[ntp:questions] Tobit LAN!Time DCF77 receiver not working

Johan Swenker no_spam_please at swenker.org
Thu Dec 24 00:33:27 UTC 2009

On Wed, 23 Dec 2009 17:50:23 +0100, Marc-Andre Alpers wrote:

> Es schrieb Rob van der Putten:
>> Maybe you can post a link to the receiver you're using.
> I can give you a Picture:
> http://666kb.com/i/bf7er4kfwd3feibip.jpg

This device looks very much like a DCF77 receiver I have.

The standard way to read these devices is with a baudrate of 50.
The DCF pulses of 100 and 200 msec give a distinct character
on the serial line. 
There used to be a program dcfd.c in the xntpd sources (yes long ago)
that could handle such a dcf77 receiver.

For "just a clock", this works great. For an accurate clock (ntp)
this works lousy. Two problems:
1) how to get a time stamp at the moment the pulse arrives in the PC
2) jitter will be large (about 1 msec) as the uart samples the signal 
with 16*baudrate. 

Regards Johan

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