Hi!!
I am doing a project based on gsm.Here i need to interface microcontroller at89c52 with gsm modem.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 MAX232. can someone please help me out to interface microcontroller and gsm?
Ramesh,
All commands to the modem MUST have a CR/LF or a response from the modem will NOT occur.
Not quite true: CR is the command terminator (unless you have reconfigured this) - the LF is superfluous.
See the modem's AT Commands manual
See also:
www.8052.com/.../174624
http://www.keil.com/forum/docs/thread9483.asp
http://www.keil.com/forum/docs/thread12316.asp
http://www.keil.com/forum/docs/thread9385.asp
This ITU standard formalises the "Hayes" AT command set - which had become a de-facto standard for modem commands.
www.itu.int/.../en
Andy,
I stand corrected. Obviously this has been dealt with numerous times before. My point was that he cannot just send the 'AT' and expect a response.