CN111953373B - A 433MHz-based broadcast message communication device - Google Patents

Abstract

The invention discloses a 433MHz-based broadcast message communication device, which includes a transmitter and a plurality of receivers. The sending end is composed of a PC end, a transmitting end MCU, a 433MHz serial wireless communication module, a GPS receiver and a special sending software running on the PC end. The invention adopts 32 frequency bands of public 433MHz for communication, which can effectively avoid interference, and the broadcast without repeater using wireless data transmission station can reach 8000m. Communication messages are encrypted with AES128 bit. The invention has low cost, reliable communication, adjustable communication distance, and does not depend on the current mobile communication network and the Internet. It is very convenient to use in public news communication and emergency news communication in enterprises, governments, schools, hospitals, military, fire protection, public security, water conservancy, construction, rural residences and other departments.

Description

A 433MHz-based broadcast message communication device

technical field

The invention belongs to the technical field of data communication, and relates to a broadcast message communication device based on 433MHz.

Background technique

In the one-to-many message communication, there are many mature solutions involved. For example, traditional mobile phone SMS group sending; widely used Internet-based communication, such as WeChat, QQ, etc.; civil walkie-talkie communication using a certain frequency band, LoRa communication, NB-IoT communication and so on are currently used in the field of Internet of Things.

The existing problems are: mass message sending relies on the signal of the network operator, and has a certain cost, and its security procedures are general. Internet-based communications, such as WeChat and QQ, are reliable at present, but are more of a private nature. Even if they are used publicly, they must rely on the Internet, and their degree of confidentiality is average. At present, civil walkie-talkie communication is difficult if there is data communication at the same time as its voice communication. Based on LoRa, NB-IoT, etc. are more used for data communication in the Internet of Things, and some also have encryption above AES128. Although there are also features such as one-to-many and ad-hoc networks, their applications are not within the scope of the present invention.

For example, in government departments, it is often necessary to release public or encrypted messages to designated departments or designated groups to notify them of important matters or to notify them of meetings. It is convenient if there are public display terminals on the desktops of the designated groups of these designated departments. If it is in the office hall and other occasions, if it is public information such as work instructions, precautions, and even weather, temperature, traffic instructions, etc., as a supplement to the data, the wireless method that can be moved at any time is undoubtedly flexible. If it is within a unit or department, the wireless encrypted message transmission has a certain degree of confidentiality.

In schools, a large number of classrooms need display terminals to display the utilization of the classrooms during classes and activities. In the student dormitory, a public display terminal is required to display messages from the school, messages from departments to students, messages from teachers to students, etc. Such as informing students to participate in academic lectures, speeches, seminars, etc.

In specific departments of the hospital, it is sometimes necessary to publish hospital-wide public or encrypted messages and notifications. Sometimes it is necessary to notify the staff of certain departments to participate in meetings and joint consultations. A display terminal installed on the office desktop with text and reminder function is convenient.

In some corporate and government segments, there are dedicated private networks dedicated to business. Many internal contacts are based on private networks. Some ban internet access and even limit mobile internet usage. In this case, wireless-based encrypted messaging has the potential to be used.

In public departments of social services, such as fire protection, public security, water conservancy, water supply and power supply and other departments, in emergency situations, as a supplement to traditional communication, public receiving terminals installed in public places, offices or dormitories are needed. In an emergency state, the alarm system of the terminal system can be very important in urgently notifying specific personnel in a race against time to complete something.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a broadcast message communication device based on 433MHz.

Its technical solutions are as follows:

A 433MHz-based broadcast message communication device includes a sender and a plurality of receivers.

The sending end is composed of a PC end, a transmitting end MCU, a 433MHz serial port wireless communication module, a GPS receiver, a 4G/GPRS interface and a special sending software running on the PC end.

The transmitter has two modes, one is the broadcast mode, which can broadcast all or part of the broadcast; the other is the point-to-point mode, which is to send data to the receiver of a specific address, so that it can be released to specific departments and specific groups of people. information.

The transmitter and receiver use a custom protocol for data communication. The format is: receiver address (2B), transmitter address (2B), data length (2B), emergency feature (1B), response feature (1B) , encryption feature (1B), CRC16 (2B), data header (5B), date and time (12B), data part (nB) encrypted by AES128-bit algorithm.

The PC end is connected to the transmitting end MCU through RS485. The PC end running special software is computer software running under Windows with a message sending interface. The software has the functions of selecting mass sending and sending to designated addresses, selecting functions of emergency messages and ordinary messages, whether to respond, whether to encrypt, etc., and finally transmit the data to the MCU of the sending end.

In the transmitter MCU, its serial port 1 is connected to the 433MHz serial port wireless communication module; its serial port 2 is connected to the 4G/GPRS interface; it is connected to the GPS receiver through an RS485 adapter. Its function is to encapsulate the message sent by the PC-side software in the memory for a custom message protocol. The encapsulated data includes the date and time information obtained by decoding the GPS timing message. The encapsulated data packet is connected to the 433MHz serial port wireless communication module in a serial port mode for transmission.

The 4G/GPRS module is a module connected to the mobile Internet, and is connected to the transmitter MCU through the serial port 2 . Multiple authorized mobile phone numbers can connect to the 4G/GPRS module through 4G signals, send transparent data to the transmitter MCU through specific software, and encapsulate a custom message protocol in the MCU in the same way , and finally launch. The purpose is that the authorized staff can use the mobile phone to remotely connect the 4G/GPRS module to publish messages to the users of this network, which is more convenient to use in emergency situations.

The 433MHz serial port wireless communication module is a serial port-based long-distance data transmission module, and is connected to the transmitting end MCU serial port 1 through its serial port. Both receive and transmit. The communication rate is generally set to 9600bps, the air baud rate is 2.5Kbps by default, and the communication channel is 32 channels every 1M from 410MHz.

The receiving end includes a 433MHz serial port wireless communication module, a 7-inch serial port color screen, a receiving end MCU and an alarm unit.

The 433MHz serial wireless communication module is consistent with the module described at the transmitting end.

The serial port of the 433MHz serial port wireless communication module is connected to the serial port 2 of the receiving end MCU. It is used to receive the wireless signal transmitted by the transmitter at a long distance, and transparently transmit it to the MCU of the receiving end.

The receiving end MCU, its serial port 1 is connected to the 7-inch serial port color screen. Serial port 2 is connected to the 433MHz wireless communication module, and its P1.0 port is connected to the alarm unit. The 433MHz wireless communication module transmits the data sent to the local machine to the MCU of the receiving end, and the MCU of the receiving end decodes the sent message according to the self-defined message protocol to obtain the data of each field. Use the decryption key stored in the receiver MCU chip hardware to decrypt the data part, filter out illegal messages, and push the data to be displayed on the 7-inch color screen through serial port 1 for display. Under normal circumstances, the message of the receiver is displayed on the 7-inch color screen. In an emergency, the receiver will send an alarm signal while receiving the message. If a response is required in the field, the receiver will respond to the sender by pressing the button.

The alarm unit is connected to the P1.0 interface of the MCU of the receiving end. With drive circuit and buzzer alarm and LED flashing function.

The 7-inch color screen of the receiving end should contain at least a Chinese character hardware font library of 6763 Chinese characters. In the message received by the receiving end, if it is a Chinese character, it is a Chinese character encoding method. A Chinese character is represented by a 2-byte Chinese character internal code, which greatly reduces the amount of wireless data transmission.

The data at the transmitter and receiver uses AES128 as a symmetric encryption algorithm. The encryption key and decryption key are the same. The encryption method is as follows: the encryption key and the program file of the transmitter MCU are burned into the single-chip microcomputer. When encrypting, the program itself reads the encryption key as a constant to encrypt data; similarly, the decryption key and The program files of the receiving end MCU are programmed into the single chip microcomputer together. When decrypting, the program itself reads the decryption key as a constant to decrypt the data.

The method to prevent the encryption key and decryption key from being illegally read is: MCU adopts STC15W4K32S4, this MCU itself has the function of hardware encryption of program files, and the encryption principle is to use the unique ID number in the world when the MCU chip is manufactured through complex algorithm. The program file is encrypted. Once the program file containing the key is burned into the MCU, the current technology and method cannot be read and decrypted. When the MCU is running normally, the program files stored in it can be automatically decrypted and run normally, and the keys stored as constants can also be read through the normal program files, thereby realizing the process of encryption and decryption.

The method of preventing program files from being illegally rewritten is: downloading password protection, without the password, the running programs of the MCU described in the transmitting end and the receiving end cannot be rewritten.

The frequency range of 433MHz wireless communication module transmission: 410Mhz ~ 441MHz, every 1MHz frequency band, a total of 32 frequency bands, the use of wireless data transmission radio station without relay broadcast can reach 8000m. In order to avoid illegal interference of the same frequency band 433MHz, the same channel, such as No. 17, and the same address, such as (9999) data, the method used is: in the data part of the custom message protocol, a 5-byte data is defined. Data header, for example: "MNPQR". Even if the frequency, channel, and receiving address of illegal data are known, the illegal data is discarded because the decryption key cannot be obtained so that the correct data header cannot be obtained. Thereby avoiding data interference.

Further, in the transmitting end, under normal circumstances, the transmitting end MCU, GPS (except antenna), 4G/GPRS module, AC 220V to +5V power supply module are all packaged in a casing. The USB-to-RS485 module is independent and external. In this way, the USB-to-RS485 module can be installed near the PC, and the transmitter can be installed at a distant location through the RS485 cable connection, which is convenient for installing the GPS antenna and the above-mentioned Wireless transmitter module antenna.

In the power supply part, a standardized industrial switching power supply is used, the output is +5V, the current is 5A, and it has the functions of lightning protection, short-circuit protection, and good heat dissipation.

The USB to RS485 module adopts photoelectric isolation type, which has lightning protection and strong industrial anti-interference. Adopt industrial RS485 signal cable.

The external GPS antenna at the transmitting end requires a gain of more than 38db, a noise value of 1.5db, a standing wave ratio of <1.5:1, circular polarization, an SMA interface antenna, and an antenna length of at least 5m. Block the environment. Can accept Beidou and GPS signals at the same time.

The antenna of the 433MHz wireless communication module at the transmitting end is also external, using an outdoor fiberglass omnidirectional antenna, the feeder length is at least 3m, the vertical polarization mode, the gain is at least 5db, the impedance is 50Ω, and the SMA interface.

At the receiving end, under normal circumstances, the MCU, the wireless communication receiving unit, the alarm unit, etc. are designed and installed on a PCB board, and a power interface with a DC005 structure is provided, using an AC 220V to +5V power adapter, External power supply, you can also use the computer USB interface to supply power.

The receiving end has a 7-inch color screen, which provides four IO interfaces of +5V, GND, RXD, and TXD, and has the functions of displaying full color, text, and images. The length is 200cm and the width is 100mm. The PCB board of the receiving end is placed behind the 7-inch color screen. There are large buttons of 12mm*12mm*5mm on the right side. There are three buttons in the vertical direction, which are emergency response, monitor off, and standby mode buttons. Design the bracket structure to stand on the desktop at an angle of 45 degrees.

The wireless module antenna at the receiving end adopts an external suction cup antenna with an SMA inner needle interface, and the antenna height is 17cm. Because the 433M wireless signal is received, the antenna connected to the receiving end can be indoors.

Compared with the prior art, the beneficial effects of the present invention:

First of all, it can be widely used in various fields of social life. For example, when government policy news is published, the news can be published in multiple locations. Post messages in public areas such as parks, plazas, neighborhoods, hotels, restaurants, and more. Normal use or emergency use in schools, hospitals, fire protection, public security, water conservancy and electricity, communications, agriculture, transportation and other departments. Secondly, the cost is low. For example, traditional enterprise-level SMS has costs, and it does not depend on mobile networks or the Internet. It can be used without application. Also, because most messages are text messages, both the receiving end and the sending end are based on word processing. The speed is fast, the cost Very low, there are dozens or hundreds of receivers, except for a slight delay in communication, the others have no effect. The third is reliability. At present, the module without relay antenna has an air rate of 2.5Kbps and almost no packet loss when the transmission distance is 8000m. In general, 5km to 6km is reliable in complex environments. When there is a first-level relay, it can reach 12-15km. Fourth, it is easy to install. The receiving end can be in the public area, in the office or at home. Fifth, as a supplement to the current local area communication. In case of emergency, users who are authorized to publish can use their mobile phones to connect to the 4G/GPRS interface, and publish data directly through broadcast messages, that is, to realize remote data wireless publishing. Of course, under normal circumstances, you can also use your mobile phone to connect to the 4G/GPRS interface for publishing.

Description of drawings

1a is a block diagram of a transmitter structure of a 433MHz-based broadcast message communication device according to an embodiment of the present invention;

1b is a structural block diagram of a receiving end of a 433MHz-based broadcast message communication device according to an embodiment of the present invention;

2 is a flowchart of providing a transmitter MCU encapsulation data packet according to an embodiment of the present invention;

3 is an embodiment of the present invention providing an embodiment of a transmitter MCU encapsulating a data packet;

FIG. 4 is a flowchart of a receiving end receiving a data packet according to an embodiment of the present invention.

Detailed ways

The technical solutions of the present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments.

In order to further illustrate the advantages of the present invention:

Experimental environment: transmitter, 30 meters above the ground, external wireless transmitter and external suction cup antenna, GPS antenna externally unobstructed. The serial communication rate between MCU and wireless module is 9600bps. Air rate 2400bps, channel 17, transmit power 30db, transmitter address 8888, directional transmission mode, encryption prefix 5 bytes, including CRC check. The packet payload is 64 bytes, and the payload contains a counter. The transmitter continuously transmits 100 packets with an interval of 1 second. The cyclic transmission method is adopted, that is, directional transmission is directed to the first receiving end, then directed transmission is directed to the second receiving end, and finally directed transmission is directed to the third receiving end, and so on.

There are 3 receiving ends. The wireless module antenna of the receiving end adopts an external suction cup antenna with SMA inner needle interface, and the antenna height is 17cm. Because the 433M wireless signal is received, the antenna connected to the receiving end can be indoors, and the serial communication rate between the MCU and the wireless module is 9600 bps. Air rate 2400bps, channel 17, receiver address: 9991, 9992, 9993, there are three receivers in total, and a four-digit digital tube is designed at the receiver to display the counter of the received packet. This counter indicates that the receiver receives the packet at a certain distance. The number of correct decodings.

In the urban multi-building area, within 5km~6km, indoor reception, the packet loss rate is less than 1%, in the open area, there is no building block, the original module test distance is 8000m to receive the signal accurately, and the actual test is within 5km~6km without packet loss. If automatic relay is used, the counter at the receiving end shows that the packet loss rate is less than 3% at about 10km. Because the use of LoRa spread spectrum greatly improves the penetration ability compared with the traditional FSK, it can achieve high power and long distance, and has strong anti-interference ability.

The transmitter and receiver must have the same sending and receiving frequency, the same air baud rate, and the same radio frequency rate, etc., in order to send and receive correctly. Even if the illegal transmitter can transmit through these parameters, because the data packet is carried out in the transmitter MCU according to the present invention, and the data packet header is encrypted by AES128, the illegal transmission information is received because the data header cannot be decrypted. end discarded. Thereby ensuring that the data is not illegally interfered with. For example: the constant string "MNPQR" stored in the MCU is encrypted in the data header part. In the experiment, because the transmitter can be set to broadcast transmission, the receiver address is set to 0xFFFF in the MCU. In this way, the three receivers Both received the signal, but the illegal data was discarded because the header could not be decrypted.

In a multi-building environment, 6km distance, 1 transmitter and 3 receivers, in the idle state, the time and date information obtained by the GPS decoding is transmitted, and displayed on the 7-inch color screen of the receiver. The experiment has been run for several months, and the device is running normally.

Embodiments of the present invention are shown in FIGS. 1 a , 1 b , 2 , 3 and 4 . Provided is a 433MHz broadcast message communication device, which includes a transmitter and a plurality of receivers.

The sending end is composed of a PC end, a transmitting end MCU, a 433MHz serial port wireless transmitter, a GPS receiver, a 4G/GPRS interface and a special sending software running on the PC end.

The PC terminal is connected to the transmitting terminal MCU through an RS485 interface bus. The message to be sent is sent to the transmitter MCU in the form of a serial port for processing. Because the transmitter is installed outdoors, it generally needs to pass through a hub, such as a 4-port RS485 interface hub with lightning protection and optoelectronic isolation.

The transmitter MCU adopts STC15W4K32S4, and its function is to receive the packaged data packet messages sent by the PC, receive GPS messages and decode them, and receive messages from the mobile phone through the 4G/GPRS interface. The data packet is encapsulated by referring to the process method shown in FIG. 2 , and the encapsulated data packet is transmitted to the 433MHz serial port wireless transmitter for transmission.

The 433MHz serial port wireless transmitter is a serial port-based long-distance data transmission module, LORA spread spectrum transmission, the model is SX1278, the transmitter MCU to the SX1278 wireless serial port module set rate 9600bps, power 1W. Working voltage +5V, The working frequency is 433MHz between 410 and 441MHz, and the air transmission rate is 2.5Kbps. It adopts the combination of point-to-point fixed-point transmission mode and broadcast mode, with antenna. In the open and no repeater mode, the transmission distance can reach 8000m.

The GPS receiver is a receiver with an RS485 interface, which can simultaneously receive GPS and Beidou signals. It mainly provides timing to the core MCU, and the timing information includes a time field and a date field, and the time field and the date field are part of the data payload.

The 4G/GPRS interface is a 4G mobile network-based interface module with serial output, which can realize transparent transmission of signals. The purpose is to transmit the message from the mobile phone (authorization required) to the core MCU through the serial port. . In specific implementation, the model that can be used is USR-780-V2, which meets the 4G/GPRS interface requirements.

The PC-side running special software is computer software running under Windows with a message sending interface. The software has the functions of selecting mass sending and sending to designated addresses, selecting functions of emergency messages and ordinary messages, whether to respond, whether to encrypt, etc., and finally transmit the data to the MCU of the sending end. It is developed with Delphi7.0 software, Connect to Microsoft SQL Server2005 database, with functions such as query, delete, statistics and modification.

As an example in the transmitting end, the constructed data packet is shown in FIG. 3 .

The receiving end includes a 433MHz serial wireless receiving end, a 7-inch color screen, an MCU with STC15W as the core, and an alarm unit.

The 433MHz serial wireless receiver has the same frequency as the transmitter, such as 433MHz (410-441 optional), the same channel, such as channel 17 (0-31 optional), and the same air transmission rate, such as 2.5 Kbps, its parameters can be configured statically, and its parameters can be dynamically configured at runtime.

The receiving end adopts a 7-inch color screen with a serial port. Obviously, there should be a difference between use in an indoor environment such as an office and use in an outdoor environment, and it is better to use a display screen of more than 10 inches outdoors. This color display itself has a basic application program environment. As long as data is sent to the control units of the color screen itself through the serial port, these control units will display text or symbols in the corresponding positions. Because the color screen itself must have a Chinese character library, the Chinese character library generally contains at least 6763 Chinese characters. When encoding Chinese characters, it is only necessary to encode one Chinese character into a 2-byte Chinese character internal code, which greatly reduces the data in the air. transmission volume.

The alarm unit is connected to the P1.0 interface of the MCU of the receiving end. With drive circuit and buzzer alarm and LED flashing function.

Referring to FIG. 4 of the example of the present invention, the process of receiving data at the receiving end is opposite to that of the transmitting device. Decode the data of each field from the defined packet.

The method to prevent the encryption key and decryption key from being illegally read is: MCU adopts STC15W4K32S4, this MCU itself has the function of hardware encryption of program files, and the encryption principle is to use the unique ID number in the world when the MCU chip is manufactured through complex algorithm. The program file is encrypted. Once the program file containing the key is burned into the MCU, the current technology and method cannot be read and decrypted. When the MCU is running normally, the program files stored in it can be automatically decrypted and run normally, and the keys stored as constants can also be read through the normal program files, thereby realizing the process of encryption and decryption.

The method of preventing the program file from being illegally rewritten is: downloading password protection, without the password, the running program of the MCU described in the transmitting end and the receiving end cannot be rewritten.

The frequency range of 433MHz wireless communication module transmission: 410Mhz ~ 441MHz, every 1MHz frequency band, a total of 32 frequency bands, the use of wireless data transmission radio station without relay broadcast can reach 8000m. In order to avoid illegal interference of the same frequency band 433MHz, the same channel, such as No. 17, and the same address, such as (9999) data, the method used is: in the data part of the custom message protocol, a 5-byte data is defined. Data header, for example: "MNPQR". Even if the frequency, channel, and receiving address of illegal data are known, the illegal data is discarded because the decryption key cannot be obtained so that the correct data header cannot be obtained. Thereby avoiding data interference.

The above are only preferred specific embodiments of the present invention, and the protection scope of the present invention is not limited thereto. Any person skilled in the art can obviously obtain the simplicity of the technical solution within the technical scope disclosed in the present invention. Variations or equivalent substitutions fall within the protection scope of the present invention.

Claims (6)

1. a broadcast type message communication device based on 433MHz, is characterized in that: be made up of a transmitter and a plurality of receivers, and the transmitter transmits the message data to be sent by serial port with PC or mobile phone short message interface. After the transmitter MCU module, the MCU module will encapsulate the data using the custom protocol method and pass it to the transmitter wireless communication module for transmission; the MCU program memory itself is encrypted by hardware, and the secret key is encrypted by the AES128 algorithm; The terminal adopts multi-address encoding, decodes the message with the encryption key stored by the receiving terminal MCU, and can publish the message point-to-point or one-to-many; the maximum length of the transmitted message is 255 bytes, and the transmitter and receiver use the same Protocol method for data communication; its format is: receiver address 2B, transmitter address 2B, data length 2B, emergency feature 1B, response feature 1B, encryption feature 1B, CRC16 2B, data header 5B, date and time 12B, using AES128 bits Algorithm encrypted payload part nB. 2. The broadcast type message communication device based on 433MHz according to claim 1, is characterized in that: the wireless communication module adopts the 433M data transmitter with extremely low power consumption, small size and high reliability; serial communication, adaptive air rate , the minimum transmission distance is 8000 meters, and the minimum power is 1W. 3. The broadcast message communication device based on 433MHz according to claim 1, is characterized in that: after the receiving end of multiple addresses splits the received data based on the receiving end MCU, the message is output to the device with the 7-inch color LCD display with Chinese character library of serial port. 4 . The 433MHz-based broadcast message communication device according to claim 1 , wherein the receivers of the plurality of addresses have the function of responding messages to the transmitters by pressing keys. 5 . 5. the broadcast type message communication device based on 433MHz according to claim 1, is characterized in that: the MCU that transmitting end and receiving end all adopt is STC15W4K32S4 single chip; At transmitting end, serial port 1 of MCU connects PC by RS485 interface, serial port 2 is connected to the 433MHz wireless communication module through the serial port, and the serial port 3 is connected to the GPS module through the RS485 interface; at the receiving end, the serial port 1 of the receiving end MCU is directly connected to the 433MHz wireless communication module, the serial port 2 is directly connected to the 7-inch serial port color screen, and the serial port 2 is directly connected to the 7-inch serial port color screen through P1.0 The interface outputs the alarm signal to the alarm unit. 6. according to the described broadcast type message communication device based on 433MHz of claim 1, it is characterized in that: the data part that the transmitting end sends encapsulates the date and time information that GPS decoding obtains, thus the receiving end can receive the information that the transmitting end transmits indoors. Time and date information for easy display on specific terminals.

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