GSM module, GSM is the RF chip, a baseband processor chips, memory, power amplifier and other devices in an integrated circuit board, which has an independent operating system, GSM RF processing, baseband processing function and provides a standard interface module. GSM module has to send SMS text messages, voice calls, GPRS data transmission based on the GSM network all the basic functions of communication. GPRS transmission rate ranging from 56K to 114Kbps, theoretical speeds of up to 171k, under the actual test transmission speed of about 25K. With respect to the access speed of 9.6kbps terms of GSM, GPRS has a faster access to data communication speed, GPRS technology also has at any time, any place can connect, always online, according to the characteristics of meter fees.

Since working life, environmental requirements and other factors, at present, the GSM module is still in widespread use in industrial applications, in all walks of life can see the GSM module application products. For example, in the field of vehicle control, vehicle use GSM module of GPS data back to the vehicle management center; electricity, water system, via GSM module implements intelligent remote meter reading, real-time monitoring of users of electricity and water; in surveying and mapping industry, as many remote mapping point installed GSM module enables real-time monitoring, data no longer collected manually; in the family, you can install a wireless alarm system, once a fire or theft occurs, you can immediately notify the police and the head of the household; in abroad, many children and senior citizens with a personal tracking device, to prevent the elderly and children lost or accident, which is also integrated GSM module. It can be said with complete GSM network construction, the scope of application of GSM module more widely.

Today, we need to understand the GSM module inside a very simple function – SMS reception. USR IOT module we are using the GPRS module GM3, the biggest feature of the module is cost-effective, itself supports text messaging, GPRS function‚

It is a GSM module, which supports the standard AT commands. SMS received its instructions are as follows:

The top is the PUD coding, we microcontroller decoding is difficult, so do not ignore it. In most cases we are using the following text format to communicate the message. The module’s default mode is coded PUD, after the completion of configuration-related AT commands can be converted to text format. Format transcoding will be described in a later article.

Let’s look at the contents of the module output:

+CIEV: “MESSAGE”,1

+CMT: “+8613912127637″,,”2016/08/12,16:47:32+08″,145,17,0,0,”+8613800514500”,145,3

123

The first part: + CIEV: “MESSAGE”, 1

This content is used to notify received a text message. Note: This pattern is printed immediately after receiving the message out and will not be stored; Enter the module itself is part of the content of responses.

You need to follow the above protocol packet is divided into three parts to be processed:

1. + CIEV for prompting receive a message
2. MESSAGE This message is received for tips
3. used to indicate the number of received information

The second part:
+ CMT: “+8613912127637” ,, “2016/08 / 12,16: 47: 32 + 08”, 145,17,0,0, “+ 8613800514500”, 145,3
123

1. + CMT for prompt receipt of SMS text format
2. “+ 8613912127637” This is the sender number. If necessary, what can be done to resolve the SMS numbers to confirm whether native or able to handle password authorization you need to do
3. “2016/08 / 12,16: 47: 32 + 08” message received time for tips
4. “+ 8613800514500” as the center of the base station number
5. number 3 145,3 inside tips for messages received byte length
6. note that the above content will be completed after a carriage return for segmentation
7. 123 for the actual content of the message. I realized not the way to read the contents inside tips packet length, but by offset addition terminator way to get the length of the packet