Re: [gpsd-dev] SemPiTernal - Bounding PPS uncertainty

[Paul Fertser]

Hey Gary,

On Fri, Apr 22, 2016 at 03:35:15PM -0700, Gary E. Miller wrote:
> > > because all the data was inverted. That's why I built that little
> > > PC board which fits in the blue plastic case
> > > - to convert NMEA GPS data lines to RS-232 with the PPS line
> > > included.  It's got _two_ chips - an inverter, and a voltage level
> > > shifter.   
> > 
> > It also works if you just wire it up without either chip.
> 
> It depends on your particular RS-232 port on your motherboard, and which
> Garmin model.

So far all the RS-232 ports on regular desktop motherboards I had
access to worked nicely with something like
https://cdn-learn.adafruit.com/assets/assets/000/005/643/original/adafruit_products_minipov3schem.png
(it's a hackish built-in AVR SPI programmer hooked almost directly to
the RS-232 signals, the MISO line that goes from the target to the
serial port is not converted anyhow at all). So it's mostly ok to
assume that an RS-232 port will accept 0V instead of -10V.

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