GE863-GPS Sim card issue

GPS/GNSS Development Boards
1

I’m having an issue with a GE863-GPS.

I reflowed it nicely (Thanks to SparkFuns skillet tutorial :smiley: ). It responds to all commands, finds numerous networks, GPS works, etc…

However, sending AT+CPIN? responds with a Sim card not inserted error. The sim card is in fact inserted and I have checked that the SIMIN line is correctly pulled to ground by the switch in the sim card holder. The sim card is connected according to the telit sim holder design guide.

Any possible ideas as to what could be the issue?

2

Yep… been there before. Here are the issues I ran into during the course of about 4 board revisions:

  1. Double check that none of the SIM lines have unexpected shorts. (I’ve reflowed GE863s 2-3 times without damaging the module, to fix shorts or other issues. YMVW)

  2. When doing a homebrew reflow I had better luck with leaving the caps off of the SIM lines, despite what the manual says. With a professionally reflowed board the caps work just fine.

  3. If you have a noisy power source (voltage ripple) or it can’t source the 2A peaks, you’ll see problems with the SIM. I’ve made a habit of putting a 2A load (using high wattage resistors) on my power circuit after assembly to make sure it really can source the required current without dropping the voltage (or catching on fire :wink: )

Hope that helps! -Brett

3

My power supply is fine, have checked it.

So it might be 1 or 2, will check tomorrow and let you know if I figure out the issue.

4

:frowning:

No shorts, and doesn’t work with caps removed.

One thing I noticed is that the SIMIN line is at 1.8V when no sim is inserted, the manual states it is 2.8V, might that be the problem?

Is there a way that I can force the module to think there is a sim card?

5

Sorry for the triple post :oops:

Anyways, been looking at it on a scope and this is the clock:

http://www.wtfs.za.net/simclk.jpg

All other sim lines look similar. The time divisions are 500ms/div and the voltage is 1v/div

6

Unfortunately, no. And the Telit module doesn’t provide any other debug capability to help you further diagnose this.

I believe you’re seeing 1.8V because the module supports both 1.8V and 2.8V/3.3V SIM cards.

One other idea - is there any chance you’re using a SIM card that might not be compatible with the Telit? I haven’t run across this, but others in the Round Solutions forum have.

I’ve used pre-paid, monthly, iPhone, and bulk SIMs from AT&T and TMobile in the US without any issues.

Good luck. I know how frustrating this can be.

7

Thanks anyway :slight_smile:

I’ve posted on the round solutions forum, will see what replies I get from there.

I’ll also go buy some cheap pre-paid sim cards from the various SA providers tomorrow.

8

People at round solutions aren’t terribly friendly…Apparently the forum is only for round solutions customers (would be nice if they were to mention this somewhere prominent), so I got no answers from there (They locked the thread).

Back to asking over here :slight_smile:

9

bretth:
Unfortunately, no. And the Telit module doesn’t provide any other debug capability to help you further diagnose this.

I believe you’re seeing 1.8V because the module supports both 1.8V and 2.8V/3.3V SIM cards.

One other idea - is there any chance you’re using a SIM card that might not be compatible with the Telit? I haven’t run across this, but others in the Round Solutions forum have.

I’ve used pre-paid, monthly, iPhone, and bulk SIMs from AT&T and TMobile in the US without any issues.

Good luck. I know how frustrating this can be.

Have tried three different operator sim cards and still doesn’t work… :?

10

I think I’ve narrowed down the problem to one of two things:

  • Faulty module

  • Bad reflow (either contacts are bad, or module got damaged in reflow process)

The way I got to this conclusion is by building my other circuit, which works 100%

P.S sorry for the double/triple/quadruaple++++++ post :oops:

11

I didn’t want to mention this earlier, but I also had some bad reflows, and I’ve killed 2 modules over the course of 18 months. As I mentioned before, the modules can be reflowed more than once, so you might have better luck the 2nd time around.

One thing to watch out for - the pads for the antennas aren’t as sturdy as the others, especially the GSM antenna pad. So after you reflow the board and lift the module off, be careful when you’re putting a new solder ball on those pads. You don’t want to scrape them or anything.

Glad you got another module working… at least you know your design/schematics are good, which is quite a relief. Or at least softens the blow of the $120-150 oops.

12

Thanks :slight_smile:

I only paid about $100 for each of them. Well…not actually, the university only paid about $100 for each of them :smiley:

They are part of my final year project (B.Eng Electronic Engineering), luckily I only need to get one device working to pass

13

Hah! Even better.

If your project ever ends up online, please post a link… always interested to see what people are doing with these things.

14

It will be online.

Its a web based child tracking system (I know the ethics behind it are a bit sketchy, but I just gotta do what I gotta do).

As soon as I the web side up and running I’ll post a link.