>> How are you planning on making ntp use the RTC as a secondary >> time source? I don't see that as a supported refclk driver. > hadn't got there yet likely using NTPsec, as the codebase is available if a > driver or generic driver won't work The PPS driver expects the pulse to be on the second. You won't get that from a RTC. If I was doing it, I use the SHM driver. Then you can do all your work in a separate program and feed an offset to ntpd. I haven't looked at RTC chips recently. You want a pulse that you can feed to the kernel's PPS capture logic. 60Hz works on a PC. 32KHz is probably too fast. (might be worth a try) You might have to add a divider. If you use the GPS HAT from Adafruit, it has a prototyping area where you could drop in a RTC and wire it up to various GPIO pins. DIP package would be convenient. The Ethernet on the PI is via USB, so it's crappy for making a nutty-good NTP server. But the PI is convenient and good enough for all but nutty uses. -- These are my opinions. I hate spam.