How to drive a lot of LEDs from a few microcontroller pins

How to drive a lot of LEDs from a few microcontroller pins.

Using the fact that many microcontroller pins have three states (+V, GND, or “high impedence”). You can drive N*(N-1) LEDs from N pins. So the little 8 pin microcontroller like a PIC12Fxxx or an ATtiny11 can drive 20 LEDs on its five available output pins, and still have one pin left for some kind of […]

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