[time-nuts] : L1 GPS timing signal(s) into local time on computer(s)

Sarah White kuzetsa at gmail.com
Sun Aug 19 15:29:22 EDT 2012


oh wow, thanks. I'll try that.

Also, I figured out that typing in "trimble thunderbolt" instead of
"thunderbolt gps" gives me zero hits for phone... but fewer hits for the
GPSDO too :(

On 8/19/2012 3:21 PM, Willy Willemse wrote:
> Sarah,
> 
> If you want to filter in ebay, you can use a"-" for a subject that you don't
> want to see. It is the same syntax as you can use in a browser.
> 
> Regards,
> 
> Willy
> 
> -----Oorspronkelijk bericht-----
> Van: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] Namens
> time-nuts-request at febo.com
> Verzonden: zondag 19 augustus 2012 19:07
> Aan: time-nuts at febo.com
> Onderwerp: time-nuts Digest, Vol 97, Issue 48
> 
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> Today's Topics:
> 
>    1. Re: L1 GPS timing signal(s) into local time on	computer(s)
>       (Sarah White)
>    2. Modern motherboard with RS232 port (Stan, W1LE)
>    3. Re: L1 GPS timing signal(s) into local time on	computer(s)
>       (KD0GLS)
>    4. Embedded NTP servers? (Michael Tharp)
>    5. Re: Modern motherboard with RS232 port (Chris Albertson)
> 
> 
> ----------------------------------------------------------------------
> 
> Message: 1
> Date: Sun, 19 Aug 2012 10:41:39 -0400
> From: Sarah White <kuzetsa at gmail.com>
> To: time-nuts at febo.com
> Subject: Re: [time-nuts] L1 GPS timing signal(s) into local time on
> 	computer(s)
> Message-ID: <5030FB23.7040508 at gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
> 
> Ken:
> 
>>From what I've read, most GPS modules which output PPS, the NMEA
> sentence has the timestamp of the next, upcoming pulse. Regardless of
> how the NMEA or other time data is, the PPS itself is only a guarantee
> "this is the boundary for a second" and NTP documentation typically
> recommends a second reference clock to "number the seconds" anyway.
> 
> Everyone:
> 
> Thanks everyone. I got many responses which confirm my initial
> conclusions. I had trouble locating a GPS thunderbolt on ebay because
> there is an HTC phone with "thunderbolt" in the name. (I got a few hits
> for the GPS module, but there is no way to filter out "phones" or I
> might just be bad at operating ebay)
> 
> uhm... yeah. As someone pointed out. It is a total nightmare to figure
> out which direction my GPS time is wandering, and finding the correct
> offset. I'm just gonna give up on this USB module, and get a real one
> with PPS
> 
> Also, I really hate google's new "shopping" experience. They started
> listing less content, and now push content from stores which charge 2-3
> times as much.
> 
> As far as existing hardware goes, I don't have any slots free in my
> desktop for a serial board...
> 
> Despite the new "google shopping" headache, I was able to determine that
> many "older" computers from the windows XP era which still have serial
> ports, and are available refurbished from walmart of all the crazy
> places. (most of the time, better price than the ones being pushed by
> google shopping, and even have XP installed and a 1 year warranty)
> 
> So no problem. I can source a suitable machine to run NTP, and for less
> than $200, guaranteed.
> 
> Will probably be using gentoo linux, as the default configuration does
> NOT expect you to run any specific kernel. I can easily recompile
> anything I need without breaking unusual, unforeseen dependencies.
> (doesn't hurt that I've been using gentoo since the stage1 install was
> preferred, all the way back to the GCC 2.x era)
> 
> I'm really aiming to run a server which ONLY runs NTP, and at most 1 or
> two other daemons (light duty on those)
> 
> Thanks so much everyone.
> 
> On 8/19/2012 7:11 AM, Ken Duffill wrote:
>> Just one further question.
>>
>> When the pps input triggers, so my linux box knows a second has just
>> ticked; is the time of that second the one the NMEA sentence has just
>> sent, or will send next?
>>
>> Or to put it another way, when I receive an NMEA sentence is this the
>> current time (as was when the sentence was constructed) or the time at
>> the next PPS 'tick'?
>>
>> Thanks in advance.
>>
>> KenD
>>
>> On 19/08/12 11:23, Bill Dailey wrote:
>>> I will jump in a bit.  I, and many have been right where you are.  You
>>> are correct...USB is a no go for accurate time.  Same on windows.  So
>>> you need a Linux box with serial port.  Anything from a Beaglebone,
>>> pandabox...or pc will work.  You certainly need a gps with a pulse per
>>> second output (most have) and you can wire that up to the appropriate
>>> line on the serial cable or send to the target computer via gpio pin. 
>>> The pps thing is fairly simple really.   If you are receiving gps data
>>> via serial connection it takes a variable amount of time to get each
>>> status report from the gps...list time etc etc in text format and
>>> sends it repeatedly.  This gets ntp to within a second or some
>>> fraction thereof...the pps part refines that..no text or anything...
>>> Just a one pulse per second separate from the gps info that acts as a
>>> exclamation point to tell ntp "right here is the actual start of the
>>> second!" alone the pps wouldn't be useful for time but with the time
>>> info ntp already has from the nmea sentences it is priceless for
>>> really precise time.   That's about it.  Once you have gps and pps
>>> configured on Linux you should be in the sub 5 microsecond range.  It
>>> gets tricky getting better than that and you have to Ntpns and really
>>> worry about hardware issues that affect precision (system clock
>>> stability etc) but it can be done.
>>>
>>> Doc
>>> KX0O
>>>
>>> Sent from my iPad
>>>
>>> On Aug 18, 2012, at 11:25 PM, Sarah White <kuzetsa at gmail.com> wrote:
>>>
>>>> Hi, this is my first post.
>>>>
>>>> First off. Windows 7 USB connection to the GPS (no serial ports / modern
>>>> computer) and I'm pretty sure that is my main problem.
>>>>
>>>> Past few months, I've been trying to figure out my timing issues. Lots
>>>> of reading & trying to figure out how to best configure everything. I'm
>>>> typically still off (randomly) by 20-100 miliseconds. I'd like to at
>>>> least get to within 50 microseconds (nanoseconds would be wonderful)
>>>>
>>>> 1) I need a computer with a serial port. The curent GPS module I'm using
>>>> is INTERNALLY RS232 --> USB converter, and recognized by my windows 7
>>>> computer as: "Prolific USB-to-Serial Comm Port (COM3)" ... the latency
>>>> and jitter is horrible, and both are seemingly random.
>>>>
>>>> 2) I need to run my stratum 1 clock (connected to the stratum 0 time
>>>> source via old-school RS232 serial) on linux or a form of BSD with
>>>> support for kernel timestamps, and a version of NTP with a driver to
>>>> supports my reference clock... points 1 and 2 seem fine.
>>>>
>>>> 3) I'm clueless about mounting an antenna, running cable, grounding /
>>>> lightning protection, etc... Really want an easy to install one.
>>>>
>>>> For software, I've used 4.2.6 (stable / production) as well as 4.2.7
>>>> (dev version) NTP and haven't been able to tell any difference.
>>>> Just using the generic NMEA driver / this is a no-name cheapo SIRF
>>>> module.
>>>>
>>>> Also, trying to wrap my head around these:
>>>>
>>>> http://linuxpps.org/wiki/index.php/LinuxPPS_installation
>>>> http://linuxpps.org/wiki/index.php/LinuxPPS_NTPD_support
>>>>
>>>> And here is where I give up. As the subject line suggests:
>>>>
>>>> HELP!!! I'd like to convert L1 GPS timing signal(s) into local time on
>>>> computer(s)
>>>>
>>>> _______________________________________________
>>>> time-nuts mailing list -- time-nuts at febo.com
>>>> To unsubscribe, go to
>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>>> and follow the instructions there.
>>> _______________________________________________
>>> time-nuts mailing list -- time-nuts at febo.com
>>> To unsubscribe, go to
>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>> and follow the instructions there.
>>>
>>
>>
>>
>> _______________________________________________
>> time-nuts mailing list -- time-nuts at febo.com
>> To unsubscribe, go to
>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
> 
> 
> 
> 
> ------------------------------
> 
> Message: 2
> Date: Sun, 19 Aug 2012 10:42:10 -0400
> From: "Stan, W1LE" <stanw1le at verizon.net>
> To: time-nuts at febo.com
> Subject: [time-nuts] Modern motherboard with RS232 port
> Message-ID: <5030FB42.8030501 at verizon.net>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> 
> Hello The Net,
> 
> For your consideration:
> 
> The INTEL model DN2800mt ITX mother board uses a ATOM CPU and
> draws about 11 watts of AC power when configured as:
> (I have not measured DC power yet.)
> 
> 30 GB OCZ Nocti mSATA solid state drive,
> WIN7 pro, 64 bit, USB keyboard and mouse
> APEX MI-0008 case.
> 
> Also has:
> parallel port available on mother board, you extend to a connector
> RS232 serial port available on mother board, you extend to a connector
> a single DC power supply from 11 to 19 V DC.
> 1 each PCIe expansion port, I will use with a premium 4 channel sound card
> SATA ports available for HDD/SDD,
> USB ports are available,
> Motherboard sound, and Gigalan.
> 
> I have not played with NTP, (yet), but it sounds like a decent time nut 
> technical challenge.
> 
> My application is for a remote site with only 13V DC power available 
> from PV/batteries.
> Then use fiber ethernet to get off site.
> 
> The INTEL website would have further details.
> 
> Stan, W1LE    Cape Cod   FN41sr
> 
> 
> 
> 
> ZZZZz
> 
> 
> 
> 
> ------------------------------
> 
> Message: 3
> Date: Sun, 19 Aug 2012 10:18:34 -0500 (CDT)
> From: KD0GLS <kd0gls at mninter.net>
> To: Discussion of precise time and frequency measurement
> 	<time-nuts at febo.com>
> Subject: Re: [time-nuts] L1 GPS timing signal(s) into local time on
> 	computer(s)
> Message-ID: <AE1D2790-AF2B-40FC-88D8-F13A61D77B42 at mninter.net>
> Content-Type: text/plain;	charset=us-ascii
> 
> In my experience (which is admittedly less than that of many others here)
> the time reported is that of the PPS pulse that just happened, and the
> documentation usually bears that out. There's a real-time clock running
> inside the receiver that is synchronized to the PPS. At the top of the
> second, the PPS is output and the RTC increments. Some number of
> milliseconds later, that RTC time value is output, which is the "current"
> time, not that of the next pulse. That's certainly the way the Motorola M12+
> Timing receiver (Motorola binary mode) and all of the SiRFstar-based NMEA
> navigation receivers I've used work.
> 
> Beware of the situation where a cold-started receiver hasn't yet acquired
> the UTC offset portion of the almanac and will report time some number of
> seconds different than UTC. The SiRF receivers are especially misleading, as
> they can be off by just one or two seconds depending on when their firmware
> was built. They are programmed with default offset values that were valid at
> the time of their manufacture. In one case I had, it was sometimes off by
> one second, sometimes not. After June 30, 2012, it was now sometimes off by
> two seconds, and then I knew what was going on. The M12+ has a default
> offset of zero, which I find much more sane. It reports GPS time (a whopping
> 16 seconds different) until the UTC offset is received. 
> 
> Sent from my iPod
> 
> On Aug 19, 2012, at 9:42, Sarah White <kuzetsa at gmail.com> wrote:
> 
>> Ken:
>>
>> From what I've read, most GPS modules which output PPS, the NMEA
>> sentence has the timestamp of the next, upcoming pulse. Regardless of
>> how the NMEA or other time data is, the PPS itself is only a guarantee
>> "this is the boundary for a second" and NTP documentation typically
>> recommends a second reference clock to "number the seconds" anyway.
>>
>> Everyone:
>>
>> Thanks everyone. I got many responses which confirm my initial
>> conclusions. I had trouble locating a GPS thunderbolt on ebay because
>> there is an HTC phone with "thunderbolt" in the name. (I got a few hits
>> for the GPS module, but there is no way to filter out "phones" or I
>> might just be bad at operating ebay)
>>
>> uhm... yeah. As someone pointed out. It is a total nightmare to figure
>> out which direction my GPS time is wandering, and finding the correct
>> offset. I'm just gonna give up on this USB module, and get a real one
>> with PPS
>>
>> Also, I really hate google's new "shopping" experience. They started
>> listing less content, and now push content from stores which charge 2-3
>> times as much.
>>
>> As far as existing hardware goes, I don't have any slots free in my
>> desktop for a serial board...
>>
>> Despite the new "google shopping" headache, I was able to determine that
>> many "older" computers from the windows XP era which still have serial
>> ports, and are available refurbished from walmart of all the crazy
>> places. (most of the time, better price than the ones being pushed by
>> google shopping, and even have XP installed and a 1 year warranty)
>>
>> So no problem. I can source a suitable machine to run NTP, and for less
>> than $200, guaranteed.
>>
>> Will probably be using gentoo linux, as the default configuration does
>> NOT expect you to run any specific kernel. I can easily recompile
>> anything I need without breaking unusual, unforeseen dependencies.
>> (doesn't hurt that I've been using gentoo since the stage1 install was
>> preferred, all the way back to the GCC 2.x era)
>>
>> I'm really aiming to run a server which ONLY runs NTP, and at most 1 or
>> two other daemons (light duty on those)
>>
>> Thanks so much everyone.
>>
>> On 8/19/2012 7:11 AM, Ken Duffill wrote:
>>> Just one further question.
>>>
>>> When the pps input triggers, so my linux box knows a second has just
>>> ticked; is the time of that second the one the NMEA sentence has just
>>> sent, or will send next?
>>>
>>> Or to put it another way, when I receive an NMEA sentence is this the
>>> current time (as was when the sentence was constructed) or the time at
>>> the next PPS 'tick'?
>>>
>>> Thanks in advance.
>>>
>>> KenD
>>>
>>> On 19/08/12 11:23, Bill Dailey wrote:
>>>> I will jump in a bit.  I, and many have been right where you are.  You
>>>> are correct...USB is a no go for accurate time.  Same on windows.  So
>>>> you need a Linux box with serial port.  Anything from a Beaglebone,
>>>> pandabox...or pc will work.  You certainly need a gps with a pulse per
>>>> second output (most have) and you can wire that up to the appropriate
>>>> line on the serial cable or send to the target computer via gpio pin. 
>>>> The pps thing is fairly simple really.   If you are receiving gps data
>>>> via serial connection it takes a variable amount of time to get each
>>>> status report from the gps...list time etc etc in text format and
>>>> sends it repeatedly.  This gets ntp to within a second or some
>>>> fraction thereof...the pps part refines that..no text or anything...
>>>> Just a one pulse per second separate from the gps info that acts as a
>>>> exclamation point to tell ntp "right here is the actual start of the
>>>> second!" alone the pps wouldn't be useful for time but with the time
>>>> info ntp already has from the nmea sentences it is priceless for
>>>> really precise time.   That's about it.  Once you have gps and pps
>>>> configured on Linux you should be in the sub 5 microsecond range.  It
>>>> gets tricky getting better than that and you have to Ntpns and really
>>>> worry about hardware issues that affect precision (system clock
>>>> stability etc) but it can be done.
>>>>
>>>> Doc
>>>> KX0O
>>>>
>>>> Sent from my iPad
>>>>
>>>> On Aug 18, 2012, at 11:25 PM, Sarah White <kuzetsa at gmail.com> wrote:
>>>>
>>>>> Hi, this is my first post.
>>>>>
>>>>> First off. Windows 7 USB connection to the GPS (no serial ports /
> modern
>>>>> computer) and I'm pretty sure that is my main problem.
>>>>>
>>>>> Past few months, I've been trying to figure out my timing issues. Lots
>>>>> of reading & trying to figure out how to best configure everything. I'm
>>>>> typically still off (randomly) by 20-100 miliseconds. I'd like to at
>>>>> least get to within 50 microseconds (nanoseconds would be wonderful)
>>>>>
>>>>> 1) I need a computer with a serial port. The curent GPS module I'm
> using
>>>>> is INTERNALLY RS232 --> USB converter, and recognized by my windows 7
>>>>> computer as: "Prolific USB-to-Serial Comm Port (COM3)" ... the latency
>>>>> and jitter is horrible, and both are seemingly random.
>>>>>
>>>>> 2) I need to run my stratum 1 clock (connected to the stratum 0 time
>>>>> source via old-school RS232 serial) on linux or a form of BSD with
>>>>> support for kernel timestamps, and a version of NTP with a driver to
>>>>> supports my reference clock... points 1 and 2 seem fine.
>>>>>
>>>>> 3) I'm clueless about mounting an antenna, running cable, grounding /
>>>>> lightning protection, etc... Really want an easy to install one.
>>>>>
>>>>> For software, I've used 4.2.6 (stable / production) as well as 4.2.7
>>>>> (dev version) NTP and haven't been able to tell any difference.
>>>>> Just using the generic NMEA driver / this is a no-name cheapo SIRF
>>>>> module.
>>>>>
>>>>> Also, trying to wrap my head around these:
>>>>>
>>>>> http://linuxpps.org/wiki/index.php/LinuxPPS_installation
>>>>> http://linuxpps.org/wiki/index.php/LinuxPPS_NTPD_support
>>>>>
>>>>> And here is where I give up. As the subject line suggests:
>>>>>
>>>>> HELP!!! I'd like to convert L1 GPS timing signal(s) into local time on
>>>>> computer(s)
>>>>>
>>>>> _______________________________________________
>>>>> time-nuts mailing list -- time-nuts at febo.com
>>>>> To unsubscribe, go to
>>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>>>> and follow the instructions there.
>>>> _______________________________________________
>>>> time-nuts mailing list -- time-nuts at febo.com
>>>> To unsubscribe, go to
>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>>> and follow the instructions there.
>>>>
>>>
>>>
>>>
>>> _______________________________________________
>>> time-nuts mailing list -- time-nuts at febo.com
>>> To unsubscribe, go to
>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>> and follow the instructions there.
>>
>>
>> _______________________________________________
>> time-nuts mailing list -- time-nuts at febo.com
>> To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
> 
> 
> 
> ------------------------------
> 
> Message: 4
> Date: Sun, 19 Aug 2012 11:21:21 -0400
> From: Michael Tharp <gxti at partiallystapled.com>
> To: Discussion of precise time and frequency measurement
> 	<time-nuts at febo.com>
> Subject: [time-nuts] Embedded NTP servers?
> Message-ID: <50310471.1090102 at partiallystapled.com>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> 
> Greetings nuts,
> 
> All this recent NTP discussion has me thinking about a dedicated NTP 
> server again. The usual solution is to use commodity hardware of some 
> persuasion (PC, mini-itx or even ARM) running ntpd, but I'm thinking we 
> can do better. The only reason a full ntpd is needed is for its software 
> PLLs that measure and compensate for deficiencies in the local 
> oscillator. But if that local oscillator is replaced by a disciplined 
> 10MHz clock, and a coincident pulse-per-second and NMEA from the GPSDO 
> fed in, then a reasonably fitted microcontroller should do the trick.
> 
> I happen to have a Ethernet-enabled widget I put together for another 
> project as a kind of drop-in module, built on a PIC18F66J60 which has a 
> built-in 10mbit Ethernet controller. The problem with it seems to be 
> relatively poor and unpredictable packet servicing latency. Usually 
> pings are 1.02ms but with some significant deviation. I imagine a lot of 
> the deficiencies with this arrangement come from the vendor-supplied IP 
> stack, which is not latency-optimized, but also the 10mbit link 
> contributes some "quantization" type problems. Microchip also makes a 
> 100mbit-capable standalone controller, ENC624J600. I'd probably use that 
> and pair it with any 72MHz ARM microcontroller. The micro would be 
> clocked by a (multiplied) 10MHz disciplined input and the 
> pulse-per-second would come in on a "input capture" channel that can 
> timestamp the pulse relative to a local counter. And since ntp is such a 
> simple protocol, it should be pretty easy to write a appropriate ntp 
> server routine that just hands out the time from GPS, including leap 
> second indications.
> 
> Thoughts? Has it been done before, preferably with open source? I'd love 
> to make it myself but I have to finish the GPSDO first :-)
> 
> -- m. tharp
> 
> 
> 
> ------------------------------
> 
> Message: 5
> Date: Sun, 19 Aug 2012 10:06:27 -0700
> From: Chris Albertson <albertson.chris at gmail.com>
> To: Discussion of precise time and frequency measurement
> 	<time-nuts at febo.com>
> Subject: Re: [time-nuts] Modern motherboard with RS232 port
> Message-ID:
> 	<CABbxVHuv_HkjMNMELkPhUmYvtjFA11YbYe-Cn45tF6UEVpneFA at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
> 
> This sounds like a newer version of the board I use.   The thing to check
> is if the CPU heat sink has a fan or not.  Having no fan indicates that the
> CPU is not using much power.  It also removes a common failure point.
> 
> To reduce power even more.  On an NTP server you can unplug the keyboard,
> mouse and monitor and if you have other servers on the LAN configure one as
> a "boot server" and have it run TFTP then your NTP server does not need a
> disk drive.  It can run off a "RAM disk".  This makes it very fast, even
> faster than a SSD and it saves some cash.  Makes backup easy too as there
> is nothing to backup if there is no local storage.  If you don't have a
> TFTP server use a small notebook size disk drive. Even a 80GB drive is
> overkill.  You can also boot from a USB thumb drive and run a RAM disk.
> 
> It is worth it to look at your electric bill to find how much you pay for
> power.  Here I'm at $0.21 per KWH.  A full size PC server can use 250W or
> more.  There are 8760 hours in a year so you get $460 per year to run that
> 250W PC.  The little Atom will pay for itself in just a few months.  The
> first time I did that calculation, my "power hogs" where given away.
> 
> 
> 
> 
> On Sun, Aug 19, 2012 at 7:42 AM, Stan, W1LE <stanw1le at verizon.net> wrote:
> 
>> Hello The Net,
>>
>> For your consideration:
>>
>> The INTEL model DN2800mt ITX mother board uses a ATOM CPU and
>> draws about 11 watts of AC power when configured as:
>> (I have not measured DC power yet.)
>>
>> 30 GB OCZ Nocti mSATA solid state drive,
>> WIN7 pro, 64 bit, USB keyboard and mouse
>> APEX MI-0008 case.
>>
>> Also has:
>> parallel port available on mother board, you extend to a connector
>> RS232 serial port available on mother board, you extend to a connector
>> a single DC power supply from 11 to 19 V DC.
>> 1 each PCIe expansion port, I will use with a premium 4 channel sound card
>> SATA ports available for HDD/SDD,
>> USB ports are available,
>> Motherboard sound, and Gigalan.
>>
>> I have not played with NTP, (yet), but it sounds like a decent time nut
>> technical challenge.
>>
>> My application is for a remote site with only 13V DC power available from
>> PV/batteries.
>> Then use fiber ethernet to get off site.
>>
>> The INTEL website would have further details.
>>
>> Stan, W1LE    Cape Cod   FN41sr
>>
>>
>>
>>
>> ZZZZz
>>
>>
>> ______________________________**_________________
>> time-nuts mailing list -- time-nuts at febo.com
>> To unsubscribe, go to https://www.febo.com/cgi-bin/**
>>
> mailman/listinfo/time-nuts<https://www.febo.com/cgi-bin/mailman/listinfo/tim
> e-nuts>
>> and follow the instructions there.
>>
> 
> 
> 





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