Topics

gPTP and usb network device


cpmcparland@...
 

I'm setting up a IP link between a debian platform and a bluetooth usb dongle running
zephyr.  usb network device interface appears to work fine with the zephyr IP stack running in
the dongle.  I want the dongle zephyr os to be time sync'd with the linux system and
am thinking gPTP would be a good way to achieve this.....particularly because its been
implemented on zephyr.  There's a note that zephyr gPTP only works on boards that
have ethernet hardware links.  Am wondering if anyone has tried using gPTP with
usb networking enabled?  Since the usb interface will likely run at 1Mb/s+ between
linux and zephyr (on dongle), I would expect it to behave reasonably well - at least for
my application's timing requirements.  Any experience or thoughts?

Regards,
Chuck McP


Jukka Rissanen
 

Hi Chuck,

the gPTP is probably not a proper solution for this kind time sync as
it is normally meant to synchronize two devices with nanosecond
accuracy in industrial ethernet environments. The actual time value is
typically not that important in these TSN solutions, main thing is the
time synchronization between devices.

Have you considered using SNTP to synchronize the time, there is
already SNTP client supported in Zephyr? This has lower resolution but
it should be fine in normal applications.


Cheers,
Jukka

On Tue, 2018-10-16 at 12:09 -0700, cpmcparland@... wrote:
I'm setting up a IP link between a debian platform and a bluetooth
usb dongle running
zephyr. usb network device interface appears to work fine with the
zephyr IP stack running in
the dongle. I want the dongle zephyr os to be time sync'd with the
linux system and
am thinking gPTP would be a good way to achieve this.....particularly
because its been
implemented on zephyr. There's a note that zephyr gPTP only works on
boards that
have ethernet hardware links. Am wondering if anyone has tried using
gPTP with
usb networking enabled? Since the usb interface will likely run at
1Mb/s+ between
linux and zephyr (on dongle), I would expect it to behave reasonably
well - at least for
my application's timing requirements. Any experience or thoughts?

Regards,
Chuck McP


cpmcparland@...
 

Jukka,

Thanks for your suggestion.  was not aware that zephyr had sntp.  That may
well be a better solution.  We have two applications with very different time
constraints--none of which are at the ns. level.  One app needs roughly 10 ms.
resolution and a second would like to see something on the order of 50 - 100 usec.

BTW, are there any "standard" solutions for time sync (at any resolution) for BLE or
bluetooth 5?

Cheers,
Chuck