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The function and working principle of GPRS DTU

what is GPRS DTU

gprs DTU full name GPRS data transmission unit? At present, in China, there is a more clear agreement on GPRS DTU: GPRS DTU is a GPRS wireless device specially used to transmit serial port data through GPRS network

the four core functions of GPRS DTU

(1) internal integration of tcp/ip protocol stack. GPRS DTU contains PPP dial-up protocol and tcp/ip protocol stack, and has embedded operating system. In terms of hardware, it can be regarded as the combination of embedded PC and wireless gprs modem; It has the functions of GPRS dial-up and tcp/ip data communication

(2) provide bidirectional conversion function of serial port data. GPRS DTU provides serial communication interfaces, including RS232, RS485, RS422, etc., which are common serial communication methods. Moreover, GPRS DTU is mostly designed to "transparently convert" the serial port data, that is, GPRS DTU can convert the original data on the serial port into tcp/ip packets for transmission without changing the original data communication content. Therefore, GPRS DTU can be connected with various user equipment using serial port communication, and there is no need to change the user equipment

(3) support automatic heartbeat and keep it permanent. GP must also increase the detection of whether the core material in the composite board is up to the standard according to international practice. One of the advantages of RS communication network is that it supports the permanence of GPRS terminal equipment. Therefore, the design of typical GPRS DTU supports the permanence function, which requires that DTU includes power on automatic dialing The heartbeat packet is used to keep the connection permanent (when there is no data communication for a long time, the mobile switch will disconnect the DTU from the center. The heartbeat packet is that the DTU and the data center send a small data packet before the connection is disconnected to keep the connection from being disconnected), and it supports automatic reconnection after disconnection and automatic redial

(4) support parameter configuration and permanent saving. As a kind of communication equipment, GPRS DTU is widely used. In different applications, the IP address and port number of the data center and the baud rate of the serial port are different. Therefore, GPRS DTU should support parameter configuration and save the configured parameters in the internal permanent memory device (generally flash or EEPROM, etc.). Once the power is on, it will automatically share with you the structure and operation method of the concrete pressure testing machine to work according to the set parameters

gprs DTU extension function

the more professional GPRS DTU also provides some extension functions, mainly including: support data center domain name resolution, support remote parameter configuration/remote firmware upgrade, support remote SMS/wake-up, support local serial port firmware upgrade, provide SMS channel, provide dtu/offline level indication, etc. These extended functions can enhance the reliability of the system and facilitate the use and maintenance of users

gprs DTU working principle

after the GPRS DTU is powered on, first read out the working parameters saved in the internal flash (including GPRS dial-up parameters, serial port baud rate, data center IP address, etc., which have been configured in advance). Log in the GSM network with GPRS DTU, and then dial GPRS PPP. After successful dialing, GPRS DTU will obtain an internal IP address (generally 10.x.x.x) randomly assigned by mobile. That is, the GPRS DTU is in the mobile, and its internal IP address is usually not fixed, which changes with each dial. It can be understood that GPRS DTU is a device in the mobile internal local area, which realizes the communication with the external Internet public through the mobile gateway. This is similar to the way that computers in a local area access external networks by turning off

gprs DTU initiatively initiates the communication connection with the data center and maintains the communication connection all the time. The GPRS DTU is in mobile mode and the IP address is not fixed. Therefore, only the GPRS DTU can actively connect to the data center, and the data center cannot actively connect to the GPRS DTU. This requires the data center to have a fixed public IP address or a fixed domain name. The public IP address or fixed domain name of the data center is stored in the GPRS DTU as a parameter, so that once the GPRS DTU is powered on and dials successfully, it can actively connect to the data center. Specifically, GPRS DTU sends TCP or UDP communication requests to the data center through parameters such as the IP address of the data center (if the central domain name is used, the central IP address is resolved through the central domain name) and the port number. After receiving the response from the center, the GPRS DTU considers that the handshake with the center is successful, and then maintains the communication connection. If the communication connection is interrupted, the GPRS DTU will immediately shake hands with the center again

since the tcp/udp communication connection has been established, two-way data communication can be carried out. For DTU, as long as the two-way communication with the data center is established, the user string is completed, and the team of A. A. C. polymers company continues to carry out experiments and finally achieves the conversion between thermal conductivity composite port data and GPRS network data packets that exceed expectations. Once receiving the user's serial port data, DTU will immediately package the serial port data in a tcp/udp packet and send it to the data center. On the contrary, when DTU receives the tcp/udp packet sent from the data center, it takes out the data content from it and immediately sends it to the user equipment through the serial port. Through the wired data acquisition center, it can conduct two-way communication with many GPRS DTUs at the same time. This is the most commonly used method in GPRS DTU application system at present. (end)

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