Hey David, to add onto what Marcus said: The minis don't have a hardware PLL (unlike the B200/B210, and all other USRPs). Before you go down the rabbit hole of modifying the FPGA, you might want to run a few B2xx-minis from an Octoclock (ignore PPS for now), and check if the phase stability is good enough for your application.
Other than that, it would be possible to use a GPIO input for PPS, but neither the software nor the FPGA expect that, and both will require modifications. For a USRP/UHD veteran such as yourself, that sounds feasible, but be aware it's a lot of work and might not give you what you need. --M On Wed, Jan 14, 2026 at 9:20 PM Marcus D. Leech <[email protected]> wrote: > On 2026-01-14 14:57, David Raeman via USRP-users wrote: > > Hello, > > > > I have a project currently hosted on a USRP E320 that involves distributed > signal coherence. During development I sometimes do over-the-wire testing > using an Octoclock’s 10MHz and PPS outputs to synchronize multiple radios > on the bench. > > > > I’m starting to investigate the viability of rehosting this application on > a USRP B206mini to reduce size and cost. As far as I can discern, this > radio only has a single port that can accept either a 10MHz reference input > or a PPS input. Is it possible to somehow use the radio with both clock and > PPS outputs from an Octoclock with out-of-the-box UHD? If not, would it be > viable for me to add a bit of FPGA logic and UHD tweaks such that software > can specify a GPIO pin as the PPS input while using the SMA as the 10MHz > input? Or are there hardware or systems constraints that would preclude > that approach? > > > > Thanks! > > David Raeman > > Synoptic Engineering > > _______________________________________________ > USRP-users mailing list -- [email protected] > To unsubscribe send an email to [email protected] > > You could probably add some FPGA functionality to implement a separate PPS > input. > > But I should warn you that the clock servo in the B205x series is simply > NOT UP TO THE TASK of building-out multi-unit coherent applications. > > The mutual phase-noise is way too high. The B205 was never intended for > such applications to begin with, and the clock servo just doesn't work that > well. > _______________________________________________ > USRP-users mailing list -- [email protected] > To unsubscribe send an email to [email protected] >
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