Hello. I just bought a gsm sim900a module for my school project. Basically, it will be used to send an sms to the user when an alarm is triggered. All i need now is to get this module working and my project will be done. I see that most tutorials are based on GSM sim 900 and I have no idea if they are similar. Someone please help me! =( =( =(
If you are keeping the project fairly simple then most, if not all, modern modules support GSM07.05 which covers SMS related operations.
I bought simply SIM900A module. Didnt work (A like probably only for "Asia")
So I flashed SIM900 FW and got registered network
And when you got NO CARRIER you must add ; after number.
ATD+123456789 works for landline and ATD+123456789; for mobile networks.
SMS works too.
dannable:
If you are keeping the project fairly simple then most, if not all, modern modules support GSM07.05 which covers SMS related operations.
So the programming is essentially the same as Sim900? Sorry, i'm really new in this. And what is the format for the phone number because i'm not sure about that either.
Thanks in advance. 
Also, this is the one i got.
How do i connect it to the arduino?
Regarding the difference of SIM900 and SIM900A, look here:
http://www.blog.zapro.dk/?p=368
And:
// Per.