I had tried with hyperterminal to make a call ATD9994238372; and press enter, it is working. Now i have to sent this command from my microcontroller to gsm modem. what is the hex value for "enter" key? Please do let me know.
@prakashvenugopal: It is very likely that two more characters will be needed.
One is the "ESC" character and the other one is the "LF" (line feed) character.
Hex value of CTRL+Z is 0x1A. If you are writing your code is C, then use this, "unsigned char ctrlz=0x1A;" or if it assembly, then use this "MOV SBUF,0x1A"