CN107070445A

CN107070445A - A kind of serial communication interface function switching circuit and method

Info

Publication number: CN107070445A
Application number: CN201710175335.0A
Authority: CN
Inventors: 周立功; 赵志华; 程溪
Original assignee: Guangzhou Zhiyuan Electronics Co Ltd
Current assignee: Guangzhou Zhiyuan Electronics Co Ltd
Priority date: 2017-03-22
Filing date: 2017-03-22
Publication date: 2017-08-18
Anticipated expiration: 2037-03-22
Also published as: CN107070445B

Abstract

The invention discloses a kind of serial communication interface function switching circuit and method, for solving to realize that multi-functional serial communication needs to consume CPU multi-channel serial ports resource or needs manual switching or the technical problem using expensive analog switch.The embodiment of the present invention includes：First receives control circuit, first sending controling circuit, second receives control circuit, second sending controling circuit, mode switching signal interface, first transmitting-receiving control signal interface, first receives enable signaling interface, first sends enable signaling interface, second receives enable signaling interface, second sends enable signaling interface, MCU is allowd to pass through control mode switch signaling interface, the low and high level of first transmitting-receiving control signal interface realizes the power and energy of the first electrical level transferring chip and second electrical level conversion chip, realize the technique effect that a serial line interface possesses multiple functions, need to consume the technical problem of CPU multi-channel serial port resources so as to solve now multi-functional serial communication.

Description

A kind of serial communication interface function switching circuit and method

Technical field

The present invention relates to circuit communication field, more particularly to a kind of serial communication interface function switching circuit and method.

Background technology

Data transmission between computer and computer or computer and terminal can use serial communication and parallel communication Two kinds of modes.Because serial communication mode has using circuit is few, cost is low, particularly in remote transmission, it is to avoid a plurality of Line characteristic inconsistent and be widely adopted.In serial communication, it is desirable to which communication two party all using a standard interface, makes not Same equipment, which can be connected easily, to be communicated.

RS-232-C interfaces (also known as EIARS-232-C) are a kind of serial communication interfaces the most frequently used at present.It is Bell System, modem producer and terminal manufacturer were combined by EIA (EIA) in 1970 The standard for serial communication formulated jointly.Its full name is " data terminal equipment (DTE) and data communications equipment (DCE) Between SERIAL BINARY DATA Fabric Interface technical standard ".

Because the appearance of RS-232-C interface standards is more early, there is weak point unavoidably, mainly there is at following 4 points：

1) signal level value of interface is higher, the chip of fragile interface circuit, but since with Transistor-Transistor Logic level it is incompatible need It can be connected using level shifting circuit with TTL circuits.

2) transmission rate is relatively low, in asynchronous transmission, and baud rate is 20kbps.

3) interface constitutes the transmission form on common ground using a signal wire and a signal line of return, this to transmit altogether Common mode disturbances are easily produced, so noise immunity is weak.

4) transmission range is limited, and maximum transmission distance standard value is 50 feet, actually also can be used only in 50 meters or so.

Due to RS-232-C deficiency, occur in that some new interface standards, RS-485 is exactly one of them, it have with Lower feature：

1) RS-485 electrical characteristic：Logical one is represented by+(2-6) V of the voltage difference of line-to-line；Logical zero is with two Voltage difference between line represents for-(2-6) V.Interface signal level is lower than RS-232-C, is just hardly damaged the chip of interface circuit, And the level is compatible with Transistor-Transistor Logic level, it can facilitate and be connected with TTL circuits.

2) RS-485 data maximum transmission rate is 10Mbps

3) RS-485 interfaces are the combinations using balance driver and differential receiver, and anti-common mode does ability by force, i.e. anti-noise Acoustic jamming is good

4) the maximum transmission distance standard value of RS-485 interfaces is 4000 feet, actually up to 3000 meters, in addition RS- 232-C interfaces only allow to connect 2 transceivers in bus, i.e., single station ability.And RS-485 interfaces allow connection in bus Up to 128 transceivers.There is multistation ability, such user can easily be set up using single RS-485 interfaces and be set Standby network.Because RS-485 interfaces have the advantages that good noise immunity, the transmission range of length and multistation ability make its into For preferred serial line interface.

RS-422 standard full name are " electrical characteristics of balanced voltage digital interface circuit ", and it defines the spy of interface circuit Property.Actually there is a signal ground, totally 5 lines.Compare RS- because receiver uses high input impedance and sends driver 232 stronger driving forces, therefore allow to connect multiple receiving nodes in bus, it can at most connect 10 nodes.RS-422 is supported Point-to-points two-way communication is a main equipment (Master), and remaining is that can not be communicated between slave unit (Salve), slave unit.. Receiver input impedance is 4k, therefore originator maximum load capability is 10 × 4k+100 Ω (terminating resistance).RS-422 four-wire interfaces Due to using individually sending and receiving passage, thus need not control data direction, any necessary signal is handed between each device Changing can be by software mode (XON/XOFF shakes hands) or hardware mode (a pair of single twisted-pair feeders).

Existing mode is to be directed to every kind of interface standard, and circuit is out used to communicate all the way for design.If for example, the tunnel of client three It is likely to use, then the serial port resource on the tunnels of CPU 3 must be consumed, per a serial ports is connect all the way, for communicating.Or It is to use jumper cap manual switching communication pattern, and is handled using logic gates；Or be using multi-disc simulation Switch chip switches over communication pattern.

Traditional implementation method is being designed independently by tri- kinds of circuits of RS-232, RS-485, RS-422, so that Realize the function that user wants, if user want use another function, user must redesign the functional circuit or Manual switching hardware circuit is realized；Or switched over manually using jumper cap, mode this first is not very intelligent, and switching is held It is error-prone, waste time and energy, and gate circuit is also utilized, so increase device again, and due to being chip, will certainly increase Quite a lot of to obtain cost, PCB surface product can also be increased；Or switched over using analog switch, the maximum shortcoming of this mode It is exactly that analog switch chip is expensive, and needs multi-disc just to fully meet 3 kinds of circuits of switching, likewise, PCB surface is accumulated It can increase a lot.Therefore, realize that multi-functional serial communication needs consumption CPU multi-channel serial ports resource or needs manual switching or use Expensive analog switch is those skilled in the art's technical issues that need to address.

The content of the invention

The embodiments of the invention provide a kind of serial communication interface function switching circuit and method, for solving to realize many work( Energy serial communication is needed to consume CPU multi-channel serial ports resource or needs manual switching or asked using the technology of expensive analog switch Topic.

A kind of serial communication interface function switching circuit provided in an embodiment of the present invention, it is characterised in that including：First connects Control circuit, the first sending controling circuit, the second reception control circuit, the second sending controling circuit, mode switching signal is received to connect Mouth, the first transmitting-receiving control signal interface, the first reception enable signaling interface, the first transmission enable signaling interface, second, which receive, to be made Can signaling interface, the second transmission enable signaling interface；

Described first input for receiving control circuit connects the mode switching signal interface, and described first receives control The output end connection described first of circuit, which is received, enables signaling interface；

The input of first sending controling circuit connects the mode switching signal interface, and described first sends control The output end connection described first of circuit, which is sent, enables signaling interface；

Described second input for receiving control circuit connects the mode switching signal interface and the first transmitting-receiving control Signaling interface processed, the described second output end connection described second for receiving control circuit, which is received, enables signaling interface；

The input of second sending controling circuit connects the mode switching signal interface and the first transmitting-receiving control Signaling interface processed, the output end connection described second of second sending controling circuit, which is sent, enables signaling interface；

Described first, which receives control circuit, is used for the mode switching signal according to input, and output first, which is received, enables signal extremely The reception control signal interface of first electrical level transferring chip so that first electrical level transferring chip is received according to described first to be made Energy signal is enabled to the receive capabilities of first electrical level transferring chip；

First sending controling circuit is used for the mode switching signal according to input, and output first, which is sent, enables signal extremely The transmission control signal interface of first electrical level transferring chip so that first electrical level transferring chip is sent according to described first to be made Energy signal is enabled to the sending function of first electrical level transferring chip；

Described second, which receives control circuit, is used for according to the mode switching signal of input and the first transmitting-receiving control signal, output Second receives enable signal to the reception control signal interface of second electrical level conversion chip so that the second electrical level conversion chip The receive capabilities enable for enabling signal to the second electrical level conversion chip is received according to described second；

Second sending controling circuit is used for according to the mode switching signal of input and the first transmitting-receiving control signal, output Second sends enable signal to the transmission control signal interface of second electrical level conversion chip so that the second electrical level conversion chip The sending function enable for enabling signal to the second electrical level conversion chip is sent according to described second.

Preferably,

Described first, which receives control circuit, includes the first transistor, first resistor, second resistance, 3rd resistor；

The first end of the first transistor connects the mode switching signal interface by the second resistance and passed through 3rd resistor ground connection, the second end ground connection of the first transistor, the described in the three-terminal link of the first transistor The first of one electrical level transferring chip, which receives, to be enabled signaling interface and connects power supply by the first resistor；

First sending controling circuit is a wire, and one end of the wire connects the mode switching signal and connect Mouthful, the other end connection described first of the wire, which is sent, enables signaling interface；

Described second, which receives control circuit, includes the first diode, the second diode, the 7th resistance；

Positive pole connection the first transmitting-receiving control signal interface of first diode, the negative pole of first diode Connect the second of the second electrical level conversion chip and receive enable signaling interface and by the 7th resistance eutral grounding；

The positive pole of second diode connects the mode switching signal interface, the negative pole connection of second diode The negative pole of first diode.

Second sending controling circuit includes second transistor, the 4th resistance, the 5th resistance, the 6th resistance；

The first end of the second transistor connects the mode switching signal interface by the 5th resistance and passed through 6th resistance eutral grounding, the second end ground connection of the second transistor, the described in the three-terminal link of the second transistor The second of two electrical level transferring chips, which sends, to be enabled signaling interface and connects the first transmitting-receiving control letter by the 4th resistance Number interface.

Preferably,

First sending controling circuit includes third transistor, the 8th resistance, the 9th resistance, the tenth resistance；

The first end of the third transistor connects the mode switching signal interface by the 9th resistance and passed through Tenth resistance eutral grounding, the second end ground connection of the third transistor, the described in the three-terminal link of the third transistor The first of one electrical level transferring chip, which sends, to be enabled signaling interface and connects power supply by the 8th resistance；

First reception controls circuit to be a wire, and one end of the wire connects the mode switching signal and connect Mouthful, the other end connection described first of the wire, which is received, enables signaling interface；

It is described second receive control circuit include the 4th transistor, the 11st resistance, the 12nd resistance, the 13rd resistance, 14th resistance；

The first end of 4th transistor connects the first transmitting-receiving control signal interface by the 13rd resistance The mode switching signal interface, the 4th transistor are connected by the 13rd resistance and the 12nd resistance simultaneously First end also by the 14th resistance eutral grounding, the second end of the 4th transistor is grounded, the 4th transistor Second receives enable signaling interface and connects power supply by the 11st resistance described in three-terminal link；

Second sending controling circuit include the 5th transistor, the 15th resistance, the 16th resistance, the 17th resistance, 18th resistance；

The first end of 5th transistor connects the first transmitting-receiving control signal interface by the 17th resistance And by the 18th resistance eutral grounding, the second end of the 5th transistor is grounded, and the 3rd end of the 5th transistor connects The second of the second electrical level conversion chip is connect to send enable signaling interface and connect the pattern by the 15th resistance Switching signal interface, the 3rd end of the 5th transistor also passes through the 15th resistance and the 16th resistance eutral grounding.

Preferably,

The embodiment of the present invention also includes the 3rd transmitting-receiving and controls circuit, the second transmitting-receiving control signal interface, the 3rd transmission to enable Signaling interface；

The input of the 3rd transmitting-receiving control circuit connects the mode switching signal interface and the second transmitting-receiving control Signaling interface processed, the output end connection the described 3rd of the 3rd transmitting-receiving control circuit, which is sent, enables signaling interface；

3rd sending controling circuit is used for according to the mode switching signal of input and the second transmitting-receiving control signal, output 3rd the 3rd transmission for sending enable signal to the 3rd electrical level transferring chip enables signaling interface so that the 3rd level conversion Chip sends the sending function enable for enabling signal to the 3rd electrical level transferring chip according to the described 3rd.

Preferably,

The 3rd transmitting-receiving control circuit includes the 6th transistor, the 19th resistance, the 20th resistance, the 21st electricity Resistance；

The first end of 6th transistor connects the mode switching signal interface by the 19th resistance and led to Cross the 20th resistance connection the second transmitting-receiving control signal interface, the second end connection of the 6th transistor described the Two transmitting-receiving control signal interfaces, the 3rd transmission described in the three-terminal link of the 6th transistor enables signaling interface and passes through institute State the 21st resistance eutral grounding.

Preferably,

The transistor is specially triode, and the first end of the transistor is specially the base stage of triode, the crystal Second end of pipe is specially the emitter stage of triode, and the 3rd end of the transistor is specially the colelctor electrode of triode.

Preferably,

The transistor is specially metal-oxide-semiconductor, and the first end of the transistor is specially the grid of metal-oxide-semiconductor, the transistor The second end be specially metal-oxide-semiconductor source electrode, the 3rd end of the transistor is specially the drain electrode of metal-oxide-semiconductor.

Preferably,

First reception enables signaling interface and described first and sends enable signaling interface connection first level turn Chip is changed, described second, which receives enable signaling interface and second, sends enable signaling interface connection second electrical level conversion chip；

The serial communication interface function switching circuit also include serial port insulating circuit, mode switching signal isolation circuit, First transmitting-receiving control signal isolation circuit, power isolation circuit；

The serial port insulating circuit is electrically connected with corresponding electrical level transferring chip, for being received to the serial port insulating circuit To signal isolated and be sent to electrical level transferring chip, the signal that electrical level transferring chip is received is sent to serial ports isolation Circuit is simultaneously outwards isolated, and the serial port insulating circuit includes Magnetic isolation module；

The VDD1 ends connection VIN input powers of the Magnetic isolation module, the OA ends of the Magnetic isolation module connect MCU RX End, the IB ends of the Magnetic isolation module connect the TX ends of the MCU and connect the VIN input powers by a resistance, described The GND1 ends of Magnetic isolation module connect the earth terminal of the MCU, and the VDD2 ends of the Magnetic isolation module connect the serial communication The power supply of interface function switching circuit, the IA ends of the Magnetic isolation module connect the ISO_RX of the corresponding electrical level transferring chip Hold and the power supply is connected by a resistance, the OB ends of the Magnetic isolation module connect the corresponding electrical level transferring chip ISO_TX ends, the GND2 ends of the Magnetic isolation module connect the earth terminal of the serial communication interface function switching circuit.

Described mode switching signal isolation circuit and described mode switching signal interface electrical connection, for the mould The signal that formula switching signal isolation circuit is received is isolated and sent to the mode switching signal interface, and the pattern is cut Changing signal isolation circuit includes the first light-coupled isolation chip；

The input pattern switching signal that the first end of first light-coupled isolation chip connects the MCU by a resistance connects Mouthful end and by a resistance eutral grounding, the second end of first light-coupled isolation chip is grounded, first light-coupled isolation chip The mode switching signal interface of serial communication interface function switching circuit described in three-terminal link, first light-coupled isolation chip The 4th end connect the power supply of the serial communication interface function switching circuit.

The first described transmitting-receiving control signal isolation circuit and the first described transmitting-receiving control signal interface electrical connection, are used for The signal that described first transmitting-receiving control signal isolation circuit is received is isolated and the first described transmitting-receiving control is sent to Signaling interface, the first transmitting-receiving control signal isolation circuit includes the second light-coupled isolation chip；

The first end of second light-coupled isolation chip connects the first input transmitting-receiving control letter of the MCU by a resistance Number interface simultaneously passes through a resistance eutral grounding, the second end ground connection of second light-coupled isolation chip, second light-coupled isolation chip Three-terminal link described in serial communication interface function switching circuit first transmitting-receiving control signal interface, second optocoupler every 4th end of off-chip piece connects the power supply of the serial communication interface function switching circuit；

The insulating power supply circuit is controlled with the electrical level transferring chip, mode switching signal isolation circuit, the first transmitting-receiving Signal isolation circuit is electrically connected, and the signal for being received to it carries out isolated from power, is the electrical level transferring chip, pattern switching Signal isolation circuit, the first transmitting-receiving control signal isolation circuit provide driving voltage.

A kind of serial communication interface function switching method provided in an embodiment of the present invention, based on a kind of above-mentioned serial communication Interface function switching circuit is performed, including：

First function switching method：

Control the mode switching signal interface for low level by the MCU, control the first transmitting-receiving control signal Interface is low level so that it is high level, described first that the first of first electrical level transferring chip, which receives and enable signaling interface, It is low level to send and enable signaling interface, and it is low level that the second transmission of the second electrical level conversion chip, which enables signaling interface, It is low level that the second of the second electrical level conversion chip, which receives and enable signaling interface,；

Second function switching method：

Control the mode switching signal interface for low level by the MCU, control the first transmitting-receiving control signal Interface is high level so that it is high level, described first that the first of first electrical level transferring chip, which receives and enable signaling interface, It is low level to send and enable signaling interface, and it is high level that the second transmission of the second electrical level conversion chip, which enables signaling interface, It is high level that the second of the second electrical level conversion chip, which receives and enable signaling interface,；

3rd function switching method：

Control the mode switching signal interface for high level by the MCU, control the first transmitting-receiving control signal Interface is low level so that it is low level, described first that the first of first electrical level transferring chip, which receives and enable signaling interface, It is high level to send and enable signaling interface, and it is low level that the second transmission of the second electrical level conversion chip, which enables signaling interface, It is high level that the second of the second electrical level conversion chip, which receives and enable signaling interface,；

4th function switching method：

Control the mode switching signal interface for high level by the MCU, control the first transmitting-receiving control signal Interface is high level so that it is low level, described first that the first of first electrical level transferring chip, which receives and enable signaling interface, It is high level to send and enable signaling interface, and it is low level that the second transmission of the second electrical level conversion chip, which enables signaling interface, It is high level that the second of the second electrical level conversion chip, which receives and enable signaling interface,.

Preferably, first function switching method also includes：Five-function switching submethod, the 6th function switching side Method；

The five-function switching submethod includes controlling the mode switching signal interface to be low electricity by the MCU Put down, control it is described first transmitting-receiving control signal interface be low level, control it is described second receive and dispatch control signal interface be high level, So that the first of first electrical level transferring chip receives enable signaling interface for high level, described first, which sends enable signal, connects Mouth is low level, and the second of the second electrical level conversion chip sends enable signaling interface for low level, the second electrical level turn It is low level to change the second of chip and receive enable signaling interface, and the 3rd of the 3rd electrical level transferring chip, which sends enable signal, connects Mouth is high level；

The 6th function switching submethod includes controlling the mode switching signal interface to be low electricity by the MCU Put down, control it is described first transmitting-receiving control signal interface be low level, control it is described second receive and dispatch control signal interface be low level, So that the first of first electrical level transferring chip receives enable signaling interface for high level, described first, which sends enable signal, connects Mouth is low level, and the second of the second electrical level conversion chip sends enable signaling interface for low level, the second electrical level turn It is low level to change the second of chip and receive enable signaling interface, and the 3rd of the 3rd electrical level transferring chip, which sends enable signal, connects Mouth is low level.

As can be seen from the above technical solutions, the embodiment of the present invention has advantages below：

The embodiment of the present invention includes first and receives control circuit, the first sending controling circuit, second receives control circuit, the Two sending controling circuits, mode switching signal interface, the first transmitting-receiving control signal interface, first, which receive, enables signaling interface, the One transmission enables signaling interface, the second reception and enables signaling interface, the second transmission enable signaling interface so that MCU can pass through Control mode switch signaling interface, the low and high level of the first transmitting-receiving control signal interface realize the first electrical level transferring chip and second The power and energy of electrical level transferring chip, realizes a serial line interface and possesses the technique effect of multiple functions, so as to solve existing Multi-functional serial communication needs to consume CPU multi-channel serial ports resource or needs manual switching or the technology using expensive analog switch Problem.In addition, by serial communication interface function switching circuit provided in an embodiment of the present invention and the 3rd transmitting-receiving control circuit, Second transmitting-receiving control signal interface, the 3rd, which send, enables signaling interface, is controlled by control mode switch signaling interface, the first transmitting-receiving The low and high level of signaling interface processed and the second transmitting-receiving control signal interface can control the power and energy of the 3rd electrical level transferring chip, So as to realize the conversion of three functions.In addition, passing through the serial communication interface function switching circuit of the embodiment of the present invention and first Function switching method, the second function switching method, the 3rd function switching method realize the switching of function, specifically, pass through MCU The low and high level of control mode switch signaling interface and the first transmitting-receiving control signal interface, so as to control the enable of each function The low and high level switching of signaling interface, realizes the switching of function so that realize any switching laws of function on a circuit, i.e., One serial ports can switch multiple functions.

Brief description of the drawings

In order to illustrate more clearly about the embodiment of the present invention or technical scheme of the prior art, below will be to embodiment or existing There is the accompanying drawing used required in technology description to be briefly described, it should be apparent that, drawings in the following description are only this Some embodiments of invention, for those of ordinary skill in the art, without having to pay creative labor, may be used also To obtain other accompanying drawings according to these accompanying drawings.

Fig. 1 is a kind of circuit of one embodiment of serial communication interface function switching circuit provided in an embodiment of the present invention Figure；

Fig. 2 is a kind of RS-232 interface and RS- of serial communication interface function switching circuit provided in an embodiment of the present invention 485 interface switching control circuit figures；

Fig. 3 is a kind of another RS-232 interface of serial communication interface function switching circuit provided in an embodiment of the present invention With RS-485 interface switching control circuit figures；

Fig. 4 is a kind of RS-232 interface, the RS- of serial communication interface function switching circuit provided in an embodiment of the present invention 485 interfaces and RS-422 interface switching control circuit figures；

Fig. 5 is a kind of electricity of the power isolation circuit of serial communication interface function switching circuit provided in an embodiment of the present invention Lu Tu；

Fig. 6 is a kind of electricity of the serial port insulating circuit of serial communication interface function switching circuit provided in an embodiment of the present invention Lu Tu；

Fig. 7 isolates for a kind of mode switching signal of serial communication interface function switching circuit provided in an embodiment of the present invention The circuit diagram of circuit；

Fig. 8 controls for a kind of transmitting-receiving of one kind first of serial communication interface function switching circuit provided in an embodiment of the present invention The circuit diagram of signal isolation circuit；

Fig. 9 is a kind of RS-232 interface, the RS- of serial communication interface function switching circuit provided in an embodiment of the present invention The application illustration of 485 interfaces and the use metal-oxide-semiconductor of RS-422 interface switching control circuits.

Embodiment

To enable goal of the invention, feature, the advantage of the present invention more obvious and understandable, below in conjunction with the present invention Accompanying drawing in embodiment, the technical scheme in the embodiment of the present invention is clearly and completely described, it is clear that disclosed below Embodiment be only a part of embodiment of the invention, and not all embodiment.Based on the embodiment in the present invention, this area All other embodiment that those of ordinary skill is obtained under the premise of creative work is not made, belongs to protection of the present invention Scope.

Referring to Fig. 1, a kind of one embodiment of serial communication interface function switching circuit provided in an embodiment of the present invention, Including：First receives control circuit, the first sending controling circuit, the second reception control circuit, the second sending controling circuit, pattern Switching signal interface, the first transmitting-receiving control signal interface, first receive enable signaling interface, first send enable signaling interface, Second, which receives enable signaling interface, the second transmission, enables signaling interface；

First receives the input connection mode switching signal interface of control circuit, and first receives the output end of control circuit Connection first, which is received, enables signaling interface；The input connection mode switching signal interface of first sending controling circuit, the first hair Send the output end connection first of control circuit to send and enable signaling interface；The second input connection mode for receiving control circuit is cut Signaling interface and the first transmitting-receiving control signal interface are changed, the second output end connection second for receiving control circuit, which is received, enables signal Interface；The input connection mode switching signal interface of second sending controling circuit and the first transmitting-receiving control signal interface, second The output end connection second of sending controling circuit, which is sent, enables signaling interface；

First, which receives control circuit, is used for the mode switching signal according to input, and output first, which is received, enables signal to first The reception control signal interface of electrical level transferring chip so that the first electrical level transferring chip is received according to first enables signal to first The receive capabilities of electrical level transferring chip are enabled；

First sending controling circuit is used for the mode switching signal according to input, and output first, which is sent, enables signal to first The transmission control signal interface of electrical level transferring chip so that the first electrical level transferring chip is sent according to first enables signal to first The sending function of electrical level transferring chip is enabled；

Second, which receives control circuit, is used for according to the mode switching signal of input and the first transmitting-receiving control signal, output second Receive and enable signal to the reception control signal interface of second electrical level conversion chip so that second electrical level conversion chip is according to second Receive the receive capabilities enable for enabling signal to second electrical level conversion chip；

Second sending controling circuit is used for according to the mode switching signal of input and the first transmitting-receiving control signal, output second Send and enable signal to the transmission control signal interface of second electrical level conversion chip so that second electrical level conversion chip is according to second Send the sending function enable for enabling signal to the first electrical level transferring chip.

It should be noted that the first electrical level transferring chip and second electrical level conversion chip are all electrical level transferring chips, such as RS-232 electrical level transferring chips, RS-485 electrical level transferring chips, RS-422 electrical level transferring chips etc..Mode switching signal interface is used Can be the mode switching signal that the processors such as any CPU or MCU are sent in reception pattern switching signal；First transmitting-receiving control Signaling interface processed is used to receive transmitting-receiving control signal, can be the transmitting-receiving control signal that the processors such as any CPU or MCU are sent； First reception enable signaling interface, the first transmission enable signaling interface, the second reception enable signaling interface, the second transmission enable letter Number interface is used to output enable signal to corresponding electrical level transferring chip, enables its sending function or receive capabilities.

Specifically, mode switching signal, the first transmitting-receiving control signal, first, which receive enable signal etc., can use height electricity Flat mode carries out signal control, specific such as table 1：

Table 1

It can be seen from Table 1 that the embodiment of the present invention is by two signal outputs, 4 control signals, it is achieved thereby that control The output of circuit is controlled to whether the reception sending function of electrical level transferring chip enables.

Above is entering to a kind of one embodiment of serial communication interface function switching circuit provided in an embodiment of the present invention The detailed description of row, below by a kind of another reality of serial communication interface function switching circuit provided in an embodiment of the present invention Example is applied to be described in detail.

Referring to Fig. 2, the embodiment of the present invention provides a kind of another embodiment of serial communication interface function switching circuit, Including：First receives control circuit, the first sending controling circuit, the second reception control circuit, the second sending controling circuit, pattern Switching signal interface, the first transmitting-receiving control signal interface, first receive enable signaling interface, first send enable signaling interface, Second, which receives enable signaling interface, the second transmission, enables signaling interface；First, which receives control circuit, includes the first transistor, first Resistance, second resistance, 3rd resistor；First sending controling circuit is a wire, one end connection mode switching signal of wire Interface, the other end connection first of wire, which is sent, enables signaling interface；Second, which receives control circuit, includes the first diode, second Diode, the 7th resistance；Second sending controling circuit includes second transistor, the 4th resistance, the 5th resistance, the 6th resistance；Tool Body, the first transistor is specially that switching tube Q1, second transistor are specially that switching tube Q2, first resistor are to the 7th resistance specific It is specially that diode D1, the second diode are specially diode D2 for resistance R1~R7, the first diode；

Switching tube Q1 first end is by resistance R2 connection mode switching signal interfaces and is grounded by resistance R3, switching tube Q1 the second end ground connection, the first of the switching tube Q1 electrical level transferring chip of three-terminal link first receives enable signaling interface and leads to Cross resistance R1 connection power supplys；

Switching tube Q2 first end is by resistance R5 connection mode switching signal interfaces and is grounded by resistance R6, switching tube Q2 the second end ground connection, the second of switching tube Q2 three-terminal link second electrical level conversion chip sends enable signaling interface and leads to Cross the transmitting-receiving control signal interface of resistance R4 connections first；

Diode D1 positive pole connection mode switching signal interface, diode D1 negative pole connection second electrical level conversion chip Second receive to enable and signaling interface and be grounded by resistance R7；Diode D2 positive pole connection first is received and dispatched control signal and connect Mouthful, diode D2 negative pole connection diode D1 negative pole.

It should be noted that the resistance of the resistance in the embodiment of the present invention need to be adjusted according to actual conditions, its resistance Concrete numerical value have no effect on the function of the embodiment of the present invention.

The embodiment of the present invention can realize the function of RS-485, RS-232 two-in-one circuit：The circuit can realize RS-485, RS-232 function any switching laws.Specifically, mode switching signal interface, DIR are common I/O mouthfuls of MCU, and first sends enable letter Number interface, first receive the control signal interface forbidden with starting for enabling signaling interface for RS-232 electrical level transferring chips, the Two, which send the transmission and reception that enable signaling interface, the second reception enable signaling interface are respectively RS-485 electrical level transferring chips, makes Can signaling interface.

Circuit function pattern is as shown in table 2：

Table 2

In table 2, MODE is the mode switching signal in the embodiment of the present invention, and DIR is the first transmitting-receiving control signal, 232_ NEN is that the first reception enables signal, and 232_nSHDN is that the first transmission enables signal, and 485_DE sends for second and enables signal, 485_nRE is that the second reception enables signal.

Referring to Fig. 3, a kind of serial communication interface function switching circuit provided in an embodiment of the present invention, including：First connects Control circuit, the first sending controling circuit, the second reception control circuit, the second sending controling circuit, mode switching signal is received to connect Mouth, the first transmitting-receiving control signal interface, the first reception enable signaling interface, the first transmission enable signaling interface, second, which receive, to be made Can signaling interface, the second transmission enable signaling interface；

First sending controling circuit includes third transistor, the 8th resistance, the 9th resistance, the tenth resistance；Third transistor First end is by the 9th resistance connection mode switching signal interface and passes through the tenth resistance eutral grounding, the second end of the first transistor Ground connection, the first of the electrical level transferring chip of three-terminal link first of third transistor sends enable signaling interface and by the 8th electricity Resistance connection power supply；First receives that control circuit be wire, one end connection mode switching signal interface of wire, wire it is another One end connection first, which is received, enables signaling interface；Second, which receives control circuit, includes the 4th transistor, the 11st resistance, the 12nd Resistance, the 13rd resistance, the 14th resistance；The first end of 4th transistor passes through the 13rd resistance connection the first transmitting-receiving control letter Number interface is simultaneously by the 13rd resistance and the 12nd resistance connection mode switching signal interface, and the first end of the 4th transistor is also By the 14th resistance eutral grounding, the second end of the 4th transistor is grounded, and the three-terminal link second of the 4th transistor, which is received, to be enabled Signaling interface simultaneously connects power supply by the 11st resistance；Second sending controling circuit includes the 5th transistor, the 15th resistance, the 16 resistance, the 17th resistance, the 18th resistance；The first end of 5th transistor is controlled by the transmitting-receiving of the 17th resistance connection first Signaling interface processed simultaneously passes through the 18th resistance eutral grounding, the second end ground connection of the 5th transistor, the three-terminal link of the 5th transistor The second of second electrical level conversion chip, which sends, enables signaling interface and by the 15th resistance connection mode switching signal interface, the 3rd end of five transistors also passes through the 15th resistance and the 16th resistance eutral grounding.

Specifically, in the present embodiment, third transistor is specially that triode Q3, the 8th resistance are specially resistance R8, the 9th Resistance be specially R9, the tenth resistance be specially R10, the 4th transistor be specially triode Q4, the 11st resistance be specially R11, 12nd resistance is specially that R12, the 13rd resistance are specially that R13, the 14th resistance are specially that R14, the 5th transistor are specially Triode Q5, the 15th resistance are specially that R15, the 16th resistance are specially that R16, the 17th resistance are specially R17, the 18th electricity Resistance is specially R18；

Above is to a kind of another embodiment of serial communication interface function switching circuit provided in an embodiment of the present invention Be described in detail, below by a kind of serial communication interface function switching circuit provided in an embodiment of the present invention another Embodiment is described in detail.

Referring to Fig. 4, the embodiment of the present invention provides a kind of another embodiment of serial communication interface function switching circuit, Including：First receives control circuit, the first sending controling circuit, the second reception control circuit, the second sending controling circuit, pattern Switching signal interface, the first transmitting-receiving control signal interface, first receive enable signaling interface, first send enable signaling interface, Second, which receives enable signaling interface, the second transmission, enables signaling interface；

First, which receives control circuit, includes the first transistor, first resistor, second resistance, 3rd resistor；First sends control Circuit processed is a wire, and one end connection mode switching signal interface of wire, the other end connection first of wire sends enable Signaling interface；Second, which receives control circuit, includes the first diode, the second diode, the 7th resistance；Second sending controling circuit Including second transistor, the 4th resistance, the 5th resistance, the 6th resistance；

Specifically, the first transistor is specially that switching tube Q1, second transistor are specially switching tube Q2, first resistor to Seven resistance are specially that resistance R1~R7, the first diode are specially that diode D1, the second diode are specially diode D2；

Switching tube Q1 first end is by R2 resistance connection mode switching signal interface and is grounded by resistance R3, switching tube Q1 the second end ground connection, the first of the switching tube Q1 electrical level transferring chip of three-terminal link first receives enable signaling interface and leads to Cross resistance R1 connection power supplys；

Switching tube Q2 first end is by R5 resistance connection mode switching signal interface and is grounded by resistance R6, switching tube Q2 the second end ground connection, the second of switching tube Q2 three-terminal link second electrical level conversion chip sends enable signaling interface and leads to Cross R4 resistance connection first and receive and dispatch control signal interface；

Control signal interface, diode D1 negative pole connection second electrical level conversion are received and dispatched in diode D1 positive pole connection first The second of chip, which receives, to be enabled signaling interface and is grounded by resistance R7；Diode D2 positive pole connection mode switching signal connects Mouthful, diode D2 negative pole connection diode D1 negative pole.

Further, the embodiment of the present invention also includes the 3rd transmitting-receiving control circuit, the second transmitting-receiving control signal interface, the 3rd Send and enable signaling interface；

The 3rd transmitting-receiving control circuit includes the 6th transistor, the 19th resistance, the 20th resistance, the 21st electricity Resistance；Specifically, the 6th transistor is specially switching tube Q6, and the 19th resistance is specially that resistance R19, the 20th resistance are specially electricity It is specially resistance R21 to hinder R20, the 21st resistance.

Switching tube Q6 first end is by resistance R19 connection mode switching signal interfaces and passes through resistance R20 connections MCU's Second transmitting-receiving control signal interface, switching tube Q6 the second end connection MCU the second transmitting-receiving control signal interface, switching tube Q6's The 3rd of the electrical level transferring chip of three-terminal link the 3rd, which sends, to be enabled signaling interface and is grounded by resistance R21.

Further, switching tube Q1 is specially triode Q1, and switching tube Q1 first end is specially triode Q1 base stage, Switching tube Q1 the second end is specially triode Q1 emitter stage, and switching tube Q1 the 3rd end is specially triode Q1 current collection Pole；Switching tube Q2 is specially triode Q2, and switching tube Q2 first end is specially triode Q2 base stage, the second of switching tube Q2 End is specially triode Q2 emitter stage, and switching tube Q2 the 3rd end is specially triode Q2 colelctor electrode；Switching tube Q6 is specific For triode Q6, switching tube Q6 first end is specially triode Q6 base stage, and switching tube Q6 the second end is specially triode Q6 emitter stage, switching tube Q6 the 3rd end is specially triode Q6 colelctor electrode.

It should be noted that the first electrical level transferring chip and second electrical level conversion chip, the 3rd electrical level transferring chip are all Electrical level transferring chip, such as RS-232 electrical level transferring chips, RS-485 electrical level transferring chips, RS-422 electrical level transferring chips etc.. Mode switching signal interface is used for reception pattern switching signal, can be that the pattern that the processors such as any CPU or MCU are sent is cut Change signal；First transmitting-receiving control signal interface is used to receive transmitting-receiving control signal, can be the processors such as any CPU or MCU hair The transmitting-receiving control signal sent；First reception enables signaling interface, the first transmission enable signaling interface, the second reception enable signal and connect Mouth, second, which send, enables signaling interface, the 3rd transmission enable signaling interface for outputing enable signal to corresponding level conversion Chip, enables its sending function or receive capabilities.

The embodiment of the present invention can realize RS-232 interface, RS-485 interfaces and RS-422 interface switching control circuit three in one circuit Function.The present invention makes full use of the switching characteristic of triode and the one-way conduction characteristic of diode, realizes RS-232, RS- 485th, the automatic switching function of tri- kinds of functional circuits of RS-422.Mode switching signal interface, the first transmitting-receiving control in the application example Signaling interface, common I/O mouthfuls that the second transmitting-receiving control signal interface is MCU, the first electrical level transferring chip is that RS-232 level turns Change chip, first send enable signaling interface, first receive enable signaling interface for RS-232 electrical level transferring chips forbid with The control signal interface of startup, second electrical level conversion chip is the first RS-485 electrical level transferring chips, and second sends enable signal It is respectively that the transmission of RS-485 electrical level transferring chips and reception enable signaling interface that interface, second, which receive and enable signaling interface,；The Three electrical level transferring chips are the 2nd RS-485 electrical level transferring chips, and the 3rd sends enable signaling interface turns for the 2nd RS-485 level The transmission for changing chip enables signaling interface.The RS-422 patterns of the present embodiment are to come real using two RS-485 electrical level transferring chips Existing.

MCU passes through control mode switch signaling interface, the first transmitting-receiving control signal interface, the second transmitting-receiving control signal interface Low and high level realize the logic of tri- kinds of function any switching laws of RS-232, RS-485, RS-422.The RS-422 moulds of the present embodiment Formula is realized using two RS-485 electrical level transferring chips.It is to utilize one in RS-422 patterns during RS-485 patterns RS-485 chips, i.e. RS-422 share 485 electrical level transferring chips with RS-485.

Circuit function explanation：

Table 3

Signaling interface logic level values when table 3 is RS-232, RS-485, RS-422 switching.

In table 3, MODE is mode switching signal interface, and 485_DIR is the first transmitting-receiving control signal interface, and 422_DIR is Second transmitting-receiving control signal interface, 232_nEN is that the first reception enables signaling interface, and 232_nSHDN sends to enable for first to be believed Number interface, 485_DE is second to send and enable signaling interface, and 485_nRE is second to receive and enable signaling interface, and 422_DE is the Three send enable signaling interface, and 422_nRE is that the 3rd reception enables signaling interface.

The functional mode to the embodiment of the present invention is described in detail below.

1st, RS-232 patterns：

When user uses RS-232, high level is exported with MCU control mode switchs signaling interface, you can open RS-232 electricity Flat conversion chip simultaneously forbids two RS-485 electrical level transferring chips (i.e. the first RS-485 electrical level transferring chips and the 2nd RS-485 electricity Flat conversion chip), concrete operating principle is as follows：

When mode switching signal interface=1, first sends to enable signaling interface=1, the second and receive and enables signaling interface =1, triode Q1 are turned on, and first receives and enable signaling interface level and drags down, and such RS-232 electrical level transferring chips are enabled (the One is sent and enables signaling interface=1, first receives and enable signaling interface=0), and 232 functions are activated；Triode Q2 is also led It is logical, send enable signaling interface level by second and be pulled low, i.e., second sends enable signaling interface=0, then the first RS-485 electricity Flat turn change chip transceiver function be all prohibited (second receive enable signaling interface=1, the second send enable signaling interface= 0), i.e., RS-485 functions are closed；Triode Q6 is not turned on, and at this moment the 3rd is sent and is enabled signaling interface and dragged down by resistance R21, i.e., and the Three send enable signaling interface=0, then the function of the 2nd RS-485 electrical level transferring chips is also prohibited.Therefore, in pattern switching letter During number interface=1,232 open, and 485 close, and 422 close.

2nd, RS-485 patterns：

When user uses RS-485, with MCU control mode switchs signaling interface, the first transmitting-receiving control signal interface, second Receive and dispatch control signal interface and export corresponding level, you can forbid RS-232 electrical level transferring chips and open RS-485 level conversion cores Piece, concrete operating principle is as follows：

2.1st, RS-485 reception patterns (default mode)

When mode switching signal interface=0, the first transmitting-receiving control signal interface=0, the second transmitting-receiving control signal interface=0 When, first, which sends enable signaling interface=0, the second, receives enable signaling interface=0, and triode Q1 is not turned on, and the first reception makes Can signaling interface drawn high by resistance R1, such RS-232 electrical level transferring chips be disabled (first send enable signaling interface=0, First reception enable signaling interface=1), RS-232 functions are prohibited；Triode Q2 is also not turned on, and second, which sends enable signal, connects Mouth is dragged down by R4 by the first transmitting-receiving control signal interface, i.e., second transmission enable signaling interface=first receives and dispatches control signal and connect Mouthful=0, second receives enable signaling interface level is dragged down by R7, i.e., second receives enable signaling interface=0, then the first RS-485 Electrical level transferring chip enters reception pattern, and (second receives to enable signaling interface=0, the second and send and enables signaling interface=0)；Three Pole pipe Q6 is not turned on, and at this moment the 3rd transmission enables signaling interface and dragged down by resistance R21, i.e., the 3rd sends enable signaling interface=0, Then the function of the 2nd RS-485 electrical level transferring chips is also prohibited, i.e., RS-422 patterns are closed.

Therefore, in mode switching signal interface=0, the first transmitting-receiving control signal interface=0, the second transmitting-receiving control signal interface When=0,232 close, and 485 receive, and 422 close.

2.2nd, RS-485 sending modes

When mode switching signal interface=0, the first transmitting-receiving control signal interface=1, the second transmitting-receiving control signal interface=0 When, first sends enable signaling interface=0, the second reception enable signaling interface is drawn by the first transmitting-receiving control signal interface by D2 Height, i.e., second receives enable signaling interface=1, and triode Q1 is not turned on, and first receives enable signaling interface is drawn high by resistance R1, So RS-232 electrical level transferring chips be disabled (first send enable signaling interface=0, first receive enable signaling interface= 1), RS-232 functions are prohibited；Triode Q2 is also not turned on, and second sends enable signaling interface is controlled by R4 by the first transmitting-receiving Signaling interface is drawn high, i.e., second, which sends enable signaling interface=first, receives and dispatches control signal interface=1, then the first RS-485 level Conversion chip enters sending mode, and (second receives to enable signaling interface=1, the second and send and enables signaling interface=1)；Triode Q6 is not turned on, and at this moment the 3rd is sent and is enabled signaling interface and dragged down by resistance R21, i.e., the 3rd sends and enable signaling interface=0, then and the The function of two RS-485 electrical level transferring chips is also prohibited, i.e., RS-422 patterns are closed.

Therefore, in mode switching signal interface=0, the first transmitting-receiving control signal interface=1, the second transmitting-receiving control signal interface When=0,232 close, 485 hairs, and 422 close.

3rd, RS-422 patterns

When user uses RS-422, with MCU control mode switchs signaling interface, the first transmitting-receiving control signal interface, second Receive and dispatch control signal signaling interface and export corresponding level, you can forbid RS-232 electrical level transferring chips and open two-way RS-485 electricity Flat conversion chip, concrete operating principle is as follows：

When mode switching signal interface=0, the first transmitting-receiving control signal interface=0, the second transmitting-receiving control signal interface=1 When, first sends enable signaling interface=0, the second reception enable signaling interface is dragged down by resistance R7, i.e., the second reception, which is enabled, to be believed Number interface=0, triode Q1 is not turned on, and first receives and enable signaling interface and is drawn high by resistance R1, such RS-232 level conversions Chip is disabled (first, which sends enable signaling interface=0, the first reception, enables signaling interface=1), and RS-232 functions are prohibited； Triode Q2 is also not turned on, and second sends enable signaling interface is dragged down by R4 by the first transmitting-receiving control signal interface, i.e., and second Send enable signaling interface=first and receive and dispatch control signal interface=0, then the first RS-485 electrical level transferring chips, which enter, receives mould Formula (second reception enable signaling interface=0, the second transmission enable signaling interface=0)；Triode Q6 is turned on, and at this moment the 3rd is sent Enable signaling interface to be drawn high by the second transmitting-receiving control signal interface, i.e., the 3rd, which sends enable signaling interface=second, receives and dispatches control letter Number interface=1, then the 2nd RS-485 electrical level transferring chips enter sending mode, i.e. RS-422 patterns and open.

Therefore, in mode switching signal interface=0, the first transmitting-receiving control signal interface=0, the second transmitting-receiving control signal interface When=1,232 close, and 485 receive, 422 hairs.

Above is to a kind of another embodiment of serial communication interface function switching circuit provided in an embodiment of the present invention It is described in detail, below by a kind of embodiment of serial communication interface function switching circuit provided in an embodiment of the present invention In isolation circuit be described in detail.

Referring to Fig. 5, a kind of embodiment of serial communication interface function switching circuit provided in an embodiment of the present invention is also wrapped Include power isolation circuit；

Power isolation circuit includes power isolation module；With the Vo interfaces of power isolation module after the resistor coupled in parallel of two electric capacity one With 0V interface tandems, the Vin interfaces and GND interfaces of an electric capacity and power isolation module are in parallel and electric with two after connect with an inductance Hold in parallel；Vo interfaces are connected with the power supply of serial communication interface function switching circuit, and 0V interfaces are cut with serial communication interface function The earth terminal connection of circuit is changed, Vin interfaces are connected by inductance and MCU power end, and GND interfaces and MCU earth terminal are connected.

Referring to Fig. 6, further, in addition to serial port insulating circuit；Serial port insulating circuit includes Magnetic isolation module；It is described The VDD1 ends connection VIN input powers of Magnetic isolation module, the OA ends of the Magnetic isolation module connect MCU RX ends, the magnetic every IB ends from module connect the TX ends of the MCU and connect the VIN input powers by a resistance, the Magnetic isolation module GND1 ends connect the earth terminal of the MCU, and the VDD2 ends of the Magnetic isolation module connect the serial communication interface function switching The power supply of circuit, the IA ends of the Magnetic isolation module connect the ISO_RX ends of the corresponding electrical level transferring chip and by an electricity The resistance connection power supply, the OB ends of the Magnetic isolation module connect the ISO_TX ends of the corresponding electrical level transferring chip, described The GND2 ends of Magnetic isolation module connect the earth terminal of the serial communication interface function switching circuit.

Referring to Fig. 7, further, in addition to mode switching signal isolation circuit；Mode switching signal isolation circuit bag Include the first light-coupled isolation chip；The input pattern that the first end of first light-coupled isolation chip connects MCU by a resistance, which switches, to be believed Number interface end simultaneously passes through a resistance eutral grounding, the second end ground connection of the first light-coupled isolation chip, the 3rd of the first light-coupled isolation chip the The mode switching signal interface end of end connection serial communication interface function switching circuit, the 4th end of the first light-coupled isolation chip connects Connect the power supply of serial communication interface function switching circuit.

Referring to Fig. 8, further, in addition to the first transmitting-receiving control signal isolation circuit；First transmitting-receiving control signal every Include the second light-coupled isolation chip from circuit；The first end of second light-coupled isolation chip connects the first defeated of MCU by a resistance Enter to receive and dispatch control signal interface and by a resistance eutral grounding, the second end of the second light-coupled isolation chip is grounded, the second light-coupled isolation First transmitting-receiving control signal interface of the three-terminal link serial communication interface function switching circuit of chip, the second light-coupled isolation core 4th end of piece connects the power supply of serial communication interface function switching circuit.

If to be protected to system, isolation circuit can be added in the circuit prime of the present invention.Wherein U1 be power supply every From module, insulating power supply is provided for circuit of the present invention；U2 is Magnetic isolation module, by CPU serial ports TX and RX signal and the present invention Circuit is isolated, if the communication speed of serial ports is very high, it is proposed that selection high-speed isolated chip；U3, U4 are light-coupled isolation chip, Common I/O mouthfuls of CPU are isolated with circuit of the present invention., can be by CPU by the effect of above isolation module and isolating chip Circuit and circuit of the present invention fully achieve isolating electrically, so not only increase the stability of system, also improve system Antijamming capability.

Analysis method：For optocoupler U3, U4, when input pattern switching signal, the first input transmitting-receiving control signal are high electricity Usually, optocoupler is turned on, i.e.,：Mode switching signal, the first transmitting-receiving control signal are also high level state；Believe when input pattern switches Number, first input transmitting-receiving control signal be low level when, optocoupler is not turned on, i.e.,：Mode switching signal, the first transmitting-receiving control signal Also it is high-impedance state, its level state depends on circuit of the present invention.

Above is to a kind of another embodiment of serial communication interface function switching circuit provided in an embodiment of the present invention It is described in detail, below by an a kind of reality of serial communication interface function switching method provided in an embodiment of the present invention Example is applied to be described in detail.

The embodiment of the present invention provides a kind of serial communication interface function switching method, is connect based on a kind of above-mentioned serial communication Mouth function switching circuit is performed, including：

First function switching method：It is low level, the transmitting-receiving control of control first by MCU control mode switchs signaling interface Signaling interface is low level so that it is high level that the first of the first electrical level transferring chip, which receives and enable signaling interface, and first sends Enable signaling interface is low level, and the second of second electrical level conversion chip sends enable signaling interface for low level, second electrical level It is low level that the second of conversion chip, which receives and enable signaling interface,；

Second function switching method：It is low level, the transmitting-receiving control of control first by MCU control mode switchs signaling interface Signaling interface is high level so that it is high level that the first of the first electrical level transferring chip, which receives and enable signaling interface, and first sends Enable signaling interface is low level, and the second of second electrical level conversion chip sends enable signaling interface for high level, second electrical level It is high level that the second of conversion chip, which receives and enable signaling interface,；

3rd function switching method：It is high level, the transmitting-receiving control of control first by MCU control mode switchs signaling interface Signaling interface is low level so that it is low level that the first of the first electrical level transferring chip, which receives and enable signaling interface, and first sends Enable signaling interface is high level, and the second of second electrical level conversion chip sends enable signaling interface for low level, second electrical level It is high level that the second of conversion chip, which receives and enable signaling interface,；

4th function switching method：It is high level, the transmitting-receiving control of control first by MCU control mode switchs signaling interface Signaling interface is high level so that it is low level that the first of the first electrical level transferring chip, which receives and enable signaling interface, and first sends Enable signaling interface is high level, and the second of second electrical level conversion chip sends enable signaling interface for low level, second electrical level It is high level that the second of conversion chip, which receives and enable signaling interface,.

Five-function switches submethod：Five-function switching submethod includes passing through MCU control mode switch signaling interfaces For low level, control first transmitting-receiving control signal interface be low level, control second receive and dispatch control signal interface be high level, make It is high level to obtain the first of the first electrical level transferring chip and receive enable signaling interface, and the first transmission enable signaling interface is low electricity Flat, the second of second electrical level conversion chip sends enable signaling interface for low level, and the second of second electrical level conversion chip receives Enable signaling interface is low level, and the 3rd of the 3rd electrical level transferring chip sends enable signaling interface for high level；

It is low level that 6th function switching submethod, which is included by MCU control mode switchs signaling interface, control first to receive Hair control signal interface is low level, controls the second transmitting-receiving control signal interface to be low level so that the first electrical level transferring chip First receive enable signaling interface be high level, first send enable signaling interface be low level, second electrical level conversion chip Second send enable signaling interface be low level, second electrical level conversion chip second receive enable signaling interface be low electricity Flat, the 3rd of the 3rd electrical level transferring chip sends enable signaling interface for low level.

Above is entering to a kind of one embodiment of serial communication interface function switching method provided in an embodiment of the present invention The detailed description of row, below by the one of a kind of serial communication interface function switching circuit and method provided in an embodiment of the present invention Individual application examples is described in detail.

The embodiment of the present invention can also realize the switching of three kinds of functions using metal-oxide-semiconductor.

Referring to Fig. 9, using metal-oxide-semiconductor come instead of the triode in the present invention.Metal-oxide-semiconductor is voltage-controlled element, as long as being added to pressure Control the conducting voltage of element, metal-oxide-semiconductor just can as triode saturation conduction, and it is minimum to turn on the pressure drop of knot.Below figure institute Show：Three triodes in the present invention are replaced with into metal-oxide-semiconductor, can also realize that RS-485, RS-232, RS-422 function are arbitrarily cut Change.

The analysis method of the replacement circuit and the analysis method of invention circuit are just the same, when Three models switch, each I/O mouthfuls of logical relation is as shown in table 4.

Table 4

Analysis refers to RS-232 patterns, RS-485 patterns, RS-422 patterns during above-mentioned circuit function illustrates.

In table 4, MODE is mode switching signal interface, and 485_DIR is the first transmitting-receiving control signal interface, and 422_DIR is Second transmitting-receiving control signal interface, 232_nEN is that the first reception enables signaling interface, and 232_nSHDN sends to enable for first to be believed Number interface, 485_DE is second to send and enable signaling interface, and 485_nRE is second to receive and enable signaling interface, and 422_DE is the Three send enable signaling interface, and 422_nRE is that the 3rd reception enables signaling interface.

It should be noted that the innovative point of the embodiment of the present invention is：1st, 3 kinds of interface standards are switched using serial ports all the way.Section Hardware resource is saved, software automatically switches, and product can be made to meet distinct interface demand.2nd, circuit hardware cost is low, and compatibility is strong. It is especially suitable for serial server circuit needs.

The advantage of the embodiment of the present invention is：Circuit components are few, reduce PCB surface product, fault rate is low, and cost is very It is low；Software exchange is convenient, program code efficiency high；Circuit is simple, and reliability is high, and practicality is very strong；Used available for various Among the circuit of serial equipment；This circuit is used can be widely；Serial server, industry control serial communication interface.Need Bright, triode can be changed to combine gate circuit by the embodiment of the present invention；Can also be by the triode in the embodiment of the present invention Metal-oxide-semiconductor is replaced with, any switching laws of three kinds of functions can be equally realized.It should be noted that this circuit form, all by soft Part automatically switches, without artificial manual switching.Traditional switching mode switches over for jumper cap, and this mode, which is switched, comes time-consuming Arduously, and easily malfunction, this circuit completely avoid this problem, and whole software automatically switches, according to those listed above Truth table is selected, and reaches full automatic effect.

Circuit hardware cost provided in an embodiment of the present invention is low.Traditional switching mode, door is added using analog switch chip Circuit is switched over, expensive, and required chip is relatively more, takes PCB surface product greatly, cost performance is not high, and simulation is opened Close conducting internal resistance big.This circuit is switched over using metal-oxide-semiconductor or triode, cheap, and speed is fast, and required device is few, accounts for It is small with area, beneficial to integrated, cost performance height.

It should be further stated that, the transistor in above-described embodiment can be switching tube, triode, metal-oxide-semiconductor etc., tool Body, the first transistor is specially metal-oxide-semiconductor, and the first end of the first transistor is specially the grid of metal-oxide-semiconductor, the of the first transistor Two ends are specially the source electrode of metal-oxide-semiconductor, and the 3rd end of the first transistor is specially the drain electrode of metal-oxide-semiconductor；Second transistor is specially MOS Pipe, the first end of second transistor is specially the grid of metal-oxide-semiconductor, and the second end of second transistor is specially the source electrode of metal-oxide-semiconductor, the 3rd end of two-transistor is specially the drain electrode of metal-oxide-semiconductor；Third transistor is specially metal-oxide-semiconductor, the first end tool of third transistor Body is the grid of metal-oxide-semiconductor, and the second end of third transistor is specially the source electrode of metal-oxide-semiconductor, and the 3rd end of third transistor is specially The drain electrode of metal-oxide-semiconductor.

It is apparent to those skilled in the art that, for convenience and simplicity of description, the system of foregoing description, The specific work process of device and unit, may be referred to the corresponding process in preceding method embodiment, will not be repeated here.

Described above, the above embodiments are merely illustrative of the technical solutions of the present invention, rather than its limitations；Although with reference to before Embodiment is stated the present invention is described in detail, it will be understood by those within the art that：It still can be to preceding State the technical scheme described in each embodiment to modify, or equivalent substitution is carried out to which part technical characteristic；And these Modification is replaced, and the essence of appropriate technical solution is departed from the spirit and scope of various embodiments of the present invention technical scheme.

Claims

1. a kind of serial communication interface function switching circuit, it is characterised in that including：First receives control circuit, the first transmission Circuit, second is controlled to receive control circuit, the second sending controling circuit, mode switching signal interface, the first transmitting-receiving control signal Interface, the first reception enable signaling interface, first, which send, enables signaling interface, the second reception enable signaling interface, the second transmission Enable signaling interface；

Described first input for receiving control circuit connects the mode switching signal interface, and described first receives control circuit Output end connection it is described first receive enable signaling interface；

The input of first sending controling circuit connects the mode switching signal interface, first sending controling circuit Output end connection it is described first send enable signaling interface；

Described second input for receiving control circuit connects the mode switching signal interface and the first transmitting-receiving control letter Number interface, the described second output end connection described second for receiving control circuit, which is received, enables signaling interface；

The input of second sending controling circuit connects the mode switching signal interface and the first transmitting-receiving control letter Number interface, the output end connection described second of second sending controling circuit, which is sent, enables signaling interface；

Described first, which receives control circuit, is used for the mode switching signal according to input, and output first, which is received, enables signal to first The reception control signal interface of electrical level transferring chip so that first electrical level transferring chip receives according to described first and enables letter Number the receive capabilities of first electrical level transferring chip are enabled；

First sending controling circuit is used for the mode switching signal according to input, and output first, which is sent, enables signal to first The transmission control signal interface of electrical level transferring chip so that first electrical level transferring chip sends according to described first and enables letter Number the sending function of first electrical level transferring chip is enabled；

Described second, which receives control circuit, is used for according to the mode switching signal of input and the first transmitting-receiving control signal, output second Receive enable signal to second electrical level conversion chip reception control signal interface so that the second electrical level conversion chip according to Described second receives the receive capabilities enable for enabling signal to the second electrical level conversion chip；

Second sending controling circuit is used for according to the mode switching signal of input and the first transmitting-receiving control signal, output second Send enable signal to second electrical level conversion chip transmission control signal interface so that the second electrical level conversion chip according to Described second sends the sending function enable for enabling signal to the second electrical level conversion chip.

2. a kind of serial communication interface function switching circuit according to claim 1, it is characterised in that

The first end of the first transistor connects the mode switching signal interface and by described by the second resistance 3rd resistor is grounded, the second end ground connection of the first transistor, the first electricity described in the three-terminal link of the first transistor The first of flat conversion chip, which receives, to be enabled signaling interface and connects power supply by the first resistor；

First sending controling circuit is a wire, and one end of the wire connects the mode switching signal interface, institute The other end connection described first for stating wire sends enable signaling interface；

Positive pole connection the first transmitting-receiving control signal interface of first diode, the negative pole connection of first diode The second of the second electrical level conversion chip receives enable signaling interface and passes through the 7th resistance eutral grounding；

The positive pole of second diode connects the mode switching signal interface, and the negative pole connection of second diode is described The negative pole of first diode；

The first end of the second transistor connects the mode switching signal interface and by described by the 5th resistance 6th resistance eutral grounding, the second end ground connection of the second transistor, the second electricity described in the three-terminal link of the second transistor The second of flat conversion chip sends to enable signaling interface and connect the first transmitting-receiving control signal by the 4th resistance and connect Mouthful.

3. a kind of serial communication interface function switching circuit according to claim 1, it is characterised in that

The first end of the third transistor connects the mode switching signal interface and by described by the 9th resistance Tenth resistance eutral grounding, the second end ground connection of the third transistor, the first electricity described in the three-terminal link of the third transistor The first of flat conversion chip, which sends, to be enabled signaling interface and connects power supply by the 8th resistance；

First reception controls circuit to be a wire, and one end of the wire connects the mode switching signal interface, institute The other end connection described first for stating wire receives enable signaling interface；

Described second, which receives control circuit, includes the 4th transistor, the 11st resistance, the 12nd resistance, the 13rd resistance, the tenth Four resistance；

The first end of 4th transistor connects the first transmitting-receiving control signal interface simultaneously by the 13rd resistance The mode switching signal interface is connected by the 13rd resistance and the 12nd resistance, the of the 4th transistor One end is also by the 14th resistance eutral grounding, and the second end of the 4th transistor is grounded, and the 3rd of the 4th transistor the End connection described second, which is received, to be enabled signaling interface and connects power supply by the 11st resistance；

Second sending controling circuit includes the 5th transistor, the 15th resistance, the 16th resistance, the 17th resistance, the tenth Eight resistance；

The first end of 5th transistor connects the first transmitting-receiving control signal interface by the 17th resistance and led to Cross the 18th resistance eutral grounding, the second end ground connection of the 5th transistor, the three-terminal link institute of the 5th transistor The second of second electrical level conversion chip is stated to send enable signaling interface and connect the pattern switching by the 15th resistance Signaling interface, the 3rd end of the 5th transistor also passes through the 15th resistance and the 16th resistance eutral grounding.

4. a kind of serial communication interface function switching circuit according to claim 1, it is characterised in that also received including the 3rd Hair control circuit, the second transmitting-receiving control signal interface, the 3rd, which send, enables signaling interface；

The input of the 3rd transmitting-receiving control circuit connects the mode switching signal interface and the second transmitting-receiving control letter Number interface, the output end connection the described 3rd of the 3rd transmitting-receiving control circuit, which is sent, enables signaling interface；

3rd sending controling circuit is used for according to the mode switching signal of input and the second transmitting-receiving control signal, output the 3rd Send and enable signal to the 3rd transmission enable signaling interface of the 3rd electrical level transferring chip so that the 3rd electrical level transferring chip The sending function enable for enabling signal to the 3rd electrical level transferring chip is sent according to the described 3rd.

5. a kind of serial communication interface function switching circuit according to claim 4, it is characterised in that

The 3rd transmitting-receiving control circuit includes the 6th transistor, the 19th resistance, the 20th resistance, the 21st resistance；

The first end of 6th transistor connects the mode switching signal interface by the 19th resistance and passes through institute The 20th resistance connection the second transmitting-receiving control signal interface is stated, the second end connection described second of the 6th transistor is received Control signal interface is sent out, the 3rd sends and enable signaling interface and by described the described in the three-terminal link of the 6th transistor 21 resistance eutral groundings.

6. a kind of serial communication interface function switching circuit according to claim 2 to 5 any one, it is characterised in that

The transistor is specially triode, and the first end of the transistor is specially the base stage of triode, the transistor Second end is specially the emitter stage of triode, and the 3rd end of the transistor is specially the colelctor electrode of triode.

7. a kind of serial communication interface function switching circuit according to claim 2 to 5 any one, it is characterised in that

The transistor is specially metal-oxide-semiconductor, and the first end of the transistor is specially the grid of metal-oxide-semiconductor, and the of the transistor Two ends are specially the source electrode of metal-oxide-semiconductor, and the 3rd end of the transistor is specially the drain electrode of metal-oxide-semiconductor.

8. a kind of serial communication interface function switching circuit according to claim 1, it is characterised in that

The serial communication interface function switching circuit also includes serial port insulating circuit, mode switching signal isolation circuit, first Receive and dispatch control signal isolation circuit, power isolation circuit；

The serial port insulating circuit is electrically connected with corresponding electrical level transferring chip, for what is received to the serial port insulating circuit Signal is isolated and is sent to electrical level transferring chip, and the signal that electrical level transferring chip is received is sent into serial port insulating circuit And outwards isolate, the serial port insulating circuit includes Magnetic isolation module；

The VDD1 ends connection VIN input powers of the Magnetic isolation module, the OA ends of the Magnetic isolation module connect MCU RX ends, The IB ends of the Magnetic isolation module connect the TX ends of the MCU and connect the VIN input powers by a resistance, the magnetic every GND1 ends from module connect the earth terminal of the MCU, and the VDD2 ends of the Magnetic isolation module connect the serial communication interface The power supply of function switching circuit, the IA ends of the Magnetic isolation module connect the ISO_RX ends of the corresponding electrical level transferring chip simultaneously The power supply is connected by a resistance, the OB ends of the Magnetic isolation module connect the ISO_TX of the corresponding electrical level transferring chip End, the GND2 ends of the Magnetic isolation module connect the earth terminal of the serial communication interface function switching circuit；

Described mode switching signal isolation circuit and described mode switching signal interface electrical connection, for being cut to the pattern The signal that signal isolation circuit receives is changed to be isolated and sent to the mode switching signal interface, the pattern switching letter Number isolation circuit includes the first light-coupled isolation chip；

The first end of first light-coupled isolation chip connects the input pattern switching signal interface end of the MCU by a resistance And by a resistance eutral grounding, the second end of first light-coupled isolation chip is grounded, the 3rd of first light-coupled isolation chip the The mode switching signal interface of the end connection serial communication interface function switching circuit, the of first light-coupled isolation chip Four ends connect the power supply of the serial communication interface function switching circuit；

The first described transmitting-receiving control signal isolation circuit and the first described transmitting-receiving control signal interface electrical connection, for institute The signal that the first transmitting-receiving control signal isolation circuit receives is stated to be isolated and be sent to the first described transmitting-receiving control signal Interface, the first transmitting-receiving control signal isolation circuit includes the second light-coupled isolation chip；

The first input transmitting-receiving control signal that the first end of second light-coupled isolation chip connects the MCU by a resistance connects Mouthful and by a resistance eutral grounding, the second end of second light-coupled isolation chip is grounded, the of second light-coupled isolation chip First transmitting-receiving control signal interface of serial communication interface function switching circuit described in three-terminal link, the second light-coupled isolation core 4th end of piece connects the power supply of the serial communication interface function switching circuit；

The insulating power supply circuit and the electrical level transferring chip, mode switching signal isolation circuit, the first transmitting-receiving control signal Isolation circuit is electrically connected, and the signal for being received to it carries out isolated from power, is the electrical level transferring chip, mode switching signal Isolation circuit, the first transmitting-receiving control signal isolation circuit provide driving voltage.

9. a kind of serial communication interface function switching method, based on a kind of serial logical described in any one in claim 1 to 8 Communication interface function switching circuit is performed, it is characterised in that including：

First function switching method：

Control the mode switching signal interface for low level by the MCU, control the first transmitting-receiving control signal interface For low level so that it is high level that the first of first electrical level transferring chip, which receives and enable signaling interface, and described first sends Enable signaling interface is low level, and the second of the second electrical level conversion chip sends enable signaling interface for low level, described It is low level that the second of second electrical level conversion chip, which receives and enable signaling interface,；

Second function switching method：

Control the mode switching signal interface for low level by the MCU, control the first transmitting-receiving control signal interface For high level so that it is high level that the first of first electrical level transferring chip, which receives and enable signaling interface, and described first sends Enable signaling interface is low level, and the second of the second electrical level conversion chip sends enable signaling interface for high level, described It is high level that the second of second electrical level conversion chip, which receives and enable signaling interface,；

3rd function switching method：

Control the mode switching signal interface for high level by the MCU, control the first transmitting-receiving control signal interface For low level so that it is low level that the first of first electrical level transferring chip, which receives and enable signaling interface, and described first sends Enable signaling interface is high level, and the second of the second electrical level conversion chip sends enable signaling interface for low level, described It is high level that the second of second electrical level conversion chip, which receives and enable signaling interface,；

4th function switching method：

Control the mode switching signal interface for high level by the MCU, control the first transmitting-receiving control signal interface For high level so that it is low level that the first of first electrical level transferring chip, which receives and enable signaling interface, and described first sends Enable signaling interface is high level, and the second of the second electrical level conversion chip sends enable signaling interface for low level, described It is high level that the second of second electrical level conversion chip, which receives and enable signaling interface,.

10. a kind of serial communication interface function switching method according to claim 9, it is characterised in that first work( Energy switching method also includes：Five-function switching submethod, the 6th function switching submethod；

The five-function switching submethod includes controlling the mode switching signal interface to be low level, control by the MCU The first transmitting-receiving control signal interface is made to be low level, control the second transmitting-receiving control signal interface to be high level so that It is high level that the first of first electrical level transferring chip, which receives and enable signaling interface, and described first, which sends enable signaling interface, is Low level, the second of the second electrical level conversion chip sends enable signaling interface for low level, and the second electrical level changes core It is low level that the second of piece, which receives and enable signaling interface, and the 3rd of the 3rd electrical level transferring chip, which sends enable signaling interface, is High level；

The 6th function switching submethod includes controlling the mode switching signal interface to be low level, control by the MCU The first transmitting-receiving control signal interface is made to be low level, control the second transmitting-receiving control signal interface to be low level so that It is high level that the first of first electrical level transferring chip, which receives and enable signaling interface, and described first, which sends enable signaling interface, is Low level, the second of the second electrical level conversion chip sends enable signaling interface for low level, and the second electrical level changes core It is low level that the second of piece, which receives and enable signaling interface, and the 3rd of the 3rd electrical level transferring chip, which sends enable signaling interface, is Low level.