SparkFun Forums

[fr83]

Hi, SparkFun.
Today received GM862-RS232 board. Thanks

Have a little problem.
GM862 shuts down after 3-4 seconds after power on, if SIM is present. That is it searches for network, status led is blinking and it suddenly shuts down. In this 3-4 second period i can issue commands and get correct results.

But if i remove SIM, it does not shut down itself, it searches for network as it should be. Thanks in advance,
Farid.

[fr83]

One more detail.
Original power supply is rated 110 volts, but here wall socket is rated 220 volts. So i used a ATX power supply instead. Absolute maximum input voltage to LT1528 is 15V. I used 12V output(can supply current up to 15A).
Any suggestions?

[sevanjam]

I am having the same problem , but we have three cellular network service providers in my country, only one of them i used didnt shut down the module... i still couldn't figure out the problem ... for the time being use a different SIM card . i hope it will work

Sevan

[sparky]

Hi,

I've noticed shut-downs with the GM862 when there are problems with power.

So I will gamble that if you have no SIM card in your GM862, it will stay on indefinitely while it searches for a network (but you have no SIM so it will always be in search mode).

If you insert a SIM, the unit will be on for 5-10 seconds, but once it tries to log on, it shuts off.

If this is the case, I've seen this happen with bad power supplies. You'll need to supply the unit with 5-10V DC that can supply up to 2A for short bursts of time (100-500ms). Overall the current consumption is average 350mA while logging onto the network but will surge to 2A. If your power supply cannot source these short bursts, the GM862 will detect this and automatically shut down. Well, that's just what I've seen...

-Nathan

[sevanjam]

Ok, but why with some SIM cards this happens and with other SIM cards it doesn't , doesn't the module follow the same steps of network logging for all SIM cards and network providers... anyway i will try to connect a power supply that supplys more than 2A although the one i use delivers exactly 2A.

Sevan

[Wexican]

Hi

I've got similar problems with GM862, I purchased a GM862 development kit, when switched on the status led flashes for a number of seconds & then switches off, funny thing is I haven't powered it up for some weeks & first time it switched on it worked perfectly. I switched it off & then back on & it hasn't worked right since. I'm using a vodafone sim in Ireland. My psu is switched mode & capable of 5A @ 9V, I've even connected a 2200uf capacitor across the power connector to the dev kit, still the same result. I suspect it'll work in a week or so again, I wonder is it that the service provider here doesn't like these modules?

Is there a list of what the led flash count means?

[karrelsj]

When I first started working on the 862 I was running into similar problems. I too thought it was for sure power. When I was talking to Telit one day I realized that it was the length of '0' signal on the on/off pad. For instance if my on/off pad was tied low for too short of time, the status led would blink for around 5 seconds then shut off. Just a thought. Try holding your on/off pad low for a longer time.

[megaady]

I had the same problem. It's not about the power supply, I am powering it with 9V @ 750mA ( commutation ) . You have to solder on the demo board the module ( one of thoose 8 ground pins from the metallic case of the module ) in order to have a strong ground. It's working fine for me now

[jayhunters14]

hi

has anyone resolved the shutdown problem?

thanks.

[landon]

I am also interested in hearing more experiences with this. I'm about to buy my 2nd module. With the first module, I used the bare bones PCB eval board. I was never able to get it to power up at all ( I pulsed the on/off line for >1 second, had exactly 3.8v applied, etc.) I never even got a light out of it.

I would highly recommend, if this is a first attempt at this module (I'm writing to anyone else reading, not the authors above) and you're a hobbiest like me - I'm a software developer, not a professional EE - that you don't do like me and go for the bare-bones. I think SFE's point of their eval boards for rs232 and usb taking care of all the power goober is well worth it. If you're like me and just want to fire it up and start working with it, don't make my mistake.

My question is about the module itself. The aluminum package pins, the 8 outer pins on the package...is there any electrical significance to all 8? The post above seems to imply that if you have a good ground on one of them, you'd be alright.

One of my mistakes was soldering all 8 to my bare pcb. When I decided I needed to back up and buy the rs232 or usb board, it was very difficult to desolder the package. You can never tell if the desolder process hosed it up in some way. When I get the rs232 eval board, I want to just plug it in, solder down one of the package ground pins and leave the rest as is, but I am unsure if all of them are electrically significant and if I can do just one solder joint for the whole package until I'm sure I have a working module.

I'm going to order the rs232 eval board, use my former module, not really solder it down until I'm sure I can light it up. If need be I'll order a 2nd module.

Any further advice would be greatly appreciated. As I learn more about it I'll also post back.

Thanks,

Landon