CN105006122A - Wireless interface communication protocol of automatic inspection robot - Google Patents

Abstract

The present invention discloses a wireless interface communication protocol for an automatic inspection robot. The wireless interface communication protocol provides a master/slave message frame structure. During the communication process, the control console is the host and the automatic inspection robot is the slave. The transmission of the message frame strictly obeys the master/slave response mechanism. In the communication protocol, the host message frame defines the start bit, address field, function field (including function module code, method code, data length), data field, and error detection field according to actual needs. The slave message frame defines: start bit, address field, function field (including accessed function module code, accessed method code, data length, status bit), data field, and error detection field. The present invention proposes an effective wireless interface communication protocol for an automatic inspection robot, which ensures effective communication between the control console and the inspection robot. The control not only provides sufficient control information, but also obtains real-time information and status feedback of the inspection robot.

Description

A wireless interface communication protocol for automatic inspection robot

technical field

The invention relates to a wireless interface communication protocol between an automatic inspection robot and a host console.

Background technique

With the advancement of equipment technology and computer network science, modern ultra-high voltage and ultra-high voltage power transmission and transformation system projects are developing in the direction of large-scale and complex, and the large-scale application of new voltage levels and new technologies makes traditional operation, Methods and methods of operation and maintenance are facing new challenges, such as a large number of equipment components/subsystems, complex cross-linking relationships, and a large number of items to be observed for component defects, etc. How to further adapt to the operation of small hydropower substations under the new situation, Adopting new technologies and means to reduce the burden of operation and maintenance on duty personnel in substations and effectively guarantee the safe and reliable operation of equipment has become the main problem in the future.

There is still a considerable distance between the existing inspection methods and technologies and the safety requirements of power production. The scope of application of the substation intelligent inspection robot is mainly unattended or few-person-attended substations, which can effectively replace manual inspections of high-voltage substation equipment in substations. The application of intelligent inspection robots for inspection operations can not only reduce equipment losses caused by personnel negligence and missed inspections, improve the operation quality of the power grid, but also reduce personnel investment in the power supply system and reduce personnel costs. Substation equipment inspection intelligent robots are mainly used in natural environments far away from towns and with complex and diverse geographical conditions. Since manual inspection work is very difficult in this environment, and it is difficult to guarantee the quality of work, only by adopting advanced inspection methods and tools can the inspection cycle be appropriately shortened, existing defects can be found in time, and the defects can be eliminated more effectively. accident hazards and ensure the safe and stable operation of the power system.

The intelligent inspection robot is developed to meet the development needs of intelligent small hydropower substations and unattended small hydropower substations, and to comprehensively improve the intelligence level of substations. It takes the intelligent inspection robot as the core, integrates robot technology, power equipment non-contact detection technology, multi-sensor fusion technology, pattern recognition technology, navigation positioning technology and Internet of Things technology, etc., and can realize all-weather, all-round and fully autonomous intelligent inspection of substations Inspection and monitoring can effectively reduce labor intensity, reduce substation operation and maintenance costs, and improve the automation and intelligence level of normal inspection operations and management. Provide innovative technical detection methods and comprehensive security guarantees for smart substations and unattended substations, and accelerate the process of unattended substations.

Contents of the invention

In order to solve the problem of wireless communication between the inspection robot and the console, the present invention provides a master/slave message frame structure. During the communication process, the console is the master, and the automatic inspection robot is the slave. In the communication protocol , the transmission of the message frame strictly obeys the wireless interface communication protocol of the master/slave response mechanism.

The technical scheme of the present invention: an automatic inspection robot wireless interface communication protocol, comprising the following steps:

1) The host console configures the host console message frame according to actual needs. The message frame structure includes: 2-byte start bit, 1-byte address field, 3-byte function field, N-byte data field, and 1-byte error detection field, the 2-byte start bit is written into the start flag 1 and the start flag 2 respectively, and the ID of the automatic inspection robot that needs to send the command is written into the address field, and the automatic inspection robot is notified that the host console will start sending message frame;

2) The host console configures the function domain according to the specific function needs; select the module to be called from the communication setting module, command setting module, data output module and other modules; the host console writes the corresponding "module code" into the message frame function At the same time, find the corresponding "method number" and the "data length" corresponding to the "method number", and write the "method code" and "data length" into the second byte of the function field in the message frame , 3 bytes, the message frame allocates the size of the data field according to the "data length", and writes each data parameter into the data field;

3) Calculate the "error detection domain" according to the calculation method of checksum = start flag 1 + start flag 2 + node ID + module number + method number + data length + parameter 1 +... + parameter N, and write it into the message frame; the host console message frame is configured and ready to be sent to the automatic inspection robot.

4) After the automatic inspection robot receives the message frame from the host console, it will analyze the information in the "module code", "method code" and "data length" in the functional domain in sequence. If the "data length" is not 0X00, it will further analyze information in the data domain, and timely adjust the opening and closing of each module function of the automatic inspection robot according to the specific information; if the automatic inspection robot needs to return a response message frame to the host console, the response message frame structure fed back by the automatic inspection robot includes : 2-byte start bit, 1-byte address field, 4-byte function field, N-byte data field, 1-byte error detection field;

5) According to the "module code" and "method code", rewrite the "data length" in the functional field of the automatic inspection robot response message frame, and write the "status bit" information into the fourth byte of the functional field. If the current status information of the inspection robot is normal, write 0X00, otherwise write 0X01, and write each data parameter of the automatic inspection robot into the data field;

6) Calculate the "error detection domain" according to the calculation method of checksum = start flag 1 + start flag 2 + node ID + module number + method number + data length + status bit + parameter 1 + ... + parameter N, and set It is written into the automatic inspection robot response message frame and sent to the host console.

Preferably, in the 3-byte functional field of step 1), 1 byte represents the functional module code, 1 byte represents the method code, and 1 byte represents the data length.

Preferably, in the step 1), the start flag 1 is 0X55, where 0X represents hexadecimal, and the start flag 2 is 0XAA.

Preferably, N in the parameter N of step 3) and step 6) represents the number of parameters.

Preferably, in the 4-byte functional field in step 4, 1 byte represents the code of the accessed function module, 1 byte represents the code of the accessed method, 1 byte represents the data length, and 1 byte represents the status bit.

The concrete division of message frame among the present invention is as follows:

The message frame sent by the host is: 2-byte start bit, 1-byte address field, 3-byte function field (where 1 byte represents the function module code, 1 byte represents the method code, and 1 byte represents the data length), N-byte data domain, 1-byte error detection domain.

The response message frame fed back by the slave is: 2-byte start bit, 1-byte address field, 4-byte function field (where 1 byte represents the code of the accessed function module, 1 byte represents the code of the accessed method, and 1 byte Section means data length, 1 byte means status bit), N byte data field, 1 byte error detection field.

Start bit: The length is 2 bytes. Its function is to notify the target node to start sending the message frame. In the master and slave, the data of the start bit is the same, and the 2 bytes are the start flag 1 (0X55) , Start flag 2 (0XAA).

Address field: the length is 1 byte, and the address field contains the address information of the message frame. In the message frame sent by the host, the address field determines the only target slave; in the message frame sent by the slave, the address field feeds back the source of the message frame to the host, that is, the local address ID.

Functional domain: The functional domains of the master/slave are slightly different. The functional domain of the master message frame includes "function module code", "method code" and "data length"; the functional domain of the slave machine message frame contains "function module Encoding", "Method Encoding", "Data Length", "Status Bit". Among them, "data length" reflects the number of parameters in the data field to be sent in this message frame, and the number of parameters is determined by "function module code" and "method code"; the function of "function module code" in the master and slave Different, for the host, the "function module code" decides to access the "function module" of the target node. In a device node, there may be multiple functional modules, for example, in the "logic controller", there may be "input and output modules", "analog-to-digital conversion modules", "communication modules", etc. "Represents the function module being accessed by this machine; "method number" determines the specific function of the "function module" of the access target node in the host, "method number" 0X60-0X6F is an asynchronous read segment, and "method number" 0X70 -0X7F is an asynchronous write segment. For the "input and output function module", there can be several operation methods, such as "setting the port direction", "output data to the port", "read data from the port", etc. For the slave, the "method number" reflects the method being accessed . The "status bit" only exists in the slave and reflects the current status information of the slave.

Data field: In the host, the data field represents the parameters passed to the method of a certain module of the target device. The length of the parameter is determined by the member "data length" in the "functional domain". For the slave, the "data field" passes the feedback parameters of the method of a module accessed by the master. For method accesses that do not require parameters, the length of the "data field" can be "0".

Since the communication protocol is an asynchronous communication protocol, in different modules, the data domain and the functional domain are configured together to realize the asynchronous communication function. The modules are divided into three categories, namely: communication setting module, command setting module, and data output module. The message frame configuration information of each module is as follows:

1. The communication setting module, "module code" 0X01, has the following 4 kinds of configuration information:

(1) Configure communication data: "method number" 70, "data length" length 0X04, the data field contains four kinds of data, each data length is 1 byte, respectively: data broadcast switch configuration, communication baud rate configuration , Data refresh rate configuration (20-100 Hz), output data switch.

When the data broadcast switch is configured with 0X00, the data broadcast is turned off; when the data broadcast switch is configured with 0X01, the data broadcast is turned on.

There are six communication baud rate configuration parameters: 0X00, 0X01, 0X02, 0X03, 0X04, and 0X05, corresponding to baud rates of 9600, 14400, 19200, 38400, 57600, and 115200 bits per second.

The length of the data output switch is 1 byte, and there are 8 bits in total. Each bit corresponds to different output data. The order from high to low is: control attitude and heading angle data output, control thermometer data output, control magnetic field meter compensation data output , Control accelerometer compensation data output, control gyroscope compensation data output, control magnetometer bare data output, control accelerometer bare data output, control gyroscope bare data output. When the corresponding bit is 0, the data output of this item is turned off, and when the bit is 1, the data output of this item is turned on.

(2) Reset the address field: "method number" 71, "data length" 0X01, the message frame only contains 1-byte data of the address field that needs to be reset.

(3) Read the communication configuration information: "method number" 60, the host sends "data length" 0X00, and the "data length" 0X04 in the slave response message frame contains 4 types of configuration information, which are: data broadcast switch configuration, communication Baud rate configuration, data refresh rate configuration (20-100Hz), output data switch, each type of information occupies 1 byte.

(4) Read the current module address field: "method number" 61, the host sends "data length" 0X00, and the "data length" 0X01 in the slave response message frame contains one type of data: the current module address.

2. Command setting module, "module code" 0X02, has the following 7 kinds of configuration information:

(1) Re-initial alignment is required: "method number" 70, "data length" 0X00, the slave does not need to return a message frame.

(2) Restore factory settings: "method number" 71, "data length" 0X00, the slave does not need to return message frames.

(3) Set the accelerometer reference vector: "method number" 72, "data length" 0X00, the slave does not need to return a message frame.

(4) Set the reference vector of the magnetometer: "method number" 73, "data length" 0X00, the slave does not need to return a message frame.

(5) Configuration information is written into the cache Flash: "method number" 60, "data length" 0X00 in the message frame sent by the master, the slave needs to return a response message frame containing status information, if the write is normal, the "status bit" 0X00, write If the input fails, the "status bit" is 0X01, and the "data length" in the response message frame is 0X00.

(6) Require the gyroscope sensor to recalibrate the zero point: "method number" 61, "data length" 0X00 in the message frame sent by the host, and the slave needs to return a response message frame containing status information, and the "status bit" 0X00 after calibration is completed, otherwise "Status bit" 0X01, "data length" 0X00 in the response message frame.

(7) Single output of data is required: "method number" 74, "data length" 0X00, this configuration information is only valid when data broadcasting is disabled, and the data configured by all output switches is output at one time.

3. The data output module, "module code" 0X03, has the following 5 kinds of configuration information:

(1) Gyroscope compensation data output: "method number" 63, "data length" 0X06, 6-byte data in sequence: short type (two-complement code) gyroscope X-axis compensation data H bit, short type (two-complement code ) Gyroscope X-axis compensation data L bit, short type (two complement code) gyroscope Y-axis compensation data H bit, short type (two complement code) gyroscope Y-axis compensation data L bit, short type (two complement code) gyroscope Gyroscope Z-axis compensation data H bit, short type (two complement code) gyroscope Z-axis compensation data L bit. Splicing H and L bit data into short data, the output data unit is 0.1deg/s (angular velocity unit, degree/second). If the X-axis gyroscope outputs 0X0003, the output data is.

(2) Accelerometer compensation data output: "method number" 64, "data length" 0X06, 6-byte data in sequence: short type (two-complement code) accelerometer X-axis compensation data H bit, short type (two-complement code ) Accelerometer X-axis compensation data L bit, short type (two’s complement) accelerometer Y-axis compensation data H bit, short type (two’s complement) accelerometer Y-axis compensation data L bit, short type (two’s complement) acceleration H bit of Z-axis compensation data of meter, L bit of Z-axis compensation data of short type (two’s complement code) accelerometer. Splicing H and L bit data into short data, the output data unit is 0.1mg (acceleration unit, milligal). If the X-axis accelerometer outputs 0X0064, the output data is.

(3) Magnetic field meter compensation data output: "method number" 65, "data length" 0X06, 6-byte data in sequence: short type (two complement code) magnetic field meter X-axis compensation data H bit, short type (two complement code ) Magnetometer X-axis compensation data L bit, short type (two complement code) magnetometer Y axis compensation data H bit, short type (two complement code) magnetometer Y axis compensation data L bit, short type (two complement code) magnetic field Z-axis compensation data H bit, short type (two-complement code) magnetometer Z-axis compensation data L bit. Splicing H and L bit data into short data, the output data unit is 0.1mGs (magnetic field unit, milligauss). If the X-axis magnetic field meter outputs 0XFEA2, the output data is.

(4) Temperature sensor data output: "method number" 66, "data length" 0X02, 2 bytes of data are: short type (two complement code) temperature sensor data H bit, short type (two complement code) temperature sensor data L bit. Splicing H and L bit data into short data, the output data unit is 0.01°C (Celsius). If the temperature sensor data outputs 0X09DD, the output data is.

(5) Heading and attitude calculation data output: "method number" 67, "data length" 0X06, 6-byte data in turn: short type (two complement code) roll data H bit, short type (two complement code) Roll data L bit, short type (two complement code) pitch data H bit, short type (two complement code) pitch data L bit, short type (two complement code) heading data H bit, short type (two complement code) heading Data L bits. Splicing H and L bit data into short data, the output data unit is 0.01deg (heading unit, angle). For example, if the X-axis rolls and outputs 0XFEA2, the output data is 0X051E for the Y-axis pitch, and the output data is 0X00C8 for the Z-axis heading.

Error detection domain: The role of the error detection domain in the master and the slave is the same, and it is used to detect whether there is an error in the transmission of the message frame. A member of the "Error Detection Domain" is the "Checksum". The checksum is equal to the low 8 bits of all members in this message frame. For master, checksum = start flag 1 + start flag 2 + node ID + module number + method number + data length + parameter 1 + ... + parameter N; for slave, checksum = start flag 1+ Start flag 2 + node ID + module number + method number + data length + status bit + parameter 1 + ... + parameter N.

Implementation steps of the wireless interface communication protocol of the automatic inspection robot of the present invention:

(1) First, the host console configures the host message frame according to actual needs. The message frame structure includes: 2-byte start bit, 1-byte address field, and 3-byte function field (where 1 byte represents the function module code, 1 Byte represents method encoding, 1 byte represents data length), N byte data field, 1 byte error detection field. Start flag bit, respectively write start flag 1 (0X55), start flag 2 (0XAA). Write the ID of the automatic inspection robot that needs to send instructions into the address field, and the function is to notify the slave that the master message frame will start sending. The host console configures functional domains according to specific functional requirements. Select the module to be called from the communication setting module, instruction setting module, data output module and other modules. The host writes the corresponding "module code" into the first byte of the function field in the message frame. At the same time, find the corresponding "method number" and the "data length" corresponding to the "method number", and write the "method code" and "data length" into the 2nd and 3rd bytes of the function field in the message frame. The message frame allocates the size of the data field according to the "data length", and writes each data parameter into the data field. Calculate the "error detection domain" according to the calculation method of checksum = start flag 1 + start flag 2 + node ID + module number + method number + data length + parameter 1 + ... + parameter N, and write it into the message in frame. The master message frame is configured and ready to be sent to the slave.

(2) Secondly, after receiving the message frame from the master, the slave will analyze the information in the "module code", "method code" and "data length" in the functional domain in turn. If the "data length" is not 0X00, then further analyze the data information in the domain, and timely adjust the opening and closing of the functions of each module of the slave according to the specific information. If the slave needs to return a response message frame to the master, the structure of the response message frame fed back by the slave includes: 2-byte start bit, 1-byte address field, 4-byte function field (1 byte for the code of the accessed function module, 1 byte accessed method encoding, 1 byte data length, 1 byte status bit), N byte data field, 1 byte error detection field. According to the "module code" and "method code", rewrite the "data length" in the function field of the response message frame of the slave machine, and write the "status bit" information into the fourth byte of the function field, if the current state information of the slave machine If normal, write 0X00, otherwise write 0X01. And write each data parameter of the slave into the data field. Calculate the "error detection domain" according to the calculation method of checksum = start flag 1 + start flag 2 + node ID + module number + method number + data length + status bit + parameter 1 + ... + parameter N, and write it sent to the master in the response message frame of the incoming slave.

The technical concept of the present invention is: in view of the wireless transmission characteristics of the inspection robot, in order to ensure the accuracy of the control information and the returned information, an asynchronous communication method based on the master/slave message structure is adopted to distribute the control information to various modules. , and according to the specific control information requirements, write the corresponding "method number" into the message frame, and match it with the corresponding "data length". After receiving the host message frame, the slave machine parses the corresponding module and method information. If it needs to return the response message frame, it writes data information such as status bits into it, and calculates the error detection field.

The beneficial effects of the present invention are mainly manifested in that a wireless interface communication protocol between the console and the inspection robot is designed by using the master/slave message structure, and the communication protocol between the console and the inspection robot can be provided by the present invention. Effective communication ensures that sufficient control information is provided and at the same time, real-time information and signal feedback of the inspection robot can be obtained.

Description of drawings

Fig. 1 is a schematic diagram of forming a host wireless communication message frame;

FIG. 2 is a schematic diagram of formation of a slave wireless communication response message frame.

Detailed ways

The present invention will be further described below.

Referring to Figures 1 to 2, a wireless interface communication protocol for automatic inspection robots is an asynchronous communication protocol based on the master/slave message frame structure. The transmission of message frames is strictly subject to the master/slave response mechanism. The wireless interface communication protocol includes the following step:

(1) First, the host console configures the host message frame according to the actual needs. The message frame structure includes: 2-byte start bit, 1-byte address field, 3-byte function field (1-byte function module code, 1-byte method encoding, 1-byte data length), N-byte data field, and 1-byte error detection field. Start flag bit, respectively write start flag 1 (0X55), start flag 2 (0XAA). Write the ID of the automatic inspection robot that needs to send instructions into the address field, and the function is to notify the slave that the master message frame will start sending. The host console configures functional domains according to specific functional requirements. Select the module to be called from the communication setting module, command setting module, data output module and other modules. The host writes the corresponding "module code" into the first byte of the function field in the message frame. At the same time, find the corresponding "method number" and the "data length" corresponding to the "method number", and write the "method code" and "data length" into the 2nd and 3rd bytes of the functional field in the message frame. The message frame allocates the size of the data field according to the "data length", and writes each data parameter into the data field. Calculate the "error detection domain" according to the calculation method of checksum = start flag 1 + start flag 2 + node ID + module number + method number + data length + parameter 1 + ... + parameter N, and write it into the message in frame. The master message frame is configured and ready to be sent to the slave.

(2) Secondly, after receiving the message frame from the master, the slave will analyze the information in the "module code", "method code" and "data length" in the functional domain in turn. If the "data length" is not 0X00, then further analyze the data information in the domain, and timely adjust the opening and closing of the functions of each module of the slave according to the specific information. If the slave needs to return a response message frame to the master, the structure of the response message frame fed back by the slave includes: a 2-byte start bit, a 1-byte address field, and a 4-byte function field (where 1 byte represents the accessed function module Encoding, 1 byte indicates the code of the accessed method, 1 byte indicates the data length, 1 byte indicates the status bit), N byte data field, 1 byte error detection field. According to the "module code" and "method code", rewrite the "data length" in the function field of the response message frame of the slave machine, and write the "status bit" information into the fourth byte of the function field, if the current state information of the slave machine If normal, write 0X00, otherwise write 0X01. And write each data parameter of the slave into the data field. Calculate the "error detection domain" according to the calculation method of checksum = start flag 1 + start flag 2 + node ID + module number + method number + data length + status bit + parameter 1 + ... + parameter N, and write it sent to the master in the response message frame of the incoming slave.

Figure 1 shows the configuration process of the console as the host sending message frames during the wireless communication process between the console and the automatic inspection robot. First, write the start flag bit and the destination robot ID into the host message frame in sequence. Secondly, according to the actual needs, select the "module code" and "method number" of the corresponding function, and find the "data length" corresponding to the "method number". Write the "data length", "module code" and "method number" into the message frame function field in turn. If the "data length" is not 0X00, then write the relevant parameters into the data field in sequence. Finally, the checksum is written into the error detection field. After the host message frame is configured, it is ready to be sent to the target inspection robot according to the target robot ID.

Figure 2 shows the process of wireless communication between the console and the automatic inspection robot. The process of automatically inspecting the robot as a slave machine to send a response message frame. First, write the start flag bit and the local robot ID into the message frame of the slave machine in sequence. Secondly, find the corresponding "data length" according to the "module code" and "method code" in the host message frame. Write the "data length", "module code" and "method number" into the message frame function field in turn. If the slave machine can correctly return the data information of the machine at present, the "status bit" is written into 0X00, otherwise it is written into 0X01. If the "data length" is not 0X00, then write the relevant parameters into the data field in sequence. Finally, the checksum is written into the error detection field. After the configuration of the slave reply message frame is ready to send it to the console.

Claims (5)

1. A wireless interface communication protocol for an automatic inspection robot, characterized in that: it may further comprise the steps: 1) The host console configures the host console message frame according to actual needs. The message frame structure includes: 2-byte start bit, 1-byte address field, 3-byte function field, N-byte data field, and 1-byte error detection field, the 2-byte start bit is written into the start flag 1 and the start flag 2 respectively, and the ID of the automatic inspection robot that needs to send the command is written into the address field, and the automatic inspection robot is notified that the host console will start sending message frame; 2) The host console configures the function domain according to the specific function needs; select the module to be called from the communication setting module, command setting module, data output module and other modules; the host console writes the corresponding "module code" into the message frame function At the same time, find the corresponding "method number" and the "data length" corresponding to the "method number", and write the "method code" and "data length" into the second byte of the function field in the message frame , 3 bytes, the message frame allocates the size of the data field according to the "data length", and writes each data parameter into the data field; 3) Calculate the "error detection domain" according to the calculation method of checksum = start flag 1 + start flag 2 + node ID + module number + method number + data length + parameter 1 +... + parameter N, and write it into the message frame; the host console message frame is configured and ready to be sent to the automatic inspection robot; 4) After the automatic inspection robot receives the message frame from the host console, it will analyze the information in the "module code", "method code" and "data length" in the functional domain in sequence. If the "data length" is not 0X00, it will further analyze information in the data domain, and timely adjust the opening and closing of each module function of the automatic inspection robot according to the specific information; if the automatic inspection robot needs to return a response message frame to the host console, the response message frame structure fed back by the automatic inspection robot includes : 2-byte start bit, 1-byte address field, 4-byte function field, N-byte data field, 1-byte error detection field; 5) According to the "module code" and "method code", rewrite the "data length" in the functional field of the automatic inspection robot response message frame, and write the "status bit" information into the fourth byte of the functional field. If the current status information of the inspection robot is normal, write 0X00, otherwise write 0X01, and write each data parameter of the automatic inspection robot into the data field; 6) Calculate the "error detection domain" according to the calculation method of checksum = start flag 1 + start flag 2 + node ID + module number + method number + data length + status bit + parameter 1 + ... + parameter N, and set It is written into the automatic inspection robot response message frame and sent to the host console. 2. A wireless interface communication protocol for an automatic inspection robot according to claim 1, characterized in that: in the 3-byte functional domain of step 1), 1 byte represents the functional module code, and 1 byte represents the method code , 1 byte indicates the data length. 3. A wireless interface communication protocol for an automatic inspection robot according to claim 1, characterized in that: in the step 1), the initial symbol 1 is 0X55, where 0X represents hexadecimal, and the initial symbol 2 is 0XAA. 4. A wireless interface communication protocol for an automatic inspection robot according to claim 1, characterized in that: N in the parameter N in the step 3) and step 6) represents the number of parameters. 5. A wireless interface communication protocol for an automatic inspection robot according to claim 1, characterized in that: in the 4-byte functional domain of step 4, 1 byte represents the code of the accessed functional module, and 1 byte represents the code of the accessed function module. Access method encoding, 1 byte indicates data length, and 1 byte indicates status bit.