[time-nuts] Precisione GPS based led clock

Tom Van Baak tvb at LeapSecond.com
Sat Nov 5 22:26:36 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 
> time.


The expanders I've seen have serial-in and serial-out. So the
trick is you daisy chain the serial lines of the chips but drive
the latches in parallel. That way you can quietly shift in all N
bits and then latch one and all.


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