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: [email protected] [mailto:[email protected]] Namens [email protected] Verzonden: zondag 19 augustus 2012 19:07 Aan: [email protected] Onderwerp: time-nuts Digest, Vol 97, Issue 48 Send time-nuts mailing list submissions to [email protected] To subscribe or unsubscribe via the World Wide Web, visit https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts or, via email, send a message with subject or body 'help' to [email protected] You can reach the person managing the list at [email protected] When replying, please edit your Subject line so it is more specific than "Re: Contents of time-nuts digest..." 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 <[email protected]> To: [email protected] Subject: Re: [time-nuts] L1 GPS timing signal(s) into local time on computer(s) Message-ID: <[email protected]> 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 <[email protected]> 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 -- [email protected] >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> > > > > _______________________________________________ > time-nuts mailing list -- [email protected] > 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" <[email protected]> To: [email protected] Subject: [time-nuts] Modern motherboard with RS232 port Message-ID: <[email protected]> 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 <[email protected]> To: Discussion of precise time and frequency measurement <[email protected]> Subject: Re: [time-nuts] L1 GPS timing signal(s) into local time on computer(s) Message-ID: <[email protected]> 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 <[email protected]> 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 <[email protected]> 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 -- [email protected] >>>> To unsubscribe, go to >>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>> and follow the instructions there. >>> _______________________________________________ >>> time-nuts mailing list -- [email protected] >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >>> >> >> >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. > > > _______________________________________________ > time-nuts mailing list -- [email protected] > 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 <[email protected]> To: Discussion of precise time and frequency measurement <[email protected]> Subject: [time-nuts] Embedded NTP servers? Message-ID: <[email protected]> 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 <[email protected]> To: Discussion of precise time and frequency measurement <[email protected]> Subject: Re: [time-nuts] Modern motherboard with RS232 port Message-ID: <cabbxvhuv_hkjmnmelkphumyvtjfa11ybye-cn45tf6uevpn...@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 <[email protected]> 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 -- [email protected] > 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. > -- Chris Albertson Redondo Beach, California ------------------------------ _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts End of time-nuts Digest, Vol 97, Issue 48 ***************************************** _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
