characterized in that: described data send and enable photoelectric isolation module comprises the first Phototube Coupling optocoupler; 1 pin of the first described Phototube Coupling optocoupler is connected with described transmission enable control pin CTR, and 2 pin and described serial ports receive pin RXD and be connected, and 3 pin are by described pull down resistor R2 ground connection, and 4 pin connect insulating power supply.
4. a kind of RS485 communicating circuit realizing internal loopback according to claim 2, it is characterized in that: described data receiver photoelectric isolation module comprises the second Phototube Coupling optocoupler, 1 pin of the second described Phototube Coupling optocoupler is connected with the second divider resistance R4 with the first described divider resistance R3,2 pin ground connection, 3 pin connect VSS end, and 4 pin connect serial ports and receive pin RXD.
5. one kind to realize the implementation method of the RS485 communicating circuit of internal loopback based on a kind of described in any one of claim 1-4 as follows:
1) after starting working, the enable control pin of the transmission described in initial condition CTR is low level " 0 ", and RS485 communication is in accepting state;
2) RS485 bus occurs differential signal " 0 ", through described data transmit-receive processing module and the process of data receiver photoelectric isolation module, the serial ports of described main control chip MCU receives pin RXD and receives signal " 0 "; RS485 bus occurs differential signal " 1 ", through data transmit-receive processing module and the process of data receiver photoelectric isolation module, the serial ports of described main control chip MCU receives pin RXD and receives signal " 1 ";
3) the enable control pin CTR of the transmission described in output low level " 1 ", RS485 communication is in accepting state, the transmission pin serial ports of described main control chip MCU sends pin TXD and sends data-signal " 1 ", through described data receiver photoelectric isolation module and the process of data transmit-receive processing module, RS485 bus produces differential signal " 1 ", the serial ports of main control chip MCU sends pin TXD and sends data-signal " 0 ", through described data receiver photoelectric isolation module and data transmit-receive processing module, RS485 bus produces differential signal " 0 ";
4) the main control chip MCU described in sends out data-signal " 1 " or " 0 ", turns back to the serial ports reception pin RXD of main control chip MCU simultaneously, realize the internal loopback sending data through described data receiver photoelectric isolation module.
CN201510609888.3A 2015-09-23 2015-09-23 RS485 communication circuit and method for realizing spontaneous self-receiving Active CN105141491B (en)

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CN106021166A (en) * 2016-05-16 2016-10-12 从兴技术有限公司 RS485 bus-based multi-host communication circuit
CN106100681A (en) * 2016-08-10 2016-11-09 浙江恒业电子有限公司 The RS485 telecommunication circuit controlled with signal transmitting and receiving
CN108173543A (en) * 2017-12-26 2018-06-15 北京航天测控技术有限公司 A kind of two-way isolation circuit of single-wire communication bus
CN109104181A (en) * 2018-08-21 2018-12-28 深圳市雷赛控制技术有限公司 A kind of RS485 circuit
CN110930682A (en) * 2019-12-26 2020-03-27 宁波三星医疗电气股份有限公司 MBUS communication circuit and MBUS communication system
CN111813728A (en) * 2020-09-02 2020-10-23 湖南慧明谦信息技术有限公司 Multi-bus and multi-channel interface realized by single serial port multiplexing mode
CN114978803A (en) * 2022-05-20 2022-08-30 淮安威灵电机制造有限公司 Isolated asynchronous communication circuit and method of household appliance and household appliance
CN115550105A (en) * 2022-10-13 2022-12-30 杭州雷风新能源科技有限公司 Low-cost isolatable two-wire system data transmission method and circuit thereof

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CN106021166A (en) * 2016-05-16 2016-10-12 从兴技术有限公司 RS485 bus-based multi-host communication circuit
CN106021166B (en) * 2016-05-16 2019-02-26 从兴技术有限公司 Multi-host communication circuit based on RS485 bus
CN106100681A (en) * 2016-08-10 2016-11-09 浙江恒业电子有限公司 The RS485 telecommunication circuit controlled with signal transmitting and receiving
CN108173543A (en) * 2017-12-26 2018-06-15 北京航天测控技术有限公司 A kind of two-way isolation circuit of single-wire communication bus
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CN114978803A (en) * 2022-05-20 2022-08-30 淮安威灵电机制造有限公司 Isolated asynchronous communication circuit and method of household appliance and household appliance
CN114978803B (en) * 2022-05-20 2023-11-21 淮安威灵电机制造有限公司 Isolation asynchronous communication circuit and method of household appliance and household appliance
CN115550105A (en) * 2022-10-13 2022-12-30 杭州雷风新能源科技有限公司 Low-cost isolatable two-wire system data transmission method and circuit thereof

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