Re: [time-nuts] Designing an embedded precision GPS time server

Hi Nick, I've got a project along those lines that I've been hacking on for the past three years or so, and always meaning to do a thorough writeup on. I'm more of a software than hardware guy, so the heart of it is a Taijiuino Due (a weird Chinese clone of the Arduino Due, so an 84MHz ATSAM3X8E,

Re: [time-nuts] Designing an embedded precision GPS time server

> Le 29 oct. 2017 à 11:29, Leo Bodnar a écrit : > > If you are making an open source thing you might want to use Laureline NTP > http://partiallystapled.com/pages/laureline-gps-ntp-server.html as a starting > point or as a performance yardstick. I have never seen one so

Re: [time-nuts] Designing an embedded precision GPS time server

Back to back with 100Mb is good, particularly for latency tests, but you’ll need a switch for general testing. FWIW, an otherwise idle switch generally has very consistent latency, and if both ports are at 100Mb, it is symmetric. Also, with any kind of managed switch you can easily monitor

Re: [time-nuts] Designing an embedded precision GPS time server

I think my test rig is likely to be a pair of units connected with a crossover cable, with test firmware on one to act as a fake client, and using spare GPIOs on test points to measure latency and the like with a scope. I don’t have the wherewithal to try and gauge the timing of switches, and

Re: [time-nuts] Designing an embedded precision GPS time server

With 1588 switch architecture counts as well because you have two major classes of switch, blocking and non blocking plus buffering etc. Most 'enterprise' switches once the flow is set up directly forward frames from the ingress port to the egress port each of which also tends to have a fairly

Re: [time-nuts] Designing an embedded precision GPS time server

> From: Nick Sayer > I believe I’m going to start with one of my GPS module breakouts and an E70 > XPlained development board. From a hardware perspective, I expect that to be > reasonably close to what the final hardware will be (the one thing I would > guess would change

Re: [time-nuts] Designing an embedded precision GPS time server

I built a couple of NTP time servers around this board: https://www.olimex.com/Products/ARM/ST/STM32-E407/open-source-hardware which supports IEEE1588. It also acts as a PTP source on the LAN. It is part of the IPv6 ntp pool and is currently serving about 1000 requests per minute. It uses a

Re: [time-nuts] Designing an embedded precision GPS time server

That looks and sounds very, very much like what I want to do. Thank you very much for your testing suggestions. When it comes time, I had indeed planned on adding it to the NTP pool if for no other reason than to contribute to the cause (but also for testing). I believe I’m going to start with

Re: [time-nuts] Designing an embedded precision GPS time server

> On Oct 26, 2017, at 19:29, Chris Caudle wrote: > > On Thu, October 26, 2017 7:38 pm, Denny Page wrote: >> If you are going to do PTP with ptp4l, or NTP with Chrony, you are going >> to want hardware timestamping support on the ethernet phy. > > Or the MAC. The

Re: [time-nuts] Designing an embedded precision GPS time server

Hoi Leo, On Fri, 27 Oct 2017 20:27:53 +0100 Leo Bodnar wrote: > Last year I have designed an NTP server with sub-microsecond turnaround > accuracy/jitter at fully saturated 100K+ packets/sec traffic (full 100Mb wire > speed) that costs just £250 from stock. > Its holdover

Re: [time-nuts] Designing an embedded precision GPS time server

Hi Nick, Last year I have designed an NTP server with sub-microsecond turnaround accuracy/jitter at fully saturated 100K+ packets/sec traffic (full 100Mb wire speed) that costs just £250 from stock. Its holdover performance on signal loss is in the order of 4-5ms/day.

Re: [time-nuts] Designing an embedded precision GPS time server

On Thu, October 26, 2017 7:38 pm, Denny Page wrote: > If you are going to do PTP with ptp4l, or NTP with Chrony, you are going > to want hardware timestamping support on the ethernet phy. Or the MAC. The processor used on BeagleBone Black has timestamping in the MAC. Not quite as accurate as

Re: [time-nuts] Designing an embedded precision GPS time server

On Thu, October 26, 2017 5:58 pm, Bob kb8tq wrote: > Why go to the green? Cheaper. > Just go with one of these Pocket Beagles I have > sitting here wondering what to do with them. Pocket Beagles do not have Ethernet. How are you going to make a network time server from a board with no network?

Re: [time-nuts] Designing an embedded precision GPS time server

Hi I suspect that once you find a group of chips that do have 1588 embedded in them that digging into all the nasty details will take a bit. Time stamping to a 1 ms resolution might not be a very helpful thing ….. There are ex-Freescale / now NXP devices that do have pretty good 1588 in them.

Re: [time-nuts] Designing an embedded precision GPS time server

If you are going to do PTP with ptp4l, or NTP with Chrony, you are going to want hardware timestamping support on the ethernet phy. I would view this as one of the principal concerns in choosing a system. I’m not sufficiently familiar with Beagles… do any of them support hardware timestamping?

Re: [time-nuts] Designing an embedded precision GPS time server

Hi Why go to the green? Just go with one of these Pocket Beagle’s I have sitting here wondering what to do with them. They were just a bit under $20 when I picked them up. I doubt the price will climb over time …… Indeed you could get two Pi Zero W’s for the pice of the Pocket Beagle. Lash an

Re: [time-nuts] Designing an embedded precision GPS time server

On 26/10/17 22:11, Chris Caudle wrote: The processor you mentioned has a Cortex-M7 at 300MHz. has a Cortex-A8 running at 1GHz plus a Cortex-M processor available as a coprocessor. Peripheral set is pretty comparable, and you can buy BBB at retail for $50 which gets you the faster higher

Re: [time-nuts] Designing an embedded precision GPS time server

On Wed, October 25, 2017 7:53 pm, Nick Sayer via time-nuts wrote: > I am considering a new project based on its cousin, the ATSAME70. What is a reasonable cost target for that at the volumes you could produce? Coming up with something that is a better value than BeagleBone Black at any kind of

Re: [time-nuts] Designing an embedded precision GPS time server

Hi So, get it up and running on the 1588 hardware built into one of these “all in one” MCU’s should be possible. Note the absence of words like easy or straightforward :) Bob > On Oct 26, 2017, at 12:45 PM, Chris Caudle wrote: > > On Thu, October 26, 2017 9:40 am,

Re: [time-nuts] Designing an embedded precision GPS time server

On Thu, October 26, 2017 9:40 am, Bob kb8tq wrote: > Since time stamping hardware does exist for 1588, why not simply put the > effort into folding that into NTP? According to the Chrony project web page chronyd already includes support for that. See "NTP timestamping" section:

Re: [time-nuts] Designing an embedded precision GPS time server

Hi Since time stamping hardware does exist for 1588, why not simply put the effort into folding that into NTP? Then you have a “generic” solution that addresses a lot of the ambiguity a wide range of cases. It shows up in many of the low end micro’s so it’s not just a “big box only” solution.

Re: [time-nuts] Designing an embedded precision GPS time server

Yo Nick! On Wed, 25 Oct 2017 17:53:46 -0700 Nick Sayer via time-nuts wrote: > This may be a fool’s errand, certainly, but looking at it from here, > I would think that such a design might offer accuracy in the > microsecond range, I'm looking at 6 Raspberry Pi's right now,

[time-nuts] Designing an embedded precision GPS time server

I’ve just completed a project (off topic) with the ATSAMS70 chip and learned a lot in a relatively short time, and I really like the result. I am considering a new project based on its cousin, the ATSAME70. The E70 has an Ethernet 10/100 MAC built in as well as the rest of the stuff the S70 has