CN218068846U

CN218068846U - Isolated RS485-CAN multiplexing circuit

Info

Publication number: CN218068846U
Application number: CN202221572255.1U
Authority: CN
Inventors: 不公告发明人
Original assignee: Shenzhen Smarton Electric Co ltd
Current assignee: Shenzhen Smarton Electric Co ltd
Priority date: 2022-06-22
Filing date: 2022-06-22
Publication date: 2022-12-16
Anticipated expiration: 2032-06-22

Abstract

The utility model provides a RS485-CAN multiplex circuit of isolation, include 485 buses and the logic circuit who comprises A line and B line, logic circuit includes the isolator, the output of isolator and MCU's input electric connection, a pull-up resistance and two diodes of establishing ties between A line and the RS485 interface chip connection, a pull-down resistance of B line series connection and ground, the A line is through two to the CAN-L department of CAN equipment behind the diode, the B line is connected with the CAN-H department of CAN equipment. The utility model discloses an use the logic circuit of suitable design, in the function of RS485 circuit, multiplexed out the function of CAN circuit, realized multiplexing of RS485 and CAN circuit, realized the low-cost scheme that possesses CAN interface and RS485 interface, the effectual problem of solving the cost, and reduced port quantity, realized the circuit of mainly using RS485 communication interface function, through switching, CAN realize the circuit of CAN function.

Description

Isolated RS485-CAN (controller area network) multiplexing circuit

Technical Field

The utility model relates to a multiplexing circuit technical field especially relates to a RS485-CAN multiplexing circuit who keeps apart.

Background

The modern digital power supply takes a digital signal processor or a microcontroller as a core, combines a power electronic power conversion technology, realizes flexible and changeable modern automatic control and complex logic functions, forms a series of products with unique functions, and is widely applied in various industries. As an interface of a digital power supply, a Controller Area Network (CAN) and an RS485 serial bus are widely used, and the physical interface standards of the two are different, and the specific application range and the specific scene of the interface are different. For high voltage ac input digital power supplies, it is also generally required that these interface circuits be safely electrically isolated from the main circuit. In some low cost applications, if both circuits are configured, the cost is significantly increased (as shown in fig. 1), and the number of interfaces is increased; in addition, in use, two interfaces can not be used simultaneously, which causes certain waste.

SUMMERY OF THE UTILITY MODEL

The utility model solves the problems that the cost is obviously increased and the number of interfaces is increased due to the configuration of two circuits; in addition, in the use, two interfaces can not be used simultaneously, which causes a certain waste problem.

In order to solve the technical problem, the utility model provides a RS485-CAN multiplex circuit who keeps apart, include 485 buses and the logic circuit who comprises A line and B line, and A line and B line respectively with RS485 interface chip looks electric connection, RS485 interface chip looks electric connection with the logic circuit, the logic circuit includes the isolator, the output and MCU's of isolator input electric connection, a pull-up resistance and two diodes of establishing ties between A line and the RS485 interface chip connection, a pull-down resistance of B line series connection is connected in ground, the A line is through two to the CAN-L department of CAN equipment behind the diode, the B line is connected with the CAN-H department of CAN equipment to be connected with resistance between the H-L of CAN equipment and CAN-H.

Preferably, the RS485 interface chip includes a TX pin, an RX pin, and a TxEn/RxEn pin, and the isolator includes an OUT1 pin, an OUT2 pin, and an IN3 pin, where the TX pin is connected to the OUT1 pin, the RX pin is connected to the IN3 pin, and the TxEn/RxEn pin is connected to the OUT2 pin.

Preferably, a trigger locking circuit is connected between the TxEn/RxEn pin and the OUT2 pin of the logic circuit connected with the RS485 interface chip.

Preferably, the voltage of the pull-up resistor is 5V, and the voltage of the pull-down resistor is 0V.

Preferably, the resistance value of the resistor is 120 Ω.

Compared with the prior art, the utility model provides a RS485-CAN multiplex circuit who keeps apart possesses following beneficial effect:

the utility model discloses an use the logic circuit of suitable design, in the function of RS485 circuit, multiplexed out the function of CAN circuit, realized multiplexing of RS485 and CAN circuit, realized the low-cost scheme that possesses CAN interface and RS485 interface, the effectual problem of solving the cost, and reduced port quantity, realized the circuit of mainly using RS485 communication interface function, through switching, CAN realize the circuit of CAN function.

Drawings

FIG. 1 is a schematic diagram of a prior art configuration circuit;

fig. 2 is a schematic circuit diagram of the present invention;

fig. 3 is a schematic diagram of the logic circuit of the present invention;

fig. 4 is a schematic diagram of the trigger lock circuit of the present invention.

In the figure: 1. 485 bus; 2. an RS485 interface chip; 3. an isolator; 4. a pull-up resistor; 5. a diode; 6. a pull-down resistor; 7. a CAN device; 8. and (4) resistance.

Detailed Description

The utility model relates to an isolated RS485-CAN multiplex circuit, as shown in figure 2-4, an isolated RS485-CAN multiplex circuit, including 485 bus 1 and logic circuit composed of A line and B line, and A line and B line are respectively connected with RS485 interface chip 2 mutually electrically, RS485 interface chip 2 is connected with logic circuit mutually electrically, logic circuit mainly realizes required logic and electrical isolation, in order to reduce the number of channels of the electrical isolation chip, realize cost reduction, logic circuit includes isolator 3, the output end of isolator 3 is connected with the input end of MCU electrically, it is here still to explain that the output end of isolator 3 is connected with the input end of DSP electrically, and MCU and DSP function effect are the same all including SCI _ Tx, SCI _ Rx, SCI _ TxEn, CAN _ Tx and CAN _ Rx, the MCU is electrically connected with a logic circuit or through DSPSCI _ Tx, SCI _ Rx, SCI _ TxEn, CAN _ Tx and CAN _ Rx, the MCU and the DSP are selected according to requirements, a pull-up resistor 4 and two diodes 5 are connected in series between the connection of the A line and the RS485 interface chip 2, wherein the voltage of the pull-up resistor 4 is 5V, the voltage of the B line is 0V, the A line passes through the two diodes 5 and then reaches the CAN-L of the CAN device 7, the B line is connected with the CAN-H of the CAN device 7, a resistor 8 is connected between the H-L of the CAN device 7 and the CAN-H, the resistance value of the resistor 8 is 120 omega, the voltage drop of the diode 5 is small and is not enough to change the original level logic, so the work of the RS485 bus 1 is not influenced, the circuit adopts a multiplexing mode and CAN be switched to the CAN mode or 485 mode (the default mode is 485 mode), the function of the selector switch is as follows: when the input control Ctr is low, txEn is equal to OUT2 of the isolator; when Ctr is high, txEn is equal to the negation of the isolator OUT 1. Thus, when the Ctr is low, the receiving and transmitting function of RS485 is realized; and when Ctr is high, the logic required by the RS485 interface chip to realize the CAN interface level is realized.

As shown IN fig. 2-3, the RS485 interface chip 2 includes a TX pin, an RX pin, and a TxEn/RxEn pin, and the isolator includes an OUT1 pin, an OUT2 pin, and an IN3 pin, where the TX pin is connected to the OUT1 pin, the RX pin is connected to the IN3 pin, and the TxEn/RxEn pin is connected to the OUT2 pin;

further, when the input control Ctr is low, txEn is equal to OUT2 of the isolator; ctr is high, txEn equals the negation of isolator OUT 1. Thus, when the Ctr is low, the receiving and transmitting function of RS485 is realized; and when Ctr is high, the logic required by the RS485 interface chip to realize the CAN interface level is realized.

As shown in fig. 3, a trigger locking circuit is connected between the TxEn/RxEn pin and the OUT2 pin of the logic circuit connected to the RS485 interface chip 2, and when the circuit is powered on, ctr output is a default low level; when the time of In input high level is longer than a certain time (depending on RC value, such as 1s convention), when the voltage at two ends of C reaches logic level high, the output of OR gate is high, at the same time, the output of OR gate reaches another input path, and is maintained, the follow-up OR gate will always output high level until the circuit is powered off, and the locking function triggered by high level is realized.

The utility model discloses a theory of operation and use flow:

when the CAN-based device is used, when the CAN-based device is required to be connected with other CAN equipment, when TxEn is low, the voltage VAB at two ends of the RS485 interface chip is 0.7V, rx of the RS485 interface chip 2 is high level, and a proper resistance value is taken to enable CAN _ Rx to be also hidden level; when TxEn is high level, the RS485 interface chip 2 is in output enabling, if Tx of the RS485 interface chip 2 is low level, the output of A line is 0V, the output of B line is 5V, the CAN-L of CAN equipment is 0.7V, the CAN-H of CAN equipment is 5V, and as VHL of CAN is more than 0.8V, the CAN equipment receives dominant level which is the same as Tx level of the RS485 interface chip;

the RS485 interface chip with TxEn as a low level is used for transmitting the recessive level of the CAN; txEn is used as a high level, tx is used as a low level, and an RS485 interface chip transmits a dominant level, so that the matching of physical levels of RS485 and CAN is realized.

It is to be understood that the present invention has been described with reference to certain embodiments and that various changes or equivalents may be substituted for elements thereof without departing from the spirit and scope of the invention as defined by the appended claims. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of the present application are intended to be covered by the present invention.

Claims

1. The utility model provides an RS485-CAN multiplex circuit of isolation, includes 485 bus (1) and logic circuit that comprises A line and B line, and A line and B line are electric connection mutually with RS485 interface chip (2) respectively, and RS485 interface chip (2) are electric connection mutually with logic circuit, and logic circuit includes isolator (3), the output of isolator (3) and MCU's input electric connection, characterized in that, a pull-up resistance (4) and two diodes (5) are established ties between A line and RS485 interface chip (2) are connected, and B line establishes ties a pull-down resistance (6) and is connected in ground, and A line passes through two behind diode (5) to CAN-L department of CAN equipment (7), and B line is connected with CAN-H department of CAN equipment (7), and is connected with resistance (8) between the H-L of CAN equipment (7) and CAN-H.

2. The isolated RS485-CAN multiplexing circuit of claim 1, wherein: the RS485 interface chip (2) comprises a TX pin, an RX pin and a TxEn/RxEn pin, the isolator comprises an OUT1 pin, an OUT2 pin and an IN3 pin, the TX pin is connected with the OUT1 pin, the RX pin is connected with the IN3 pin, and the TxEn/RxEn pin is connected with the OUT2 pin.

3. The isolated RS485-CAN multiplexing circuit of claim 1, wherein: and a trigger locking circuit is connected between the TxEn/RxEn pin and the OUT2 pin of the logic circuit, which are connected with the RS485 interface chip (2).

4. The isolated RS485-CAN multiplexing circuit of claim 1, wherein: the voltage of the pull-up resistor (4) is 5V, and the voltage of the pull-down resistor (6) is 0V.

5. The isolated RS485-CAN multiplexing circuit of claim 1, wherein: the resistance value of the resistor (8) is 120 omega.