Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

You are plotting "offset". This is simply the communications path delay. It does not measure your system's deviation from UTC. NTP takes into consideration the offset. Here is the way to understand what NTP does with offset. Let's say we lived 200 years ago and wanted to set a grandfather

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

Sorry, I conflated terms. NTP uses offset and delay differently. In NTP speak "delay" is the round trip time. "offset" is the difference from local system clock to reference clock after accounting for delay. It is like cause by asymmetric trans time. But still, I think my main point is

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

Hi The point is that some chip sets have better access to timer / counters than others do. One of the Soekris (sp?) boards is an example of this. We also are moving into an era where fairly fancy ARM CPU’s are grafted onto FPGA’s. Once you have that, you are no longer dependent on somebody

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

Hi Bob, On Sat, Feb 18, 2017 at 08:36:51AM -0500, Bob Camp wrote: > Hi > > > On Feb 18, 2017, at 4:53 AM, David J Taylor > > wrote: > > > > Hi, > > > > I was wondering whether there is some data/information available on the > > claimed +/- 100 ns jitter? > > > I

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

Hi > On Feb 18, 2017, at 4:53 AM, David J Taylor > wrote: > > Hi, > > I was wondering whether there is some data/information available on the > claimed +/- 100 ns jitter? I guess the previous was not complete enough. I routinely measure PPS jitter on GPS

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

Hi, I was wondering whether there is some data/information available on the claimed +/- 100 ns jitter? Regarding the PPS -> USB (using the CTS line of a FTDI FT232R), I plotted, using some lines of Python, the time offset as attached. Just to get an overview how it is 'worst case', i.e., user

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

> > The Intel guys have some *very* fast timers flying around their cpu’s. > They would laugh > at the idea of a 10 or 100 MHz clock. If you can configure the pin to grab > the data off those timer, you > have way better than 100 ns at the timer. We're most certainly getting off topic, but the

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

Hi Roughly speaking, if you have a 10 MHz clock driving a timer and the pin latches data from that timer, you get 100 ns “buckets and +/- 100 ns “jitter”. You can find MCU’s that will do this for < $1. If you go crazy, you can spend < $10 and still get a very fancy MCU on a board with all

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

On Tue, 14 Feb 2017 10:31:30 -0500, you wrote: >On 14/02/2017 7:26 AM, Bob Camp wrote: > >> A direct port might be a +/- 100 ns sort of thing most of the time and a >> +/-10 us >> thing every so often under some OS’s. Most desktop operating systems are not >> designed to prioritize random pin

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

On Thu, Feb 16, 2017 at 10:42 AM, Christopher Hoover wrote: > Ntp has support to pick up hardware packet timestamps from the Linux > kernel. I wrote the patch; it was merged years ago. > > I'm wrong about this. The patch I wrote added support for SO_TIMESTAMPNS (see [1]).

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

Yes, that is the normal "best practice case". But the OPand myself some years go both have a difference use case. In this case no other machine needs to know the time. I only care about one computer. The reason I used NTp back then and he is using it now is to calibrate the rate of a

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

> Le 16 févr. 2017 à 13:05, Mike Cook a écrit : > > >> Le 16 févr. 2017 à 04:09, MLewis a écrit : >> >> On 15/02/2017 1:17 PM, Chris Albertson wrote: >>> Why set up a dedicated NTP server if you only have two computers that will >>> use it? ... You

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

shouldbeq...@gmail.com said: > I run PTP on a Raspberry Pi using its onboard USB connected NIC, and onboard > NICs on HP and Dell servers, I see +- 5 microsoconds jitter in the one way > delay across 4 fanless HP switches, ... Could you please say more? USB 2 has a 125 microsecond polling

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

sub Millisecond is EASY. my Apple 27" iMac is doing that right now using just Internet pool servers. Yes I have a very good Internet connection. 100 Mbit fiber and then the last meter is 1000BaseT But still, milliseconds are really EASY. It is sub microseconds that requires things like PTP

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

Yo Chris! On Wed, 15 Feb 2017 23:48:39 -0800 Chris Albertson wrote: > An ntpd that is running as > strum one that has no other ntpd connected to it has VERY little to do That would be a marginal configuration. I have yet to see a GPS that did not lose sat lock, or

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

Yo Chris! On Wed, 15 Feb 2017 23:55:02 -0800 Chris Albertson wrote: > On Wed, Feb 15, 2017 at 11:48 PM, Chris Albertson > wrote: > > On Wed, Feb 15, 2017 at 10:30 PM, Ruslan Nabioullin > > wrote: > >> On 02/15/2017

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

Ntp has support to pick up hardware packet timestamps from the Linux kernel. I wrote the patch; it was merged years ago. -ch 73 de AI6KG On Thu, Feb 16, 2017 at 9:59 AM, Denny Page wrote: > If your Ethernet chipset (mac or phy) has timestamping capabilities, you > can

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

On Thu, Feb 16, 2017 at 7:55 AM, Chris Albertson wrote: > > But PTP requires special hardware. You may not have this. > I have to disagree. I run PTP on a Raspberry Pi using its onboard USB connected NIC, and onboard NICs on HP and Dell servers, I see +- 5

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

If your Ethernet chipset (mac or phy) has timestamping capabilities, you can use Chrony which has hardware timestamp support. This greatly improves accuracy, and generally eliminates the CPU loading issue. Denny ___ time-nuts mailing list --

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

Hi Whatever you do on the server, the same impacts will be felt on the client side. You may be able to do this or that on a server to allocate resources. On a client workstation, resource allocation is likely to be a bit more difficult. You may not even have control over which OS is being

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

> Le 16 févr. 2017 à 04:09, MLewis a écrit : > > On 15/02/2017 1:17 PM, Chris Albertson wrote: >> Why set up a dedicated NTP server if you only have two computers that will >> use it? ... You could save some money and just run NTP on the two computers. >> ... NTP is

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

Hi > On Feb 16, 2017, at 1:30 AM, Ruslan Nabioullin wrote: > > On 02/15/2017 01:17 PM, Chris Albertson wrote: >> Why set up a dedicated NTP server if you only have two computers >> that will use it?Your server will be accurate to a few >> microseconds but your two

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

> But notice that only 1/2 of the wires in a standard Ethernet cable are in > use. Unless you are using Gigabit Ethernet. -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

Your processing machine is going to be running NTP with a reference clock being your local status 1 NTP server I think the processing machine would see a lighter load if it's NTP was using GPS as the reference rather thennother NTP server. In other words the processing box, the one with the

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

On Wed, Feb 15, 2017 at 11:48 PM, Chris Albertson wrote: > On Wed, Feb 15, 2017 at 10:30 PM, Ruslan Nabioullin > wrote: >> On 02/15/2017 01:17 PM, Chris Albertson wrote: >>> >>> Why set up a dedicated NTP server if you only have two computers >>>

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

The desktop PCs can each be configured with as many reference clocks as you like. That is independent of how many stratum 1 NTP servers a company needs to operate.Maybe you are running some stratum 2 servers on your routers and using more from the Internet.All these choices are

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

On 15/02/2017 1:17 PM, Chris Albertson wrote: Why set up a dedicated NTP server if you only have two computers that will use it? ... You could save some money and just run NTP on the two computers. ... NTP is almost zero load on the CPU and the best thing is the NTP accuracy is not effected by

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

On 02/15/2017 01:17 PM, Chris Albertson wrote: Why set up a dedicated NTP server if you only have two computers that will use it?Your server will be accurate to a few microseconds but your two computers will only by good to a few milliseconds because ethernet is not nearly as good as PPS.

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

On Tue, Feb 14, 2017 at 9:38 PM, MLewis wrote: > That dual set model is new to me. Interesting to see its fall-back on > failures. And the offline model. > > It's the poor-man's version of that model that I was aiming for (and one, > not two sets of receiver-with-server): >

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

Hi > On Feb 14, 2017, at 9:23 PM, Chris Albertson > wrote: > > On Tue, Feb 14, 2017 at 7:31 AM, MLewis wrote: > >> >> >> - a dedicated machine/box for unencumbered acceptance of PPS, and >> - for systems with a business need, a dedicated

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

>> >> Best practice today is to have two independent NTP servers and two GPS >> receivers. It is best if these are independent as you can make them, >> different buildings if you can. I would even use different brands of >> hardware to protect against a bug. This is an often missed

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

On 14/02/2017 9:23 PM, Chris Albertson wrote: On Tue, Feb 14, 2017 at 7:31 AM, MLewis wrote: - a dedicated machine/box for unencumbered acceptance of PPS, and - for systems with a business need, a dedicated NTP server/box disciplined by the PPS source (with dedicated

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

On Tue, Feb 14, 2017 at 7:31 AM, MLewis wrote: > > > - a dedicated machine/box for unencumbered acceptance of PPS, and > - for systems with a business need, a dedicated NTP server/box disciplined > by the PPS source (with dedicated communication), while maintaining >

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

> On Feb 14, 2017, at 15:14, J. Grizzard wrote: > > I really recommend the PC Engines apu2c hardware. Just a touch over $100, > schematics available, hardware serial port, GPIO, 1588-capable PHY, CPU > crystal accessible if you want to try a clockblock-type hack,

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

I really recommend the PC Engines apu2c hardware. Just a touch over $100, schematics available, hardware serial port, GPIO, 1588-capable PHY, CPU crystal accessible if you want to try a clockblock-type hack, great support, and just decent all around. There's also test pads for the PHY that could

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

Hi If you want a 1588 PHY and are on a budget: https://www.digikey.com/products/en/development-boards-kits-programmers/evaluation-boards-embedded-mcu-dsp/786?k=freescale+freedom==freescale+freedom=24619=ffe00312%2C7e80098=0=0=0=1=0=0=0=25 Drop NTP into it and let it rip. Bob > On Feb 14,

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

Something like this would make a great NTP server. https://www.digikey.com/products/en?keywords=P0286-ND Too bad they didn't include a PTP 1588 capable PHY... On Tue, Feb 14, 2017 at 12:33 PM, Chris Albertson wrote: > Here is a something that could work. It has a

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

> Hence, wouldn't Best Practice be boxes loaded with only the bare OS and > software for the time-related tasks? If you find yourself in a situation like this -- where your timing seems to improve the less load you have -- that's a sure sign that you're doing the timing wrong in the first

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

Hi > On Feb 14, 2017, at 10:31 AM, MLewis wrote: > > > > On 14/02/2017 7:26 AM, Bob Camp wrote: >> Hi >> >> A direct port might be a +/- 100 ns sort of thing most of the time and a >> +/-10 us >> thing every so often under some OS’s. Most desktop operating systems are

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

Here is a something that could work. It has a real serial port and you could add more ethernet controllers, uses very little power and cost only $60. www.newegg.com/ There are other boards like

[time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

Beware of Atom based devices... Many of the Atom chips have a problem where a couple of the critical clock output signals have a design problem and they start failing after around 18 months. This problem just became public in the last month or so when Cisco warned of impending failures in a

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

On 14/02/2017 7:26 AM, Bob Camp wrote: Hi A direct port might be a +/- 100 ns sort of thing most of the time and a +/-10 us thing every so often under some OS’s. Most desktop operating systems are not designed to prioritize random pin interrupts. A dirt cheap MCU coded with a few (hundred)

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

> On Feb 13, 2017, at 23:47, Hal Murray wrote: > > There is a whole class of low power mother boards targeted at the embedded > market. A few of them have multiple Ethernets - goof for building firewalls. > I haven't found any low cost ones. This one might be of

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

Hi A direct port might be a +/- 100 ns sort of thing most of the time and a +/-10 us thing every so often under some OS’s. Most desktop operating systems are not designed to prioritize random pin interrupts. A dirt cheap MCU coded with a few (hundred) lines of assembly code may be a better

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

mlewis...@rogers.com said: > Know of any with an Ethernet port, preferably two, that aren't run from a > USB controller? You didn't put a qualifier on your "any". (or I missed it) If you want a Raspberry Pi class board, the BeagleBone Black has a real Ethernet, but only one. If you need 2

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

rnabioul...@gmail.com said: > Hi, generally speaking, what are the performance differences between the > following: 1. direct RS-232 (i.e., what I believe is a standard PCI card > offering RS-232---essentially UARTs interfaced more-or-less directly to the > PCI bus); 2. RS-232 via USB; 3. PPS

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

On 14/02/2017 12:24 AM, Chris Albertson wrote: Pretty dramatic difference between a "real" serial port and USB. Like two orders of magnitude or more. If you computer lacks a serial port, just buy a new computer. The Raspberry Pi or the like costs about $40 the serial port has a pin that

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

Pretty dramatic difference between a "real" serial port and USB. Like two orders of magnitude or more. If you computer lacks a serial port, just buy a new computer. The Raspberry Pi or the like costs about $40. But the money you save on electric power will pay off that $40 in less than a

Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

Yo Ruslan! On Mon, 13 Feb 2017 11:07:49 -0500 Ruslan Nabioullin wrote: > Hi, generally speaking, what are the performance differences between > the following: 1. direct RS-232 (i.e., what I believe is a standard > PCI card offering RS-232---essentially UARTs interfaced

[time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

Hi, generally speaking, what are the performance differences between the following: 1. direct RS-232 (i.e., what I believe is a standard PCI card offering RS-232---essentially UARTs interfaced more-or-less directly to the PCI bus); 2. RS-232 via USB; 3. PPS decoding PCI cards (which might also