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

David Woolley david at djwhome.demon.co.uk
Sat Oct 14 16:22:12 UTC 2006


In article <BEEJJJBHFJKBIOKDKFJLEEHNCBAA.Torsten.Krieger at krieger-mis.de>,
Torsten.Krieger at krieger-mis.de (Torsten Krieger) wrote:

> it seems to receive the DFC signal from Mainflingen correctly. I do not know
> much of the receiver Hardware since it is proprietary and not well
> documented, I only know that it receives the raw serial signal with 50 baud.

If it is interfacing at 50 bits per second through a UART (the actual
signal is 1 baud), the receiver's baseband processing is trivial and
you are processing the raw baseband signal with only low pass filtering
applied.  The internals may not be published, but there are not exactly
any trade secrets in such a receiver.

The 50 baud serial interface is a hack in ntpd which makes use of the
error behaviour of UARTs when presented with the raw DCF signal.

The signal is not being processed as a proper aynchronous serial signal
and things like UART parity and framing errors do not have their standard
meanings, so would not be presented as such in error messages.




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