2 Nov
2011
2 Nov
'11
3:42 p.m.
On 2 Nov 2011 at 21:03, Tony Duell wrote:
If you count an n-input decoder/demux, then no, you can drive 2**n
lines; Charlieplexing is n*(n-1). e.g., if you have 6 output pins,
you can drive 64 LEDs using a traditional demux or 30 LEDs using
Charlieplexing with no additional logic. It saves money, but can't
beat regular muxing. CP also suffers from issues with leakage
current, where some LEDs remain dimly illuminated.
--Chuck
Charlie Allen
of Maxim. Pretty nuch the right idea, but most
variations also make use of the ability to float a line (high
impedance) as well.
I think that's required to avoid other LEDs turning on, isn't it. If a
pin has to be either high or low, then (without giving it much
thought) can you do any better than conventional multiplexing?