CN113422599A - RS485 automatic receiving and transmitting control device and communication equipment - Google Patents
RS485 automatic receiving and transmitting control device and communication equipment Download PDFInfo
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- CN113422599A CN113422599A CN202110714564.1A CN202110714564A CN113422599A CN 113422599 A CN113422599 A CN 113422599A CN 202110714564 A CN202110714564 A CN 202110714564A CN 113422599 A CN113422599 A CN 113422599A
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- 238000004891 communication Methods 0.000 title claims abstract description 12
- 230000002457 bidirectional effect Effects 0.000 claims description 24
- 239000003990 capacitor Substances 0.000 claims description 23
- 239000011324 bead Substances 0.000 claims description 22
- 230000001960 triggered effect Effects 0.000 abstract description 8
- 230000001052 transient effect Effects 0.000 description 21
- 230000001629 suppression Effects 0.000 description 18
- 230000005540 biological transmission Effects 0.000 description 9
- 238000010586 diagram Methods 0.000 description 4
- 238000001914 filtration Methods 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 238000007599 discharging Methods 0.000 description 1
- 230000002452 interceptive effect Effects 0.000 description 1
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03K—PULSE TECHNIQUE
- H03K19/00—Logic circuits, i.e. having at least two inputs acting on one output; Inverting circuits
- H03K19/0175—Coupling arrangements; Interface arrangements
- H03K19/017509—Interface arrangements
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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
- G06F13/42—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
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Abstract
The invention relates to the technical field of communication, and provides an RS485 automatic receiving and transmitting control device and communication equipment, wherein the circuit comprises: an RS485 transceiver and a monostable trigger circuit; and the data transmitting end is connected with the input end of the monostable trigger circuit, the data transmitting end is also used for receiving a TX signal, the data receiving end is used for outputting an RX signal, the enabling end is connected with the output end of the monostable trigger circuit, and the first differential bus end and the second differential bus end are used for being connected with the 485 bus. According to the invention, the monostable characteristic of the monostable trigger circuit is adopted, the monostable trigger is triggered when the device sends data to the superior device, so that the RS485 transceiver is always in a sending state, the RS485 is automatically switched into a receiving state when the superior device does not send data, the automatic switching of the RS485 receiving and sending states is realized through hardware, software control is not needed, and the difficulty of system software development is reduced.
Description
Technical Field
The invention belongs to the technical field of communication, and particularly relates to an RS485 automatic receiving and transmitting control device and communication equipment.
Background
The RS485 interface is a serial bus based on balanced transmission and differential reception, and is widely applied to many industrial fields. When the RS485 works in a half-duplex mode, only sending or receiving can be carried out at the same time, and the sending and receiving directions need to be controlled to carry out complete interactive communication, so that normal receiving and sending are ensured.
In the prior art, software is usually adopted to control the receiving and sending of the RS485, so that the difficulty of system software development is increased.
Disclosure of Invention
In view of this, embodiments of the present invention provide an RS485 automatic transceiver control device and a communication device, so as to solve the problem in the prior art that software is used to control the RS485 transceiver, which increases difficulty in system software development.
The first aspect of the embodiments of the present invention provides an RS485 automatic transceiver control device, including: an RS485 transceiver and a monostable trigger circuit;
and the data transmitting end is connected with the input end of the monostable trigger circuit, the data transmitting end is also used for receiving a TX signal, the data receiving end is used for outputting an RX signal, the enabling end is connected with the output end of the monostable trigger circuit, and the first differential bus end and the second differential bus end are used for being connected with the 485 bus.
Optionally, the monostable trigger circuit includes: 555 timer, switch unit, first capacitor, second capacitor, first resistor, second resistor and third resistor;
a 555 timer, wherein a low level trigger end is respectively connected with the first end of the first resistor, the control end of the switch unit and the input end of the monostable trigger circuit, a voltage control end is connected with the first end of the first capacitor, a high level trigger end is respectively connected with the first end of the switch unit, the first end of the second capacitor, the first end of the second resistor and the discharge end of the 555 timer, an output end is respectively connected with the first end of the third resistor and the output end of the monostable trigger circuit, a power supply end is connected with the first power supply end, and a ground end is grounded;
the second end of the first capacitor, the second end of the second capacitor and the second end of the switch unit are all grounded;
the second end of the first resistor is connected with a second power supply end; the second end of the second resistor and the second end of the third resistor are both connected with the first power supply end.
Optionally, the switch unit includes: the first switch tube, the second switch tube, the fourth resistor, the fifth resistor and the sixth resistor;
the first end of the first switch tube is connected with the first end of the fourth resistor and the control end of the second switch tube respectively, the second end of the first switch tube is grounded, and the control end of the first switch tube is connected with the first end of the fifth resistor and the first end of the sixth resistor respectively;
the first end of the second switch tube is connected with the first end of the switch unit, and the second end of the second switch tube is grounded;
the second end of the sixth resistor is connected with the control end of the switch unit;
the second end of the fourth resistor is connected with the first power supply end; the second end of the fifth resistor is grounded.
Optionally, the first switch tube and the second switch tube are both NPN-type triodes.
Optionally, the apparatus further comprises: a bus matching circuit;
and a first end of the bus matching circuit is connected with a first differential bus end of the RS485 transceiver, a second end of the bus matching circuit is connected with a second differential bus end of the RS485 transceiver, and a third end and a fourth end of the bus matching circuit are used for being connected with the 485 bus.
Optionally, the bus matching circuit includes: the first magnetic bead, the second magnetic bead, the seventh resistor, the eighth resistor, the thirteenth resistor, the first bidirectional transient suppression diode and the second bidirectional transient suppression diode;
the first end of the first magnetic bead is connected with the first end of the seventh resistor, the first end of the thirteenth resistor and the second end of the bus matching circuit respectively, and the second end of the first magnetic bead is connected with the first end of the first bidirectional transient suppression diode and the third end of the bus matching circuit respectively;
a first end of the second magnetic bead is connected with a first end of the eighth resistor, a second end of the thirteenth resistor and a first end of the bus matching circuit respectively, and a second end of the second magnetic bead is connected with a first end of the second bidirectional transient suppression diode and a fourth end of the bus matching circuit respectively;
the second end of the seventh resistor is connected with the first power supply end;
the second end of the eighth resistor, the second end of the first bi-directional transient suppression diode and the second end of the second bi-directional transient suppression diode are all grounded.
Optionally, the bus matching circuit further includes: a third bidirectional transient suppression diode;
and the first end of the third bidirectional transient suppression diode is connected with the second end of the first magnetic bead, and the second end of the third bidirectional transient suppression diode is connected with the second end of the second magnetic bead.
Optionally, the apparatus further comprises: a reception matching circuit;
and a first end of the receiving matching circuit is connected with a data receiving end of the RS485 transceiver, and a second end of the receiving matching circuit is used for outputting an RX signal.
Optionally, the receiving matching circuit includes: the first diode, the second diode, the ninth resistor, the tenth resistor and the eleventh resistor;
the anode of the first diode is connected with the first end of the tenth resistor, the first end of the eleventh resistor and the second end of the receiving matching circuit respectively, and the cathode of the first diode is connected with the cathode of the second diode and the first end of the ninth resistor respectively;
a second end of the tenth resistor is connected with the second power supply end;
the second end of the ninth resistor is connected with the first end of the receiving matching circuit;
the second end of the eleventh resistor and the anode of the second diode are both grounded.
A second aspect of the embodiments of the present invention provides a communication device, including any one of the RS485 automatic transmission and reception control apparatuses in the first aspect of the embodiments of the present invention.
The embodiment of the invention provides an RS485 automatic receiving and transmitting control device and communication equipment, wherein the device comprises: an RS485 transceiver and a monostable trigger circuit; and the data transmitting end is connected with the input end of the monostable trigger circuit, the data transmitting end is also used for receiving a TX signal, the data receiving end is used for outputting an RX signal, the enabling end is connected with the output end of the monostable trigger circuit, and the first differential bus end and the second differential bus end are used for being connected with the 485 bus. According to the monostable characteristic of the monostable trigger circuit, the monostable trigger is triggered when the superior device sends data, the monostable trigger outputs a first level which can be a high level for example, so that the RS485 transceiver is always in a sending state, and when the superior device does not send data, the monostable trigger outputs a second level which can be a low level for example, the RS485 transceiver is automatically switched to a receiving state, so that the RS485 transceiver is automatically switched to the receiving state, the automatic switching of the RS485 transceiver state is realized through hardware, software control is not needed, and the difficulty in system software development is reduced.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive exercise.
Fig. 1 is a schematic circuit structure diagram of an RS485 automatic transceiver control device according to an embodiment of the present invention;
fig. 2 is a schematic circuit structure diagram of another RS485 automatic transceiver control device according to an embodiment of the present invention;
fig. 3 is a schematic circuit diagram of an RS485 automatic transceiver control device according to an embodiment of the present invention;
fig. 4 is a waveform diagram of input and output signals of the monostable flip-flop circuit according to the embodiment of the invention.
Detailed Description
In the following description, for purposes of explanation and not limitation, specific details are set forth, such as particular system structures, techniques, etc. in order to provide a thorough understanding of the embodiments of the invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present invention with unnecessary detail.
In order to explain the technical means of the present invention, the following description will be given by way of specific examples.
Referring to fig. 1, the embodiment of the present invention provides an RS485 automatic transceiving control device, including: an RS485 transceiver U1 and a monostable trigger circuit 11;
the RS485 transceiver U1 comprises a data sending end (4 pins) connected with the input end of the monostable trigger circuit 11, the data sending end (4 pins) is also used for receiving a TX signal (UART _ TX), a data receiving end (1 pin) is used for outputting an RX signal (UART _ RX), enabling ends (2 pins and 3 pins) are connected with the output end of the monostable trigger circuit 11, and a first differential bus end (7 pins) and a second differential bus end (6 pins) are used for being connected with a 485 bus.
The monostable trigger circuit is a basic pulse unit circuit with two working states of a steady state and a transient state. When no external signal is triggered, the circuit is in a steady state. Under the trigger of an applied signal, the circuit is turned from a steady state to a transient state, and after the Tw time, the circuit automatically returns to the steady state again.
According to the characteristic of the monostable trigger circuit, when the upper-level equipment sends data, the monostable trigger circuit is triggered, the monostable trigger circuit is turned to a temporary stable state and outputs a first level, for example, the first level can be a high level, and an RS485 transceiver U1 is enabled and is in a sending state; during the time Tw, if the upper device continues to transmit data, the monostable trigger circuit is always in a steady state, and the RS485 transceiver U1 is always in a transmission state. When the superior device stops sending data, the monostable trigger circuit is not triggered any more, returns to a steady state after the time Tw, outputs a second level, for example, the second level can be a low level, and the RS485 is automatically switched to a receiving state; according to the embodiment of the invention, the automatic switching of the RS485 receiving and transmitting states is realized through hardware according to the characteristics of the monostable trigger circuit, software control is not needed, and the difficulty of system software development is reduced. Meanwhile, when the upper-level equipment sends data, the RS485 transceiver U1 is always in a sending state, the bus driving capacity is strong, the sending distance is long, and the performance is good.
In some embodiments, the RS485 transceiver U1 may be model SN65HVD3082 EDR.
The enabling end of the RS485 transceiver U1 may include a first enabling end (pin 2) and a second enabling end (pin 3); the first enable terminal and the second enable terminal are both connected to the output terminal of the monostable flip-flop 11.
In some embodiments, referring to fig. 3, the monostable flip-flop circuit 11 may include: a 555 timer U2, a switch unit 111, a first capacitor C1, a second capacitor C2, a first resistor R1, a second resistor R2 and a third resistor R3;
555 timer U2, low level trigger end (2 pin) is connected with the first end of the first resistor R1, the control end of the switch unit 111 and the input end of the monostable trigger circuit 11 respectively, voltage control end (5 pin) is connected with the first end of the first capacitor C1, high level trigger end (6 pin) is connected with the first end of the switch unit 111, the first end of the second capacitor C2, the first end of the second resistor R2 and the discharge end (7 pin) of the 555 timer U2 respectively, output end (3 pin) is connected with the first end of the third resistor R3 and the output end of the monostable trigger circuit 11 respectively, power supply ends (4 pin and 8 pin) are connected with the first power supply end VCC _5V, and ground end (1 pin) is grounded;
the second end of the first capacitor C1, the second end of the second capacitor C2 and the second end of the switch unit 111 are all grounded;
a second terminal of the first resistor R1 is connected to a second power supply terminal VCC _3V 3; the second terminal of the second resistor R2 and the second terminal of the third resistor R3 are both connected to the first power terminal VCC _ 5V.
Referring to fig. 4, the 555 timer U2 is triggered at the falling edge of the TX signal, the 555 timer U2 is in a transient state, and the output terminal outputs a high level. The second falling edge is triggered again in the time Tw (that is, in the charging and discharging time of the second capacitor C2), and still outputs a high level, and the RS485 transceiver U1 is in a transmitting state; when the TX signal is not sent any more, the 555 timer U2 cannot be triggered again at the Tw time, the voltage of the second capacitor C2 continuously rises, and when the voltage of the second capacitor C2 reaches the preset voltage, the 555 timer U2 outputs a low level, and the RS485 transceiver U1 is in a receiving state. The delay time Tw can be adjusted by the second resistor R2 and the second capacitor C2 to meet the actual application requirement. For example, the Tw period is not less than 10bit data bit width.
In some embodiments, referring to fig. 3, the switching unit 111 may include: the circuit comprises a first switch tube Q1, a second switch tube Q2, a fourth resistor R4, a fifth resistor R5 and a sixth resistor R6;
a first switch tube Q1, a first end of which is connected to the first end of the fourth resistor R4 and the control end of the second switch tube Q2, respectively, a second end of which is grounded, and a control end of which is connected to the first end of the fifth resistor R5 and the first end of the sixth resistor R6, respectively;
a second switching tube Q2, having a first end connected to the first end of the switching unit 111 and a second end grounded;
a second end of the sixth resistor R6 is connected to the control end of the switch unit 111;
a second terminal of the fourth resistor R4 is connected to the first power supply terminal VCC _ 5V; the second terminal of the fifth resistor R5 is connected to ground.
In some embodiments, the first switch Q1 and the second switch Q2 may be NPN transistors.
When the TX signal is at a high level, the first switch Q1 is turned on, the second switch Q2 is turned off, and the switch unit 111 is turned off; when the TX signal is at a low level, the first switch Q1 is turned off, the second switch Q2 is turned on, and the switch unit 111 is turned on.
In some embodiments, referring to fig. 2, the RS485 automatic transmission and reception control device may further include: a bus matching circuit 12;
and a first end of the bus matching circuit 12 is connected with a first differential bus end of the RS485 transceiver U1, a second end of the bus matching circuit is connected with a second differential bus end of the RS485 transceiver U1, and a third end and a fourth end of the bus matching circuit are used for being connected with a 485 bus.
The bus matching circuit 12 is used for output matching, and improves the anti-interference capability and transmission distance of the device.
In some embodiments, referring to fig. 3, bus matching circuit 12 may include: a first magnetic bead L1, a second magnetic bead L2, a seventh resistor R7, an eighth resistor R8, a thirteenth resistor R13, a first bidirectional transient suppression diode TVS1, and a second bidirectional transient suppression diode TVS 2;
a first magnetic bead L1, a first end of which is connected to the first end of the seventh resistor R7, the first end of the thirteenth resistor R13, and the second end of the bus matching circuit 12, respectively, and a second end of which is connected to the first end of the first bidirectional transient suppression diode TVS1 and the third end of the bus matching circuit 12, respectively;
a second magnetic bead L2, a first end of which is connected to the first end of the eighth resistor R8, the second end of the thirteenth resistor R13, and the first end of the bus matching circuit 12, and a second end of which is connected to the first end of the second bidirectional transient suppression diode TVS2 and the fourth end of the bus matching circuit 12, respectively;
a second terminal of the seventh resistor R7 is connected to the first power supply terminal VCC _ 5V;
the second terminal of the eighth resistor R8, the second terminal of the first bidirectional transient suppression diode TVS1, and the second terminal of the second bidirectional transient suppression diode TVS2 are all grounded. In some embodiments, referring to fig. 3, the bus matching circuit 12 may further include: a third bidirectional transient suppression diode TVS 3;
a third bidirectional transient suppression diode TVS3, having a first terminal connected to the second terminal of the first bead L1 and a second terminal connected to the second terminal of the second bead L2.
In the embodiment of the invention, the seventh resistor R7 is configured as a pull-up resistor, the eighth resistor R8 is configured as a pull-down resistor, and the thirteenth resistor R13 is used for matching, so that the transmission distance of signals can be effectively increased. The first magnetic bead L1 and the second magnetic bead L2 are used for filtering high-frequency noise on a transmission path, and the anti-interference capability of the device is improved. The first and second bidirectional transient suppression diodes TVS1 and TVS2 are used for preventing surge, and the safety of the device is improved.
In some embodiments, referring to fig. 2, the RS485 automatic transmission and reception control device may further include: a reception matching circuit 13;
and a first end of the receiving matching circuit 13 is connected with a data receiving end of the RS485 transceiver U1, and a second end is used for outputting an RX signal.
In some embodiments, referring to fig. 3, the reception matching circuit 13 includes: a first diode D1, a second diode D2, a ninth resistor R9, a tenth resistor R10, and an eleventh resistor R11;
a first diode D1 having an anode connected to the first terminal of the tenth resistor R10, the first terminal of the eleventh resistor R11, and the second terminal of the receiving matching circuit 13, and a cathode connected to the cathode of the second diode D2 and the first terminal of the ninth resistor R9;
a second terminal of the tenth resistor R10 is connected to the second power supply terminal VCC _3V 3;
a second end of the ninth resistor R9 is connected to a first end of the reception matching circuit 13;
the second terminal of the eleventh resistor R11 and the anode of the second diode D2 are both grounded.
In some embodiments, referring to fig. 3, the RS485 automatic transmission and reception control device may further include: a third capacitance C3;
a third capacitor C3, having a first terminal connected to the first power terminal VCC _5V and a second terminal connected to ground. For power supply filtering.
In some embodiments, referring to fig. 3, the apparatus may further include: a twelfth resistor R12;
and a twelfth resistor R12, a first end of which is connected with the data transmitting end (pin 4) of the RS485 transceiver U1, and a second end of which is connected with the input end of the monostable trigger circuit 11.
Corresponding to any one of the RS485 automatic transceiving control devices, an embodiment of the present invention further provides a communication device, which includes any one of the RS485 automatic transceiving control devices and has advantages of the RS485 automatic transceiving control device, and details are not repeated herein.
The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications and substitutions do not substantially depart from the spirit and scope of the embodiments of the present invention, and are intended to be included within the scope of the present invention.
Claims (10)
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| CN202110714564.1A CN113422599A (en) | 2021-06-25 | 2021-06-25 | RS485 automatic receiving and transmitting control device and communication equipment |
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| CN202110714564.1A CN113422599A (en) | 2021-06-25 | 2021-06-25 | RS485 automatic receiving and transmitting control device and communication equipment |
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Cited By (3)
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| CN113848788A (en) * | 2021-09-27 | 2021-12-28 | 厦门四信通信科技有限公司 | Expansion circuit, system and control method |
| CN113985851A (en) * | 2021-10-29 | 2022-01-28 | 雅迪科技集团有限公司 | Electric vehicle locator communication circuit with bus protection and anti-interference functions |
| CN114006835A (en) * | 2021-11-01 | 2022-02-01 | 南京四方亿能电力自动化有限公司 | RS485 communication interface online self-diagnosis system based on specific code element identification technology |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113848788A (en) * | 2021-09-27 | 2021-12-28 | 厦门四信通信科技有限公司 | Expansion circuit, system and control method |
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| CN113985851B (en) * | 2021-10-29 | 2024-03-08 | 雅迪科技集团有限公司 | Electric vehicle positioner communication circuit with bus protection and anti-interference functions |
| CN114006835A (en) * | 2021-11-01 | 2022-02-01 | 南京四方亿能电力自动化有限公司 | RS485 communication interface online self-diagnosis system based on specific code element identification technology |
| CN114006835B (en) * | 2021-11-01 | 2023-10-20 | 南京四方亿能电力自动化有限公司 | RS485 communication interface on-line self-diagnosis system based on specific code element identification technology |
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Application publication date: 20210921 |