Any chance of a link to where this challenge is, so we can read the exact rules for ourseleves ( your abridged version doesn't seem to allow resistors to be used :-o ) and see how the winner so far managed to do nine LED's ?
I've managed to get up to eight LED's but can't see a way to go above that yet. The 'niner' may have used some neat trick but may not have exploited it to the full yet. Has it been proven to work or is it just theoretical or simply a claimed nine LED's ? I'll admit I'm intrigued.
This hasn't been fully tested, but I did check that a LED via 1K8 from +V to an I/O set as an input didn't come on and does when the output is set low.<code><pre><font size=2 face='Courier'>| O0 O1 O2 O4 |
`---.-------.-------.-------.---'
.|. .|. .|. .|.
| | | | | | | |
|_| |_| |_| |_|
| | | |
A }--|>|--{ | |
| | | |
B `--|<|--{ | |
| | |
C }--|>|--{ |
| | |
D }--|<|--{ |
| | |
E | }--|>|--{
| | |
F | `--|<|--{
| |
G }----------|>|--{
| |
H `----------|<|--' </font></pre></code> <code><pre><font size=2 face='Courier'> A B C D E F G H </font></pre></code> <code><pre><font size=2 face='Courier'>
O4 : I I I I 0 1 0 1
O2 : I I 0 1 1 0 I I
O1 : 0 1 1 0 I I 1 0
O0 : 1 0 1 0 1 0 1 0 </font></pre></code>
If anyone can find a way to turn Output Pin 0 into an Input that will allow 12 LED's. I've tried COUNT and PULSIN but that didn't seem to work.
[Edit] Actually, you'd have to move the R's around because as it is they end up with two LEDs paralleled with a single, so when the single lights so do the other two. SHould work with the LED's moved, but I'm not editing that lot.
Edited by - hippy on 26/08/2006 05:54:16
whats 'tristate'?,