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Mar 19 2009, 7:01 AM
hiii... i m using SIM300 GSM Module in my project.
i need to interface it with the P89V51RD2. Hardware part is done but i m stuck up in software part.. i m not gettin how to start using AT comands for it.. i m using KEIL Software 4 d programming.. module is interfaced with the microcontroller on UART and dat is ready on the PCB..but i m nt able to start with software part including configuration n oder things.. plz help me:-(

Mar 19 2009, 7:14 AM
do u hv a list of the AT commands?
if you have them, then to send them to the GSM modem through the controller simply type
and aftrwads the rest of the commands with some delay in between.
and dont forget to include <stdio.h> as a header file.
Hope that helps.


Mar 19 2009, 7:59 AM
Thnx a lot 4 d reply. I hv list of all AT commands. ...... Bt i dnt kno how to check GSM Module using AT commands? like connector of our GSM Module is already mounted on d PCB and i m using RS232 for burning d program on d hardware.... plz help me

Mar 19 2009, 8:08 AM
u need a serial cable for that. connect one end of the serial cable with the on board GSM module and the other end with the serail port of th PC. Then open hyperterminal on the PC and give some name to the connection. Then select the working com port of the PC(usually its Com1 only) and finally in the com1 properties click on the restore default option.
a new connection will be established. Then at the very first type AT and press enter. If the modem replies back OK that means ur GSM modem is working fine.
try until this first.

Mar 19 2009, 10:06 AM
But How to start GSM Module on board? for that i dint get any AT command for Power ON...
Mar 19 2009, 10:11 AM
Can i use dis command AT+CPOWD for Power ON?
Mar 19 2009, 10:13 AM
im nt gttng u. wht do u mean by startng the GSM modem onboard?

u need to switch on the power supply of ur board n thn connect the DB-9 connector of the GSM modem with th serial port of ur PC through serial cable.

Mar 19 2009, 10:25 AM
I m working on d project of Energy Meter..First let me clear that we are not using a readymade GSM Modem.... we have bought a separate GSM Module n mounted on PCB....n fst v r trying to initiate GSM Module using software....so along with GSM Module we ahve interfaced an LED...so whenever the GSM is ON that LED shud glow!!!
Mar 19 2009, 10:56 AM
i have used a SIM 300 GSM modem in my projects also. n if im not wrong there is a db9 connector on it along with a power jack(used for supply). rite?
Mar 19 2009, 11:20 AM
we have 30*2 connector along with the GSm Module.....n that connector is soldered on PCB....n i donno whether it is called db9 connentor or something else....!!!!
Mar 19 2009, 11:25 AM
i know one db9 connector which we are using is RS232.......if u r talking about this db9 connector then wat is it got to do with GSM Module?
Mar 19 2009, 11:40 AM
see, i guess one db-9 connector will be there to program the controller.
im talking abt the db9 connector which is on the SIM 300 GSM module. through that db9 connector u can communicate the PC and th GSM.
Mar 19 2009, 11:45 AM
We dint get any db9 connector with GSM Modul!....!!!. but d one which v r usin can be connected 2 PC to burn our program on the microcontroller...so now how is it going to help to initiate our GSM?.
Mar 19 2009, 11:50 AM

This is the program that i wrote...so can i use this code to start off with my GSM Module?
Mar 19 2009, 12:06 PM
the first command should always be
then u can write the commands according to what you want the GSM to do.
I dnt knw about the meaning of the first command that you used ie
n can upload a snap of ur project?
Mar 19 2009, 12:15 PM
i can upload a snap....but it vl tk tym so i vl do it 2morrow........will wait 4 ur cooperation 2morrow....
Mar 23 2009, 8:53 AM
I want to know that whether we have to burn the "AT" command on the microcontroller or we can check the GSM Module by directly using Hyper Terminal???
Mar 23 2009, 12:00 PM
well if you are checking your module to be working or not then you can test it using Hyper terminal.

ofcourse when you are making controller based application you have to burn the commands inside it so that controller can send it.

and.. you forgot to send \r after each command sent to modem from controller.

no need to send \n after every command.
Mar 23 2009, 9:34 PM
Hello pakvainim
According to the Sim300 pdf you need to set the PWRKEY pin (Power on)
low for 1.5 seconds then high.
The modem will send the text "RDY"

As far as I can see AT+CPOWD =1 will turn the modem off,
but AT+CPOWD =0 will not turn it on.

Can you write some code into your micro to read whatever the modem sends to you
and pass that back to your PC for you to read in Hyperterminal.

Can you supply a circuit diagram of your project ?
Mar 24 2009, 12:07 PM
you will only get RDY message if modem is configured with specific baudrate using AT+IPR. so do not expect any message from modem if modem is in autobaud mode.

you can check modem configuration using AT+IPR?
if you get 0 then modem is configured for autobaud.
Mar 25 2009, 11:45 AM
After establishing connection to hyper terminal how can be send AT command? The window gets opened but i m not able to type AT command on the Hyper Terminal....now what shoul I do?.....plzzzzz help me out!!!

Thanks in Advance!!!
Mar 25 2009, 6:14 PM
just write AT+xxxxx and press send buttion
Mar 25 2009, 6:15 PM
send button means enter key
Mar 25 2009, 9:00 PM
You *are* able to send AT in Hyperterminal, it just doesn't appear on the screen
as you type.
The reply from the modem "OK", will appear if all is working.

Make sure Hyperterminal is set to the same baud rate as your modem.

Mar 26 2009, 2:24 AM
With modem, we have DB9 connector but with module there is no DB9 connector.

I want help regarding interfacing SIM300 with 8051. Please help me.
Mar 26 2009, 5:25 AM
so to set baud rate the very first command we need to send is "AT+IPR=xxxx " right? But i m confused 'coz i read that initially we should only send "AT" command, to check the module, and we should get "OK" back in reply.....so now i m confused whether i should use simple "AT" command or "AT+IPR=xxxx"
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