[ntp:questions] Re: AW: Re: AW: convert_rawdcf: parity check FAILED on my embedded Linux system
Hans Jørgen Jakobsen
hjj at wheel.dk
Sun Oct 15 12:12:24 UTC 2006
On Sun, 15 Oct 2006 11:28:09 GMT, 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.
> Uwe wrote:
>>The DCF Signals is 1 pulse every 1 second. the 59th pulse is omitted to
>>mark the minute transition.
>>AAdditonal information is coded into the pulselength of the second pulses.
>>0.1 sec for a low bit, 0.2sec for a high bit.
>>on a 50Baud (0.02s/bit) serial line with inverted sense this is received as
>>HHHHLLLLLHHHHHHHH S=StartBit, s=StopBit(s)
>>____S01234567s____ 0xf0 for a low bit
>>____S01234567s____ 0x00 for a high bit
I dont think its that simple in practice.
The DCF receivers I have used have some large jitter on both start and
length of pulse. Add to that noise impulses.
Try and print the bits and figure out what signal you get.
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