CN213754497U - Self-adaptive RS485 automatic receiving and transmitting conversion circuit - Google Patents

Abstract

The utility model discloses an automatic receiving and dispatching converting circuit of self-adaptation RS485 includes high-speed opto-coupler isolating circuit, 485 chip basic circuits, 555 monostable timer and multichannel dial switch circuit. The high-speed optical coupler isolation circuit comprises two optical couplers, a plurality of resistors and a plurality of capacitors; the 485 chip basic circuit comprises a differential transceiver, a plurality of resistors and a plurality of resistors; the 555 monostable timer and the multi-channel dial switch circuit comprise a 555 chip, a diode, a plurality of resistors, a plurality of capacitors and a dial switch. The utility model discloses can realize long distance, high baud rate communication has the automatic receiving and dispatching of support hardware, and the function of long distance high speed communication and self-adaptation baud rate, and communication stability is good.

Description

Self-adaptive RS485 automatic receiving and transmitting conversion circuit

Technical Field

The utility model belongs to the technical field of the communication, concretely relates to 485 communication isolation circuits at electric energy acquisition terminal.

Background

The RS485 has the characteristics of strong common-mode interference resistance, long transmission distance, support of multi-node communication, easiness in network expansion and the like, and is a preferred serial interface in the industrial control industry. The RS485 communication interface circuit adopts a two-wire differential level mode for transmission and is in a half-duplex mode, so that the receiving and transmitting states need to be switched during communication. The existing hardware implementation scheme is based on NPN triode and other discrete components to control the commutation; the data transmitting end TXD is connected with the data input end of the transmitter, and is connected with the enabling ends of the transmitter and the receiver after the phase reversal of the triode, when the high level is transmitted, the transmitter is in a high-resistance state, the high level is realized by a pull-up resistor on the bus, when the low level is transmitted, the transmitter is opened, and the low level on the TXD is transmitted; because the high level is realized by a pull-up resistor, the driving capability is limited, and the scheme cannot be applied to the communication occasions with long distance and high baud rate due to the influence of the switching speed of the triode.

SUMMERY OF THE UTILITY MODEL

An object of the utility model is to avoid the weak point among the above-mentioned prior art and provide an automatic receiving and dispatching converting circuit of self-adaptation RS485, it can realize the circuit of long distance, high baud rate serial ports communication in electric energy collection terminal.

The adopted technical scheme is as follows: a self-adaptive RS485 automatic receiving and transmitting conversion circuit comprises a high-speed optical coupling isolation circuit, a 485 chip basic circuit, a 555 monostable timer and a multi-path dial switch circuit; the 555 monostable timer controls the 485 sending and receiving state conversion, and the multi-path dial switch can realize the flexible selection of different communication baud rates.

The high-speed optical coupler isolation circuit comprises an optical coupler U101, a resistor R105, a resistor R102, a capacitor C101, an optical coupler U102, a resistor R104, a resistor R106, a resistor R103 and a capacitor C102; 7 feet of optical coupler U101, 8 feet access supply terminal 5V, 2 feet access VDD5V of its input end, 3 feet are connected with MCU's data transmission foot through resistance R101, simultaneously access VDD5V through resistance R105, 6 feet output end and 485 chip basic circuit are connected, 5V is received through resistance R102 simultaneously, 7 feet of optical coupler U102, 8 feet access supply terminal 5V, 2 feet access VDD5V of its input end, 3 feet pass through resistance R104 and 485 chip basic circuit are connected, simultaneously access VDD5V through resistance R106, 6 feet of output end are connected with MCU's data reception foot, receive 5V through resistance R103 simultaneously.

The 485 chip basic circuit comprises a differential transceiver U103, a resistor R107, a capacitor C140, a capacitor C105, a resistor R110, a resistor R111, a capacitor C106, a capacitor C107 and a resistor R127; the 8 pins of the differential transceiver are connected with a power supply end 5V, the 6 pins are connected with the power supply end 5V through a resistor R110, the 7 pins are grounded through a resistor R111, the 6 pins and the 7 pins are respectively connected with a filter capacitor to the ground, a matching resistor R127 is connected between the 6 pins and the 7 pins, and the 5 pins are grounded; the pin 1 and the pin 4 are respectively connected with the output of the high-speed optocouplers U102 and U101.

The 555 monostable timer and the multi-channel dial switch circuit comprise a 555 chip U104, a diode V201, a resistor R126, a capacitor C142, a dial switch SW1, resistors R128-R133, capacitors C144-C149, a capacitor C108 and a capacitor C143; pins 6 and 7 of a 555 timer U104 are connected to a power supply 5V, resistors R128-R133 and capacitors C144-C149 are connected to a power supply ground through a dial switch SW1, a 2 pin is connected through a diode V201, a 4 pin of a 485 chip U103 is connected through a resistor R126, and a 5 pin is connected to the power supply ground through a capacitor C137; a pin 3 of the 555 timer U104 is connected to a pin 2 and a pin 3 of the 485 chip U103; when the falling edge of the start bit of the TXD is controlled by the MCU to arrive, the monostable timer U104 is triggered to enter a transient state, and the 3 pin outputs a high level, so that the 485 chip U103 becomes a transmitting state, and the diode V201 and the diode R126 form a discharging loop, so that the timer cannot be triggered again in the transmitting process of one frame of data; when the last falling edge of the TXD arrives, the U104 starts to time, the 3 pin of the U104 outputs low level after the time delay constant 1.1RC is reached, and the U103 becomes a receiving state to receive data from the differential bus. The RC parameter of the dial switch circuit is set according to different communication baud rates, and the delay time constant is slightly larger than 1 bit data bit width, which is not enough to cause the data frame format error of a receiving party.

The capacitor C102 is connected in parallel with a capacitor C1021, and a mechanical switch is installed on the pins at the two ends of the capacitor C1021. Because the accidental capacitor C102 can be damaged, in order to be maintained in time without a professional tool, the capacitor C1021 is replaced by the damaged capacitor C102 by opening the two mechanical switches, so that the quick recovery work is guaranteed.

Compared with the prior art, the utility model provides an accurate monostable timer control baud rate has following beneficial effect from the automatic receiving and dispatching converting circuit of RS 485:

(1) the whole circuit has a stable and isolated power supply system, isolation transmission of signals is realized by adopting high-speed optical coupler isolation, generation of high common mode voltage is effectively inhibited, the damage rate of 485 is greatly reduced, and the stability of the system is improved.

(2) The 555 timer is used for controlling the receiving and transmitting conversion to realize long-distance and high-baud rate communication; different communication baud rates can be selected by changing the position of the dial switch, and the function of self-adapting to the communication baud rate is realized.

Drawings

FIG. 1 is a schematic diagram of a basic circuit of a high-speed optical coupling isolation circuit and a 485 chip of the present invention;

fig. 2 is a schematic diagram of the monostable timer 555 and the multi-way dial switch circuit of the present invention.

Detailed Description

As shown in fig. 1 and fig. 2, the technical solution adopted by the present invention is: a self-adaptive RS485 automatic receiving and transmitting conversion circuit comprises a high-speed optical coupling isolation circuit, a 485 chip basic circuit, a 555 monostable timer and a multi-path dial switch circuit; the 555 monostable timer controls the 485 sending and receiving state conversion, and the multi-path dial switch can realize the flexible selection of different communication baud rates.

The high-speed optical coupler isolation circuit comprises an optical coupler U101, a resistor R105, a resistor R102, a capacitor C101, an optical coupler U102, a resistor R104, a resistor R106, a resistor R103 and a capacitor C102; 7 feet of optical coupler U101, 8 feet access supply terminal 5V, 2 feet access VDD5V of its input end, 3 feet are connected with MCU's data transmission foot through resistance R101, simultaneously access VDD5V through resistance R105, 6 feet output end and 485 chip basic circuit are connected, 5V is received through resistance R102 simultaneously, 7 feet of optical coupler U102, 8 feet access supply terminal 5V, 2 feet access VDD5V of its input end, 3 feet pass through resistance R104 and 485 chip basic circuit are connected, simultaneously access VDD5V through resistance R106, 6 feet of output end are connected with MCU's data reception foot, receive 5V through resistance R103 simultaneously.

The 485 chip basic circuit comprises a differential transceiver U103, a resistor R107, a capacitor C140, a capacitor C105, a resistor R110, a resistor R111, a capacitor C106, a capacitor C107 and a resistor R127; the 8 pins of the differential transceiver are connected with a power supply end 5V, the 6 pins are connected with the power supply end 5V through a resistor R110, the 7 pins are grounded through a resistor R111, the 6 pins and the 7 pins are respectively connected with a filter capacitor to the ground, a matching resistor R127 is connected between the 6 pins and the 7 pins, and the 5 pins are grounded; the pin 1 and the pin 4 are respectively connected with the output of the high-speed optocouplers U102 and U101.

The 555 monostable timer and the multi-channel dial switch circuit comprise a 555 chip U104, a diode V201, a resistor R126, a capacitor C142, a dial switch SW1, resistors R128-R133, capacitors C144-C149, a capacitor C108 and a capacitor C143; pins 6 and 7 of a 555 timer U104 are connected to a power supply 5V, resistors R128-R133 and capacitors C144-C149 are connected to a power supply ground through a dial switch SW1, a 2 pin is connected through a diode V201, a 4 pin of a 485 chip U103 is connected through a resistor R126, and a 5 pin is connected to the power supply ground through a capacitor C137; a pin 3 of the 555 timer U104 is connected to a pin 2 and a pin 3 of the 485 chip U103; when the falling edge of the start bit of the TXD is controlled by the MCU to arrive, the monostable timer U104 is triggered to enter a transient state, and the 3 pin outputs a high level, so that the 485 chip U103 becomes a transmitting state, and the diode V201 and the diode R126 form a discharging loop, so that the timer cannot be triggered again in the transmitting process of one frame of data; when the last falling edge of the TXD arrives, the U104 starts to time, the 3 pin of the U104 outputs low level after the time delay constant 1.1RC is reached, and the U103 becomes a receiving state to receive data from the differential bus. The RC parameter of the dial switch circuit is set according to different communication baud rates, and the delay time constant is slightly larger than 1 bit data bit width, which is not enough to cause the data frame format error of a receiving party.

The capacitor C102 is connected in parallel with a capacitor C1021, and a mechanical switch is installed on the pins at the two ends of the capacitor C1021. Because the accidental capacitor C102 can be damaged, in order to be maintained in time without a professional tool, the capacitor C1021 is replaced by the damaged capacitor C102 by opening the two mechanical switches, so that the quick recovery work is guaranteed.

Compared with the prior art, the utility model provides an accurate monostable timer control baud rate has following beneficial effect from the automatic receiving and dispatching converting circuit of RS 485:

(3) the whole circuit has a stable and isolated power supply system, isolation transmission of signals is realized by adopting high-speed optical coupler isolation, generation of high common mode voltage is effectively inhibited, the damage rate of 485 is greatly reduced, and the stability of the system is improved.

(4) The 555 timer is used for controlling the receiving and transmitting conversion to realize long-distance and high-baud rate communication; different communication baud rates can be selected by changing the position of the dial switch, and the function of self-adapting to the communication baud rate is realized.

Claims (2)

1. The utility model provides an automatic receiving and dispatching converting circuit of self-adaptation RS485 which characterized in that: the circuit comprises a high-speed optical coupling isolation circuit, a 485 chip basic circuit, a 555 monostable timer and a multi-path dial switch circuit; the high-speed optical coupler isolation circuit comprises an optical coupler U101, a resistor R105, a resistor R102, a capacitor C101, an optical coupler U102, a resistor R104, a resistor R106, a resistor R103 and a capacitor C102; the optical coupler U101 has 7 pins and 8 pins connected to a power supply terminal 5V, the input end 2 pin is connected to VDD5V, the 3 pin is connected to a data transmitting pin of the MCU through a resistor R101, and is connected to VDD5V through a resistor R105, the output end of the 6 pin is connected to a 485 chip basic circuit, and is connected to 5V through a resistor R102, the 7 pins and 8 pins of the optical coupler U102 are connected to the power supply terminal 5V, the input end 2 pin is connected to VDD5V, the 3 pin is connected to the 485 chip basic circuit through a resistor R104, and is connected to VDD5V through a resistor R106, the output end 6 pin is connected to a data receiving pin of the MCU, and is connected to 5V through a resistor R103; the 485 chip basic circuit comprises a differential transceiver U103, a resistor R107, a capacitor C140, a capacitor C105, a resistor R110, a resistor R111, a capacitor C106, a capacitor C107 and a resistor R127; the 8 pins of the differential transceiver are connected with a power supply end 5V, the 6 pins are connected with the power supply end 5V through a resistor R110, the 7 pins are grounded through a resistor R111, the 6 pins and the 7 pins are respectively connected with a filter capacitor to the ground, a matching resistor R127 is connected between the 6 pins and the 7 pins, and the 5 pins are grounded; pins 1 and 4 are respectively connected with the output of the optocoupler U102 and the output of the optocoupler U101; the 555 monostable timer and the multi-way toggle switch circuit comprise a 555 chip U104, a diode V201, a resistor R126, a capacitor C142, a toggle switch SW1, a resistor R128, a resistor R129, a resistor R130, a resistor R131, a resistor 132, a resistor R133, a capacitor C144, a capacitor C145, a capacitor C146, a capacitor C147, a capacitor C148, a capacitor C149, a capacitor C108 and a capacitor C143; pins 6 and 7 of a 555 timer U104 are connected to a power supply 5V, resistors R128-R133 and capacitors C144-C149 are connected to a power supply ground through a dial switch SW1, a 2 pin is connected through a diode V201, a 4 pin of a 485 chip U103 is connected through a resistor R126, and a 5 pin is connected to the power supply ground through a capacitor C137; the pin 3 of the 555 timer U104 is connected to the pin 2 and the pin 3 of the 485 chip U103.

2. The adaptive RS485 automatic transmit-receive conversion circuit according to claim 1, wherein: the capacitor C102 is connected in parallel with a capacitor C1021, and a mechanical switch is installed on the pins at the two ends of the capacitor C1021.

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