Hi, I can send the command "AT+CMGR=1" To GSM modem, but after that i cannot access the message from it. The modem is "Iwow" and microcontroller is 89c52. I have used Tx, Rx and ground pin of RS232. whether it is necessary to use RTS and CTS pins for this modem? When i send the command "AT+CMGR=1" to GSM modem, a pulse will be coming at TI pin of microcontroller. meanwhile there is no pulse at RI pin, indicating no message has been retrieved from GSM modem. But if i connect it to Hyperterminal i can read the message.
Please find a solution to this problem..
I have used MAX232 as a transceiver( To convert to TTL LEVEL). Programming is done using C code. When i send the AT command like, AT+CMGR=1 a pulse wil be observed at TI pin of Microcontoller(checked using digital probe). But later, pulse is not observed at RI pin.since there is no indication of data at RI pin, the program will halt at the statement- while(RI==0);
wether GSM modem is not accepting that format?( GSM Modem used is of 'IWOW').
"When i send the AT command like, AT+CMGR=1 a pulse wil be observed at TI pin of Microcontoller"
I asked you to explain what that meant - you haven't explained it, you have simply repeated it!
You haven't stated specifically what chip you're using - there are many different variants from different manufacturers with "89C52" as the basic number. You need to state manufacturer, and include all prefix and suffix details.
eg, the Philips (now NXP) P89C51X2/52X2/54X2/58X2 don't have a "TI" pin.
I'm assuming you mean the TxD pin - which is the UART output?
Similarly, there is no "RI" pin - do you mean RxD, the UART input?
"a pulse wil be observed at TI pin of Microcontoller"
Why do you say "a pulse"? - do you really mean just one, single pulse? If you are seeing just one, single pulse, then that is certainly wrong! You should see a whole stream of pulses as the UART sends the "AT+CMGR=1" string!
"checked using digital probe"
What kind of "digital probe"? You need to use an oscilloscope and check that the pulses are well-formed and have the correct timing.
You need to check that the pulses arrive at the modem's input pin.
Did you confirm whether the modem requires RTS and/ot CTS?
Did you do the Search?
Did you note that AT Commands need to be terminated with a CR character, ASCII code 0x0D?
Did you check your cable wiring?
Did you check your baud rate setting?
Did you try the simulator?
If you connect the microcontroller to hypoterminal, do you see the string sent correctly?
"GSM Modem used is of 'IWOW'"
Never heard of it. Please post a link.