This email is not a question, but more of a comment.
I’ve been working for about a week on re-purposing a USRP as a digital
feedback
controller, rather than a software radio. The USRP hardware platform
provides
you with quite a good starting point for this sort of general purpose
digital
signal processing application. Nice, fast, and fairly high resolution
analog
front end. And the total ADC + DAC latency is only 250 ns (by my
measurements),
which means PID feedback controllers with lock bandwidths up to 1MHz are
quite
achievable (something that can be quite a pain to do with analog
components).
And of course a digital feedback controller, being programmable, can be
made to
do also sorts of fancy “smart” things that are a pain to do in analog
(hold or
reset the integrator when told to do so, or make the loop gains
setpoint-dependent, or your great idea here).
Despite this seeming like a killer app, I haven’t really found much
discussion
of it in this list’s archives or on the gnuradio wiki. So I’m mentioning
the
idea in public, for future mailing list archive searchers. If, at some
point,
my FPGA code reaches a level of maturity where am I not too embarassed
to share
it, maybe I will post it somewhere. Or maybe someone on this list will
now pipe
in that this is all old hat and has already been done.
Aviv