High-real-time LoRa wireless networking data transmission method

Abstract

The invention discloses a high-real-time LoRa wireless networking data transmission method. LoRa wireless networking comprises a master node and a plurality of slave nodes; the method comprises the following steps of: dividing time slots into a host time slot, a high-speed time slot, a preemption time slot and a polling time slot; the host time slot is used for the main node to send a polling frame; the high-speed time slot is used for the slave node to respond to the real-time state and data, and when the state of the slave node changes or emergency alarm data is uploaded, a slave node preemption frame is sent in the preemption time slot; the slave node preemption frame comprises a slave node address; and the master node adds the slave node address analyzed in the preemption time slot into a high-speed time slot list, and the added slave node is regarded as successful preemption to obtain the right to use the high-speed time slot. According to the high-real-time LoRa wireless networking data transmission method provided by the invention, the LoRa technology can be applied in a real-time control system, real-time communication is realized in a scene with high-density deployment and low-concurrency node equipment, and the real-time performance is not influenced by the number of nodes.

Description

Technical Field

[0001] The present invention relates to the technical field of LoRa wireless networking, and in particular to a high-real-time LoRa wireless networking data transmission method. Background Art

[0002] LoRa networking uses spread-spectrum frequency modulation technology (Chirp Spread Spectrum, CSS), which is usually used for wireless networking communication within 2 to 5 kilometers. Currently, common networking methods mainly include LoRaWAN, LoRaMesh, private LoRa networks, and hybrid networking with other wireless signals, etc., which are widely used in scenarios such as farm monitoring, photovoltaic power generation monitoring, remote meter reading, and environmental monitoring.

[0003] Existing LoRa networking technologies all face problems such as network congestion and co-frequency signal interference when deployed at high density. Although some private LoRa protocols solve the co-frequency interference problem through host polling or slave timing upload methods, they are only applicable to application scenarios with large collection intervals and low requirements for data real-time performance.

[0004] LoRa networking methods are usually based on time-division multiplexing, frequency-division multiplexing, or a combination of the two for scheduling technology. For example, LoRaWAN is a typical standard networking technology. The gateway calculates and schedules to divide frequencies and time slots, and node devices report data at specific time slots. When there are many devices, the collection period of a single device may reach several minutes or more. When the networking scale is large (>50 units), the network congestion delay is large, and co-frequency interference is likely to occur, resulting in data loss. Among them, LoRaWAN usually uses more than 8 receiving frequencies for a single subnet, occupying a large bandwidth. In addition, a network server is required to manage the entire network, resulting in high costs. The LoRaMESH networking technology features an automatic network topology, realizes the data forwarding function between nodes, extends the communication distance, and is more flexible in spatial deployment. The disadvantage is still worse data real-time performance. Some private LoRa networks have also been optimized in terms of low-latency transmission based on similar technologies, but the improvement in the real-time performance of the entire network data transmission is limited, and they are still not applicable to some scenarios with high density deployment and high real-time control requirements. Summary of the Invention

[0005] The technical problem to be solved by the present invention is: to provide a high-real-time LoRa wireless networking data transmission method.

[0006] The technical solution adopted by the present invention to solve the above technical problem is: a high-real-time LoRa wireless networking data transmission method, where the LoRa wireless networking includes a master node formed by a LoRa master node gateway device and several slave nodes formed by LoRa slave node gateway devices;

[0007] The method includes:

[0008] The time slots are divided into host time slots, high-speed time slots, preemption time slots, and polling time slots;

[0009] The host time slot is the first time slot for the master node to initiate polling and is used for the master node to send a polling frame;

[0010] The high-speed time slot is used for the slave node to reply with real-time status and data, and the high-speed time slot is defined in the master node's polling frame;

[0011] Set the preemption time slot. When the status of the slave node changes or there is emergency alarm data to be uploaded, the slave node sends a preemption frame in the preemption time slot; the slave node preemption frame includes the slave node address;

[0012] The master node adds the slave node address parsed in the preemption time slot to the high-speed time slot list. The added slave node is regarded as having successfully preempted and obtains the right to use the high-speed time slot;

[0013] If the slave node sends a slave node preemption frame but the master node does not receive or does not correctly parse the address of the slave node, it is regarded as a preemption failure.

[0014] Preferably, when the status of the slave node device changes or there is emergency alarm data to be reported in real time but the slave node fails to preempt, after a randomly set waiting time, if the slave node has not been added to the high-speed time slot list, it continues to send a slave node preemption frame in the preemption time slot until the preemption is successful.

[0015] Preferably, the polling time slot is used for the slave nodes polled one by one by the master node to reply with real-time status and data;

[0016] The slave nodes are divided into two address queues, namely the high-speed time slot list and the polling time slot list; the time slot scheduler is responsible for scheduling the right to use all time slots;

[0017] When the time slot scheduler finds that the data of a slave node address in the high-speed time slot list no longer changes within a set period, it deletes the slave node from the high-speed time slot list, and the master node no longer requests the data of the slave node device in real time. The slave node device joins the polling time slot list;

[0018] When the time slot scheduler finds that the status data of a certain slave node in the polling time slot list changes, or there is a control instruction from the upper computer for the slave node, it adds the slave node to the high-speed time slot list.

[0019] Preferably, slave nodes are classified into high-privilege slave nodes, medium-privilege slave nodes, and low-privilege slave nodes according to the real-time requirements of the slave nodes. When there are high-privilege slave nodes in the high-speed time slot list, the master node polls frames to call high-privilege slave nodes, does not call medium-privilege slave nodes and low-privilege slave nodes, and there is no polling time slot. Devices in the polling time slot list are not called, and the preemption time slot is reserved;

[0020] When the highest level of the slave nodes in the high-speed time slot list is a medium-privilege slave node, the master node polls frames to call all the slave nodes in the high-speed time slot list, and there is no polling time slot;

[0021] When the highest level of the slave nodes in the high-speed time slot list is a low-privilege slave node, the master node polls frames to call all the slave nodes in the high-speed time slot list, and at the same time cyclically calls 1 slave node in the polling time slot list.

[0022] Preferably, the slave node judges the right to use the time slot by parsing the master node polling frame. When the call address corresponding to the master node polling frame is the address of the slave node, the slave node calculates the time to initiate a response according to the number and sequential position of the time slots. When the timer arrives, a slave node preemption frame or a response frame is sent to the corresponding time slot.

[0023] Preferably, the timing for the slave node to send the slave node preemption frame is to select a random time period starting from the start time of the preemption time slot.

[0024] Preferably, the high-real-time LoRa wireless networking data transmission method includes the following steps:

[0025] S1. Initialize LoRa communication parameters;

[0026] S2. Initialize the time slot scheduler;

[0027] S3. Send the master node polling frame;

[0028] S4. Judge whether there is a high-speed time slot;

[0029] If there is a high-speed time slot, receive and parse the high-speed time slot data, and judge whether the status data of the slave node has changed;

[0030] If the status data has changed, go to step S5;

[0031] If the status data of the slave node has not changed, delete the node from the high-speed time slot list and then go to step S5;

[0032] If there is no high-speed time slot, go to step S5;

[0033] S5. Judge whether the parsing of the high-speed time slot is completed;

[0034] If the parsing of the high-speed time slot is not completed, return to step S4;

[0035] If the high-speed time slot parsing is completed, go to step S6;

[0036] S6. Determine whether there is preemptive time slot data;

[0037] If there is preemptive time slot data, add the node address to the high-speed time slot list and then go to step S7;

[0038] If there is no preemptive time slot data, go to step S7;

[0039] S7. Determine whether there is polling time slot data;

[0040] If there is polling time slot data, parse the polling time slot data and determine whether the status data of the slave node has changed;

[0041] If the status data has changed, add the node address to the high-speed time slot list and then go to step S8;

[0042] If the status data has not changed, go to step S8;

[0043] If there is no polling time slot data, go to step S8;

[0044] S8. Determine whether there is a control instruction issued;

[0045] If there is a control instruction issued, add the node address to the high-speed time slot list and then go to step S3;

[0046] If there is no control instruction issued, go to step S3.

[0047] Preferably, the high-real-time LoRa wireless networking data transmission method includes the time slot response and status reporting method of the slave node, and the time slot response and status reporting method of the slave node includes the following steps:

[0048] S21. Initialize LoRa communication parameters;

[0049] S22. Receive the master node polling frame;

[0050] S23. Align the start time of the time slot;

[0051] S24. Determine whether there is a high-speed time slot allocated for response,

[0052] If there is a high-speed time slot for response, calculate the time slot time and start the high-speed time slot response timer, and then go to step S25;

[0053] If there is no high-speed time slot for response, go to step S25;

[0054] S25. Determine whether the polling time slot address is equal to the address of this node;

[0055] If the polling time slot address is equal to the address of the local node, calculate the polling time slot duration, start the polling time slot response timer, and then proceed to step S26;

[0056] If the polling time slot address is not equal to the address of the local node, proceed to step S26;

[0057] S26. Determine whether the status data has changed.

[0058] If the status data has changed, determine whether a high-speed time slot has been allocated. If a high-speed time slot has been allocated, start the preemption time slot transmission timer and then proceed to step S27;

[0059] If the status data has not changed, proceed to step S27;

[0060] S27. Determine whether there is a control command.

[0061] If there is a control command, execute the control command and then proceed to step S22;

[0062] If there is no control command, proceed to step S22.

[0063] The beneficial effects of the present invention are as follows: The high-real-time LoRa wireless networking data transmission method of the present invention can apply LoRa technology in a real-time control system, achieve real-time communication in a scenario with high-density deployment and low-concurrency node devices, the real-time performance is not affected by the number of nodes, the data delay can be as short as 2 seconds, and the real-time performance is not affected by the number of nodes. The present invention solves the problem of co-channel interference, can send real-time control commands to all slave node devices within the subnet, and can simultaneously collect the real-time status of the slave node devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 is the topological structure diagram of the LoRa wireless networking in the present invention;

[0065] Figure 2 is the definition structure diagram of the time slots and each frame in the present invention;

[0066] Figure 3 is the state diagram of the time slot scheduler;

[0067] Figure 4 is the working flow chart of the time slot scheduler;

[0068] Figure 5 is the response and status reporting flow chart of the slave node. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0069] Now, the present invention will be further described in detail with reference to the accompanying drawings and preferred embodiments. These drawings are all simplified schematic diagrams, only illustrating the basic structure of the present invention in a schematic manner, and therefore only showing the components related to the present invention.

[0070] A high-real-time LoRa wireless networking data transmission method. The LoRa wireless networking includes a master node formed by a LoRa master node gateway device and several slave nodes formed by LoRa slave node gateway devices. As Figure 1 shown, the LoRa wireless networking consists of 1 master node and several slave node devices such as slave node 1#, slave node 3#, slave node 3#, slave node 4#, etc. It usually forms a star layout and can also be applied to other layouts such as LoRaMESH networks. The master node in the LoRa network can also use 2 LoRa master node gateway devices that are hot standby for each other, or two LoRa channels.

[0071] As Figure 2 shown, the method includes: dividing time slots into host time slots, high-speed time slots, preemptive time slots, and polling time slots. There is only 1 polling time slot, which is not mandatory. The polling time slot is used for the slave nodes polled one by one by the master node to respond with real-time status and data. The master node polling frame includes a frame header, time slot width, number of time slots, addresses of several high-speed slave nodes, polling node address, control instructions, and frame checksum. The slave node data frame includes a frame header, slave node address, slave node data, and frame checksum. The slave node preemptive frame includes a frame header, slave node address, and frame checksum.

[0072] The host time slot is the first time slot when the master node initiates polling and is used for the master node to send a polling frame;

[0073] The high-speed time slot is used for the slave nodes to respond with real-time status and data, and the high-speed time slot is defined in the master node polling frame; there can be multiple high-speed time slots, and the "high-speed slave node address n" (0 ≤ n ≤ number of slave nodes) called in the master node polling frame responds with status and data in the corresponding time slot;

[0074] Set preemptive time slots, and the preemptive time slots are divided into several segments according to the time slot length.

[0075] As Figure 3 shown, the time slot scheduler is responsible for scheduling the usage rights of all time slots, dividing the slave nodes into two address queues, namely the high-speed time slot list and the polling time slot list. Each time the master node polling frame is sent, it will call the slave nodes in the high-speed time slot list and 1 slave node in the polling time slot list. The polling time slot list contains all slave nodes. All host time slots are dedicated time slots for the master node to initiate polling, and all slave nodes align their time after receiving the master node polling frame.

[0076] As Figure 3The figure shows the state diagram of the time slot scheduler. ① When it is found within a set period that the data of a slave node address in the high-speed time slot list no longer changes, the slave node is deleted from the high-speed time slot list, and the master node no longer requests the data of the slave node device in real time. That is, the slave node device does not need to send the slave node data frame in real time, and the slave node device is added to the polling time slot list;

[0077] ② When the time slot scheduler finds that the status data of a certain slave node has changed in the polling time slot list, or there is a control instruction from the upper computer for this slave node, the slave node is added to the high-speed time slot list;

[0078] ③ When the status of the slave node changes or there is emergency alarm data to be uploaded, a slave node preemption frame is sent in the preemption time slot;

[0079] ④ The master node adds the slave node address parsed in the preemption time slot to the high-speed time slot list. The added slave node is regarded as successful in preemption and obtains the right to use the high-speed time slot;

[0080] ⑤ If the slave node sends a slave node preemption frame, but the master node does not receive or correctly parse the address of the slave node, it is regarded as a preemption failure.

[0081] Because the slave node preemption frame is very short, in order to avoid multiple slave node devices preempting at the same time, preferably, a waiting time algorithm that waits at any time can also be built in. When the status of the slave node device changes or there is emergency alarm data to be reported in real time but the slave node preemption fails, after a randomly set waiting time, if the slave node has not been added to the high-speed time slot list, continue to send the slave node preemption frame in the preemption time slot until the preemption is successful.

[0082] As Figure 4 shown in the figure is the working flow chart of the time slot scheduler. The master node initiates polling, parses the high-speed time slot list that needs to be called in real time according to the polling result, and then initiates the next polling, repeating like this.

[0083] Specifically, in an optional implementation manner, a high-real-time LoRa wireless networking data transmission method includes the following steps:

[0084] S1. Initialize LoRa communication parameters, such as frequency points, transmission power, spreading parameters, etc.;

[0085] S2. Initialize the time slot scheduler, defaulting to no high-speed time slots;

[0086] S3. Send a master node polling frame, including real-time control commands;

[0087] S4. Determine whether there are high-speed time slots;

[0088] If there are high-speed time slots, receive and parse the high-speed time slot data, and determine whether the status data of the slave node has changed;

[0089] If the status data has changed, go to step S5;

[0090] If the status data of the slave node has not changed, delete the node from the high-speed time slot list and then go to step S5;

[0091] If there are no high-speed time slots, go to step S5;

[0092] S5. Determine whether the parsing of the high-speed time slots is completed;

[0093] If the parsing of the high-speed time slots is not completed, return to step S4;

[0094] If the parsing of the high-speed time slots is completed, go to step S6;

[0095] S6. Determine whether there is preemption time slot data;

[0096] If there is preemption time slot data, add the node address to the high-speed time slot list and then go to step S7;

[0097] If there is no preemption time slot data, go to step S7;

[0098] S7. Determine whether there is polling time slot data;

[0099] If there is polling time slot data, parse the polling time slot data and determine whether the status data of the slave node has changed;

[0100] If the status data has changed, add the node address to the high-speed time slot list and then go to step S8;

[0101] If the status data has not changed, go to step S8;

[0102] If there is no polling time slot data, go to step S8;

[0103] S8. Determine whether there is a control instruction issued;

[0104] If there is a control instruction issued, add the node address to the high-speed time slot list and then go to step S3;

[0105] If there is no control instruction issued, go to step S3.

[0106] Specifically, in an optional implementation manner, the slave nodes are divided into high-privilege slave nodes, medium-privilege slave nodes, and low-privilege slave nodes according to the real-time requirements of the slave nodes. When there are high-privilege slave nodes in the high-speed time slot list, the master node polls and calls the high-privilege slave nodes, does not call the medium-privilege slave nodes and the low-privilege slave nodes, and there are no polling time slots, does not call the devices in the polling time slot list, and retains the preemption time slots;

[0107] When the highest level of the slave nodes in the high-speed time slot list is the intermediate privilege slave node, the master node polls all slave nodes in the high-speed time slot list without polling time slots;

[0108] When the highest level of the slave nodes in the high-speed time slot list is the low privilege slave node, the master node polls all slave nodes in the high-speed time slot list and simultaneously circularly calls 1 slave node in the polling time slot list.

[0109] As Figure 5 shown is the flowchart of the response and status reporting of the slave node.

[0110] A high-real-time LoRa wireless networking data transmission method includes a response and status reporting method for slave nodes. The response and status reporting method for slave nodes includes the following steps:

[0111] S21. Initialize LoRa communication parameters, such as frequency point, transmission power, spreading parameter, etc.;

[0112] S22. Receive the master node polling frame; include real-time control commands;

[0113] S23. Align the start time of the time slot;

[0114] S24. Determine whether there is a high-speed time slot allocated for response,

[0115] If there is a high-speed time slot for response, calculate the time slot time, start the high-speed time slot response timer, and then go to step S25;

[0116] If there is no high-speed time slot for response, go to step S25;

[0117] S25. Determine whether the polling time slot address is equal to the address of this node;

[0118] If the polling time slot address is equal to the address of this node, calculate the polling time slot time, start the polling time slot response timer, and then go to step S26;

[0119] If the polling time slot address is not equal to the address of this node, go to step S26;

[0120] S26. Determine whether the status data has changed,

[0121] If the status data has changed, determine whether there is a high-speed time slot allocated. If there is a high-speed time slot allocated, start the preemptive time slot transmission timer and then go to step S27;

[0122] If the status data has not changed, go to step S27;

[0123] S27. Determine whether there is a control instruction,

[0124] If there is a control instruction, after executing the control instruction, go to step S22;

[0125] If there is no control instruction, go to step S22.

[0126] Specifically, in an optional implementation, the slave node determines the right to use the time slot by parsing the master node polling frame. When the call address corresponding to the master node polling frame is the address of the slave node, the slave node calculates the time to initiate a response based on the number and sequential position of the time slots. When the timer arrives, the slave node sends a slave node preemption frame or a response frame to the corresponding time slot.

[0127] Specifically, in an optional implementation, the timing for the slave node to send a slave node preemption frame is to select a random time period starting from the start moment of the preemption time slot. This method can significantly reduce the co-channel interference problem caused by slave node concurrency.

[0128] The high-realtime LoRa wireless networking data transmission method of the present invention can apply LoRa technology in a real-time control system, achieve real-time communication in a scenario with high-density deployment and low-concurrency node devices, the real-time performance is not affected by the number of nodes, the data delay can be as short as 2 seconds, and the real-time performance is not affected by the number of nodes. The present invention solves the co-channel interference problem, can send real-time control commands to all slave node devices within the subnet, and can simultaneously collect the real-time status of the slave node devices.

[0129] The present invention can be used in control systems with high real-time requirements, such as agricultural Internet of Things (irrigation scheduling), valve pipeline control, industrial automation, smart fishing farms, remote monitoring, etc. It can execute control instructions and report status and alarm data in a timely manner, providing a good user experience, facilitating remote monitoring for users, improving production and work efficiency, and enhancing the reliability and security of the system. Using LoRa networking technology reduces the system construction cost.

[0130] What is described in the above specification is only the specific implementation manner of the present invention. Various examples do not constitute a limitation to the essence of the present invention. Those of ordinary skill in the art can modify or deform the above-described specific implementation manner after reading the specification without departing from the essence and scope of the invention.

Claims

1. A high real-time LoRa wireless networking data transmission method, characterized in that: The LoRa wireless network includes a master node formed by a LoRa master node gateway device and a number of slave nodes formed by LoRa slave node gateway devices; The method comprises: The time slots are divided into host time slots, high-speed time slots, preemption time slots, and polling time slots; The host time slot is the first time slot when the master node initiates polling and is used for the master node to send polling frames; High-speed time slots are used to respond to real-time status and data from the slave node. High-speed time slots are defined in the master node polling frame. Set the preemption time slot. When the state of the slave node changes or emergency alarm data is uploaded, send the slave node preemption frame in the preemption time slot. The slave node preemption frame includes the slave node address. The master node adds the slave node address parsed in the preempted time slot to the high-speed time slot list. The added slave node is deemed to have successfully preempted and obtains the right to use the high-speed time slot; If the slave node sends a slave node preemption frame, but the master node does not receive it or does not correctly resolve the address of the slave node, it is considered that the preemption has failed.

2. A high real-time LoRa wireless networking data transmission method according to claim 1, characterized in that: When the status of the slave node device changes or there is emergency alarm data to be reported in real time but the slave node preemption fails, after a randomly set waiting time, if the slave node has not been added to the high-speed time slot list, it continues to send slave node preemption frames in the preemption time slot until the preemption is successful.

3. A high real-time LoRa wireless networking data transmission method according to claim 1, characterized in that: The polling time slot is used for the slave nodes polled one by one by the master node to respond with real-time status and data; Divide the slave nodes into two address queues, namely the high-speed time slot list and the polling time slot list; The time slot scheduler is responsible for scheduling the use of all time slots; When the time slot scheduler finds that the data of a slave node address in the high-speed time slot list does not change within a set period, the slave node is deleted from the high-speed time slot list, the master node no longer requests the data of the slave node device in real time, and the slave node device is added to the polling time slot list; When the time slot scheduler finds that the status data of a slave node has changed in the polling time slot list, or when there is a control instruction from the host computer for the slave node, the slave node is added to the high-speed time slot list.

4. A high real-time LoRa wireless networking data transmission method according to claim 3, characterized in that: According to the real-time requirements of slave nodes, slave nodes are divided into high-level authority slave nodes, intermediate-level authority slave nodes, and low-level authority slave nodes. When there are high-level authority slave nodes in the high-speed time slot list, the master node polls the frame to call the high-level authority slave node, and does not call the intermediate-level authority slave node and the low-level authority slave node. In addition, there is no polling time slot, and the device in the polling time slot list is not called, and the preempted time slot is reserved; When the highest level of slave nodes in the high-speed time slot list is a medium-level authority slave node, the master node polls the frame to call all slave nodes in the high-speed time slot list without polling time slots; When the highest level of slave nodes in the high-speed time slot list is a low-level authority slave node, the master node polls all slave nodes in the high-speed time slot list and cyclically calls one slave node in the polling time slot list.

5. A high real-time LoRa wireless networking data transmission method according to claim 1, characterized in that: The slave node determines the right to use the time slot by parsing the master node polling frame. When the calling address corresponding to the master node polling frame is the slave node address, the slave node calculates the time to initiate a response based on the number of time slots and the sequential position. When the timer arrives, the slave node sends a preemption frame or a response frame to the corresponding time slot.

6. A high real-time LoRa wireless networking data transmission method according to claim 1, characterized in that: The timing for the slave node to send the slave node preemption frame is to select a random time period from the start time of the preemption time slot.

7. A high real-time LoRa wireless networking data transmission method according to claim 1, characterized in that: The steps include: S1. Initialize LoRa communication parameters; S2, initialize the time slot scheduler; S3, sending a master node polling frame; S4, determine whether there is a high-speed time slot; If there is a high-speed time slot, the high-speed time slot data is received and parsed to determine whether the status data of the slave node has changed; If the status data has changed, go to step S5; If the status data of the slave node does not change, the node is deleted from the high-speed time slot list and the process goes to step S5; If there is no high-speed time slot, go to step S5; S5, judging whether the high-speed time slot is resolved; If the high-speed time slot is not resolved, return to step S4; If the high-speed time slot analysis is completed, go to step S6; S6, determine whether there is time slot preemption data; If there is time slot preemption data, then add the node address to the high-speed time slot list and go to step S7; If there is no preempted time slot data, go to step S7; S7, determine whether there is polling time slot data; If there is polling time slot data, the polling time slot data is parsed to determine whether the status data of the slave node has changed; If the status data has changed, then add the node address to the high-speed time slot list and go to step S8; If the status data does not change, go to step S8; If there is no polling time slot data, go to step S8; S8, judging whether a control instruction has been issued; If a control instruction is issued, the node address is added to the high-speed time slot list and then goes to step S3; If no control instruction is issued, go to step S3.

8. A high real-time LoRa wireless networking data transmission method according to claim 1, characterized in that: The method includes a time slot response and status reporting method of a slave node, wherein the time slot response and status reporting method of the slave node includes the following steps: S21, initialize LoRa communication parameters; S22, receiving a master node polling frame; S23, aligning the time slot start time; S24, determine whether there is a high-speed time slot allocated for response, If there is a high-speed time slot for answering, the time slot time is calculated, and the high-speed time slot answering timer is started, and then the process goes to step S25; If there is no high-speed time slot for the response, go to step S25; S25, determine whether the polling slot address is equal to the current node address; If the polling slot address is equal to the node address, the polling slot time is calculated, and the polling slot response timer is started and the process goes to step S26; If the polling slot address is not equal to the current node address, go to step S26; S26, determine whether the status data has changed, If the status data changes, it is determined whether a high-speed time slot is allocated. If a high-speed time slot is allocated, the preemption time slot sending timer is started and the process goes to step S27; If the status data does not change, go to step S27; S27, determine whether there is a control instruction, If there is a control instruction, the control instruction is executed and the process goes to step S22; If there is no control instruction, go to step S22.

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