Chrony and DCF77 RS-232 receiver

Server operators
1

I have ordered an Expert Mouse DCF77 RS-232 receiver as extra to my GPS-PPS-USB receiver.

Does anybody have a clue how you connect this to Chrony or to NTP?

As I want extra accuracy by using both for time-source.

However I can not find how they do it for Chrony and the NTP papers are not very good either.

Anybody some helpful info on how to do it? Would be much appreciated.

2

You need some RS232 to UBS reduction. It may not work with all. Mine DCF77 have RS232 and I have only one usb to serial dongle which works with it. Seems other one does not give proper power. With that I have, PPS is not working (not sure, it receiver does not have it or serial reduction does not support it).

For the software, I have used NTPD for long time (you need to compile it, because DFC receivers are not enabled by default (in debian, ubuntu…). Check this blog https://weberblog.net/ntp-server-via-dcf77-on-a-raspberry-pi/

For the chrony, there is relative new project GitHub - mlichvar/ntp-refclock: Wrapper for ntpd reference clock drivers, I am running it this way now. Ntpd crashed sometimes with bad signal. This seems to be more stable.

3

Thanks but I have a real RS-232 port onmy system, so I need no USB-converter.
Else I could have ordered the receiver with an USB-connector, they sell those too.

I will check out the github, thanks!

4

I have found a better way to connect to Chrony with a DCF-receiver.

It’s called radioclk and can be installed with NTP, however if you unpack the debian package by hand then it doesn’t require ntpd.

It can be called like this:

refclock SHM 0 refid GPS offset 0.127 precision 1e-3 
refclock SHM 1 refid PPS lock GPS precision 1e-9 prefer
refclock SHM 2 refid DCF  precision 1e-7

I don’t have the receiver yet, but chrony doesn’t complain about it, the deamon is running but not receiving anything yet.

More info can be found here, but you can also extract the .deb by hand and move the files, then it will work.

http://www.buzzard.me.uk/jonathan/radioclock.html

I hope to have the receiver next week, then I can say if it works or not.

5

Too bad, I’m too far away from the DCF tranceivers.

Oh well, still have GPS+PPS.