[time-nuts] GPSDO with a RaspberryPi
azelio.boriani at screen.it
Thu Feb 28 08:43:03 EST 2013
The 24bit counter counts up to 9999999 then is reset to 0 to get a PPS out
of a 10MHz clock. The most significant bit is high from 0x800000 to
0x98967F, so that you have a 161.1392ms wide high pulse when driving the
PPS output with the MSB.
On Thu, Feb 28, 2013 at 1:28 PM, Herbert Poetzl <herbert at 13thfloor.at>wrote:
> On Thu, Feb 28, 2013 at 01:26:17AM +0100, Azelio Boriani wrote:
> > First try at a simple GPSDO for the RaspberryPi. See here:
> > http://www.c-c-i.com/exchange/ for the file PiAutoTIC1.zip
> > Thanks to Bob Smither for his file exchange site.
> Pardon my ignorance, but where does the 161ms PPS length
> come from?
> 2^24 = 16777216 so with 50/100ns clock intervals, we
> should either see 83.88ms or 167.77ms (typo?)
> Otherwise, nice project, thanks for sharing and thanks
> for releasing it as open-source (btw, you might want
> to use some license, like GPLv2 for that).
> Nitpick: the SI symbol for second is 's' not 'S', i.e.
> lowercase instead of upper, because 'S' stands for
> siemens (which is the SI unit of electric conductance)
> > This project is completely open-source, VHDL and C sources are
> > available. Can be implemented also with any uP but the C source
> > must be heavily modified.
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