Hi,
Thank you very much for all the comments.
I have read a few articles about DTMF detection algorithms,
but all of them is oriented on DSP. Even if a DSP is used,
a lot of tests are performed to insure a detection method
is well enough.
So, it looks like an interesting and not common task to
implement it on a 8-bit micro. However, I have no more
time to be involved in the problem right now.
Thank you,
Oleg