Hello,

there is an application note of Microchip dealing with this. Look at
AN543!

Hope this helps.
Imre


+-----------------------------------------------------------------------+
| The information transmitted is intended only for the person or entity |
| to which it is addressed and may contain confidential and/or          |
| privileged material.  Any review, retransmission, dissemination or    |
| other use of, or taking of any action in reliance upon, this          |
| information by persons or entities other than the intended recipient  |
| is prohibited. If you received this in error, please contact the      |
| sender and delete the material from any computer.                     |
+-----------------------------------------------------------------------+

On Thu, 8 Nov 2001, Brandon Stewart wrote:

> Greetings all, this is my first time on PICLIST!  I am trying to generate
> DTMF tones using only a PIC, a 16F877.  I want to use the PWM to do this.
> Do you think it is possible to generate the two frequencies *almost*
> simultaneously?  I mean say freq. 1 is piped out the PWM for delta T mS, and
> then Freq. 2 is piped out some delta T ms, and that this pattern continues
> for about a second.  Would this be good enough to work, to fool the phone
> system?
>
> P.S- I have read the archives, but found little good info there.  Everyone
> says to use separate hardware, but that is NOT what I want to do here!
>
>
> Thanks in advance,
> Brandon Stewart
> Georgia Tech
>
> --
> http://www.piclist.com hint: PICList Posts must start with ONE topic:
> [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads
>
>
>

--
http://www.piclist.com hint: The list server can filter out subtopics
(like ads or off topics) for you. See http://www.piclist.com/#topics