I have used the Dallas DS1806 hex digipots with both VFO's and VGA's from a
PIC with excellent results for generating wave patterns for laser sheet
scanners for entertainment.  They have 64 positions on each pot and you
shift in 48 bits in this case.

I was hoping that there might be some IC's now with I2C or 3 wire interface
for direct generation of sine or square wave as well as signal amplitude
control.  Anyone know of such devices?

Bill Arkin
**25 Years of Laser Services**
           Holo-Spectra Inc.
           7742B Gloria Ave.
         Van Nuys, CA 91406
              818 994-9577
           www.lasershs.com


>Hi,
>
>just looked up the places you4ve suggested.
>
>> You can buy such beasties off the shelf from Burr-Brown:
>> PGA102 for example lets you switch between gains of 10 and 100,
>> other PGA*** chips have other options. (PGA stands for Programmable
>> Gain Amplifier)
>
>They have a binary programmable PGA 103 amp. Problem with it: price.
>
>> If you want to make your own you can use a digital potentiometer
>> (some are made by Dallas I believe) as a feedback resistor in an
>> op-amp to provide programmable gain.
>
>Looks promising, I will give this a try.
>
>> Those digital pots are some form of D/A. I don't remember the exact
>> configuration but if you look at their data sheets and app notes you
>> might be able to duplicate their function with just the PIC and some
>> discreetes, maybe someone else can shed more light on this...
>
>They have a app-note about lcd-contrast control which covers also
>( nobody knows why ) gain adjustable amps.
>
>Sombody knows who also produces ee-pot4s ?
>
>Kind regards
>
>        Stefan
>