[ntp:questions] Only Garbage from Raw DCF
nomail at example.com
Fri Jan 30 19:24:05 UTC 2015
Andreas Mattheiss <please.post at publicly.invalid> wrote:
> ok, let's go all technical ;-)
> I wanted to play around a bit, building a reference clock from a cheap
> DCF77 module (similar, but not identical to the infameous "Conrad
> module"). It basically churns out 100/200ms pulses. I was planning on
> using flavour 5 of the Type 8 module. I feed the signal from the module
> into a level converter, based on the MAX232. This has been done many times
> before, if I peruse success stories on the net.
> Alas, it won't work for me. I seem to get something out of pin 2 of my
> plug; I can stick a LED in and get a long "on" signal with 100/200ms gaps
> when connecting the LED one way, short 100/200ms bursts when swapping
> anode and cathode. This I think is correct, since logic-0 is >+3V in
> RS-232 and logic-1 is <-3V (the MAX232 already does inverting for me).
No, it is the wrong way around. Your signal should be < -3 most of the
time, and pulse to > +3 during the 100/200ms pulses.
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