This. I've had some timing issues ( unrelated to NTP ) with certain combinations of FlightAware RTLSDR USB sticks and Pi models. IIRC USB and Ethernet share the same bus on the Pis, and that can cause bumps.
GPIOs run right off the SOC, avoiding that. On Fri, Jun 21, 2019 at 7:25 AM Denys Fedoryshchenko < nuclear...@nuclearcat.com> wrote: > On 2019-06-21 14:19, Niels Bakker wrote: > > * j...@west.net (Jay Hennigan) [Fri 21 Jun 2019, 05:19 CEST]: > >> On 6/20/19 07:39, David Bass wrote: > >>> What are folks using these days for smaller organizations, that need > >>> to dole out time from an internal source? > >> > >> If you want to go really cheap and don't value your time, but do value > >> knowing the correct time, a GPS receiver with a USB interface and a > >> Raspberry Pi would do the trick. > > > > Have you tried this? Because I have, and it's absolutely terrible. > > GPS doesn't give you the correct time, it's supposed to give you a > > good 1pps clock discipline against which you can measure your device's > > internal clock and adjust accordingly for drift due to it not being > > Cesium-based, influenced by room temperature etc. > > > > You're unlikely to get the 1pps signal across USB, and even then > > there'll likely be significant latencies in the USB stack compared to > > the serial interface that these setups traditionally use. > > I think it depends on recipe you are using. > Raspberry have low latency GPIO, and some receivers have 1pps output. > https://www.satsignal.eu/ntp/Raspberry-Pi-NTP.html >
