CN105740183B - Serial port communication circuit - Google Patents
Serial port communication circuit Download PDFInfo
- Publication number
- CN105740183B CN105740183B CN201610049934.3A CN201610049934A CN105740183B CN 105740183 B CN105740183 B CN 105740183B CN 201610049934 A CN201610049934 A CN 201610049934A CN 105740183 B CN105740183 B CN 105740183B
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- Prior art keywords
- serial communication
- level
- voltage stabilizing
- voltage
- processor
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Classifications
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F13/00—Interconnection of, or transfer of information or other signals between, memories, input/output devices or central processing units
- G06F13/38—Information transfer, e.g. on bus
- G06F13/382—Information transfer, e.g. on bus using universal interface adapter
- G06F13/385—Information transfer, e.g. on bus using universal interface adapter for adaptation of a particular data processing system to different peripheral devices
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F13/00—Interconnection of, or transfer of information or other signals between, memories, input/output devices or central processing units
- G06F13/38—Information transfer, e.g. on bus
- G06F13/42—Bus transfer protocol, e.g. handshake; Synchronisation
- G06F13/4282—Bus transfer protocol, e.g. handshake; Synchronisation on a serial bus, e.g. I2C bus, SPI bus
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
- H02H9/02—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess current
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
- H02H9/04—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess voltage
- H02H9/045—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess voltage adapted to a particular application and not provided for elsewhere
- H02H9/047—Free-wheeling circuits
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F2213/00—Indexing scheme relating to interconnection of, or transfer of information or other signals between, memories, input/output devices or central processing units
- G06F2213/0002—Serial port, e.g. RS232C
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F2213/00—Indexing scheme relating to interconnection of, or transfer of information or other signals between, memories, input/output devices or central processing units
- G06F2213/38—Universal adapter
- G06F2213/3852—Converter between protocols
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- Engineering & Computer Science (AREA)
- Theoretical Computer Science (AREA)
- Physics & Mathematics (AREA)
- General Engineering & Computer Science (AREA)
- General Physics & Mathematics (AREA)
- Power Engineering (AREA)
- Emergency Protection Circuit Devices (AREA)
Abstract
The invention discloses a serial port communication circuit, which comprises a first processor serial port communication end and a second processor serial port communication end level conversion module, wherein the first processor serial port communication end is connected with a first bus; and the level conversion module is used for converting the level between the serial port communication end of the first processor and the serial port communication end of the second processor. And the level conversion module is respectively connected with the first processor serial port communication end and the second processor serial port communication end. The invention can solve the problem of level mismatching in serial port communication from hardware, provides convenience for serial port debugging, adds protective circuits at both ends of a chip for preventing components from being damaged by lightning stroke and overlarge surge current, and adds voltage stabilizing circuits at power supply positions at both ends to serve as secondary protection of the circuit and prevent voltage instability under heavy current.
Description
Technical field
The present invention relates to electronic communication field, more particularly to a kind of serial communication circuit.
Background technology
Universal serial port (UART) has powerful vitality as a kind of simple, applicable communication interface.Various new
In the case of communication modes emerge in an endless stream, universal serial port (UART) still plays irreplaceable role in communication field.
In embedded development, software and hardware development engineer is often downloaded, debugs and is tracked with universal serial port (UART), so
And when in use, it is frequently encountered level mismatch problem, charged plug occurs sparkling and chip breakdown, voltage instability is caused to lead
The problems such as communication data is caused to lose, much bothers to AccessPort, calibration tape.
At present, a kind of automatic identification and communication system based on serial ports level, it is integrated with this mainly by integrated control chip
Control the chip NOR gate circuit being connected and the level sampling being connected with NOR gate circuit protection circuit composition.This
Although method can solve level mismatch problem, it is mainly used for the mating terminal device of secure payment, it is necessary in same system
It uses on system or same pcb board, and is not applied to for backboard insertion serial communication, and in prior art circuits, only use
General-purpose diode carries out the protection of circuit, without pressure stabilization function and Anti-surging electric current, lightning stroke etc., to the protection of chip far from
It is enough.
The content of the invention
It, can only be in same system or same PCB with solution the object of the present invention is to provide a kind of serial communication circuit
The enterprising line level of plate matches and due to the impact to system such as surge current, lightning stroke；The technical issues of reducing circuit safety.
For realization more than goal of the invention, the present invention provides a kind of serial communication circuit, including first processor serial communication
End, second processor serial communication end and level switch module；The level switch module includes the first level input, the
Two level inputs and level conversion unit；Wherein, the input voltage of the second electrical level input terminal is greater than or equal to described
The input voltage of first level input；The level conversion unit respectively with the first level input, second electrical level input terminal,
First processor serial communication end and the connection of second processor serial communication end；
The level conversion unit, for by the first level input incoming level and second electrical level input terminal incoming level
Mutually converted.
Further, the serial communication circuit further includes the first protection module and the second protection module；Described first
Protection module is connected respectively with first processor serial communication end and level conversion unit, second protection module respectively with
Second processor serial communication end and level conversion unit connection；
First protection module and the second protection module, for being protected to telecommunication circuit.
Further, the serial communication circuit further includes the first Voltage stabilizing module and the second Voltage stabilizing module；Described first
Voltage stabilizing module is connected respectively with the first level input and level conversion unit, and second Voltage stabilizing module is electric with second respectively
Flat input terminal and level conversion unit connection；
First Voltage stabilizing module and the second Voltage stabilizing module, for carrying out voltage stabilizing to incoming level.
Further, the level conversion unit includes field-effect tube, first resistor, second resistance, 3rd resistor, described
The source electrode of field-effect tube is connected respectively with one end of first resistor and first processor serial communication end, the first resistor
The other end is connected respectively with one end of second resistance and the first level input, the other end of the second resistance and field-effect
The grid connection of pipe, the drain electrode of the field-effect tube connect respectively with one end of 3rd resistor and second processor serial communication end
It connects, the other end of the 3rd resistor is connected with second electrical level input terminal.
Further, first protection module includes the first transient voltage suppressor diode, second protection module
Including the second transient voltage suppressor diode；
One end of first transient voltage suppressor diode leads to respectively with the source electrode of field-effect tube, first processor serial ports
Believe one end connection of end and first resistor, the other end of first transient voltage suppressor diode is connected with simulation；The
One end of two transient voltage suppressor diodes is electric with the drain electrode of field-effect tube, second processor serial communication end and the 3rd respectively
One end connection of resistance, the other end of second transient voltage suppressor diode are connected with simulation.
Further, first Voltage stabilizing module includes the first zener diode, and second Voltage stabilizing module includes second
Zener diode；
The cathode of first zener diode is electric with the first level input, one end of first resistor and second respectively
One end connection of resistance, the anode of first zener diode are connected with simulation, the cathode point of second zener diode
One end not with second electrical level input terminal, 3rd resistor is connected, and the anode of second zener diode is connected with simulation.
Further, first zener diode and the second zener diode are Zener diodes..
Compared with prior art, the beneficial effects of the invention are as follows：
1st, the technical solution of level conversion is carried out to processor serial port telecommunication circuit with level switch module, is obtained
With serial ports level, fast response time and technique effect simple in structure.
2nd, the technical solution protected with protection module telecommunication circuit, obtaining prevents lightning stroke and surge current pair
Circuit damages or the technique effect of interference.
3rd, the technical solution of voltage stabilizing is carried out to level input with Voltage stabilizing module, obtaining prevents level input electric current
The excessive technique effect for causing component damage.
Description of the drawings
Fig. 1 is the main block diagram of the serial communication circuit of the present invention；
Fig. 2 is that the serial communication circuit of the present invention includes the block diagram of protection module；
Fig. 3 is that the serial communication circuit of the present invention includes the block diagram of Voltage stabilizing module.
Fig. 4 is the physical circuit figure of the serial communication circuit of the present invention.
In figure, first processor serial communication end 1；Second processor serial communication end 2；Level switch module 3, wherein
First level input 31, second electrical level input terminal 32, level conversion unit 33；First protection module 4；Second protection module 5；
First Voltage stabilizing module 6；Second Voltage stabilizing module 7.
Specific embodiment
The invention will be further described in the following with reference to the drawings and specific embodiments.
Specific embodiment 1：
As shown in Figure 1, the present invention provides a kind of serial communication circuit, including first processor serial communication end 1, second
Processor serial port communication ends 2 and level switch module 3；
Wherein, level switch module 3 includes the first level input 31, second electrical level input terminal 32 and level conversion list
Member 33；The input voltage of second electrical level input terminal 32 is greater than or equal to the input voltage of the first level input 31；Level conversion
Unit 33 respectively at the first level input 31, second electrical level input terminal 32, first processor serial communication end 1 and second
Reason device serial communication end 2 connects；
Level conversion unit 33, for 31 incoming level of the first level input and second electrical level input terminal 32 to be inputted electricity
It is flat mutually to be converted.
Specifically, when needing using serial communication circuit, to the first level input 31 and second electrical level input terminal
32 incoming levels, level conversion unit 33 can solve 31 voltage of the first level input and 32 voltage of second electrical level input terminal it
Between level bi-directional conversion problem.
When the transmitting terminal at first processor serial communication end 1 is high level, pass through level switch module 3, second processing
Device serial communication end 2 will also become high level, when the transmitting terminal at first processor serial communication end 1 is low level, pass through electricity
Flat modular converter 3, second processor serial communication end 2 will also become low level；
When the receiving terminal at second processor serial communication end 2 is high level, pass through level switch module 3, the first processing
Device serial communication end 1 will give tacit consent to high level, when the receiving terminal at second processor serial communication end 2 is low level, pass through level
Modular converter 3, first processor serial communication end 1 will also become low level.
Embodiment 2：
It is further improved as shown in Fig. 2, being done on the basis of embodiment 1 to serial communication circuit, serial communication circuit
Further include the first protection module 4 and the second protection module 5；First protection module 4 respectively with first processor serial communication end 1
And level conversion unit 33 connects, the second protection module 5 respectively with second processor serial communication end 2 and level conversion list
Member 33 connects；
First protection module 4 and the second protection module 5, for being protected to telecommunication circuit；
Specifically, in the serial communication circuit course of work, after instantaneous voltage is more than circuit normal working voltage, the
Avalanche breakdown will occur for one protection module 4 or the second protection module 5, so as to be supplied to the logical of one super-low impedance of transient current
Road, the result is that transient current is drawn away by the first protection module 4 or the second protection module 5, so as to avoid protected device,
And make to be always maintained at blanking voltage by protective loop before voltage recovers normal value.After this, when transient pulse terminates
After, to high-impedance state, entire circuit enters normal voltage shape for automatic recovery again for the first protection module 4 or the second protection module 5
State.It is connect respectively at first processor serial communication end 1 and second processor serial communication end 2 there are one protection circuit, prevents wave
It is too big to gush electric current, damages level switch module and two processors, improves the security performance of circuit.
Embodiment 3：
It is further improved as shown in figure 3, being done on the basis of embodiment 2 to serial communication circuit, serial communication circuit
Further include the first Voltage stabilizing module 6 and the second Voltage stabilizing module 7；First Voltage stabilizing module 6 respectively with the first level input 31 and
Level conversion unit 33 connects, second Voltage stabilizing module 7 respectively with second electrical level input terminal 32 and level conversion unit 33
Connection；
First Voltage stabilizing module 6 and the second Voltage stabilizing module 7, for carrying out voltage stabilizing to incoming level；
Specifically, regulator circuit operates mainly in reverse bias area, before voltage does not reach breakdown voltage, the first voltage stabilizing
Electric current generation is not had on 6 or second Voltage stabilizing module 7 of module, but when revers voltage reaches breakdown voltage, each small electric
The increase of pressure will generate sizable electric current, and the voltage at the both ends of the first Voltage stabilizing module 6 and the second Voltage stabilizing module 7 is just at this time
A quite small voltage value of variable quantity can be held in, so as to play pressure stabilization function.
Embodiment 4：
It is further embodied as shown in figure 4, being done on the basis of embodiment 3 to serial communication circuit, level conversion list
Member 33 includes the source electrode difference of field-effect tube Q1, first resistor R1, second resistance R2,3rd resistor R3, the field-effect tube Q1
Be connected with one end of first resistor R1 and first processor serial communication end 1, the other end of the first resistor R1 respectively with
One end of second resistance R2 and the first level input 31 connect, and the other end of the second resistance R2 is with field-effect tube Q1's
Grid connect, the field-effect tube Q1 drain electrode respectively with one end of 3rd resistor R3 and second processor serial communication end 2
Connection, the other end of the 3rd resistor R3 are connected with second electrical level input terminal 32；
First protection module 4 includes the one the second transient voltage suppressor diode D4, and the second protection module 5 includes transient state electricity
Constrain diode D4 processed；
One end of the one the second transient voltage suppressor diode D4 respectively with the source electrode of field-effect tube Q1, the first processing
Device serial communication end 1 and the connection of one end of first resistor R1, the one the second transient voltage suppressor diode D4's is another
End is connected with simulation；One end of transient voltage suppressor diode D4 respectively with the drain electrode of field-effect tube Q1, second processor string
Port communications end 2 and the connection of one end of 3rd resistor R3, the other end and the simulation ground of the transient voltage suppressor diode D4 connect
It connects；
First Voltage stabilizing module 6 includes the first zener diode D1, and the second Voltage stabilizing module 7 includes the second zener diode D2；
The cathode of the first zener diode D1 respectively with the first level input 31, first resistor R1 one end and
One end connection of second resistance R2, the anode of the first zener diode D1 are connected with simulation, two pole of the second voltage stabilizing
The one end of the cathode of pipe D2 respectively with second electrical level input terminal 32,3rd resistor R3 is connected, the second zener diode D2's
Anode is connected with simulation.
Specifically, by taking the level bi-directional conversion between carrying out 3.3V-5V as an example, in actual work, the input of the first level
31 input 3.3V of end, second electrical level input terminal 32 input 5V.
3.3V turns the 5V circuit courses of work：
When the TX ends at first processor serial communication end 1 are high level, due to the Vgs=0 of field-effect tube, so field is imitated
Should pipe cut-off, pull-up 3rd resistor R3 the RX ends at second processor serial communication end 2 are pulled to high level.
When the TX ends at first processor serial communication end 1 are low level, due to the Vgs of field-effect tube>0, field-effect tube
Vds>0, so field-effect tube turns on, then the RX ends at second processor serial communication end 2 are also low level.
5V turns the 3.3V circuit courses of work：
When the RX ends at second processor serial communication end 2 are high level, field-effect tube is ended, then first processor serial ports
The TX ends of communication ends 1 are high level；
When the RX ends at second processor serial communication end 2 are low level, the diode current flow in field-effect tube, then first
The TX ends of processor serial port communication ends 1 are low level.
In the present invention, what the first protection module 4 and the second protection module 5 used is Transient Voltage Suppressor (following letter
Claim：" TVS "), have the response time is fast, transient power is big, leakage current is low, breakdown voltage deviation is small, clamp voltage be relatively easy to control,
Without damage limit, it is small the advantages that, when instantaneous voltage be more than circuit normal working voltage after, avalanche breakdown will occur for TVS, from
And the access of one super-low impedance of transient current is supplied to, the result is that transient current is drawn away by TVS, so as to avoid being protected
Device is protected, and makes to be always maintained at blanking voltage by protective loop before voltage recovers normal value.After this, when instantaneous arteries and veins
After punching terminates, TVS diode is recovered automatically to high-impedance state again, and entire circuit enters normal voltage state.In the first processing
Device serial communication end 1 and second processor serial communication end 2 are connect respectively there are one TVS pipe, can prevent that surge current is too big, are damaged
Field-effect tube and two processor chips improve the security performance of circuit.
In the present invention, it is the first zener diode D1 that the first Voltage stabilizing module 6, which uses, and the second Voltage stabilizing module 7, which uses, is
The cathode of second zener diode D2, the first zener diode D1 is connected on the first level input 31 that level is 3.3V.It is optional
The zener diode for being SMBJ5914B with concrete model, characteristic are：Voltage of voltage regulation is 3.6V, and certain allowance is left compared with 3.3V,
Pressure stabilization function is primarily served, similarly, the cathode of the second zener diode D2 is connected on the second electrical level input terminal 32 that level is 5V.It can
The zener diode that concrete model is SMBJ5914B is selected, characteristic is：Voltage of voltage regulation is 5.6V, and certain allowance is left compared with 5V,
Primarily serve pressure stabilization function.Before voltage does not reach breakdown voltage, electric current generation is not had on diode, but works as revers voltage
When reaching breakdown voltage, the increase of each small voltage will generate sizable electric current, and the voltage at diode both ends is just at this time
A quite small voltage value of variable quantity can be held in, so as to play pressure stabilization function, needs reversal connection in circuit.
It is above-mentioned simply by taking 3.3V and 5V as an example, but the first level input 31 and second electrical level input terminal 32 can be arbitrary
Level value, premise is greater than or equal to the first level input 31 for second electrical level input terminal 32, then by the steady of zener diode
Piezoelectricity presses desirable value and carries out type selecting, this circuit structure is simple, it can be achieved that level conversion between serial ports, and with preventing surge
Electric current and the protection circuit of voltage stabilizing, provide a convenient for AccessPort.
In addition to the implementation, the present invention can also have other embodiment, all to use equivalent substitution or equivalent transformation shape
Into technical solution, all fall within the present invention claims protection domain in.
Claims (7)
1. a kind of serial communication circuit, special including first processor serial communication end and second processor serial communication end
Sign is, further includes level switch module, the level switch module include the first level input, second electrical level input terminal with
And level conversion unit；Wherein, the input voltage of the second electrical level input terminal is greater than or equal to first level input
Input voltage；The level conversion unit respectively with the first level input, second electrical level input terminal, first processor serial ports
Communication ends and the connection of second processor serial communication end；
The level conversion unit, for the first level input incoming level and second electrical level input terminal incoming level to be carried out
Mutually conversion；
The level conversion unit includes field-effect tube, first resistor, second resistance, 3rd resistor, the source of the field-effect tube
Pole is connected respectively with one end of first resistor and first processor serial communication end, the other end of the first resistor respectively with
One end of second resistance and the connection of the first level input, the other end of the second resistance and the grid of field-effect tube connect
It connecing, the drain electrode of the field-effect tube is connected respectively with one end of 3rd resistor and second processor serial communication end, and described
The other end of three resistance is connected with second electrical level input terminal.
2. serial communication circuit as described in claim 1, which is characterized in that the serial communication circuit further includes the first protection
Module and the second protection module；First protection module respectively with first processor serial communication end and level conversion list
Member connection, second protection module are connected respectively with second processor serial communication end and level conversion unit；
First protection module and the second protection module, for being protected to telecommunication circuit.
3. serial communication circuit as described in claim 1, which is characterized in that the serial communication circuit further includes the first voltage stabilizing
Module and the second Voltage stabilizing module；First Voltage stabilizing module connects respectively with the first level input and level conversion unit
It connects, second Voltage stabilizing module is connected respectively with second electrical level input terminal and level conversion unit；
First Voltage stabilizing module and the second Voltage stabilizing module, for carrying out voltage stabilizing to incoming level.
4. serial communication circuit as claimed in claim 2, which is characterized in that the serial communication circuit further includes the first voltage stabilizing
Module and the second Voltage stabilizing module；First Voltage stabilizing module connects respectively with the first level input and level conversion unit
It connects, second Voltage stabilizing module is connected respectively with second electrical level input terminal and level conversion unit；
First Voltage stabilizing module and the second Voltage stabilizing module, for carrying out voltage stabilizing to incoming level.
5. serial communication circuit as claimed in claim 4, which is characterized in that first protection module includes the first transient state electricity
Constrain diode processed, second protection module includes the second transient voltage suppressor diode；
One end of first transient voltage suppressor diode respectively with the source electrode of field-effect tube, first processor serial communication end
And one end connection of first resistor, the other end of first transient voltage suppressor diode are connected with simulation；Second wink
One end of state voltage suppression diode respectively with the drain electrode of field-effect tube, second processor serial communication end and 3rd resistor
One end connects, and the other end of second transient voltage suppressor diode is connected with simulation.
6. serial communication circuit as claimed in claim 5, which is characterized in that first Voltage stabilizing module includes the first voltage stabilizing two
Pole pipe, second Voltage stabilizing module include the second zener diode；
The cathode of first zener diode respectively with the first level input, one end of first resistor and second resistance
One end connects, and the anode of first zener diode with simulating is connected, the cathode of second zener diode respectively with
One end connection of second electrical level input terminal, 3rd resistor, the anode of second zener diode are connected with simulation.
7. serial communication circuit as claimed in claim 6, which is characterized in that first zener diode and the second voltage stabilizing
Diode is Zener diode.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201610049934.3A CN105740183B (en) | 2016-01-25 | 2016-01-25 | Serial port communication circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201610049934.3A CN105740183B (en) | 2016-01-25 | 2016-01-25 | Serial port communication circuit |
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| Publication Number | Publication Date |
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| CN105740183A CN105740183A (en) | 2016-07-06 |
| CN105740183B true CN105740183B (en) | 2018-05-18 |
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| CN201610049934.3A Active CN105740183B (en) | 2016-01-25 | 2016-01-25 | Serial port communication circuit |
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Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108345552A (en) * | 2018-02-24 | 2018-07-31 | 上海康斐信息技术有限公司 | The input/output control circuit of serial communication |
| CN110412911B (en) * | 2019-07-15 | 2024-04-05 | 广东爱美信电器有限公司 | Serial port communication level matching circuit and intelligent control system |
| CN112104230B (en) * | 2020-08-10 | 2021-08-24 | 广州亚美智造科技有限公司 | Vehicle-mounted voltage reduction device and vehicle-mounted system |
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| CN200950538Y (en) * | 2006-09-30 | 2007-09-19 | 湖南威科电力仪表有限公司 | RS-485 Communication interface protective circuit |
| CN202160203U (en) * | 2011-06-30 | 2012-03-07 | 青岛海信移动通信技术股份有限公司 | Level switch circuit and communication switch interface |
| CN103138739A (en) * | 2013-03-22 | 2013-06-05 | 福建联迪商用设备有限公司 | Serial port level conversion method and circuit |
| CN203660524U (en) * | 2014-01-03 | 2014-06-18 | 西安星展测控科技有限公司 | RS232 and RS422 signal converter possessing serial port protection function |
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2016
- 2016-01-25 CN CN201610049934.3A patent/CN105740183B/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN200950538Y (en) * | 2006-09-30 | 2007-09-19 | 湖南威科电力仪表有限公司 | RS-485 Communication interface protective circuit |
| CN202160203U (en) * | 2011-06-30 | 2012-03-07 | 青岛海信移动通信技术股份有限公司 | Level switch circuit and communication switch interface |
| CN103138739A (en) * | 2013-03-22 | 2013-06-05 | 福建联迪商用设备有限公司 | Serial port level conversion method and circuit |
| CN203660524U (en) * | 2014-01-03 | 2014-06-18 | 西安星展测控科技有限公司 | RS232 and RS422 signal converter possessing serial port protection function |
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| Publication number | Publication date |
|---|---|
| CN105740183A (en) | 2016-07-06 |
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