>Price by price I would go for a commercial programmable wave form
>generator and then use the PIC to control it.  I understand that it
>could be funny to use a hammer to set a bolt, but it is not the right
>tool, you will have *limitations*.

I share the same opinion. For example, AD9835 DDS chip is relatively cheap
and with stable base oscillator, it can generate mentioned frequencies
without any problem, if the base oscillator is stable enough. In most
times, it is not...

>You will not want a microcontroller being driven by a jittering
>programmable oscillator, if you need clock stability and precision.
>Don't let miraculous solutions fool you.

:-) More than year ago, I started to develop my bench top signal generator.
When I looked at Analog's DDS chips, I thought that I found miraculous
solution - frequency generator which is able to generate fequencies with
milihertz precision. It seems simple, but as soon as someone think a bit
about it, it is not so simple. Till today, the whole project is not yet
finished, because it took me more than eight months to find and build
reasonably stable base oscillator.
BTW, I tested two commercial DDS based signal generators and the results
was disasterous. Both of them claimed something like 1-20.000.000 Hz,
precision 0.001 Hz and both of them was +/- 10 - 50 Hz off most time,
drifting like crazy (at 10.000.000). In one unit, there was used normal
crystal oscillator as a master - they did not bother to use any form of
temperature compensation...

PavelK

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