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Topic: 100+ led knight rider (Read 1 time) previous topic - next topic


Aug 08, 2008, 09:44 pm Last Edit: Aug 08, 2008, 09:50 pm by nykffa Reason: 1
I've been going around this project of making a 144 led "knight rider" and I made it work (in code at least) with port manipulation and charlieplexing. However I am sure there is a easier way to do it.

I would like to open a discussion around this.

How do you make a knight rider or "shooting star" with more than 100 led's?


If you just need to turn the LED's on / off, you can use shift registers. But 144 Leds will require 18 8 bit shift registers or 9 16 bit registers. This can probably cause timing issues, depending on how fast you need to update the LED's.

There are also the max7219 IC that can control 64 LED's


I don't see why charlieplexing should end up overly difficult.  It should be pretty easy to produce charlieplexing "infrastructure" that allows your main code to look like
Code: [Select]
for (i=0; i <144; i++) {

It might not be the smallest code "behind the scenes", but that isn't necessarily an issue that one should worry about.  Code to manipulate a 20led two-dimensional charlieplexed array fits easily on a 1kbyte ATtiny11, for example.

I've been thinking about a generalized led array code generator sort of application and library that would create code for you given an array size (in one to three dimensions), a wiring scheme (multiplex, charlieplex, etc.) and so on...  It all depends on how quickly people outgrow blinking lights.  (*I* still haven't outgrown blinking lights!  The other project that would be neat is the beginning electronics book "how to make blinking lights"...)


Please write that book, I will buy it and read it.  

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