logs archiveBotHelp.net / Freenode / #43oh / 2015 / September / 19 / 1
cambazz
hello everyone
so I was reading code of rtc_c in ccs, and there is a comment like /* Setup Calendar Alarm for 10:04pm (for the flux capacitor) */
is this a joke, or is there a flux capacitor in the msp432 board
Spirilis
hawww
cambazz
hey spirillis, i am using ccs now. playing with rtc_c
ike
new arduino
again
http://www.anarduino.com/miniwireless/
128Mb flash
+ RF
it's "Built in the USA" TM
by hillbilly rednecks
;)
with chinese components
apple bomb http://img-9gag-fun.9cache.com/photo/aBrPo62_460s.jpg
hi cambazz
how are you
cambazz
oh hello
not bad playing with things
clocks
ike
I know
you like clocks
https://en.wikipedia.org/wiki/Precision_Time_Protocol
Precision Time is not real you know
for example GPS sats
all they do is to send time
you get time from 4 sats
and you use that info to get 3D coordinates + time
and there is a catch
gravity on earth is little bit stronger than in sat's orbit
so clocks on earth run slower
*so clocks on earth run faster than clocks on sat's
but ... gps sats are moving so their clocks run faster then the clocks on earth
wow
I'm so wrong
sorry
the truth is
"Because an observer on the ground sees the satellites in motion relative to them, Special Relativity predicts that we should see their clocks ticking more slowly (see the Special Relativity lecture). Special Relativity predicts that the on-board atomic clocks on the satellites should fall behind clocks on the ground by about 7 microseconds per day because of the slower ticking rate due to the time dilation effect of their relative motion."
"A prediction of General Relativity is that clocks closer to a massive object will seem to tick more slowly than those located further away (see the Black Holes lecture). As such, when viewed from the surface of the Earth, the clocks on the satellites appear to be ticking faster than identical clocks on the ground. A calculation using General Relativity predicts that the clocks in each GPS satellite should get
ahead of ground-based clocks by 45 microseconds per day."
"The combination of these two relativitic effects means that the clocks on-board each satellite should tick faster than identical clocks on the ground by about 38 microseconds per day (45-7=38)! This sounds small, but the high-precision required of the GPS system requires nanosecond accuracy, and 38 microseconds is 38,000 nanoseconds. If these effects were not properly taken into account, a navigational fix based
on the GPS constellation would be false after only 2 minutes, and errors in global positions would continue to accumulate at a rate of about 10 kilometers each day! The whole system would be utterly worthless for navigation in a very short time."
cambazz
ike: you can sync within 10ns of the UTC clock, with these navspark modules, 6usd/each + antenna
which are being shipped now, and meanwhile I hooked up a ds1307 + ds3231 and trying to discipline the ds1307
but no luck, since i dont have a rtc with calibration. I have one ds1340 but that one dont have a 1pps output.
i also made a 1s ticker with ccs, using TimerB ticking 32768
which i found grossly imprecise. that 32khz xtal on a 5529
Rickta59
what time is it?
ike
https://www.youtube.com/watch?v=LVPNXsc4wsQ
cambazz
ah its been years i have not eaten peanut jelly
ricta it is 22:26:49
there is this mailing list called time-nuts, and it seems there are many people who has time and atomic clocks as their hobby
Rickta59: so are there any RTC's on the tiva-C board?
Rickta59
i haven't had a watch since I was like 12 years old
yes i think so
the tm4c1294?
cambazz
well, I tried the Timer based RTC, on both 5529 and 2553, and it skews like crazy
no i mean the tiva-c, tm4c123
Rickta59
isn't all dependent on the xtal you use?
cambazz
yes, it is very diffucult to get a proper xtal, so they add some ticks per 64 minutes, to calibrate the clock.
in some ic2
ics
i want to make something remniscent of that using a launchpad, for example something that counts time and generates 1pps signal, with the ability to insert 1/1024 of a second
add or substract
ike
cambazz you can buy from ebay some cheap ppm xtals
http://www.ebay.com/itm/1pcs-TCXO-10MHz-10-000M-Ultra-precision-Crystal-Oscillators-DIP-0-5ppm-NT-/331425347108?hash=item4d2a7d7624
http://www.ebay.com/itm/CRYSTAL-TCXO-26MHZ-SMD-MPN-X1G0041310010-EPSON-/391197389333?hash=item5b152e7215
http://leapsecond.com/pages/atomic-bill/
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