Wing Kent Kwan wrote:
>
> how can I generation the DTMF only use the PIC or MCU??????
> THANK!

I'd use a lookup table with linear interpolation for generating the two sine
waves, a highly optimized routine to mix them, and an isochronous 256-level
software PWM for the D/A. But that's just me. Other's would probably go ahead
and use Eric Smith's DTMF dialer:

http://www.brouhaha.com/~eric/pic/dtmf.html

If you really insist on complexity then you are welcomed to look at:

http://www.dattalo.com/technical/software/pic/picsine.html
http://www.dattalo.com/technical/software/pic/twist.asm
http://www.dattalo.com/technical/software/pic/pwm256.txt

For three routines that can be combined to give a really precise DTMF waveform.

BTW, the sinewave routine has recently been updated and is now about 25% faster.
I also have a version that works (but is not yet fully optimized) for the 18cxxx
core:

http://www.dattalo.com/technical/software/pic/sine18.asm

(You gpasm users please be for-warned: this routine uses features that are only
available in gpasm-0.0.8 - which will be released fairly soon. MPASM users also
should be warned, I know that this routine will need modification to be
assembled.)

Scott