GPRS Shiled Lights

When powering on the GPRS shiled what do the lights mean? Is there a document for this? Right now, my LD1 light is blinking green at approx 2 blinks a second, the PWR light is green, and the status light is Red.

I have a GPRS Shield, Arduino Uno, and a SIM Card, but I cannot send an SMS or get a response from the GPRS Shiled, and I think the lights are trying to tell me why, but I don’t know. Thanks.

Anyone in Tech support, help on this?! Thank you.

Hi. I purchased the shield and went through some work to get it all working. The two lights are provide the status of the module. Red solid on is good. The green one blinking at 500 ms is not good. It means that is it unable to connect to the cellular network (but its trying). That can be a several of different things: No cell service, SIM is locked to a particular phone, SIM is not happy with your module.

  1. Make sure you have cell service. Put the SIM into a real phone and make sure you can make/receive a call/text message
  2. I used a prepaid AT&T GoPhone account (in the US). If you chose that route, there are a few other issues you may need to deal with… If you need that info, let me know.
  3. There are two different types of SIM cards. You need a version 2 SIM (which is the default for AT&T).

The shield does work well (although I went through brief period where I thought it wouldn’t) and is great for the price. There are PDF’s available on the internet that give you all the commands (I assume you can talk to it through your Arduino, if not that’s another matter). Just Google SIM900. That’s where I found out what the lights mean. Slow blink Green (about every 3 sec) is good.


My SIM card is locked, that’s the issue. I need to get an AT&T unlocked card, GoPhone is a cheap option, thanks.

I will let you know after I get one if it works.

I bought a GpPhone over the internet for $10 with a SIM. The problem is that the card that comes with it is locked to the phone. You can call AT&T customer service and ask them to unlock it (tell them you don’t like the phone and want to use it in another one). If you go this route the phone comes with two SIM cards, one in the phone, one on a card that says GoPhone. I made the mistake of putting in the GoPhone card. The one that comes in the phone is the one to use.

An alternative is to go to an AT&T store and just buy a SIM card with a GoPhone account ($5.95).

Good luck.