CN214900831U - Hardware multiplexing circuit based on UART communication - Google Patents

Abstract

The utility model discloses a hardware multiplexing circuit based on UART communication, including UART connecting circuit, RS485 level conversion chip, RS232 level conversion chip and DB9 interface. The UART connecting circuit comprises a diode D1, a diode D2 and a pull-up resistor R2, wherein the anode of the diode D1 and the anode of the diode D2 are connected with a UART _ RXD pin of the single chip microcomputer and are connected with 3V3 voltage through a pull-up resistor R2, the cathode of the diode D1 is connected with the UART _ RXD pin of the RS485 level conversion chip, and the cathode of the diode D2 is connected with the UART _ RXD pin of the RS232 level conversion chip. And the UART _ TXD pin of the RS485 level conversion chip and the UART _ TXD pin of the RS232 level conversion chip are connected with the UART _ TXD pin of the single chip microcomputer. Therefore, the problem that the UART interface resource of the single chip microcomputer is insufficient is solved.

Description

Hardware multiplexing circuit based on UART communication

Technical Field

The utility model relates to a technical field of UART communication, in particular to hardware multiplexing circuit based on UART communication.

Background

At present, when the single chip microcomputer is communicated with an RS232 chip and an RS485 chip, a UART interface is adopted for communication.

RS232 realizes full duplex by two wires, and the two wires are respectively arranged without mutual influence and can be carried out simultaneously; although the RS485 can implement full duplex by using four wires, it is rare in practical application that half duplex is implemented by using only two wires, and thus, switching between the "receiving state" and the "transmitting state" is involved, and the switching involves two situations:

1. the driver program already contains the accepting switch under the condition of half duplex, and the driver program can automatically switch according to the action of reading or writing. In this case, RS485 is programmed no different from RS 232.

2. The driver program does not have automatic switching, and at the moment, in order to complete the switching, an additional GPIO must be used to connect with the receiving enabling end of the RS485 transceiver module, and before data is received and sent, the enabling end is firstly set to enable the receiving enabling end to be in a correct receiving state or a correct sending state.

However, the number of the existing single chip microcomputer is generally 5 UART interfaces. When 485 and 232 chips are larger than the number of UART interfaces in the circuit, a single chip microcomputer is required to be added to meet the requirement, and the hardware cost is greatly increased.

SUMMERY OF THE UTILITY MODEL

Problem to prior art existence, the utility model aims at providing a hardware multiplexing circuit based on UART communication aims at solving the problem that the hardware cost increased when singlechip UART resource was not enough.

In order to achieve the above object, the utility model provides a hardware multiplexing circuit based on UART communication, including UART connecting circuit, RS485 level conversion chip, RS232 level conversion chip and DB9 interface;

the UART connecting circuit comprises a diode D1, a diode D2 and a pull-up resistor R2, wherein the anode of the diode D1 and the anode of the diode D2 are connected with a UART _ RXD pin of a singlechip, and are connected with 3V3 voltage through a pull-up resistor R2, the cathode of the diode D1 is connected with the UART _ RXD pin of an RS485 level conversion chip, and the cathode of the diode D2 is connected with the UART _ RXD pin of an RS232 level conversion chip;

and the UART _ TXD pin of the RS485 level conversion chip and the UART _ TXD pin of the RS232 level conversion chip are connected with the UART _ TXD pin of the singlechip.

The utility model discloses a set up UART connecting circuit between the UART interface of singlechip and RS485 level conversion chip and RS232 level conversion chip for RS485 level conversion chip and RS232 level conversion chip can multiplex a UART interface, thereby avoid the not enough problem of UART interface resource of singlechip.

Drawings

Fig. 1 is a schematic circuit diagram of an embodiment of the hardware multiplexing circuit based on UART communication according to the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work belong to the protection scope of the present invention.

Referring to fig. 1 of the specification, an embodiment of the present invention provides a hardware multiplexing circuit based on UART communication, which includes a single chip 100, a UART connection circuit 200, an RS485 level conversion chip 300, an RS232 level conversion chip 400, and a DB9 interface 500.

The UART connection circuit 200 includes a diode D1, a diode D2, and a pull-up resistor R2, wherein the anode of the diode D1 and the anode of the diode D2 are connected to the UART _ RXD pin of the monolithic computer 100 and are connected to the voltage of 3V3 through the pull-up resistor R2, the cathode of the diode D1 is connected to the UART _ RXD pin (RXD pin in the drawing) of the RS485 level conversion chip 300, and the cathode of the diode D2 is connected to the UART _ RXD pin (R1 _ OUT in the drawing) of the RS232 level conversion chip 400. When the UART _ RXD pin of the RS485 level shifter chip 300 and the UART _ RXD pin of the RS232 level shifter chip 400 do not receive information sent from the external device from the DB interface, they are at a high level, and the diode D1 and the diode D2 are not turned on, so the UART _ RXD pin of the single chip microcomputer 100 is also at a high level. When the UART _ RXD pin of the RS485 level shift chip 300 receives information sent from the external device from the DB interface, the UART _ RXD pin thereof becomes a low level, the diode D1 is turned on, the UART _ RXD pin of the singlechip 100 is pulled to a low level, and the operating principle of the RS232 level shift chip 400 is consistent with that of the RS485 level shift chip 300.

The UART _ TXD pin of the single chip microcomputer 100 is directly connected to the UART _ TXD of the RS485 level conversion chip 300 and the UART _ TXD pin of the RS232 level conversion chip 400 through a wire, and when the single chip microcomputer 100 transmits information through the UART _ TXD pin, the information is directly transmitted to the UART _ TXD pins of the RS232 level conversion chip 400 and the RS485 level conversion chip 300.

The A, B, Y, Z pin of the RS485 level conversion chip 300 and the T1_ OUT and R1_ IN pins of the RS485 level conversion chip 300 are connected to the DB9, so as to realize the transmission and reception of information with external devices through the DB9 interface 500.

The utility model discloses a set up UART connecting circuit 200 between singlechip 100's UART interface and RS485 level conversion chip 300 and RS232 level conversion chip 400 for RS485 level conversion chip 300 and RS232 level conversion chip 400 can multiplex a UART interface, thereby avoid singlechip 100's the not enough problem of UART interface resource.

The above is only the preferred embodiment of the present invention, not used in the present invention, and any slight modifications, equivalent replacements and improvements made by the technical entity of the present invention to the above embodiments should be included in the protection scope of the technical solution of the present invention.

Claims (1)

1. A hardware multiplexing circuit based on UART communication is characterized by comprising a UART connecting circuit, an RS485 level conversion chip, an RS232 level conversion chip and a DB9 interface;

the UART connecting circuit comprises a diode D1, a diode D2 and a pull-up resistor R2, wherein the anode of the diode D1 and the anode of the diode D2 are connected with a UART _ RXD pin of a singlechip, and are connected with 3V3 voltage through a pull-up resistor R2, the cathode of the diode D1 is connected with the UART _ RXD pin of an RS485 level conversion chip, and the cathode of the diode D2 is connected with the UART _ RXD pin of an RS232 level conversion chip;

and the UART _ TXD pin of the RS485 level conversion chip and the UART _ TXD pin of the RS232 level conversion chip are connected with the UART _ TXD pin of the singlechip.

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