We have a couple ideas for some remotely located arduino projects that we want to control and or receive data from on a internet connected server so we decided to check out the Seeed GPRS Shield.
We actually ordered this shield through Amazon.com (for the same price) just so we could get the free 2 day shipping with our Amazon Prime account so we can’t comment on the shipping times from Seeed.
While waiting for the arrival, we went to T-Mobile and picked up a SIM card for the device and had them put it on the $2/day unlimited plan (unlimited talk, text and 2G data) so only pay on the days the device is on and connected to the network.
What we received was a small box containing the shield and an antenna.
We quickly connected the antenna, mounted the shield on an Arduino UNO r3 and started searching the net for a library or some example code. Quickly it became apparent that there is a serious lack of documentation in a central location for this shield. Seeed does have a wiki page for the shield that does have some great information and a couple code examples but we just felt there should be more. So after a couple hours of searching we pulled together various pieces of code, a pdf for the Sim900 AT commands and some other information (note: all information can found in links at the bottom of this post), then it was time to play!
Of course the first thing we wanted to do was send an SMS to test the device so after about 5 minutes of playing around, SUCCESS! Now to receive… NOT so easy! This is where the documentation was really lacking. We just wanted to setup a simple led connected to the board/shield and have it toggle on and off when it receives an SMS. We searched the net a bit more and found an example controbuted by MChobby, for more information please visit: http://mchobby.be/wiki/index.php?title=SmsCommand.
After modifying SofwareSerial.h _SS_MAX_RX_BUFF to 128 bytes and loading the sketch … it worked!
We also tested making an http get request using the HTTP command set for the Sim900 as well as making a direct data connection to one of our servers. All these examples can be found below.
If you have any questions let us know, and don’t forget the forums at Arduino.cc are an invaluable tool.
Resources:
SIM900_AT_Command_Manual_V1.03
Useful Links:
GPRS Shield – GOF_Wiki GPRS Shield – Open Source,Open Minded
