sim900 c code startcode to work with

[Brecht]

Dear,

Im a student

I would like to connect this* gprs-module to lpc1768, this is an arm-processor.

So I would have to write C/C++ files, Im currently using mbed.org but this library doesnt include gsm/gprs-files.

I need to send data like I would feed data to pachube/cosm.com,
I would send data to a webserver basically (the gprs part is done by me, the webserver is made by somebody else)

I would only receive a simple command like 'reset the system'

Is it possible for me to use code from this:

https://code.google.com/p/gsm-s...

I would like to have a startcode to work with/modify
but starting from scratch would not be possible for my current programming skilllevel/time schedule

thanks if you can help me out..

ps: somebody told Im supposed to use sockets, is this true or false?

*https://www.open-electronics.org/small-breakout-for-sim900-gsm-module/

 

[GSM Man]

Your link to the code is broken so we can't view that.
Look at the last FAQ on this page **broken link removed**; it shows you how to send data to a web server.
Sockets is an operating system API for communicating over a network. If you were writing a program for the PC you would use sockets.

 

[Brecht]

thank you for the reply

its to clear to me if still got some research to do, so this site is very useful

if I bump in some new clearly defined problems, i can post them later on

sincere

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https://code.google.com/p/gsm-shield-arduino/source/browse/branches/CompatibleVer/?r=42

i hope this link works now

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Do I need to use sockets on the microcontroller side if I want to receive data?

the thing that confuses me is that Im using at-command but also sockets while I get the impression everything is done by at-commands

and sockets is used in wifi / networks?
or does my gprs have its own ip-adres?

but unfortunately I dont really know yet where Im talking about..

please help

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let say I use

http://www.prasannatech.net/2008/07/socket-programming-tutorial.html

http://www.pythonprasanna.com/Papers%20and%20Articles/Sockets/tcpserver.c

how would at-commands fit in here?

also do I need to use udp or tcp?

thx..

 

[GSM Man]

Do I need to use sockets on the microcontroller side if I want to receive data?
the thing that confuses me is that Im using at-command but also sockets while I get the impression everything is done by at-commands
and sockets is used in wifi / networks?

You don't use Sockets on a micro-controller. You control the SIM900 by sending it AT commands; which, once you get a grasp of the concept, is quite simple. You'll need to do a bit of research to figure out what is required. Check out this web site: http://www.developershome.com/sms/atCommandsIntro.asp

does my gprs have its own ip-adres?

Once you connect make a connection to the network the SIM900 will be given an IP address.

let say I use
http://www.prasannatech.net/2008/07/socket-programming-tutorial.html
http://www.pythonprasanna.com/Papers and Articles/Sockets/tcpserver.c
how would at-commands fit in here?

These examples use Sockets and are not applicable

also do I need to use udp or tcp?

If you are sending to a Web Server then you would use TCP.

 

[Brecht]

wow supergreat reply

thank you!

they confused me with these sockets, at-commands is pretty simple

I used arduino prototype to start with.. it was just basically nothing but at-commands (link: **broken link removed**)

I will use tcp

thanks again.. supergreat help

I will keep working on it

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allow me to ask one more question:

how is the receiving done?

is this a loop that makes the microcontroller do an aerial search for a system that wants to connect with it (lets say every second),
and the computer tries to make connection ( lets say for a duration of 5 seconds)

is this how it gets done ? Is this kind of thinking correct?

thanks for help..

 

[GSM Man]

I'm not exactly sure of what you are asking.

Once the SIM900 is turned on (and it's been configured properly) it will start search for cell towers - often it will find several in the area. It will register itself with the one that is part of your service provider's network (i.e AT&T, T-Mobile, etc.) and that has the best connection. It will continue to monitor the connection without any intervention on your part and switch cell towers if necessary; for example if your device is moving.

When you want to send data to your web server, you send AT commands to create a GPRS connection and then send your data - as outline in **broken link removed**

 

[Brecht]

Dear,

sorry I might have been incomplete with my question

I also wish to send data from the web server to the microcontroller/gprs-module

Is this done similar as sending data to the web server?
I was thinking this would be some kind of loop that uses one or more at-commands..

thanks for the help..

 

[GSM Man]

I also wish to send data from the web server to the microcontroller/gprs-module.

Getting a web server to send a request to your SIM900 is a bit tricky and there are several obstacles you have to overcome to accomplish that:

• The SIM900 must be put into Server mode - this can be really tricky if you want to simultaneously support client mode

• Since the SIM900 will get it's IP address from the network, and is therefore not known in advance, you must have a means to tell your clients what the SIM900's IP address is - your service provider may give you a fixed IP address, but in most cases it won't

• Your service provider must allow incoming connections - for security purposes, most service providers block incoming requests

Assuming you can meet those 3 points, you can configure the SIM900 to be a server by following the instruction in this document: http://www.svtehs.com/simcom/docs/SIM900_AN_TCPIP_V100.pdf


However, if you want to both send data to the server and get data from it there's another way...
In a network-based conversation between 2 devices one is considered the client (the one that makes a request) and one is considered the server (the one that replies to the request). When you open a browser and go to a web site, your browser (computer) is the client and the web site is the server. When you make a request to the server you can give it parameters that tell it to do something. And the web server can return just about anything as a response to your request. It can return a web page, picture, XML data, or text that means something to your application - all depends on how your server is configured.

Let's say you have a web site with a web page named "StoreData.php", and the purpose of the web page is to store data you send it in a database. To make the example simple lets send the data in a "GET" request. A request to this page may be something like "74.125.228.35/StoreData.php?Data=this_is_my_data". Once you've established a GPRS connection you could make this request by sending the following:

AT+CIPSTART='TCP','74.125.228.35','80' \n                       // Will return 'CONNECT OK' to indicate it's connected to the server
AT+CIPSEND\n                                                    // Issue Send Command (wait for module to return '>' to indicate it's ready to receive data

GET /StoreData.php?Data=this_is_my_data HTTP/1.1\n             // Send request 
Host: 74.125.228.35\n
Accept: */*\n
Accept-Language: en-us\n
\n
Ctrl-Z

Anything the server returns as a response will be sent out the SIM900's serial port after you send the Ctrl-z. For example, in this case it could return a status message or the ID of the data it just stored.


To get the data from the server you could have another page "GetData.php" that returns data to the SIM900. A request to this page may be something like "74.125.228.35/GetData.php?ID=1". The following commands would accomplish that:

AT+CIPSTART='TCP','74.125.228.35','80' \n                       // Will return 'CONNECT OK' to indicate it's connected to the server
AT+CIPSEND\n                                                    // Issue Send Command (wait for module to return '>' to indicate it's ready to receive data

GET /GetData.php?ID=1 HTTP/1.1\n                     // Send request 
Host: 74.125.228.35\n
Accept: */*\n
Accept-Language: en-us\n
\n
Ctrl-Z

The server will return the data you requested - the SIM900 will send it out the serial port after you send the Ctrl-Z.

 

[Brecht]

ok thx!

very helpful again..

 

[Brecht]

Dear GSM Man,

currently I use pachube/cosm to send data to,
Is there a site (free or pay) that I can use to test the receiving part?

sincere