CN102184153A - RS-485 transmitting-receiving automatic conversion circuit - Google Patents
RS-485 transmitting-receiving automatic conversion circuit Download PDFInfo
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- CN102184153A CN102184153A CN2011100927254A CN201110092725A CN102184153A CN 102184153 A CN102184153 A CN 102184153A CN 2011100927254 A CN2011100927254 A CN 2011100927254A CN 201110092725 A CN201110092725 A CN 201110092725A CN 102184153 A CN102184153 A CN 102184153A
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Abstract
The invention discloses an RS-485 transmitting-receiving automatic conversion circuit which comprises an RS-485 transmitting-receiving circuit and a monostable trigger, wherein the RS-485 transmitting-receiving circuit consists of an RS-485 chip U1, the monostable trigger consists of a 555 timer U2, and the monostable trigger controls the conversion of the receiving and transmitting states of the RS-485 transmitting-receiving circuit. By using the circuit disclosed by the invention, the complexity of programming is reduced, and because the zero delay of RS-485 transmitting and receiving data conversion is realized by virtue of hardware, the reliability of RS-485 data transmission is improved.
Description
Technical field
The present invention relates to a kind of based on hard-wired RS-485 transmitting-receiving automatic switching circuit.
Background technology
RS-485 is a kind of serial communication link layer protocol that transmits based on differential signal, and it has solved the too near defective of RS-232 protocol transmission distance, be industrial extensive employing than the long distance data communications link layer protocol.Because it uses a pair of twisted-pair feeder to transmit differential signal, belongs to half-duplex operation, so need receive conversion with transmit status.The RS-485 chip is in accepting state usually, in the time will sending data, is made it to wait for after transmission finishes by software the RS-485 chip being transformed into accepting state again into sending data mode by software control RS-485 chip.The particular register that finishes generally by UART of transmission provides the state indication, perhaps sends about required time by the software data estimator, time-delay a period of time guarantee data send finish after, be transformed into accepting state again.
When receiving and dispatching conversion with software control RS-485, there is following problem: during by the transmitting-receiving of software control data conversion, be converted to when receiving data sending data, have certain transfer delay, wanting to send data and real sending between the data, there is certain transfer delay; If the conversion opportunity that software control sends and receives is improper, then can cause loss of data; During receiving by software control and sending data-switching, introduce easily and disturb, make the UART unit receive unnecessary hash.
Summary of the invention
Receive and dispatch the problems referred to above that conversion exists for solving software control RS-485, the invention provides a kind of RS-485 transmitting-receiving automatic switching circuit, its technical scheme of taking is:
This circuit comprises RS-485 transmission circuit that is made of RS-485 chip U1 and the monostalbe trigger that is made of 555 timer U2, the conversion of monostalbe trigger control RS-485 transmission circuit accepting state and transmit status.
In the RS-485 transmission circuit, 4 pin of RS-485 chip U1 are that data send pin, 1 pin is the Data Receiving pin, 4 pin are connected Data Out pin and the Data In pin with communication function single-chip microcomputer respectively with 1 pin, and 2 pin enable pin for receiving, and 3 pin enable pin for sending, 6 pin and 7 pin constitute the RS-485 differential bus, wherein 6 pin are received on power supply+5V by biasing resistor R1, and 7 pin are received power supply on the ground by biasing resistor R3, and meet terminal build-out resistor R2 between 6 pin and 7 pin; In monostalbe trigger, 6 pin and 7 pin of 555 timer U2 are received on power supply+5V by pull-up resistor R4, receive power supply on the ground by capacitor C 1, receive 2 pin by feedback diode D1, and 5 pin are received power supply on the ground by capacitor C 2; 3 pin of 555 timer U2 are received 2 pin and 3 pin of RS-485 chip U1, and 2 pin of 555 timer U2 are received 4 pin of RS-485 chip U1; When the negative edge of Single-chip Controlling Data Out arrives, the 3 pin output high level of U2, U1 becomes transmit status, when Data Out remains low level, 3 pin of U2 remain high level always, U1 also is a transmit status always, thereby U1 sends the logical zero state of Data Out, when the rising edge of Data Out arrives, U2 picks up counting, the 3 pin output low levels of time-delay back U2, and U1 becomes accepting state, biasing resistor R1 and R3 draw state into logical one to the RS-485 differential bus, thereby U1 continues the logical one state of Data Out is sent.
This circuit has reduced the complexity of programming, has realized that by hardware RS-485 receives and send the zero propagation of data-switching, has improved the RS-485 reliability of data transmission.
Description of drawings
Accompanying drawing is a circuit diagram of the present invention.
Embodiment
The present invention will be further described below in conjunction with accompanying drawing:
As shown in the figure, in the RS-485 transmission circuit, the model of RS-485 chip U1 can be selected 75176B for use, its 4 pin are that data send pin, 1 pin is the Data Receiving pin, 4 pin and 1 pin are connected the Data Out pin and the DataIn pin of single-chip microcomputer or other control circuit respectively, the single-chip microcomputer model can be selected the 80C51 single-chip microcomputer for use, and it has communication function, can carry out exchanges data by 485 buses, 2 pin of U1 enable pin for receiving, 3 pin enable pin for sending, and 6 pin and 7 pin constitute the RS-485 differential bus, and wherein 6 pin are received on power supply+5V by biasing resistor R1,7 pin are received power supply on the ground by biasing resistor R3, and meet terminal build-out resistor R2 between 6 pin and 7 pin.In monostalbe trigger, 6 pin and 7 pin of 555 timer U2 are received on power supply+5V by pull-up resistor R4, receive power supply on the ground by capacitor C 1, and 6 pin are connected the positive pole of feedback diode D1 with 7 pin simultaneously, 2 pin connect the negative pole of feedback diode D1, and 5 pin are received power supply on the ground by capacitor C 2.3 pin of the 555 timer U2 of U2 are received 2 pin and 3 pin of RS-485 chip U1, and 2 pin of 555 timer U2 are received 4 pin of RS-485 chip U1.
When not sending data, will remain high level by monolithic processor controlled Data Out, 2 pin of U2 are high level, and output pin 3 pin of U2 are low level, thereby 2 pin of U1 and 3 pin are low level, and U1 is in accepting state.When sending data, because the start bit of data is low levels, when promptly Data Out is low level, 2 pin of U2 also are low level, and at this moment 3 pin of U2 are output as high level, thereby 2 pin of U1 and 3 pin also are high level, U1 will be in transmit status, and start bit will be sent on the RS-485 differential bus.In like manner, if the data bit that sends is a low level, U1 also will be in transmit status, and logical zero also will be sent on the RS-485 differential bus.If the data bit that sends is a high level, in the 40uS after the rising edge of Data Out arrives, the 3 pin output of U2 also is high level, U1 also is in transmit status, logical one will be sent on the RS-485 differential bus, and behind the 40uS, the output of 3 pin of U2 becomes low level, U1 becomes accepting state, the RS-485 differential bus is a high-impedance state, at this moment, and biasing resistor R1, R3 will draw state into logical one to the RS-485 differential bus, thereby U1 sends the logical one state of Data Out.Thereby realize the conversion of monostalbe trigger control RS-485 transmission circuit accepting state and transmit status.
Claims (3)
1. a RS-485 receives and dispatches automatic switching circuit, comprise RS-485 transmission circuit that constitutes by RS-485 chip U1 and the monostalbe trigger that constitutes by 555 timer U2, it is characterized in that: the conversion of monostalbe trigger control RS-485 transmission circuit accepting state and transmit status.
2. a kind of RS-485 transmitting-receiving automatic switching circuit according to claim 1, it is characterized in that: in the RS-485 transmission circuit, 4 pin of RS-485 chip U1 are that data send pin, 1 pin is the Data Receiving pin, 4 pin and 1 pin are connected the Data Out pin and the Data In pin of the single-chip microcomputer with communication function respectively, 2 pin enable pin for receiving, 3 pin enable pin for sending, 6 pin and 7 pin constitute the RS-485 differential bus, wherein 6 pin are received on power supply+5V by biasing resistor R1,7 pin are received power supply on the ground by biasing resistor R3, and meet terminal build-out resistor R2 between 6 pin and 7 pin; In monostalbe trigger, 6 pin and 7 pin of 555 timer U2 are received on power supply+5V by pull-up resistor R4, receive power supply on the ground by capacitor C 1, receive 2 pin by feedback diode D1, and 5 pin are received power supply on the ground by capacitor C 2; 3 pin of 555 timer U2 are received 2 pin and 3 pin of RS-485 chip U1, and 2 pin of 555 timer U2 are received 4 pin of RS-485 chip U1; When the negative edge of Single-chip Controlling Data Out arrives, the 3 pin output high level of U2, U1 becomes transmit status, when Data Out remains low level, 3 pin of U2 remain high level always, U1 also is a transmit status always, thereby U1 sends the logical zero state of Data Out, when the rising edge of Data Out arrives, U2 picks up counting, the 3 pin output low levels of time-delay back U2, and U1 becomes accepting state, biasing resistor R1 and R3 draw state into logical one to the RS-485 differential bus, thereby U1 continues the logical one state of Data Out is sent.
3. a kind of RS-485 transmitting-receiving automatic switching circuit according to claim 2, it is characterized in that: the model of described RS-485 chip U1 is 75176B.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2011100927254A CN102184153A (en) | 2011-04-01 | 2011-04-01 | RS-485 transmitting-receiving automatic conversion circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2011100927254A CN102184153A (en) | 2011-04-01 | 2011-04-01 | RS-485 transmitting-receiving automatic conversion circuit |
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| CN102184153A true CN102184153A (en) | 2011-09-14 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN2011100927254A Pending CN102184153A (en) | 2011-04-01 | 2011-04-01 | RS-485 transmitting-receiving automatic conversion circuit |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105207693A (en) * | 2015-09-30 | 2015-12-30 | 浙江锦马自动化科技有限公司 | RS485 repeater with pure hardware arbitration function |
| CN108599799A (en) * | 2018-03-20 | 2018-09-28 | 四川万益能源科技有限公司 | RS485 circuits and communication system |
| CN112838972A (en) * | 2020-12-31 | 2021-05-25 | 广州航天海特系统工程有限公司 | Enabling control method, device and equipment based on RS-485 transceiver and storage medium |
-
2011
- 2011-04-01 CN CN2011100927254A patent/CN102184153A/en active Pending
Non-Patent Citations (1)
| Title |
|---|
| JAN AXELSON: "Designing RS-485 Circuits", 《CIRCUIT CELLAR》 * |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105207693A (en) * | 2015-09-30 | 2015-12-30 | 浙江锦马自动化科技有限公司 | RS485 repeater with pure hardware arbitration function |
| CN105207693B (en) * | 2015-09-30 | 2017-08-04 | 浙江锦马自动化科技有限公司 | A kind of RS485 repeaters with pure hardware mediation function |
| CN108599799A (en) * | 2018-03-20 | 2018-09-28 | 四川万益能源科技有限公司 | RS485 circuits and communication system |
| CN108599799B (en) * | 2018-03-20 | 2024-04-23 | 四川万益能源科技有限公司 | RS485 circuit and communication system |
| CN112838972A (en) * | 2020-12-31 | 2021-05-25 | 广州航天海特系统工程有限公司 | Enabling control method, device and equipment based on RS-485 transceiver and storage medium |
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Application publication date: 20110914 |