Telit GM862-GPS resetting itself

GPS/GNSS Development Boards
1

Hello, I have a very weird issue with the module, it resets itself like 15 seconds after the AT+CPIN= command.

I have the USB evaluation board (the red one) and I was supplying the board at first with a 5V DC transformer, I thought maybe was something to do with the dropout (it dropped sometimes about 4.2V, so it’s very close to the 3.8V supply) so I switched to a 12V with the same result.

When I turn on the module the stat led starts to blink fast, I can use the GPS commands, and everything works fine, when I enter the pin code, the module register itself into the network (I measured the current to check it was all right, about 210 mA peak in the registration phase) and then, after about 15-20 seconds, one of two things happens:

  1. The module restarts so the stat led starts blinking fast (and I have to enter the pin code again).

  2. The module hangs and becomes totally unresponsive (with the stat led completely off) and the only way I can get it working again is unplugging and plugging the DC supply and the USB cable (the on/off button doesn’t works here). At this time the current is about 90mA.

I need help, if someone can give me any advice, or tell me what is going on, i would be really appreciated.

Thanks in advance.

2

I use the 5V 1A wall wart. With anything less the module will shut itself off when attempting to make a connection.

Donnie

3

The 5V transformer that I mentioned in my original post is the 5V 1Amp sold here in SFE. The 12V that I mentioned is 1.2Amp, I already make sure that it fulfills the module requirements.

Any other idea?

Thanks.

4

I would remove the module and check for bent pins. When mine would turn off I could push button to turn it back on, only to go off again when trying to connect. I see where you are having to remove power and USB to get any activity again. Perhaps a faulty board. Check the pins is what I would do next. I did have one that did not seat correctly the first time. I was lucky nothing got hurt.

Donnie

5

There might be a problem with the capacitor close to the supply pins. It has to supply a momentary high current when the unit tries to connect to the network.

Leon

6

Thanks for the answers.

Well I checked what lenswerks suggested about the connections and everything seems to be fine (no bent pins, no moving parts…), honestly I don’t know if there is something wrong with the board, but I prefer to discard that possibility for now.

I’m no expert in how GSM networks works so here I go: is there any possibility that my cellphone provider is sending something to the module (in all this registration process) that may cause it to crash?

Maybe something to do with the IMEI, honestly I have no idea, but in short: is there any way that my module is behaving like that because of them?

Thanks.

7

Have you checked that capacitor I mentioned. When I first used a GE-863 I left it off the PCB to see what happened and I got exactly the same symptoms. When I added it the problem disappeared.

Leon

8

After you do the check what Leon mentioned and if it still does not work then…

Did you set the module for North American frequencies? - they don’t come set for the US network. AT#BND=1

I use a AT&T Pay-As-You-Go SIM card for these. You can get one at the AT&T store for 25$. When using a Python script doing the M2M stuff 25$ will last for quite some time.

9

Ok I have an update on this:

I managed today to send a test SMS to my cellphone, it worked, of course I had to do it fast before the module went crazy.

Then I called my cellphone with the module, my cell started ringing and I answered (of course I didn’t expect to hear anything as there is no microphone attached to the module yet) then the call drops some seconds later.

I think this reduces the possible causes, I think the network is just fine.

Now I have some answers:

Leon, what you actually suggested is that I desolder the capacitor, try again and see what happens, and then solder it again? it seems pretty difficult to me, the capacitor is really tiny.

Another idea: can I power the module using an external voltage power by the pinholes without damaging the board/circuit?

Thanks

10

I meant that you should check that the capacitor is properly soldered.

Leon

11

Update: It seems that the antenna I’m using is this one (I didn’t buy the whole thing directly myself):

http://www.sparkfun.com/commerce/produc … cts_id=290

The information is pretty vague but, it seems to be 3.5 dbi gain.

The Hardware User Guide of the telit module (http://www.telit.com/module/infopool/do … php?id=871) says:

Antennas used for this OEM module must not exceed 3dBi gain for mobile and fixed operating configurations.

(page 14)

You think this could be the cause of all the resetting thing, or that gain limit is to not exceed the Tx power of the regulations of the GSM standard?

Thanks.

12

I’ve found out that the antenna gain limit is because US regulations and laws in the telecommunications field, good thing for me my country lacks those regulations…

Anyway, today I tried the module with a sim card from another company (I sould have done this from the very beginning) and the module is not resetting itself anymore, in fact its working like a charm, so I discard by now any hardware related issue.

How can I find the problem right now? maybe a very verbose mode in the module which reports every step in the communication?

What do you think?

Thanks.