Howdy,

What I need must be such a common thing, that I thought I'd ask the PIC
list's assembled wisdom before I set out to possibly re-invent the wheel.

I'm using a 16C84 for an alarm controller, and I'd like to use the PIC to
also generate a "siren" waveform (to be externally amplifed), rather than
build that function in separate hardware.

The other approach to keep cost low would be to use a dedicated "siren
sound" IC, but I haven't found a commercial one yet.  I do know that they
exist as tiny COB (chip on board) modules in cheapo personal alarms, but
does anyone know of any sources for them... Digikey lists some COB modules
that generate melodies such as "happy birthday" etc, but can't supply one
for a siren sound.

Basically, what the siren waveform needs to be is as follows:

1. a frequency modulated square wave output, (ie: *not* being amplitude
modulated, should make it easier to do)

2. output waveform is centered on 3 kHz.

3. waveform should sweep back and forth between say 2500 and 3500 Hz, at a
rate of 15 Hz or so.


A routine with settable parameters for the frequency deviation (sweep) and
sweep rate would be ideal, to optmize the "effectiveness" of the sound
produced ... the trick is to resonate with the output transducer.  Of
course, armed with the basic routine, I could (and would) add the settable
parameters.

Many thanks in advance for any help that may come forth.
....Gregg