Re: [time-nuts] Maxim DS1342
Le 12 nov. 2013 à 03:13, Chris Albertson a écrit : You want to drive the RTC with an external PPS to get time/date into an Arduino? Why not feed the PPS to the Arduino and have it compute date and time? It is really not that hard to count seconds. You don't really need an external chip to do that. Typically you need more fine time resolution them just a seconds counter. Especially if you are using an Arduino, you are maybe building a robot or real-time controller and want to measure something like Milliseconds per revolution so you need a faster running counter and then you want to calibrate that counter A typical method is to have the PPS trap the faster counter, than you can see how many periods per second your counter is moving. You can mount for a 1,000 seconds and get a pretty good idea. Then you use the fast counter, now that you know it's rate for you timing. So you don't need an external chip if you are willing to track the rate of the free running clock. True, if you don't need to know what your epoch is. Although the DS indicates GPS PPS is a choice for the reference, why bother as you get your date and time to a better resolution on first fix than any RTC is going to give you. The advantage of this chip I think, is that if you have a reference, you get to keep time with much better resolution than a normal RTC without GPS. If I am interpreting the DS correctly, the 1Hz out is held within 7,8ms of the reference, which is pretty good over very long Tau. Maybe the key is that one of the accepted references is 50/60Hz power line frequency. That nets billions of end users. -- Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@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@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Maxim DS1342
hmur...@megapathdsl.net said: A 32 KHz clock is also useful for running (well, crawling) in low power mode. That can be important when running off batteries. I suspect the reason that chips don't have an option to drive the RTC from a 1 PPS input is that there is no volume in that corner of the market. Does anybody other than a time-geek even know what PPS means? (There is a wiki page, actually 2, a disambiguation page for PPS and a another page for Pulse Per Second.) The product planners for single chip CPUs systems have a list of important customers. If you are buying a million chips a year, they will make sure that one of their next generation of chips is a good fit for your application. Good fit means it gets the job done and has a reasonable cost. If you are a startup with a sensible business plan that turns into a million chips a year, they will help you select one of their chips to get off the ground and discuss the good-fit/price part when you get closer to placing a large order. My million-a-year may be off by a factor of 10 (or more) either way, but I think it's the right ballpark. I think the volume argument is sound for sure, but OTOH what is required to implement a single multi-purpose I/O as an external 1 Hz input is a handful of transistors. It could be a differentiating feature to some vendors, and in fact it is not unique to Maxim in terms of RTC chips. For CPU chips specifically, volume would be an issue and lack of big client requests for this as an embedded function is likely. I also agree that the required precision is an issue, and this is manifest in Microchip's RTC chips where they have calibration circuitry to compensate for slight 32 kHz crystal differences if so desired. Obviously the time nuts market is even smaller still :-) Thanks for your thoughts. Russ ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Maxim DS1342
Thanks for the input all, I think the target market for what I have in mind is hobbyist more than time nut. I also believe the Sparkfun product I originally pointed to is an example of a mass market offering that is 'good enough' for almost anyone. There is a small niche of those wanting to use the GPSDO they already have, and know they can use one of several types of coded solutions to make a clock. These would be weekend hackers that may, or may not, care that the displayed result is within x parts per billion or trillion, i.e. just a thing to solder-up on a weekend, steal some code to use it and drive a display of some type, and possibly come up with a use for it I never thought of, which is a cool thing. My main concern was that someone had something like this already, since this group has it's eyes on everything in this space I thought if anyone knew, they'd be on this list. It is a project that is worth doing for my own reasons. Russ ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Harvard Time
Hi: Two exhibits based on time: March 6 - December 6, 2013 Time, Life Matter: Science in Cambridge and Time Time Again: How Science Culture Shape the Past, Present, Future http://www.fas.harvard.edu/~hsdept/chsi-exhibitions.html -- Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Maxim DS1342
just a thing to solder-up on a weekend Never underestimate the attraction of something you can solder-up on a weekend. It kept Heathkit alive for years. But if you're trying to make money from it, the problem is finding a market and marketable ideas. Bob From: Russ Ramirez russ.rami...@gmail.com To: time-nuts@febo.com Sent: Tuesday, November 12, 2013 11:22 AM Subject: Re: [time-nuts] Maxim DS1342 snip ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] linux-gpib working on a RasPI
On Mon, 11 Nov 2013 20:44:59 +, cfo wrote: I have finally succeded in making linux-gpib build and load the agilent_82357a_gpib module. I have put the howto online here http://www.eevblog.com/forum/reviews/using-a-raspberry-pi-with-linux-gpib- and-a-beiming-or-agilent-usb-gpib-adapter/ or http://tinyurl.com/pry8fqu CFO (Bingo) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Maxim DS1342
The microchip pics on the bench here actually have the oscillators in them for the 32Khz xtal. That is, the gain and feedback to make the crystal run are in them. All that is needed is some capacitance to ground. This is why the SOSC (Secondary Oscillator) uses two pins. You can also use a single input to trigger the counters. With correct RTC routines, in software you should have no problem running a clock from a single PPS. Really, other than a programmer and some code required, An RTC in a low power micro, that can 'wake up' and do things at multiple 10's of Mhz for periods of time seems much more flexible than a single RTC. Especially when the micro is drawing only uA when acting as an RTC... Dan On 11/12/2013 12:37 AM, time-nuts-requ...@febo.com wrote: russ.rami...@gmail.com said: Looking across the TI and Microchip lines a bit, it strikes me as odd that more micros supporting integrated RTCs actually use two I/Os for a 32 kHz crystal option. Why they support an RTC is not mysterious at all, but why not the option at to drive the 1 Hz clock directly rather than dividing 32 kHz down to 1 Hz and using an extra I/O is odd when these I/Os are usually configurable anyway. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Harvard, Time and the Dipleidoscope
Dr. Sara Schechner, curator, just posted this on the sundial reflector: The Collection of Historical Scientific Instruments (CHSI) at Harvard University would like to invite you to an informal gathering during this year's HSS Annual Meeting, held in Boston. We will open our museum doors on Friday, 22 November 2013 from 7:30pm to 9:30pm. Wine and cheese will accompany the visit of our two current exhibits: Time, Life Matter: Science in Cambridge AND Time Time Again: How Science Culture Shape the Past, Present, Future. For more information, go to our website: http://www.fas.harvard.edu/~hsdept/chsi-exhibitions.html We are located on the Oxford Street side of the Science Center at Harvard University: Collection of Historical Scientific Instruments Science Center 136 and 251 1 Oxford Street, Cambridge, MA. (map: http://hmsc.harvard.edu/files/museums/files/hmsc_map.pdf) Please join us for this special occasion. We are eager to see old friends and make new ones! Please RSVP to either Dr. Sara Schechner (sche...@fas.harvard.edu) or myself, your two hosts. The Harvard Collection of Historical Scientific Instruments is simply outstanding and there are two large exhibits running at present. I presented a paper on the Dent Dipleidoscope at the August annual meeting of the North American Sundial Society, held in Cambridge this year at Harvard. We toured the Harvard exhibits and enjoyed a lengthy behind-the-scene tour of their extensive collection storage area in the basement. This is surely the largest room of rolling shelves filled with scientific antiques I've ever seen! I serve as Registrar for NASS, maintaining an 8.6 GB database of sundials throughout North America. Sundials, of course, were our first time-telling instruments! By 1850, the Industrial Revolution and the extensive train system in England led to demand for more accurate time than sundials and mechanical clocks of the day could provide. For example, train schedules used London Time (as opposed to local solar time) and showed train arrivals/departures to the nearest minute. The Dent Dipleidoscope was the first instrument available to the layman that allowed identifying correct time within just a few seconds. It was easy to use and relatively inexpensive. My presentation was titled, The Dent Dipleidoscope: A Sundial By Another Name. So, as Time Nuts, we can appreciate that time accuracy has come a long way in just 150 years! If you should happen to be in Cambridge for this event, do visit The Coop bookstore near the Harvard campus. It is an amazing, 5-story high place! Larry McDavid W6FUB On 11/12/2013 9:32 AM, Brooke Clarke wrote: Hi: Two exhibits based on time: March 6 - December 6, 2013 Time, Life Matter: Science in Cambridge and Time Time Again: How Science Culture Shape the Past, Present, Future http://www.fas.harvard.edu/~hsdept/chsi-exhibitions.html -- Best wishes, Larry McDavid W6FUB Anaheim, California (SE of Los Angeles, near Disneyland) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Harvard, Time and the Dipleidoscope
Hi Larry: Where did you see the Dipleidoscope? http://www.prc68.com/I/Dent.shtml Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html Larry McDavid wrote: Dr. Sara Schechner, curator, just posted this on the sundial reflector: The Collection of Historical Scientific Instruments (CHSI) at Harvard University would like to invite you to an informal gathering during this year's HSS Annual Meeting, held in Boston. We will open our museum doors on Friday, 22 November 2013 from 7:30pm to 9:30pm. Wine and cheese will accompany the visit of our two current exhibits: Time, Life Matter: Science in Cambridge AND Time Time Again: How Science Culture Shape the Past, Present, Future. For more information, go to our website: http://www.fas.harvard.edu/~hsdept/chsi-exhibitions.html We are located on the Oxford Street side of the Science Center at Harvard University: Collection of Historical Scientific Instruments Science Center 136 and 251 1 Oxford Street, Cambridge, MA. (map: http://hmsc.harvard.edu/files/museums/files/hmsc_map.pdf) Please join us for this special occasion. We are eager to see old friends and make new ones! Please RSVP to either Dr. Sara Schechner (sche...@fas.harvard.edu) or myself, your two hosts. The Harvard Collection of Historical Scientific Instruments is simply outstanding and there are two large exhibits running at present. I presented a paper on the Dent Dipleidoscope at the August annual meeting of the North American Sundial Society, held in Cambridge this year at Harvard. We toured the Harvard exhibits and enjoyed a lengthy behind-the-scene tour of their extensive collection storage area in the basement. This is surely the largest room of rolling shelves filled with scientific antiques I've ever seen! I serve as Registrar for NASS, maintaining an 8.6 GB database of sundials throughout North America. Sundials, of course, were our first time-telling instruments! By 1850, the Industrial Revolution and the extensive train system in England led to demand for more accurate time than sundials and mechanical clocks of the day could provide. For example, train schedules used London Time (as opposed to local solar time) and showed train arrivals/departures to the nearest minute. The Dent Dipleidoscope was the first instrument available to the layman that allowed identifying correct time within just a few seconds. It was easy to use and relatively inexpensive. My presentation was titled, The Dent Dipleidoscope: A Sundial By Another Name. So, as Time Nuts, we can appreciate that time accuracy has come a long way in just 150 years! If you should happen to be in Cambridge for this event, do visit The Coop bookstore near the Harvard campus. It is an amazing, 5-story high place! Larry McDavid W6FUB On 11/12/2013 9:32 AM, Brooke Clarke wrote: Hi: Two exhibits based on time: March 6 - December 6, 2013 Time, Life Matter: Science in Cambridge and Time Time Again: How Science Culture Shape the Past, Present, Future http://www.fas.harvard.edu/~hsdept/chsi-exhibitions.html ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
