SparkFun Forums

[bradlyjlewis]

I Just bought the GM862 board with GPS

Without the SIM card, I can talk to the device
When I put the SIM card in, it powers down.

I see from previous posts that this may be a power supply issue.
However, I have not modified the USB board and I've got a like new computer with v2.0 USB

If I need to add a capacitor due to circuit design flaw, where should it be added, what value and what type?

Also, if the USB powered aspect does not work, can I connect power to the power connector while the USB is plugged in without hurting anything?

If so, what type of power supply? (volts, current rating)

And why isn't there documentation on this for a $303 package?

Thanks

[leon_heller]

It sounds like an inadequate supply. You need a 100 uF tantalum capacitor close to the GM862. The normal operating current is quite low, but the current momentarily peaks at 3A or so when transmitting. The board should have that capacitor on it, however, if it was properly designed.

Leon

[bradlyjlewis]

Leon,

It has a SMD capacitor about 1 inch from the the GM862 unit.

I hooked up a 5 volt 500 mA wall wart to it and parralleld a 470 uF capacitor across the aformentioned capacitor and now it works fine.

I'm having trouble sending an SMS message and also the unit doesn't get a carrier.

I have used the AT#BND=1 but still get error of "No Carrier"

when i type atd 5034444444 then I can hear my amplified speakers (nearby antenna) make noise as the GM862 tries to connect.

My cell phone gets great reception.

Is there some setting to tell it that it's got an antenna connected?

Anybody know of a good tutorial on this piece?

[maokh]

if you are in a US market, AT#BND=1 isnt suggested...This configures 900/1900, of which 900 is not a GSM band in the united states. There are a lot of 1900 systems in operation, so maybe your carrier might have service on this band...

You will want to use AT#BND=3, which configures the unit for 850/1900. That way, your unit will work in both US bands.

Please send the following output:

AT#SERVINFO
AT+CSQ?
AT#CPIN?

Also, when you perform the call test, use this instead:

ATD5034444444;

semi-colon tells it to make a voice call, otherwise, it will try to perform a CSD call. I have not been able to get CSD to work on Cingular, for example.