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Now lets get this party started!

OK, now we are ready to go into details on how to make an internet connection from the PIC18F450. This sounds fun!
We need some login information that enables us to access the internet. This is called by the network provider “internet settings” , “internet setting file” or something like that. For example if you bought a brand new Nokia phone, and when you insert the SIM card into it, some providers sends the internet settings as soon as they detect that this phone is for the first time to be connected to there network (they do that by IMEI). Other providers, you have to call the customer service so that they send you the internet settings. So, we really need to know the contents of the internet setting file that the provider send so that we can know: APN, username and password.

Before going into details, the first thing that you must do, is call the customer service from the SIM that you are going to use from any cellular phone, and ask them if SIM is GPRS enables or not. Because some providers are not default enabled, so you need to call them first.

What is APN?
It stands for Access Point Name. This name gives you a gateway rout to the network that you want to connect to like WAP or internet or VPN. The question now is how am I going to get the APN of my network provider?

Two ways to get the APN:

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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
}

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Some people will say that we can reduce the voltage of the PIC18F452 or any type of PIC to 4.1v as it operates from 2.0V to 5.5V. But sadly this is not possible because to run the USART of the PIC18F452 it needs a minimum voltage of 4.9 volt (as far as I know). And we are not allowed to put the 5v input directly to the GM862 because this will ruin the whole module. What need now is a level shifter.

There are many techniques out there that enables you to make a level shifter. I used the 2 of 74HC4050 (Datasheet) and it worked fine with baudrate 19600. When you use these level shifter, one will be from low to high (4.0v ->5.0v) and the other will be from high to low (5.0v -> 4.0).

First we need to test everything is working fine before making any connections. In the IC that is used as a high to low converter; insert 5.0v as an input and check with a voltmeter the reading of the output. If its not 4.0v then you did something wrong with the connections and you need to revise the 74HC4050 connection. And do the vice versa to the second IC.

After the test, you are now ready to connect the PIC18F452.