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interfacing gsm and microcontroller

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amjd

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Hi!!

I am doing a project based on gsm.Here i need to interface microcontroller at89s52 with gsm.I am using a sim300 modem.Main objective is to send sms using gsm by providing AT commands from microcontroller.sim300 responds properly when AT commands are given from hyperterminal, but it doesnt respond when i send the AT commands serially from microcontroller.I am not able to figure out where i have gone wrong. I have connected uc and gsm using rs232 connector. can someone please help me out to interface microcontroller and gsm?
 

amjd said:
I have connected uc and gsm using rs232 connector. can someone please help me out to interface microcontroller and gsm?
Click to expand...
The SIM300 is a TTL level interface not rs232 - from your post I assume you have a level-shifter in the circuit (MAX232), which may be the problem. It would help if you showed a schematic of your circuit.
 

HEY , U NEED TO CONNECT RX OF MICROCONTROLLER TO THE 2ND PIN OF DB9 OF MODEM AND TX TO THE 3RD PIN OF MODEM.

i.e if u r using

MICRO CONTROLLER -> max232 -> DB9 connector -> "RS232 Cable" -> modem

then u must have cross connection at "quoted" rs 232 cable i.e. 2 and 3 pins must be swapped between 2 ends of RS232 cable ,
check it out it will work, I suffered a lot due to same problem but it was d solution, do it and move ahead coz programming part is real challenge w8ng for u

:D:D:D
 

HEY , U NEED TO CONNECT RX OF MICROCONTROLLER TO THE 2ND PIN OF DB9 OF MODEM AND TX TO THE 3RD PIN OF MODEM.

i.e if u r using

MICRO CONTROLLER -> max232 -> DB9 connector -> "RS232 Cable" -> modem
Click to expand...

one more question is there,whether <CR> is required to be sent at the end of AT command?if it is so then is it to be serially transferred?
 

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