John said:
Jamie wrote: [...]
I think you'll find if you don't have a latency problem with the
serial link to the chip, you should be able to do all the FMing you
want..
The problem with the uC on these little boards is not the serial link.
Well, at least not if 100Hz sweeps suffice. The problem is that they are
too small to calculate the numbers on the fly and usually have to little
flash left to store them in a LUT. Plus that would be a major
time-consuming hack.
Fancy ramped, modulated DDS sinewave generation at 200K samples/sec would be no
sweat for a $4 ARM, and you get a mux'd ADC and a DAC for free. But yes, it
would take some code slinging.
And I'll probably do that if this becomes a product, with whatever
processor the local SW folks can handle without a major learning curve.
Just not right now, got to watch work load, expenses and time line. So
it'll be analog for now.
If you do go ARM, let me know if you'd like some example C code to butcher. We
have an app that uses an ADC interrupt to do a filtering + PID algorithm, ADC in
to DAC out, on an LPC1754. The algorithm is pretty fancy, and we run it at 100
KHz with the internal uP clock throttled down to 50 MHz. We pay $3.55 each,
pre-programmed by a distributor.
Bring your programmer and we'll go to Zeitgeist and we'll explain our code and
the DDS theory. Your treat, of course.