problem after turning ON SIM300

[doitnow]

dear all,
i am using at89c52 along with SIM300
i am using it for sending/receiving TEXT- SMS
one of the program function is to send a SMS whenever SIM300 is turned on (sending sort of initial h/w status through sms)
here i am having a problem; coz out of 10 tries i am getting SMS in 7-8 tries only for remaining 2-3 tries it simply doesn't send any sms
i am giving 30-sec of delay after powering up the SIM300 as a booting time
i don't know why am I not getting 100% result

any suggestion
regards

 

[horace1]

does the device reply with OK to the commands you send it?
when I send SMS text or TCP/IP packets I have a sequence of commands I go thru and if any fail I restart
in particular have you checked the signal level?

 

[doitnow]

thanks for the reply

yes I check for "AT" command response and then only I get proceed
what do you mean by , checking signal level?

my confusion is if something is wrong with my program or set-up; then it should not work at all isn't it?

but here it works most of the time and I am unable to figure out what's getting wrong when it doesn't ???
regards

 

[horace1]

on the WISM0228 which was the last GSM modem I used there is a command at+csq which gives signal quality
I seem to remember a value less than 9 was poor signal quality and the device would probably not work

looking at my code to initiailse the modem I sent
AT, AT_PSSTKI, AT_CSQ, AT_CNUM, AT_CMGF
to make sure all was OK then I would send a GSM text, a UDP datagram or make a TCP connection

I found it sometimes took several attempts to make a succesful connection in particular when using TCP/IP
In practice I attempted to transmit 10 times and if it failed then gave up and showed an error message

 

[doitnow]

in fact i suspected that earlier and hence I even tried changing my work-bench to a place where full coverage was available.

i even tried using SIM-card with mobile-phone as well (& with that i get all the sms that i send)

am i making any mistake or omitting any procedure while SIM300 is booting ???

 

[horace1]

I remember being told that it can sometimes take a couple of minutes for a modem to connect to the network after being switched on.
As ours WISM0228 was in a battery powered device it was only switched on when required - I noticed it could take several attempts to make a sucessful connection and send a UDP datagram. Similar with GPS, it could take time to get fix and often failed completly inside some buildings.

When you send an SMS and it fails does the modem tell you fails or does it report sucess and it fails to arrive at the destination. If the former you just keep trying until it works.

 

[doitnow]

thankx; but my program try to send SMS only after it receives proper response of "AT" command that is first sends AT check response and if it is desired it will start sending SMS (i hope when you receive correct response to AT command you can considered modem is ready, right?)
what surprises me is that if I send sms using mobile phone or using PC(with serial comm software) it sends all the 10 or 100% SMSs; but by using same commands (as that of used with PC) through my hardware doesn't produces the same result

 

[horace1]

with the WISM0228 it send it the following commands to send a GSM message
at
at*psstki=0 PSSTKI SIM Toolkit interface configuration
at+csq CSQ Signal Quality
at+cnum CNUM Subscriber number
at+cmgf=1 CMGF Messages Format
at+cmgs= ... send message

if any of them fail I start again

on power up it can sometimes take two or three attempts to send a message