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

[Phil Salkie]

On Fri, Apr 22, 2016 at 6:35 PM, Gary E. Miller <address@hidden> wrote:
> Yo Hal!
>
> On Fri, 22 Apr 2016 06:07:40 -0700
> Hal Murray <address@hidden> wrote:
>
>> address@hidden said:
>> > If you recall, we had an issue with connecting the Garmin GPS
>> > hockey puck to a serial port - even after converting the 0 to 5VDC
>> > data lines to RS-232's -10 to +10VDC, we still couldn't read it,
>
> RS-232 is +/- 12V.

Technically, the spec allows anything between -3 and -25 on the down
(mark) side, and anything between +3 and +25 on the up (space) side -
0VDC is in the undefined zone, which is why some receivers will see it
as a mark, and some see it as a space - that's why I put together the
converter board (with the extra channel to provide the PPS, and the
LED to see it pulsing.)