On Mon, Oct 16, 2017, at 03:45 PM, jimlux wrote: > I have beagles, but others have pis. > > There seem to be dozens of GPS receivers out there in a variety of form > factors. > > What's the current "best" inexpensive choice for run of the mill > time-setting/1pps that's a "catalog" item > > Plenty of online "how-to" from 2013 and 2014, but we here on the list > know that the "cheap GPS" receiver business is a very moving target - 4 > years is a long time.
It's a bit old-school, but I have an Oncore UT+ attached to my Pi 2 Model B timing server at home. A simple MOSFET-based level shifter[1] converts the serial and PPS signal from the 5V the Oncore outputs to the 3.3V the Pi requires and is sufficiently fast to not make a significant difference in timing (I can't see any delay, even with my oscilloscope turned down to 5ns per div). I also built a little interface board with a supercapacitor-based backup for the Oncore's RAM that holds the level shifter. The Oncore driver for NTP is a bit chatty, so I have it save logs to a small ramdisk[2][3][4] with the log being rotated every two days. Works well. I suppose using a 3.3V unit would be nice, but I had a bunch of Oncores lying around that needed use, so why not? :) Cheers! -Pete [1] <https://www.adafruit.com/product/757> [2] The line in fstab is, omitting quotes, "tmpfs /tmp tmpfs defaults,noatime,nosuid,size=100M 0 0" [3] The entry in the ntp.conf file is "logfile /tmp/ntp.log", which was done after making the change detailed at [4] [4] <http://lists.ntp.org/pipermail/hackers/2010-November/005004.html> -- Pete Stephenson _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
