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Interfacing the PIC18F452 with the GM862 module is relatively simple. What will be left is only the code that needs to be burned on the PIC. By the way,no full codes will be posted here. I will only post the codes that will give you a good kick start because I think it is better to understand than to copy and paste. And there is a Chinese saying:

Give a man a fish, you feed him for a day.
Teach him to fish, and you feed him for lifetime.

This is a sample project that I made and it only deals with making phone calls and I will upload other videos for SMS, GPRS and Data Call:

Now looking at the schematics you will find all the details on how to connect both the module and the PIC.

After doing the above connections, you need to start the module first and then initiate the baudrate that both of them will work on. The Telit module works on different values of baudrates (300, 1200, 2400, 4800, 9600, 19200, 38400, 57600, 115200). For me I shall work with baudrate 19200, but you can choose whatever baudrate that you want.

To start the module, you simply connect the ON_OFF pin to the ground for at least 1 sec (note: this pin is normally high). So you can do this by two ways. First way is to connect a switch and give the ON signal by hand, which is not a good idea. The second way which all of you will do, is to let the PIC18F452 do the job of turning the module ON. We will connect a transistor as shown in the schematic (PN2222A) such that when the base voltage is high, it allows the current to pass to the ground. So, you will need to make PORTC.PIN5 to be HIGH for 1 sec and then toggle it back to LOW (safety factor make it 1.1 sec).

So, after initializing the baudrate on the PIC you need to do the following at the start of your program:

while(recieved_serial!='AT;\nOK\r\n'){
send_serial('AT\r');
delay_ms(300);   //Delay 300 mSec
}

(continue reading…)