What is GPRS DTU
The full name of GPRS DTU is GPRS data transmission unit. At present, there is actually a more explicit agreement on GPRS DTU in China: GPRS DTU is a GPRS wireless device specially used to transmit serial data through GPRS network.
The four core functions of GPRS DTU
(1) Internally integrated TCP / IP protocol stack. The GPRS DTU encapsulates the PPP dial-up protocol and TCP / IP protocol stack and has an embedded operating system. From the hardware, it can be seen as a combination of an embedded PC and a wireless GPRS MODEM; it has GPRS dial-up Internet access and TCP / IP data The function of communication.
(2) Provide two-way conversion function of serial data. GPRS DTU provides serial communication interfaces, including RS232, RS485, RS422, etc. are all commonly used serial communication methods, and most of GPRS DTU design serial port data into a "transparent conversion" method, that is to say GPRS DTU can Convert the original data on the serial port into TCP / IP data packets for transmission without changing the original data communication content. Therefore, GPRS DTU can be connected to various user equipments using serial communication, and there is no need to modify the user equipments.
(3) Support automatic heartbeat and keep online forever. One of the advantages of the GPRS communication network is that it supports GPRS terminal equipment to be permanently online. Therefore, typical GPRS DTUs are designed to support permanent online functions. This requires the DTU to include automatic dialing on power-up and the use of heartbeat packets to stay permanently online. When there is no data communication, the mobile gateway 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. , Automatic redialing and other features.
(4) Support parameter configuration and permanent storage. As a communication device, GPRS DTU has a wide range of applications. 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 storage device (usually FLASH or EEPROM, etc.). Once powered on, it will automatically work according to the set parameters.
Extended function of GPRS DTU
The more professional GPRS DTU also provides some extended functions, mainly including: support for data center domain name resolution, support for remote parameter configuration / remote firmware upgrade, support for remote SMS / telephone wakeup, support for local serial port firmware upgrade, provision of SMS channel, and provision of DTU online Offline level indication, etc. These extended functions can enhance the reliability of the system and facilitate user's use and maintenance.
Working principle of GPRS DTU
After the GPRS DTU is powered on, first read out the working parameters saved in the internal FLASH (including GPRS dialing parameters, serial port baud rate, data center IP address, etc., which have been configured in advance). Log in to the GSM network with GPRS DTU, and then dial GPRS PPP. After dialing successfully, GPRS DTU will obtain an internal IP address (generally 10.XXX) randomly assigned by the mobile. In other words, the GPRS DTU is in the mobile intranet, and its intranet IP address is usually not fixed and changes with each dial. We can understand that GPRS DTU is a device in a mobile internal local area network, and communicates with external Internet public network through a mobile gateway. This is similar to the way that computers in a local area network access an external network through a gateway.
GPRS DTU actively initiates the communication connection with the data center and keeps the communication connection always present. Because GPRS DTU is in the mobile intranet, and the IP address is not fixed. Therefore, the data center can only be actively connected by the GPRS DTU, but not by the data center. 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 as a parameter in the GPRS DTU, so that the GPRS DTU can actively connect to the data center once the power-on dialing is successful. Specifically, the GPRS DTU initiates TCP or UDP communication requests to the data center through the data center's IP address (if the center domain name is used, the center IP address is resolved first through the center domain name) and port number and other parameters. After receiving the response from the center, the GPRS DTU considers that the handshake with the center is successful, and then keeps this communication connection always present. 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 is possible. For DTU, as long as the two-way communication with the data center is established, it is relatively simple to complete the conversion between the user's serial data and the GPRS network data packet. Once the user's serial data is received, DTU immediately encapsulates the serial data in a TCP / UDP packet and sends it to the data center. Conversely, when the DTU receives the TCP / UDP packet from the data center, it takes out the data content and immediately sends it to the user device through the serial port. Through wired data collection center, two-way communication with many GPRS DTU at the same time. This is currently the most commonly used method in the GPRS DTU application system.
The full name of GPRS DTU is GPRS data transmission unit. At present, there is actually a more explicit agreement on GPRS DTU in China: GPRS DTU is a GPRS wireless device specially used to transmit serial data through GPRS network.
The four core functions of GPRS DTU
(1) Internally integrated TCP / IP protocol stack. The GPRS DTU encapsulates the PPP dial-up protocol and TCP / IP protocol stack and has an embedded operating system. From the hardware, it can be seen as a combination of an embedded PC and a wireless GPRS MODEM; it has GPRS dial-up Internet access and TCP / IP data The function of communication.
(2) Provide two-way conversion function of serial data. GPRS DTU provides serial communication interfaces, including RS232, RS485, RS422, etc. are all commonly used serial communication methods, and most of GPRS DTU design serial port data into a "transparent conversion" method, that is to say GPRS DTU can Convert the original data on the serial port into TCP / IP data packets for transmission without changing the original data communication content. Therefore, GPRS DTU can be connected to various user equipments using serial communication, and there is no need to modify the user equipments.
(3) Support automatic heartbeat and keep online forever. One of the advantages of the GPRS communication network is that it supports GPRS terminal equipment to be permanently online. Therefore, typical GPRS DTUs are designed to support permanent online functions. This requires the DTU to include automatic dialing on power-up and the use of heartbeat packets to stay permanently online. When there is no data communication, the mobile gateway 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. , Automatic redialing and other features.
(4) Support parameter configuration and permanent storage. As a communication device, GPRS DTU has a wide range of applications. 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 storage device (usually FLASH or EEPROM, etc.). Once powered on, it will automatically work according to the set parameters.
Extended function of GPRS DTU
The more professional GPRS DTU also provides some extended functions, mainly including: support for data center domain name resolution, support for remote parameter configuration / remote firmware upgrade, support for remote SMS / telephone wakeup, support for local serial port firmware upgrade, provision of SMS channel, and provision of DTU online Offline level indication, etc. These extended functions can enhance the reliability of the system and facilitate user's use and maintenance.
Working principle of GPRS DTU
After the GPRS DTU is powered on, first read out the working parameters saved in the internal FLASH (including GPRS dialing parameters, serial port baud rate, data center IP address, etc., which have been configured in advance). Log in to the GSM network with GPRS DTU, and then dial GPRS PPP. After dialing successfully, GPRS DTU will obtain an internal IP address (generally 10.XXX) randomly assigned by the mobile. In other words, the GPRS DTU is in the mobile intranet, and its intranet IP address is usually not fixed and changes with each dial. We can understand that GPRS DTU is a device in a mobile internal local area network, and communicates with external Internet public network through a mobile gateway. This is similar to the way that computers in a local area network access an external network through a gateway.
GPRS DTU actively initiates the communication connection with the data center and keeps the communication connection always present. Because GPRS DTU is in the mobile intranet, and the IP address is not fixed. Therefore, the data center can only be actively connected by the GPRS DTU, but not by the data center. 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 as a parameter in the GPRS DTU, so that the GPRS DTU can actively connect to the data center once the power-on dialing is successful. Specifically, the GPRS DTU initiates TCP or UDP communication requests to the data center through the data center's IP address (if the center domain name is used, the center IP address is resolved first through the center domain name) and port number and other parameters. After receiving the response from the center, the GPRS DTU considers that the handshake with the center is successful, and then keeps this communication connection always present. 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 is possible. For DTU, as long as the two-way communication with the data center is established, it is relatively simple to complete the conversion between the user's serial data and the GPRS network data packet. Once the user's serial data is received, DTU immediately encapsulates the serial data in a TCP / UDP packet and sends it to the data center. Conversely, when the DTU receives the TCP / UDP packet from the data center, it takes out the data content and immediately sends it to the user device through the serial port. Through wired data collection center, two-way communication with many GPRS DTU at the same time. This is currently the most commonly used method in the GPRS DTU application system.
Incremental encoders provide speed, direction and relative position feedback by generating a stream of binary pulses proportional to the rotation of a motor or driven shaft. Lander offers both optical and magnetic incremental encoders in 4 mounting options: shafted with coupling, hollow-shaft, hub-shaft or bearingless. Single channel incremental encoders can measure speed which dual channel or quadrature encoders (AB) can interpret direction based on the phase relationship between the 2 channels. Indexed quadrature encoders (ABZ) are also available for homing location are startup.
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