GPRS modem is a wireless data terminal of the IoT. It uses the GPRS network (also known as G network) of the common operator network to provide users with the function of wireless long-distance data transmission. It adopts high-performance industrial grade 8/16/32-bit communication processor and industrial-grade wireless module, and uses embedded real-time operating system as software support channel to supply RS232 and RS485 (or RS422) interfaces together, which can directly connect serial devices to complete the data transparent transmission function.
Four functions of GPRS Modem:
1.Internal integrated TCP/IP protocol stack
GPRS modem encapsulates PPP dial-up protocol and TCP/IP protocol stack internally and has embedded operation system. From the perspective of hardware, it can be regarded as the combination of embedded PC and wireless GPRS modem. It has the functions of GPRS dial-up network and TCP/IP data communication.
2.Function of supplying serial data bidirectional transmission
GPRS modem provides serial communication interface, including RS232, RS485, RS422 and other commonly used serial communication methods, and GPRS modem mostly plans serial port data into transparent conversion method in planning, that is to say, GPRS modem 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 modem can connect with all kinds of user equipment that use serial communication, and not necessarily change the user equipment.
3.Support active heartbeat and stick to permanent online
One of the strengths of the GPRS communication network is to support the GPRS terminal equipment to be permanently online. Therefore, the typical GPRS modem supports the permanent online function in planning. This requires modem to include active dialing after power-on, and use the heartbeat package to insist on permanent online (when there is no long-term data communication, the mobile gateway will disconnect the modem from the center. The heartbeat packet is that the modem and the data center send a small data packet before the connection is disconnected, so that the connection is not disconnected), support the active disconnection and active redialing and other features.
4.Support parameter equipment, permanent preservation
As a communication device, GPRS modem is widely used. In different applications, the IP address and port number of data center and baud rate of serial port are different. Therefore, GPRS modem should support parameter equipment and store the configured parameters in internal permanent memory devices (FLASH or EEPROM, etc.). Once the power is on, it will work actively according to the set parameters.