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Half-duplex automatic receiving-transmitting switching circuit of RS485

An automatic switching, half-duplex technology, applied in the direction of electrical digital data processing, instruments, computers, etc., can solve the problems of time delay, slow data sending and receiving, etc.

Inactive Publication Date: 2010-06-02
北京东方信联科技有限公司
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0016] Therefore, every time you switch the working state of the RS485 communication chip, you need to change the level of the control pin R / D of the MCU, which will cause the entire data to be sent and received slowly, resulting in a time delay

Method used

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  • Half-duplex automatic receiving-transmitting switching circuit of RS485
  • Half-duplex automatic receiving-transmitting switching circuit of RS485
  • Half-duplex automatic receiving-transmitting switching circuit of RS485

Examples

Experimental program
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Effect test

Embodiment 1

[0051] see figure 2 , which is a structural diagram of the first embodiment of the RS485 half-duplex transceiver automatic switching circuit of the present invention.

[0052]In this embodiment, the TXD of the MCU is connected to the RS485 communication chip through the current limiting resistor R4 and then through the transistor Q1.

[0053] The TXD of the MCU is connected to the base of the transistor Q1 through the current limiting resistor R4.

[0054] The emitter of the triode Q1 is grounded; the collector of the triode is connected to the / RE pin and the DE pin of the RS485 communication chip, and the collector is connected to the power supply VCC through the third resistor R3.

[0055] The DI pin of the RS485 communication chip is grounded; the RO is connected to the RXD pin of the MCU; the A pin is connected to VCC through the first resistor R1; the B pin is connected to the ground through the second resistor R2. At the same time, the A pin and the B pin are connect...

Embodiment 2

[0071] see image 3 , which is a structural diagram of the second embodiment of the RS485 half-duplex transceiver automatic switching circuit of the present invention.

[0072] In this embodiment, the TXD of the MCU is also connected to the RS485 communication chip through the current limiting resistor R4 and then through the transistor Q1.

[0073] The TXD of the MCU is connected to the base of the transistor Q1 through the current limiting resistor R4.

[0074] The emitter of the triode Q1 is grounded; the collector of the triode is connected to the / RE pin and the DE pin of the RS485 communication chip, and the collector is connected to the power supply VCC through the third resistor R3.

[0075] The DI pin of the RS485 communication chip is connected to the TXD of the MCU; the RO is connected to the RXD pin of the MCU; the A pin is connected to VCC through the first resistor R1; the B pin is connected to the ground through the second resistor R2. At the same time, the A ...

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Abstract

The invention provides a half-duplex automatic receiving-transmitting switching circuit of an RS485, which comprises a microprocessor, an RS 485 communication chip and an RS 485 bus, wherein the data receiving pin of the microprocessor is connected with the receiver output end of the RS 485 communication chip; the data transmitting pin of the microprocessor is connected with the base of a triode through a current-limiting resistor; the collector of the triode is connected with the receiver output enabling end and a transmitter output enabling end of the RS 485 communication chip, and is connected with a power supply through a third resistor at the same time; the emitter of the triode is earthed; the transmitter input end of the RS 485 communication chip is earthed; the pin A of the RS 485 communication is connected with the power supply through a pull-up resistor; and the pin B of the RS 485 communication chip is earthed through a pull-down resistor. The half-duplex automatic receiving-transmitting switching circuit of the RS485 provided by the invention can automatically switch the working states of transmitting and receiving.

Description

technical field [0001] The invention relates to the technical field of communication interfaces, in particular to an RS485 half-duplex transceiver automatic switching circuit. Background technique [0002] Half-duplex (Half Duplex) data transmission means that data can be transmitted in both directions of a signal carrier, but cannot be transmitted at the same time. Specifically, it means that at any moment in the communication process, information can be transmitted from M to N, and from N to M, but at the same time, it can only be transmitted in one direction. When using the half-duplex mode, the transmitter and receiver at each end of the communication system are switched to the communication line through the receiving / transmitting switch to switch the direction, so time delay will occur. [0003] The RS485 standard is a half-duplex communication protocol. RS485 is suitable for both the sender and receiver to share a pair of lines for communication, and it is also suita...

Claims

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Application Information

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IPC IPC(8): G06F13/40G06F15/163
Inventor 胡玉斌韩大庆徐罕聪
Owner 北京东方信联科技有限公司
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