[time-nuts] IEEE 1588 PTP support on raspberry pi 4 compute module

[Bob kb8tq]

Hi

Two very separate chunks to this:

To get 1588 to work well, you either need very lightly loaded hardware ,  no hardware or 1588 compatible
switches and routers. In most cases “home use” cases NTP will get you into the microsecond(s) level. It
does not take any fancy hardware and NTP drivers exist for just about everything. If you happen to have
a WiFi setup as part of your “net” forget about any sort of timing accuracy dimensioned in microseconds.

====

Time wise, a < $10 single band GPS module ( ublox 8 series or whatever ) will get you well below 100 ns.
That’s much “better” time than NTP or 1588 will reliably transfer. The F9P ( or better the F9T ) will do some 
neat stuff, you will loose it’s “value” as soon as you try to move it over the ethernet. 

Simple answer:

Plug one of the many ublox modules into a random PC or server, bring up NTP, get things pointed at it, 
move on. For added points, bring up three or four NTP servers …..

Bob

> On Oct 20, 2020, at 4:49 PM, John De Witt <jhdewitt at gmail.com> wrote:
> 
> First post, please be patient with me. Reading the list for a handful of years and grateful to the community.
> 
> Am interested in low cost GNSS time source to keep clocks during internet outage.
> 
> Just read that compute module raspberry pi 4 supports IEEE 1588 Precision Time Protocol.
> 
> Exciting to me ~25usd base for microsecond or better performance over network.
> 
> Anyone planning on using this? Ethernet is handled by BCM54210 which states in data sheet: “IEEE 1588v2 compliant – One-step or two-step clock – On-chip timestamping”
> 
> Thinking of pairing it with ZED-F9P with PPS would be fun to have PTP GPS stratum 1 on LAN for cheap. Ok enough rambling thank you have a nice day.
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