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.
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...