Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!uunet!microsoft!alonzo
From: alonzo@microsoft.UUCP (Alonzo GARIEPY)
Newsgroups: comp.sys.handhelds
Subject: Re: Phone tones
Message-ID: <51114@microsoft.UUCP>
Date: 28 Feb 90 22:12:31 GMT
References: <4501@jarthur.Claremont.EDU>
Reply-To: alonzo@microsoft.UUCP (Alonzo GARIEPY)
Organization: Microsoft Corp., Redmond WA
Lines: 28

In article <4501@jarthur.Claremont.EDU> bgribble@jarthur.Claremont.EDU (Bill Gribble) writes:
> Question:
> (and I hope the answer is yes, 'cause I don't want to do it myself)
> Did anyone ever come up with a way to generate multiple tones from
> the hp's speaker?  (i.e. phone tones) 
> The more I think about it, the more reasonable it sounds.  If the tone 
> BEEP generates is a sine wave, there must be a lookup or some call
> to generate the waves.  If this could be diverted to another table/function,
> multiple tones could be generated by simple addition of two sine waves.

I don't know if you saw my posting on this; I will send it under separate
cover.

The tone is a combination of two sine waves.  This makes it somewhat 
more difficult to synthesize with the beeper.  Since the beeper has 
only two levels 1 and -1 (and maybe 0) you have to do something like 
Pulse Duration Modulation to get a complex signal.  If there is a 0 
then a simple combination of two sinusoids may be possible without PDM.

In any case, the amount of distortion is horrendous.  It will take 
someone with more time than I have to experiment with this.  My posting 
contained all the information you need to try this once you have some
familiarity with hp28 machine code.  It includes sample machine code to 
drive the beeper, the frequencies for touch tone dialing, and some 
reasonable approximations to these frequencies.  I am told that this was 
tried once at HP and given up as not worth too much effort.

alonzo