SIM900A network registration problem

[rimpul]

Hi,

I am using SIM900A gsm module in my project, simcard is not getting registered with the network, during power on when i measure the voltage at SIM_VDD pin it shows 1.33v and suddenly drops zero,and the netlight LED glows faster, but as per the datasheet the voltage at the SIM_VDD pin should be 2.88v constant .
Can any one suggest me what could be the reason for this?

thanks,
Rimpul

 

[nandhu015]

Possible power supply problem.

How do you power the modem?

 

[rimpul]

Hi,

I am powering the modem using a LDO (regulator) 4.2v. LD39300

 

[booker]

Hello, use that command AT+CPIN? , and tell as the SIM900A answer!!!

 

[oufuqiang]

1. use mobile phone to test your SIM card.
2. use scope to monitor VBAT wavefrom.

 

[antilop]

Hello, use that command AT+CPIN? , and tell as the SIM900A answer!!!

Hi booker, I´m new here with my new SIM900A just arrived to me, purchased from china (ebay). Command at+cpin? says me +CPIN: PH-NET PIN, clear result for modem locked for Asia. I have seen some of your posts, where you mentioned good results with firmware flash and I will probably follow your way in near future. My very first question: What about separatelly purchased prepaid China Mobile SIM card? Could be some solution? Means, is this modem somehow able to work here in Europe as roamer with original domestic card from Asia or not, as any network out of originally listed ones cannot be reached forever?

 

[u7karsh]

I guess it would be best if you first test ur LD39300 and also check for any possible short circuits in ur connection.. if all goes well then there is definitely some problem with ur module or sim

 

[Valentyn Piddubny]

Hi guys,

I have the same problem with my module from China with Sim900A.


I tried different power source but it didn't help. I really don't know what to do. Please help.
Module are see network for sim card but doesn't connect. I thought maybe some at command exist for connection, but there is no. Really don't know what to do.

 

[throwaway18]

http://www.blog.zapro.dk/?p=368

Region restrict:
from version 1137B06SIM900A32_ST, operation in the countries listed in
the table below are supported.

China
India
Singapore
Malaysia
Thailand
Indonesia
Cambodia
Vietnam
Laos
Burma
Brunei
Philippines
East Timor

Some people say it may be possible to load older firmware to make it work

 

[Valentyn Piddubny]

Thank you,
I haven't words to express my feeling.

Then I will try to find way how to load old firmware. Could you advise some links to read how to do it? Of course I will do google, but not always I can find what I need. Like at this example.

Thank you again.

http://www.blog.zapro.dk/?p=368

Region restrict:
from version 1137B06SIM900A32_ST, operation in the countries listed in
the table below are supported.

China
India
Singapore
Malaysia
Thailand
Indonesia
Cambodia
Vietnam
Laos
Burma
Brunei
Philippines
East Timor

Some people say it may be possible to load older firmware to make it work

 

[jedreg]

Command at+cpin? says me +CPIN: PH-NET PIN, clear result for modem locked for Asia.

I had the same problem in central Europe. I checked architecture (32 or 64 bit) with AT+CGMR command and then picked up matching SIM900 firmware, flashed it into SIM900A and now it works fine. You can find details on my blog.