[time-nuts] inexpensive, black box, GPS or NTP based TTL time capture?

Iain Young iain at g7iii.net
Wed Oct 25 06:45:49 UTC 2017

Hi Michael,

You Wrote:

> We are using BeagleBone Black + GPS 1 pps etc in our time-transfer system
> You can see the overlays in
> https://github.com/openttp/openttp/tree/develop/software/system/device-tree-overlays

Very interesting, I will have to clone the git repo, and have a closer

I have my own 'fleet' of Beaglebone Blacks and Greens monitoring LORAN 
and GPS. Working to add my small rubidiums and some LF and HF Clocks as
well. One day I will get the time to document the entire thing!

I am using the PRUSS to do Time Interval Measurements (details can be
found in the list archive), and feeding a PPS via TIMER4, and the highly
accurate timer that the Beaglebones have onboard.

Is there a particular reason you used the GPIO rather than TIMER4 ?
(If your google for Dan Drown DMTIMER, you will find the Linux Driver)

He also has coded up the TCLKIN pin, so that you can clock the
Beaglebone from an external reference, which also may be of interest.
(That bit I still need to do - I have the code enabled, just need to
plug a reference in to the Beaglebones!)

FreeBSD also has a driver for the TIMER4 input


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