CN1728703A - A protocol conversion method between Modbus and DeviceNet - Google Patents

Abstract

The invention relates to a protocol conversion method between Modbus and DeviceNet. It uses Modbus bus to connect with microprocessor through RS485 bus interface, DeviceNet bus connects to microprocessor through CAN transceiver and controller, and microprocessor also connects EEPROM and data and program memory to build a protocol conversion hardware platform, and The protocol conversion model between Modbus and DeviceNet provided by the present invention is adopted to realize the protocol conversion between Modbus and DeviceNet, and to realize that the Modbus device is connected to the DeviceNet network as a DeviceNet slave station in the form of a DeviceNet object.

Description

A protocol conversion method between Modbus and DeviceNet

technical field

The invention relates to a method for implementing protocol conversion between two industrial communication protocols, Modbus and DeviceNet, and is especially suitable for the application of Modbus devices connected to the DeviceNet network, belonging to the field bus control technology field.

Background technique

In view of the fact that fieldbus standards are diversified, systems in practical applications often contain multiple bus networks. In order to realize the network information integration of different communication protocols, the development of communication adapters, or protocol converters, has become a major research content in the field of fieldbus control technology.

The Modbus protocol was originally developed by Modicon, and it is now one of the most popular general industrial standard protocols in the world in the industrial field. Last year, my country promulgated the national standard GB/Z 19582.1-2004 "Industrial Automation Network Specification Based on Modbus Protocol" and implemented it from 2005-03-01.

Modbus communication uses master-slave technology, that is, only one device (master device) can initiate transmission (query), and other devices (slave devices) make corresponding responses according to the data provided by the master device query. The master device can communicate with the slave devices individually, and can also communicate with all slave devices in a broadcast manner. If it communicates alone, the slave device will return a message as a response, if it is inquired by broadcast, it will not make any response.

At present, Modbus generally adopts the standard RS-485 communication interface as its physical layer transmission mode, the communication baud rate is 1200BPS～57600BPS, and the master-slave half-duplex mode.

The DeviceNet field bus protocol is a Can-based application layer protocol proposed by Rockwell Corporation, which clearly defines the contents of the physical layer, data link layer and application layer. In the DeviceNet network system, the pre-defined master-slave connection mode of the protocol specification is generally used at present, that is, the devices in the network are divided into slave stations and masters (or scanners). The master station can communicate in point-to-point or broadcast mode, while the slave station can only communicate with the master station generally, and the slave stations cannot communicate with each other. The communication rate stipulated by DeviceNet is 125KBPS, 250KBPS and 500KBPS three kinds.

Because the hardware and software implementation cost of the Modbus field bus interface is very low, it is widely used in domestic low-voltage electrical appliances, DCS control, instrumentation and other fields. But compared to DeviceNet, Modbus is a low-speed network, and its half-duplex communication mode cannot meet the requirements in applications with relatively high real-time requirements. Therefore, in the actual multi-bus structure system, the Modbus/DeviceNet field bus protocol conversion device can realize the upgrade of the communication network at a lower cost, and connect the original equipment with the Modbus communication interface to the DeviceNet network.

The existing foreign and domestic Modbus/DeviceNet communication adapters mainly include the following types:

■AnyBus-Communicator Serial To DeviceNet Gateway of HMS

■WRC’s 1782-JD family of DeviceNet toserial Communications products of Western Reserve Controls

■Serial Interface for DeviceNet OEMs from Real Time Automation

■UNIGATE RS232/485-DeviceNet from Deutschmann Automation GmbH

These protocol conversion devices can convert the input and output information conforming to Modbus into the input and output information of the DeviceNet network. The advantage is that the I/O data in the network can be packaged and exchanged centrally, reducing network load and improving system communication capabilities.

However, for most bus network devices, the information exchanged with the system not only includes real-time I/O data, but also a large number of configuration parameters and diagnostic information. Using the general I/O mode, the information can only be processed as I/O data. Since the data volume is large but has no real-time requirements, it will cause a huge waste of network communication capabilities; if it is not transmitted or selectively transmitted in a small amount data, it will reduce the information collection and control capabilities of the system on the device.

Therefore, constructing Modbus equipment or subnet objects on the DeviceNet level is a requirement for a new type of protocol converter.

Contents of the invention

The purpose of the present invention is to provide a protocol conversion method between Modbus and DeviceNet, to realize that the Modbus device is connected to the DeviceNet network as a DeviceNet slave station in the form of a DeviceNet object.

In order to achieve the above object, the present invention adopts following technical scheme:

A protocol conversion method between Modbus and DeviceNet is characterized in that the Modbus bus is connected with the microprocessor through the RS485 bus interface, the DeviceNet bus is connected with the microprocessor through a CAN transceiver and a controller, and the microprocessor is also connected with EEPROM and data , program memory, and build a protocol conversion hardware platform, thereby adopting the following protocol conversion model between Modbus and DeviceNet to realize the protocol conversion between Modbus and DeviceNet: the configuration file is generated by the configuration port, and then the microprocessor program is extracted from the configuration file) Unit attributes, on the one hand, generate the scan list of the Modbus master station, and on the other hand, generate the path configuration of DeviceNet. The data defines the class number, instance number, attribute number, attribute number, combination object, and parameter object connection path value of the DeviceNet application object ;The input data from Modbus to DeviceNet is read into the protocol mapping area by the Modbus network according to the configuration of the scan list, and then read into the DeviceNet application object, and sent to the DeviceNet network; the output data from DeviceNet to Modbus is sent to it by the combination object and parameter object The command converter is interpreted by the microprocessor as the commands in the command area of the protocol mapping area, and then sends Modbus commands to the Modbus network from the aperiodic scanning list corresponding to the commands, and updates the data in the protocol mapping area.

The specific steps of the above-mentioned protocol conversion are as follows:

①. The configuration file is stored in the non-volatile memory EEPROM, and stored by PC download or program burning. The editing of the file content is defined by the user according to the fixed format according to the needs;

②. Initialize the Modbus communication port according to the configuration file;

③. Initialize the identification object and DeviceNet object related information according to the DeviceNet device information in the configuration file;

④. Initialize the data unit in the protocol mapping area according to the number of unit attributes in the configuration file and the number of unit data bytes; the Modbus periodic scan list is generated by the unit attribute as the data unit that is periodically updated, and the data unit that is not periodically updated by the unit attribute Generate Modbus aperiodic scan list. Each record in the scan list consists of unit number, Modbus node address, Modbus register address, function code and data size.

⑤. Correspond the data units in the protocol mapping area with the instance attributes of the DeviceNet application object one by one, and then configure the DeviceNet path; generate the input instance attributes and output instance attributes of the combined object according to the periodically updated instance attributes according to the read and write properties. Periodically updated instance attributes are all listed in the parameter object instance attributes; DeviceNet connection object production and consumption paths are configured as input instance data attribute items and output instance data attribute items of combined objects;

⑥. According to the protocol mapping area data unit attribute corresponding to the DeviceNet application object instance attribute, when DeviceNet has output I/O data or write output parameters, convert the operation into command information in the command area of the protocol mapping area; and then scan by querying Modbus List, get the corresponding record items, generate Modbus messages, and update the unit data in the protocol mapping area after the response is correct.

In the protocol conversion model between above-mentioned Modbus and DeviceNet, described configuration file comprises the communication pattern of Modbus communication port and baud rate parameter, DeviceNet equipment information and protocol mapping area unit property; Described unit property comprises Modbus address, Read and write properties, whether to operate periodically, the number of units of bytes; the protocol mapping area includes a data area and a command area, and the data area is in units; the command area includes a status word, a unit number and a data register; the DeviceNet The path configuration file is generated by the unit attribute, including the application object class number, the combined object instance attribute list, the parameter object instance attribute list, and the connection object instance path; the Modbus scan list includes a periodic scan list and an aperiodic scan list, by The configuration file is generated. DeviceNet output command conversion is used to implement class 3 transmission services and I/O output of DeviceNet equipment, and convert them into command area information in the protocol mapping area; constructing the described DeviceNet application object is defined by the user's configuration file, and its attribute content is the same as There is a one-to-one correspondence between data units in the protocol mapping area.

According to the above-mentioned protocol conversion method, one or more Modbus slave stations can be directly converted into one or more DeviceNet objects with the same characteristics. From the perspective of the DeviceNet interface, it can be completely regarded as a complete specific DeviceNet device, not just Some packed I/O data.

Compared with the prior art, the present invention has the following obvious outstanding substantive features and significant advantages: the present invention provides a protocol conversion model between Modbus and DeviceNet on the hardware platform for constructing protocol conversion between Modbus and DeviceNet, thereby The protocol conversion between Modbus and DeviceNet is realized, and the Modbus device is connected to the DeviceNet network as a DeviceNet slave station in the form of a DeviceNet object.

Description of drawings

Fig. 1 is a schematic diagram of a method model of an embodiment of the present invention.

Fig. 2 is a structure diagram of unit attribute data according to the embodiment of the present invention.

Fig. 3 is a schematic diagram of a configuration file format according to an embodiment of the present invention.

Detailed ways

A preferred example of the present invention is described in detail below in conjunction with accompanying drawing:

The protocol conversion method between Modbus and DeviceNet is to use the Modbus bus to connect with the microprocessor through the RS485 bus interface, and the DeviceNet bus to connect with the microprocessor through the CAN transceiver and controller, and the microprocessor is also connected to EEPROM and data and program memory. Build the protocol conversion hardware platform, thus adopt the following protocol conversion model between Modbus and DeviceNet (see Figure 1), realize the protocol conversion between Modbus and DeviceNet: the configuration file 1 is generated by the configuration port, and then the microprocessor program from the configuration file 1. Extract unit attributes 2. On the one hand, generate the scan list 5 of the Modbus master station; The connection path value of the parameter object is 7; the input data from Modbus to DeviceNet is read into the protocol mapping area 8 by the Modbus network according to the configuration of the scan list, and then read into the DeviceNet application object and sent to the DeviceNet network; the output data from DeviceNet to Modbus The combination object and parameter object 7 are sent to the command converter 9, interpreted by the microprocessor as the command in the command area of the protocol mapping area 8, and then the Modbus command is sent to the Modbus network by the corresponding aperiodic scan list of the command, and Update protocol map area data.

The specific steps for the transformation of this agreement are as follows:

①. The basic content of configuration file 1 is shown in Figure 3, which consists of three parts: communication mode word, DeviceNet device information and unit attributes. The communication mode word saves the communication baud rate and communication mode of the Modbus subnet, and other information defined by the user; the DeviceNet device information saves the object class number, instance number, instance number, and attribute number contained in each instance of the application object 4, And the path configuration needed for the composite object parameter object 7. The configuration file 1 is generated by the user, and its specific format agreement is consistent with the interpretation of the user program.

②. Extract the communication mode word information in the configuration file 1, and initialize the Modbus communication port.

③. Extract part of the unit attribute information in configuration file 1 to obtain unit attribute 2, as shown in FIG. 2 is the data structure of a single unit attribute word. In Figure 2, the unit attribute contains 4 bytes, the highest byte A saves the Modbus slave address corresponding to the unit, the second and third byte B save the device Modbus register address corresponding to the unit data, and the fourth byte The 7th bit C indicates the read-write attribute, the 6th bit D indicates the periodic update flag, and the 5th to 0th bits indicate the number of data bytes in the unit.

4. Generate the Modbus scan list 5 by the unit attribute 2, generate the Modbus periodic scan list for the periodically updated data unit by the unit attribute, and generate the Modbus aperiodic scan list for the aperiodically updated data unit by the unit attribute. Each record in the scan list consists of unit number, Modbus node address, Modbus register address, function code, data size, etc. For example: use 0x03 function code to read one or more register values, and the contents of the scan list record items are: 0x01 (unit number), 0x01 (slave station address), 0x0001 (register address), 0x03 (function code), 0x02 ( data bytes).

⑤. The data in the data area of the protocol mapping area 8 is sorted according to the unit numbers from small to large, corresponding to the unit data. The protocol mapping area can be opened in the RAM area of the single-microprocessor platform, or in the dual-port RAM area of the dual-microprocessor platform.

⑥. Path configuration 3 extracts the DeviceNet device information in the configuration file 1, initializes the instance of the DeviceNet application object 4, and corresponds the instance attributes with the data units in the protocol mapping area one by one according to the instance number and the number of attributes. At the same time, path configuration 3 fills in the data path of the complete combination object and parameter object instance, the content of the path is: class number-instance number-attribute number, that is, the attribute path of the application object 4. Wherein, the combination object includes the data whose attribute of the protocol mapping area unit is updated periodically, and the parameter object includes the data whose attribute of the protocol mapping area unit is updated aperiodically.

⑦. For data from DeviceNet to Modbus, it is also performed through command conversion 6. For the data from combination object and parameter object, command conversion 6 compares new data and old data whether there is any change, if there is, then according to its corresponding unit number and unit attribute, generate a command item and write into the command area of protocol mapping area 8, And notify the Modbus to scan the list 5, and then send it to the Modbus slave device in the form of a Modbus message. After the response is correct, update the corresponding data in the protocol mapping area and the instance data of the DeviceNet application object.

Claims (4)

1. the method for converting protocol between Modbus and DeviceNet, it is characterized in that adopting the Modbus bus to be connected with microprocessor by the RS485 bus interface, the DeviceNet bus is connected with microprocessor with controller by the CAN transceiver, microprocessor also connects EEPROM and data, program storage, build the protocol conversion hardware platform, thereby adopt protocol conversion model between following Modbus and DeviceNet, realize the protocol conversion between Modbus and DeviceNet: by configuration mouthful generation configuration file (1), microprocessor program is from configuration file (1) extraction unit attribute (2) then, generate the scan list (5) of Modbus main website on the one hand, generate the path configurations (3) of DeviceNet on the other hand, the path configurations data definition class-mark of DeviceNet application (4), instance number, attribute number, attribute number and compound object, the access path value of parameter object (7); Be read into agreement map section (8) by the Modbus network according to the configuration of scan list to the input data of DeviceNet by Modbus, read the DeviceNet application then, deliver to the DeviceNet network; Deliver to command converter (6) to the dateout of Modbus by compound object and parameter object (7) by DeviceNet, be interpreted as the order of the command area of agreement map section (8) by microprocessor, then by the pairing aperiodicity scan list of order, send out Modbus and order the Modbus network, and New Deal map section data more.

2. the method for converting protocol between Modbus according to claim 1 and DeviceNet is characterized in that the concrete steps of protocol conversion are as follows:

1., configuration file (1) is stored in the nonvolatile memory EEPROM, stores by PC downloading mode or burning program mode, the editor of file content is by user's definition according to fixed format as required;

2., according to configuration file (1) initialization Modbus communication port;

3., according to DeviceNet facility information initialization sign object and DeviceNet object-related information in the configuration file (1);

4., according to the quantity and cell data byte number initializtion protocol map section (8) data cell of configuration file cell attribute (2); Producing the tabulation of Modbus periodic scan by cell attribute (2) for the data cell that periodically updates, is that aperiodicity data updated unit produces Modbus aperiodicity scan list by cell attribute.Every record of scan list (5) is made up of unit number, Modbus node address, Modbus register address, function code and size of data;

5., agreement map section (8) data cell is corresponding one by one with DeviceNet application (4) instance properties, carry out DeviceNet path configurations (3) then; The instance properties that periodically updates is generated the input instance properties of compound object respectively and exports instance properties according to read-write character, the instance properties of acyclic renewal is all listed in the parameter object instance properties; DeviceNet connecting object production and consumption path configurations is the input instance data attribute item and the output instance data attribute item of compound object;

6., according to DeviceNet application (4) instance properties corresponding protocols map section (8) data cell attribute, when DeviceNet has output I/O data or when writing output parameter, this operation is converted to the command information of agreement map section command area; By inquiry Modbus scan list, obtain the corresponding record item then, generate the Modbus message, after response is correct, this cell data of New Deal map section more.

3. the method for converting protocol between Modbus according to claim 1 and DeviceNet is characterized in that described configuration file (1) comprises communication mode and baud rate parameter, DeviceNet facility information and the agreement map section cell attribute of Modbus communication port; Described cell attribute (2) comprises Modbus address, read-write character, whether periodical operation, unit byte number; Described agreement map section (8) comprises data field and command area, and the data field is unit with the unit; The command area comprises status word, unit number and data register; Described DeviceNet path configurations file (3) is generated by cell attribute (2), comprises application class-mark, the tabulation of compound object instance properties, the tabulation of parameter object instance properties, connecting object example path; Described Modbus scan list (5) comprises periodic scan tabulation and aperiodicity scan list, is generated by configuration file (1).The conversion of DeviceNet output command is used for carrying out the class 3 transmission services and the I/O output of DeviceNet equipment, converts them to the command area information of agreement map section (8); Make up configuration file (1) definition of described DeviceNet application (4) by the user, its property content is corresponding one by one with agreement map section (8) data cell.

4. the method for converting protocol between Modbus according to claim 1 and DeviceNet, it is characterized in that one or more Modbus slave stations directly are converted to the one or more DeviceNet objects with same characteristic features, from the DeviceNet interface, can be considered as a complete concrete DeviceNet equipment fully, and be not only the I/O data of some packings.

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