hi, i am trying to interface gsm mobile(ericson )with 8051. mobile and microcontroller responding correctly if i connect with computer serial port(com).but i connect gsm mobile with 8051 with null modem conection mobile is not respoding.in hypertermminal i used without any flow control signals.can you please help me in this?suggest me exate requaired signals to complete communication between mobile and 8051.
Do you know what a paragraph is? It's when you break your text down into small sections.
Your post is really hard to read as you have just rolled everything into one big blob!
"i am trying to interface gsm mobile (ericson) with 8051"
Note: that's "Ericsson"
Exactly what "mobile" are you using?
Note that trying to use a real phone is often more trouble than it's worth: " href= "http://www.8052.com/forum/read.phtml?id=101998">www.8052.com/.../read.phtml
"responding correctly if i connect with computer serial port (com)."
If you have a real phone, are you using a special adaptor cable for this? If so, you will need to build an equivalent adaptor cable for the 8051...
"i connect gsm mobile with 8051 with null modem conection mobile is not respoding"
Of course it won't!
A Null-modem cable is what you use to connect two DTE devices in place of a modem; When connecting to a real modem (or phone acting as a modem) you need a straight-through cable.
Remember: the "TX" pin on a modem (DCE) is an Input - it supplies the data to be transmitted.
"in hypertermminal i used without any flow control signals"
Even if you set Hypoterminal to "No Flow Control", the COM port may still be asserting RTS.
You need to read the mobile's Manual to determine what control signals it requires (generally, RTS is required).
"suggest me exate requaired signals to complete communication between mobile and 8051"
See above - read the Manual!
Do you know what a paragraph is? It's when you break your text down into small sections. Come on, why patronize?
Anyway, I had a similar problem, when I tried to have a 8051 communicate with an Ericsson T68i over the serial port. When I connected the T68i to the PC (RX, TX and GND pins only - RTS is NOT required), with the use of max232 level shifter of course, I had no problems. When I in Hyperterminal (9600, 8bits, no parity, 1 stop bit, no flow control) typed e.g. "AT" I got the reply "OK". When I then connected the T68i to the 8051 and tried to read the response from the T68i and display it on a LCD I only got rubbish.
... printf("AT\r\n"); getString(buf); //get string without echo LCD_DisplayString(buf);
In my case the problem was that I didn't realize the T68i inserts a couple of 0x0D and 0x0A (3 in total if I remember correctly) in front of the reply. So modifying the above to:
... printf("AT\r\n"); buf[0]=getCharacter(); // disregard '\n' buf[0]=getCharacter(); buf[0]=getCharacter(); getString(buf); //get string without echo LCD_DisplayString(buf);
solved my problem. The LCD now displays "OK"
AT Commands are terminated by the single character specified in the S3 register - usually CR
With command echo enabled, the modem echoes the CR and appends the repsonse formatting character specified in the S4 register - usually LF
printf("AT\r\n");
The LF (\n) here is spurious - it probably accounts for the extras you are seeing...