[ntp:questions] Using Trimble TSIP under Linux

DaveB g8kbv at uko2.co.uk
Mon Nov 26 14:12:14 UTC 2012

In article <k6jeah$ri$1 at dont-email.me>, david-
taylor at blueyonder.co.uk.invalid says...
> On 28/10/2012 08:28, Rob wrote:
> > David Taylor <david-taylor at blueyonder.co.uk.invalid> wrote:
> >> First problem with gpsd resolved, I needed a "-n" on the command-line!
> >>
> >> Next step is to see how the time a GPIO pin is triggered can be written
> >> into the SHM memory block, or whatever....
> >
> > gpsd writes the time into the SHM block.
> > you need a serial port with data and DCD, and connect the pulse per
> > second output of the trimble to the DCD.
> > when that works you will have two SHM blocks, one with the time from
> > the serial messages and another with the time from the PPS.
> Thanks, Rob,  Herein lies a problem in that the Raspberry Pi doesn't 
> have a serial port, let alone one with a DCD line, so you need to use 
> one of the available I/O pins to raise the interrupt.  I gather that the 
> kernel supports this, but I'm then unsure how to get NTP to read the 
> time from gpsd, and the PPS from another source.  There is some work 
> described here:
>    https://github.com/davidk/adafruit-raspberrypi-linux-pps
> but I'm unsure how to make that work with my later version of Linux.

Ah, but it does, on the GPIO port, but it's logic is at 3.3V levels, not 
even TTL, so take care.

I've yet to make use of it myself though, and I forget what it shows up 
as in Linux.

I did find however, that the LAN port has some strange latency 
behaviour, then realised (from Linux's device listing) that the LAN port 
is in reality a USB<>LAN converter.


Dave B.

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