[time-nuts] Thunderbolt controllers

Mark Sims holrum at hotmail.com
Mon Jul 7 10:59:54 EDT 2008


Yeah,  you really do need a display...  this is the 21st century...  monkeys got better things to do than count blinkenlights (or read a message scrolling across a six character LCD).   

You need a processor of some sort to decode the TSIP messages.  It actually takes a significant amount of code to do it right, so you need a fairly decent one (you could cram it into a small PIC with assembly language,  but monkeys got better things to do than all that tedious mucking around in PICspace).  

Once you have a processor that you can program in a decent language,  interfacing it to some sort of LCD display module is rather trivial.  Then it can clearly and distinctly tell you the reason your oscillator has gone wobbly.  Even a simple two line text display is orders of magnitude better than any blinkenlight.

I got 46 seconds of holdover last night.  It happened when the two satellites it was tracking got into a bad PDOP/low signal situation and the receiver had to scramble to find something less garbagey to track.  That explained that 50ns phase shift in the cesium reference data.

It also went through a period of rather high PPS offset (over 20ns,  instead of the typical  Do you actually need a display?
> 
> How about a LED or 3.  My straw man is:
>   off - no power
>   on - OK
>   blink - trouble
> 
> You can convey a few bits of information with only one LED.  Just encode a 
> small integer in the number of blinks.  Code 3 would go:
>   blink, blink, blink, pause
>   bling, blink, blink, ...
> 
> 
> Yes, it's fun to show more information, but if you really want to see more, 
> you probably want to collect that data so you can track things over weeks or 
> months, and you probably have a PC already doing that.
> 

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