| Re: [chrony-users] Time synchronisation over a high-latency packet radio network |
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On Wed, 8 May 2019, Stuart Longland wrote:
On 8/5/19 9:41 am, Bryan Christianson wrote:
How about using a USB GPS device.
Navisys have the GR-701W (https://www.globalsources.com/gsol/I/Car-GPS/p/sm/1145283340.htm?WT.pos_kw=prod_PrdtKWSImage_1_0_GR-701W_NonSP&WT.sad_id=1145283340#1145283340) which provides a PPS signal over USB and give you ± 10usecs precision.
Unfortunately they seem not to give any prices anywhere.
Cost and available power might be a factor for your application though.
USB is an option, but we don't require 10us precision (1 second is
enough for this application) and interfacing USB devices to a
PocketBeagle requires some external components, namely a USB-A connector
and a high-side USB power switch IC.
Which means you do not need pps. Again, that Adafruit gps is probably as cheap
as it gets and you do not have to try to get the pps into your computer. Just
read the output on the usb (You might need usb converter to connect to the
output of the adafruit I am not sure if the data in/out is serial or usb.
https://cdn.hackaday.io/images/9290121516436944161.jpg is one project
where I did do such an interface… and you can barely see the SOIC-8 part
tucked in beside that lower electrolytic capacitor and row of headers.
Doable, and I've made future provision for it, but as stated, I'm trying
to keep costs down. If more hardware is the answer, my first stop will
be for a battery-powered RTC rather than a GPS.
really cheap rtc will have trouble keeping 1 sec accuracy for any length of
time, especially if your device is subject to temperature variations ( which
it would seem yours will).
--
Stuart Longland (aka Redhatter, VK4MSL)
I haven't lost my mind...
...it's backed up on a tape somewhere.
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