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 Robotics / Handy Board / 7710
7709  |  7711
Subject: 
Re: LED's
Newsgroups: 
lugnet.robotics.handyboard
Date: 
Wed, 5 Apr 2000 14:33:36 GMT
Original-From: 
Richard Drushel <drushel@apk!stopspam!.net>
Viewed: 
2893 times
  
[Derek Healy] spake unto the ether:

Hi, could anyone tell me how I might light LED's in sequence so that they
would simulate a rev counter of an automobile & to also simulate the speed
counter.

This is just an idea skeleton, but not too hard to flesh out, if
you've worked with TTL.  The Handy Board memory map maps some upper 32K
addresses to I/O "ports".  Look at the schematic and you can see which
addresses generate which enable lines.  Some are used already, but some
are free.  Put an 8-bit latch on one of the output ports.  Have your
software map whatever your actual speed values are from 0-7.  Use this
0-7 value to set the highest bit and every one below it in the latch.
Attach LEDs to the latch outputs.  If you do it right, you should get the
rising/falling bargraph effect you're looking for.

Numeric example:  say your hardware returns a 16-bit unsigned
integer (range 0-65535).  Divide 65536 into 8 equal parts so you know
where the threshold changes are:  0, 8192, 16384, 24567, 32768, 40960,
49152, and 57344.  Read your speed value and use these thresholds to map
it to 0-7.  Say the value was 22438; that maps to level 2.  So, set bits
2, 1, and 0 at the memory address corresponding to your output latch.
The corresponding 3 LEDs should light.  If the speed went up to 39345,
that's level 4, so set bits 4-0 in the output latch; if the speed fell to
4154, that's level 0, so set bit 0 in the output latch.

The actual hardware to do this can be easily reverse-engineered
from the Handy Board schematic, as Fred does exactly the same thing for
motor outputs; just drive LEDs instead of motors.

*Rich*
--
Richard F. Drushel, Ph.D.            | "Aplysia californica" is your taxonomic
Department of Biology, Slug Division | nomenclature.  /  A slug, by any other
Case Western Reserve University      | name, is still a slug by nature.
Cleveland, Ohio  44106-7080  U.S.A.  |     -- apologies to Data, "Ode to Spot"



Message is in Reply To:
  LED's
 
Hi, could anyone tell me how I might light LED's in sequence so that they would simulate a rev counter of an automobile & to also simulate the speed counter. I need to know how I might wire them up and how I might be able to program them using time (...) (25 years ago, 5-Apr-00, to lugnet.robotics.handyboard)

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