I’m currently refactoring the output logic of ODR-DabMod, a Digital Audio Broadcasting modulator, which has separate UHD and SoapySDR blocks. The intention is to make all features available to both USRPs and the LimeSDR. These include a digital predistortion prototype (which needs feedback after power amplifier, implemented with continuous TX and occasional RX bursts, with relative timestamps), and the ability to sync the transmission to a specific GPS-derived time (for single-frequency networks, where several units are transmitting from different remote sites). The latter also needs an external disciplined REFCLK, which I understood is supported.
Long story short: I’m also interested in the ability to set the HW time on the PPS rising edge.
My code assumes system time is synced using NTP, and the second change (in system time) is close to the PPS edge. To summarise: software waits until the second changes (+ margin, say 100ms), and tells the device “on the next PPS edge set your HW time to current_second+1”.
If I understand the discussion correctly, the LimeSDR doesn’t support anything like that for now. Is anybody working on this already? Could I help in any way (FPGA/SW dev)?