Seeedstudio GPRS shield question

Using Arduino Networking, Protocols, and Devices
1

Here is the Seeedstudio GPRS shield:

http://www.seeedstudio.com/depot/gprs-shield-p-779.html?cPath=132_134

The wiki page says "Make sure your SIM card is unlocked".

http://www.seeedstudio.com/wiki/index.php?title=GPRS_Shield_v0.9b

What does unlocked SIM card mean? Does one have to get some specially made/hacked SIM card to make it work? I was trying to get a prepaid T-mobile (USA) phone with SIM card to send SMS with the shield. Can someone with experience using this shield give me some answers? Thank you!

2

Has anyone used T-mobile prepaid phone sim card on any GPRS shield? Could you share some experience with me? Thanks.

3

What does unlocked SIM card mean?

If you enter a wrong PIN three times your SIM card gets locked and you have to enter your PUK to reactivate it. If you use your SIM card in embedded environments and make a small mistake in the software you have your SIM locked in no time, that's probably why they explicitly mention it.

Can someone with experience using this shield give me some answers?

You probably first have to ask some questions :).

What does not work? Show us the code you used when it didn't work. Show us the output you get, etc.

4

Thanks. I don't have the shield yet. I want to use it with a T-mobile prepaid phone SIM in USA for short messages. I wonder if that works at all, taking that T-mobile SIM and sticking it in the shield then use AT command to send SMS. I hope someone will say "yeah, I did just that and it works."

5

I've got this shield. It works perfectly: SMS & Data !

6

When you use the SIM on a phone, when you boot the phone up and if you need to key in the 4-pin thingy, then it's considered as locked.
The command AT+CPIN=? will let you know whether it's locked or not.
It's kinda scary if you wrongly write them in the firmware (after 3 times, it's locked).
For a GSM module which I wrote the library for (not SIM900), I omitted this SIM pin code function fearing someone might wrongly enter them for 3 times!

7

vlp_arduino:
I've got this shield. It works perfectly: SMS & Data !

Thanks!

What AT commands do you use for data?

8

48X24X48X:
When you use the SIM on a phone, when you boot the phone up and if you need to key in the 4-pin thingy, then it's considered as locked.
The command AT+CPIN=? will let you know whether it's locked or not.
It's kinda scary if you wrongly write them in the firmware (after 3 times, it's locked).
For a GSM module which I wrote the library for (not SIM900), I omitted this SIM pin code function fearing someone might wrongly enter them for 3 times!

Thank you! I don't think I saw a pass word screen when I power up the phone. I will surely give it a try when I get the shield.