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SIM900 works with some Sim card don't with another

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Newbie level 5
Nov 27, 2009
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SIM900 works with some SIM cards and don't with another ones...

Hi everybody,

...I have developed a SIM900 PCB board made by me and I have a small question about it...

1...I can startup the module using a Movistar (Spanish Company) SIM and make calls without any problem...using a 5V 2A adapter or Nokia LiIon 900maH battery...
2...When I use a EroskiMovil SIM card (Low cost spanish company and virtual operator, that uses Vodafone network)...I can start the module, but when I put the pin and gives me OK, the module allways response:
RDY...stay ok for about 5seconds and...
RDY again...and then is shut down and only is possible restart the module powering off the supply and power on again...the powerkey don't respond after that...

I have tried all the recommendations I have found on the forum:
a) Make AT&F to restart default parameters
b) Check the SIMcard connections, only I use 22omh resistors, 100nF on SIM_VDD and 20pf on SIMDATA PIN (Movistar card works fine)
c) The signal quality report is 21,0....and then is 14,0 with movistar and 11,0 with EroskiMovil the time that the network is on...5 seconds approx...

I suspected that was the band that is using, that makes the VBAT goes down and reset the module, but the two companies that I have tried uses the PGSM_MODE band...and with movistar there aren't any problem....All the companies have top of signal quality where I'm testing it...

Also i have tried with wall DC power suply adapter and BQ24070 regulator (4.35V) also with 900maH Nokia battery (4.1V) that uses a lot of Nokia mobiles...

The only thing that I don't know is how much are the capacity of the sim card that don't work...How can I know that?...I have read on the forum that the Sim card have to be at max 32K it truth?...

The firmware version is: 1137B05SIM900M64_ST

Can you give me any idea and anything to test to find what the hell I'm doing bad?...

Thanks a lot in advance,

Any idea will we very appreciated with me,



Hello Patadino,

Did you solve your problem?

It looks like a modem firmware related problem...try to update your fw.

This is good idea.
In internet you can find version: 1137B08SIM900M64_ST (B08) and the problems disappear.
Of course if your module is witout any defects. Modules of SimCom have bad the quality control in the factory, this is the reason why is a lot of problems with use of them.

for example hardware look at links:
Hi polo and guest2003,

First of all...lot of thanks for your posts...

I have updated the firmware and the SIM900 is working now OK!...

It was the version, I had 1137B06SIM900M64_ST (B06), that with Vodafone sim cards register on the network and after that the module switch off.

Thanks a lot for the posts!...

...PS. Reading the "Flash customer loader thread", an user called 'dinuka' is making embedded applications on the SIM900, but the version that he has aviable is that it comes with the development sowfware (B07 think). Has anyone newer firmware version that supports Embedded AT commands?...



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