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How 'bot the 74HC148 8-to-3 Priority Encoder?

http://www.fairchildsemi.com/pf/MM/MM74HC148.html

Alternatively, maybe a shift register? Like the 74HC165? Clock, data,
reset...

- -Randy Glenn

This coming from the guy with a system tray 7 icons wide... by 2
tall...
=================================================
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- -----Original Message-----
From: pic microcontroller discussion list
[mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Robert Shady
Sent: February 15, 2001 20:21
To: PICLIST@MITVMA.MIT.EDU
Subject: [PICLIST] [PIC]: IR line detection & Obstacle detection


PROJECT:
  Infared line detection circuit

DESCRIPTION:
  Ability to correctly identify a significant variance in contrast by
sampling at least 6-8 phototransistors while emitting infared light.

PROBLEM:
  Is there some way (using a flip-flop, or otherwise) to only use 2-3
pins to sample all 8 inputs?  I'm currently using a 16F84A to do
this,
run some servos, an LCD, etc (yes, a "robot").  The line detection
routines I've seen on the net use a 1-1 sensor to pin
configuration...
There just HAS to be a better way... :)

OTHER USES:
  Obstacle detection.  I've heard of a similar circuit altered
slightly
to provide obstacle detection up to 1m or so.  Modification was
something along the lines of sending a modulated pulse and
"listening"
for that specific pulse, and computing the delay.  Has anybody heard
of
this?  Any ideas, code, resources, etc. for either of these would be
greatly appreciated...

P.S. I'm not necessarily looking for the solution, just a pointer in
the right direction on the best way of doing either or both of these.
Thanks.

While I'm at it, where is the best place to pic up some ultrasonic
stuff for obstacle detection (might as well do both, this is a
learning
experience, right?)

- -- Rob


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