[time-nuts] Precisione GPS based led clock

Hal Murray hmurray at megapathdsl.net
Sat Nov 5 18:35:51 EDT 2011

tvb at LeapSecond.com said:
> If you use 16- or 24-bit serial-parallel-latches or "port expanders" then
> you only need 2 or 3 pins of the microcontroller. Use one or more '595 or
> look at the wonderful chips by Unitrode/Allegro. 

There is still the problem of updating all of the expander chips at the same 

Here is a possibly crazy idea: use the decimal point.

I think this recipe works:
  1: figure out which digits you want to change
  2: starting from the right, turn on the decimal points of those digits
  3: again, starting from the right, update the digits and turn off the 
decimal points
  The clock "ticks" when you turn off the bottom decimal point.

When reading:
  If the bottom decimal point is on, ignore the decimal points.  You are in 
step 2.
  If the bottom decimal point is off but others are on, you are in step 3.  
The digits with the decimal points on need to be bumped by one.

These are my opinions, not necessarily my employer's.  I hate spam.

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