Circuit for converting single-path USART serial port communication into multi-path RS485 communication

Abstract

The utility model belongs to the technical field of long-distance communication, and aims to solve the problem of converting USART (Universal Synchronous Asynchronous Receiver Transmitter) communication into multi-path RS485 communication. According to the circuit for converting the single-path USART serial port communication into the multi-path RS485 communication, a main control circuit is connected with an X interface and is used for providing an RS485 read-write direction signal; the IIC and USART circuit is connected between the X interface and the analog switch circuit and is used for controlling USART channel selection through an IIC signal; the analog switch circuit is connected between the I IC and USART circuit and the USART to RS485 circuit and is used for realizing gating of one path of USART to multiple paths of RS485, the USART to RS485 circuit is also connected with the X interface, and the USART to RS485 circuit is used for realizing conversion between a USART signal and an RS485 signal. Through the combination of the main control circuit, the X interface, the I IC, the USART circuit, the analog switch circuit, the USART to RS485 circuit and the power supply circuit, single-path USART serial port communication can be converted into multi-path RS485 communication.

Description

Technical Field

[0001] This utility model belongs to the field of long-distance communication technology, specifically relating to a single-channel USART serial communication to multi-channel RS485 communication circuit. Background Technology

[0002] The RS485 communication protocol boasts advantages such as long-distance transmission capability, multi-device connectivity, strong anti-interference capability, and simplified cabling requirements. USART is a full-duplex universal synchronous / asynchronous serial transceiver module; this interface is a highly flexible serial communication device. Currently, in fields such as industrial automation, remote monitoring, data acquisition and control systems, and intelligent buildings, the demand for long-distance, multi-device connectivity, and high anti-interference capabilities is increasing.

[0003] How to convert USART communication to multiple RS485 communication channels has become an urgent problem to be solved. Utility Model Content

[0004] In order to solve at least one of the above-mentioned technical problems in the prior art, this utility model provides a single-channel USART serial communication to multi-channel RS485 communication circuit.

[0005] This utility model is implemented using the following technical solution: a single-channel USART serial communication to multi-channel RS485 communication circuit, including a main control circuit, an X interface, an IIC and USART circuit, an analog switch circuit, a USART to RS485 circuit, and a power supply circuit; wherein the main control circuit is connected to the X interface to provide RS485 read / write direction signals; the IIC and USART circuit is connected between the X interface and the analog switch circuit to control the USART channel selection through the IIC signal; the analog switch circuit is connected between the IIC and USART circuit and the USART to RS485 circuit to enable the selection of one of the multiple channels of USART to RS485; the USART to RS485 circuit is also connected to the X interface to convert USART signals to RS485 signals; the power supply circuit is connected to the X interface, the IIC and USART circuit, the analog switch circuit, and the USART to RS485 circuit to provide the voltage required by the internal circuit.

[0006] Preferably, the control chip for the IIC and USART circuits is TCA9555PWR, powered by an external +3.3V power supply. The input +3.3V power supply is regulated and filtered by capacitor C61. The SDA and SCL pins of the TCA9555PWR chip are connected to the +3.3V power supply through weak pull-up resistors R163 and R164. The A0, A1, and A2 pins of the TCA9555PWR chip are connected to GND through pull-down resistors R17, R21, and R25. The P00-P07 and P10-P17 pins of the TCA9555PWR chip are connected to the USART select signal, respectively.

[0007] Preferably, multiple TCA9555 devices can share the same I2C bus by configuring the high and low levels of the A0, A1, and A2 pins of the TCA9555PWR chip.

[0008] Preferably, the control chip for the analog switch circuit is a 74HC4066. The E pin of the 74HC4066 chip is connected to the USART channel selection signal; the Y and Z pins of the 74HC4066 chip are connected to the USART read / write signal and the USART read / write selection signal, respectively.

[0009] Preferably, the control chip for the USART to RS485 conversion circuit is SP3485, powered by an external +3.3V power supply. The input +3.3V power supply is regulated and filtered by capacitor C5. The RO and DI terminals of the SP3485 chip are connected to the USART read / write signals, respectively. The #RE and DE terminals of the SP3485 chip are connected to the RS485 direction control signals. The A terminal of the SP3485 chip is connected to the pull-up bias resistor R13 for the RS485 signal, and the B terminal is connected to the pull-down bias resistor R3 for the RS485 signal, and is connected to the A terminal through the matching resistor R9.

[0010] Preferably, the power supply circuit uses a TPS563202 to convert the externally input +5V voltage to +3.3V.

[0011] Compared with the prior art, the beneficial effects of this utility model are:

[0012] This application, through the combination of a main control circuit, an X interface, an IIC and USART circuit, an analog switch circuit, a USART to RS485 converter circuit, and a power supply circuit, can realize the conversion of single-channel USART serial communication to multi-channel RS485 communication. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1 This is a structural block diagram of this embodiment;

[0015] Figure 2 This is the IIC and USART selection circuit diagram of this embodiment;

[0016] Figure 3 This is the analog switch circuit diagram of this embodiment;

[0017] Figure 4 This is the circuit diagram for the USART to RS485 converter in this embodiment. Detailed Implementation

[0018] The technical solutions of the present utility model will be clearly and completely described in conjunction with the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other implementation methods obtained by those skilled in the art without creative effort are within the protection scope of the present utility model.

[0019] It should be noted that the structures, proportions, sizes, etc., shown in the accompanying drawings of this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed in the specification, and are not intended to limit the conditions under which this utility model can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportional relationships, or adjustments to the size, without affecting the effects and purposes that this utility model can produce, should fall within the scope of the technical content disclosed in this utility model. It should be noted that in this specification, relational terms such as "first" and "second" are only used to distinguish one entity from several other entities, and do not necessarily require or imply any actual relationship or order between these entities.

[0020] This utility model provides an embodiment:

[0021] A single-channel USART serial communication to multi-channel RS485 communication circuit is characterized by comprising a main control circuit, an X interface, an IIC and USART circuit, an analog switch circuit, a USART to RS485 circuit, and a power supply circuit. The main control circuit is connected to the X interface to provide RS485 read / write direction signals. The IIC and USART circuit is connected between the X interface and the analog switch circuit to control USART channel selection via IIC signals. The analog switch circuit is connected between the IIC and USART circuit and the USART to RS485 circuit to enable selection of one channel of the multi-channel RS485 communication. The USART to RS485 circuit is also connected to the X interface and is used to convert USART signals to RS485 signals. The power supply circuit is connected to the X interface, the IIC and USART circuit, the analog switch circuit, and the USART to RS485 circuit to provide the voltage required by the internal circuitry.

[0022] In this embodiment, the control chip for the IIC and USART circuits is the TCA9555PWR, powered by an external +3.3V power supply. The input +3.3V power supply is regulated and filtered by capacitor C61. The SDA and SCL pins of the TCA9555PWR chip are connected to the +3.3V power supply through weak pull-up resistors R163 and R164, configuring the register to select the address and enabling the 16-bit I / O interface as an output, thereby realizing the selection of the 16-bit USART signal by the IIC signal. The power supply circuit uses a TPS563202 to convert the external +5V voltage to +3.3V. The A0, A1, and A2 pins of the TCA9555PWR chip are connected to GND through pull-down resistors R17, R21, and R25. The P00~P07 and P10~P17 pins of the TCA9555PWR chip are connected to the USART selection signal, respectively.

[0023] When implementing single-channel USART to multi-channel RS485 conversion using IIC and USART circuits, expansion is required. By configuring the high and low levels of pins A0, A1, and A2 of the TCA9555PWR, up to 8 TCA9555 devices can share the same IIC bus, which means that a maximum of 128 channels of RS485 communication can be converted from a single-channel USART serial communication.

[0024] The control chip for the analog switch circuit is 74HC4066. The chip's four enable pins 1 to 4E are connected to the USART channel selection signal, and the independent pins 1 to 4Y are connected to the USART read / write signal and 1 to 4Z are connected to the USART read / write selection signal. When the USART channel selection signal is high, the USART read / write signal is connected to the read / write selection signal, realizing the conversion between level signals.

[0025] The control chip for the USART to RS485 converter is the SP3485, powered by an external +3.3V power supply. The +3.3V input is regulated and filtered by capacitor C5. The chip's RO pin is connected to the USART read signal, and the DI pin is connected to the USART write signal. The USART to RS485 converter operates on a half-duplex communication model, allowing only data transmission or reception at a time. The RS485 direction signal provided by the main control circuit is connected to pins #RE and DE. By controlling the high and low levels of the #RE and DE pins, the direction of data transmission varies with the level, thus enabling data transmission and reception. The SP3485 chip's A terminal is connected to an RS485 signal pull-up bias resistor R13, and its B terminal is connected to an RS485 signal pull-down bias resistor R3, both connected to the A terminal via a matching resistor R9 to enhance system stability.

[0026] The above description is merely a preferred embodiment of this utility model, but the protection scope of this utility model is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this utility model should be included within the protection scope of this utility model. Therefore, the protection scope of this utility model should be determined by the scope of the claims.

Claims

1. A circuit for converting single-channel USART serial communication to multi-channel RS485 communication, characterized in that: Includes main control circuit, X interface, IIC and USART circuit, analog switch circuit, USART to RS485 converter circuit and power supply circuit; The main control circuit is connected to the X interface to provide RS485 read / write direction signals. The IIC and USART circuits are connected between the X interface and the analog switch circuit to control the USART channel selection via the IIC signal. The analog switch circuit is connected between the IIC and USART circuits and the USART to RS485 circuit to enable the selection of one of the multiple RS485 channels from the USART. The USART to RS485 circuit is also connected to the X interface and is used to convert USART signals to RS485 signals. The power supply circuit is connected to the X interface, the IIC and USART circuits, the analog switch circuit, and the USART to RS485 circuit to provide the voltage required by the internal circuits.

2. The single-channel USART serial communication to multi-channel RS485 communication circuit according to claim 1, characterized in that: The control chip for the IIC and USART circuits is the TCA9555PWR, which is powered by an external +3.3V power supply. The input +3.3V power supply is regulated and filtered by capacitor C61. The SDA and SCL pins of the TCA9555PWR chip are connected to the +3.3V power supply through weak pull-up resistors R163 and R164. The A0, A1, and A2 pins of the TCA9555PWR chip are connected to GND through pull-down resistors R17, R21, and R25. The P00-P07 and P10-P17 pins of the TCA9555PWR chip are connected to the USART select signal, respectively.

3. The single-channel USART serial communication to multi-channel RS485 communication circuit according to claim 2, characterized in that: By configuring the high and low levels of the A0, A1, and A2 pins of the TCA9555PWR chip, multiple TCA9555 devices can share the same I2C bus.

4. The single-channel USART serial communication to multi-channel RS485 communication circuit according to claim 3, characterized in that: The control chip for the analog switch circuit is 74HC4066. The E pin of the 74HC4066 chip is connected to the USART channel select signal; the Y and Z pins of the 74HC4066 chip are connected to the USART read / write signal and the USART read / write select signal, respectively.

5. The single-channel USART serial communication to multi-channel RS485 communication circuit according to claim 4, characterized in that: The control chip for the USART to RS485 converter is SP3485, powered by an external +3.3V power supply. The input +3.3V power supply is regulated and filtered by capacitor C5. The RO and DI terminals of the SP3485 chip are connected to the USART read / write signals, respectively. The #RE and DE terminals of the SP3485 chip are connected to the RS485 direction control signals. The A terminal of the SP3485 chip is connected to the pull-up bias resistor R13 for the RS485 signal, and the B terminal is connected to the pull-down bias resistor R3 for the RS485 signal, and is connected to the A terminal through the matching resistor R9.

6. The single-channel USART serial communication to multi-channel RS485 communication circuit according to claim 5, characterized in that: The power supply circuit uses TPS563202 to convert the external input +5V voltage to +3.3V.

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