In the Internet of Things (IoT) technology period, the connection between things is mainly carried out on the Internet, the middle of the Internet not only can be connected according to the medium of the network line, but also according to the 4G, WIFY, etc. to carry out the wireless network connection, in the wireless network of long-distance communication, the key choice is the 4G technology. 4G module is the key medium of the connection between things, the key components of the smart terminal connected to the Internet technology, many emerging economies are increasingly expanding the requirements of 4G communication module, the working frequency signal receiver and data signal growth amplifier and other components are integrated together to complete the integration. Many emerging economies are increasingly expanding their requirements for 4G communication modules, which integrate components such as operating frequency signal receivers and data signal growth amplifiers to complete the integration.

　　The 4G module used is Longchamp 4G module U9300C, the module contains serial communication and USB port, so to the linux core plus 3G module promotion (USB to serial driver) and PPP concordance application, followed by compiling the program core and download to the microcontroller development board. Mainly contains two parts of Linux to promote the layer of strong support and module start-stop script production regulation.

The first part of the network layer 4G communication

4G communication is mainly carried out using AT instructions, the format of AT instructions is as follows　　

1) Each AT instruction line starts with an AT identifier (Note: part of “ ” start), and ends with

as the end;　　

2) Each instruction line can consist of several instructions separated by “;”;　　

3) The specification of AT instructions is in accordance with G ** Rec. 07.07, 07.05, 3GPP TS 27.005, 27.007 and ITU-T Rec. V25ter;　　

4) Each extended instruction is guaranteed to have a test instruction to verify that the instruction does not contain the type or scope of the main parameter;　　

5) Instructions with a main parameter generally guarantee a load instruction to load the present value of the main parameter;　　

6) Setting instruction is used to set the main parameter and perform the corresponding function.

U9300C AT Instruction Instruction line construction:　　

AT CMD1 CMD2=12; CMD1 ; CMD2=,, 15; CMD2?; CMD2=?　　1 2 3 4 5 6 7 8 9

　　1: Instruction as prefix; 2: Basic instruction; 3: Assist main parameter; 4: Expansion instruction (as prefix is “ ”); 5: Expansion instruction dissolve; 6: Assist main parameter, which can be ignored unwritten; 7: Read instruction, which verifies the value of today's assist variable; 8: Detection instruction, which obtains the category and scope of the main parameter; 9: Instruction terminator.

The second part of the driving layer is equipped

The main thing is to equip the core and add the 4G push module to the core

The third part of the AT module communication problems have the following points to note

Problem description: The module is unable to connect to MQTT, and the connection data information pushed by the profiling is correct. Match Article 5 and do one less step. 

 (1) After obtaining the module, look for some AT command methods on the Internet, mainly querying the AT command format. 

 (2) pc side according to the network debugging assistant to enable a server side, you can apply peanut shells to carry out IP projection. 

 (3) serial communication motherboard immediately connected to the module, according to the serial communication push AT instruction (general instruction after there), observe the module to return to the data information and whether it can be connected to the network debugging assistant server side

 (4) after the success of the connection, and can transmit data, network debugging assistant can receive the module to push the data information, indicating that the module according to the serial communication has long gone away.

 (5) through the transmission, based on the steps of the above AT instruction in the microcontroller design program writing, according to the two serial communication motherboard load module to accept and push the data information. First use the microcontroller design according to the module to the computer on the end of the network debugging assistant to transmit data, the computer on the end of the server connected to the module and can accept the module data information, so as to show that the data information AT instruction is not a problem (here is a pit, stepped in today).