[time-nuts] GPS 18x PC/LVC 3.90 (August 28, 2013)

David J Taylor david-taylor at blueyonder.co.uk
Tue Sep 17 03:59:02 EDT 2013


From: Kiwi Geoff

Thanks for the firmware upgrade pointer David.

Folks may remember that the 18x had some terrible issues with "serial
latency" in earlier versions, where the serial NMEA could complete in
the following second epoch. Sometimes you had the right UTC time, and
sometimes you didn't.
[]
David, the new (3.90) version has a similar latency to version 3.70
and thankfully not back to the bad old days of crossing second epoch
boundaries !

And finally,  to go off "time nuts" topic (but just briefly ;-):

David, if you are like me and are fascinated with algorithms, here is
a wonderful bit of history that has just been brought back to life. A
working emulator of Clive Sinclair's Scientific Calculator, and how
they took a four function calculator chip from Texas Instruments and
in 320 words made the worlds first single chip Scientific Calculator.

It did not have the accuracy of the HP35's Cordic algorithms, but
still amazing - enjoy some UK history:

http://righto.com/sinclair

Regards, Kiwi Geoff (Christchurch, New Zealand).
=======================

Thanks, Geoff!

I've updated the page:

  http://www.satsignal.eu/ntp/Garmin-GSP18x-LVC-firmware-issue.htm#3.90

to include your new results, for which I am most grateful.

Thanks for the pointer to the Sinclair algorithms page.  I'd seen that 
through some other list (possibly Raspberry Pi), and it brings back memories 
of being RAM/ROM limited!  I remember Prof. Oatley (Cambridge electron 
microscopes) getting his HP-35 and us all being fascinated by it.  Must have 
been a month's wages at the time!  I have operated mechanical calculating 
machines, and I recall that our Engineering Department library had a 
calculator with a green CRT readout.  Computing was a paper-tape operated 
IBM 1130, and GPS and the Internet hadn't even been thought of (1968).  I 
had heard of Atomic Clocks, but never seen one.  I suppose someone at 
Cambridge must have had one somewhere.  I do recall the amateur astronomers 
discovering that the stated location for the Observatory was some 200m out 
(IIRC) when they were making transit timings.  Presumably using 60 KHz MSF 
for timing, if not for surveying (would not have shown 200m error).  Those 
were the days when they switched off the street lights for important 
observations!

Cheers,
David
-- 
SatSignal Software - Quality software written to your requirements
Web: http://www.satsignal.eu
Email: david-taylor at blueyonder.co.uk 



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