[ntp:questions] Re: AW: Re: AW: convert_rawdcf: parity check FAILED on my embedded Linux system

Uwe Klein uwe_klein_habertwedt at t-online.de
Sun Oct 15 15:01:21 UTC 2006


Torsten Krieger wrote:
> Hi Uwe,
> 
> I made a small c program which reads the serial port /dev/refclock-0
> character by character, ntpd switched off. Shall I see one character by
> second (second = 1/60 minute) 0xf0 for low bit and 0x00 for high bit? If
> this should be the case then something went wrong with my serial interface.
It has been a couple of years that i had contact with DCF and
I have never used this in conjuction with ntpd.

if the raw DCF carrier detection is used as RXD and
the serial line is configured properly raw, 50Baud 8bits/char no parity,
ignore parity and framing errors (IGNPAR) , break as zero ...
25 or 40 Baud worked better for me.
you should receive 1 byte ( or a framing error/break ) every second for 59 seconds
every 60 seconds.

100ms -->  5 Bit times -> 1 stop and 4 LSbit low, rest high -> 0xf0
200ms --> 10 bit Times -> 1 stop and 9 LSbit low, the high -> either 0x00 or framing error
only jitter between leading and trailing edge is relevant.
The distance between acceptable low and high indicating chars is always big enough.

uwe

ER Hmm: What do you receive?




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