Discussion in "GSM and CDMA Discussion" started by    prajwalsnh    Feb 6, 2014.
Thu Feb 06 2014, 06:41 pm
#1
Hello i bought a new sim900 gsm modem. I tried to send an sms via serial port in PC using terminal 1.90b software. But its not sending the sms. can anybody tel what may be the problem??? The AT commands i used is,

AT
AT+CMGF=1
AT+CMGS="Mobile Number"

Its working fine till the last AT command but once we type the text to be sent and then press cntrl+z its not sending the sms.
Thu Feb 06 2014, 10:12 pm
#2
Make sure you are using the full number.
eg on my Wavecom system, a number starting 44xxxxxxxxx will dial a voice call
but only +44xxxxxxxxx will send an SMS

Do you get the > after you enter the number ?


[ Edited Fri Feb 07 2014, 12:38 am ]
Fri Feb 07 2014, 12:12 pm
#3
@ExperimenterUK

Yes sir i'm getting '>' after i type the number. As you said i also tried +MobileNumber but the result is same. Now my modem is not responding to at commands. Actually yesterday i tried an at command to set the baud rate, after taking that at command the module is not responding to any at command. the command i tried is,

AT+IPR=0 {To set the modem to autobauding mode}

Now modem is not responding to anything Is my module damaged?
Sat Feb 08 2014, 03:01 am
#4
It's probably waiting for the sync char..
That is..power on..
Send “A” (without the quotes) wait 3 seconds then send AT(enter)

Try the sim card in a phone to make sure it is able to send texts.


[ Edited Sat Feb 08 2014, 03:05 am ]
Sun Feb 09 2014, 03:01 pm
#5
@ExperimenterUK

Yes sir the modem is working now. I did as u said above.Thank you very much. Sir i think the modem is not detecting the sim. Because i tried to initiate a call from modem using the following command,

ATD+Mobilenumber,

But the response it is" NO CARRIER". I also added + with mobile number and tried. But the result is same.
Sun Feb 09 2014, 09:49 pm
#6
check the network state using AT+CREG? You will get "+CREG: "
if its 0, then no network
if 1 registered to network
if 5 registered in roaming.

You can also check which network is selected using AT+COPS command.
Wed Feb 12 2014, 11:22 am
#7
@AjayBhargav

Sir i'm getting following response,

+CREG: 0,1

OK

I think its not registered. How to register the network??
Thu Feb 13 2014, 12:00 am
#8
@ prajwalsnh
there should be no security ,pin or puk code on sim
also attach the antenna to it
also try to replace antenna as wll as sim for checking purpose
i often face this sort of problem and it solved after antenna replacement or
proper soldering of antenna to GSM antenna pin
Thu Feb 13 2014, 12:19 pm
#9
@majoka

Sir the antenna is already soldered to the board. I also changed the sim and tried but no use. The antenna is a wired antenna not stub antenna. is that a problem? should we use stub antenna?
Fri Feb 14 2014, 06:45 am
#10


Sir i'm getting following response,
+CREG: 0,1
OK
I think its not registered. How to register the network??

prajwalsnh



+CREG: 0,1
suggests it is registered and so the antenna must be okay.
Is it a full antenna or could you screw an antenna into
the end of it ?

Have you confirmed that the Sim card can send texts in
a mobile phone ?

Check the power supply.
Some Simcom modems need as much as three amps
when transmitting.


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