[Discuss-gnuradio] Using a USRP as a PID feeback controller

[Aviv Keshet]

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