I'm developing an application that connects to a nokia phone using data cable, issuing AT+ commands (e.g. at+csq, at+creg, etc).
My problem is the time one command take: "AT".
I use the "AT" command to "check if the phone is alive": once in a while (every 30 seconds approx.) I send the command AT (whose answer should be OK) to the phone. If I don't find any "OK" in my serial port's input buffer then I state that the cellular is not present. Else, if I receive "OK" on the serial port, the cellular is present.
I have put a little tweaking thing in the function I used to check the presence of the cellular that prints out the time the function needed to check the presence of the cellular.
When I start the program this value is 73/80 (1/1000 of a second).
The second time is 88/92, the third 105/107, and so on.
After an hour or two, this value grows up to a second.
An important thing to note is that other commands (like at+csq or at+cbc) spend always the same amount of time during the execution of my program (plus/minus 20 milliseconds, of course). The only command that takes always more amount of time to complete is "AT".
I'm using this nokia phone model:
Nokia Mobile Phones
formerly known as Nokia 7110, I think.
please help me,
Fontani Marco - firstname.lastname@example.org