Page 235 - Making PIC Microcontroller Instruments and Controllers

UNDERSTANDING THE GOUNTERS:

COUNTING MARBLES

Proiect 3

As you may have guessed, this is not really about counting marbles. It is about count
iog pulses that may represent any number of thjngs you are intercsted in counting.
These pulses may come slow or fast, regnlarly or landonrly, or in some other way, and
we need to know how to handle them h all situations. We use the counters for count
ing the events. The marbles just happen to be an interesring medium for us to play wiih:
They are easily obtained, are easy to handle, and are inexpensjve (and they do ro11l).
See Figure l7.l.
You need to know a few things about this problem beiore we stafl, however They are
r Thic i( nol trivial by a long.horl
I There is a limit to how fast the marbles can go by in the redl world, and the programs
we create have to be faster than that,
I There is a considerable difference between counting marbles that go by one at a
time in an orderly fashion and those that go by one next to the other, helter skelier,
fast. In this project, we will count rhem one by one, and then h the later parl of the
project we will count them going by much taster
"real-world"
I Signal bouce or signaljitter is a problem in any situation. Especially
so with these shiny glass marbles.
I As can be expected, therc are many ways to get ajob like this one done meaning
that not everything wiil have been explored when we are done with this chapter

We have asked for and been given the following assurances from Mr Marbles the
owner ard manager of ihe local Marbles Inc. plant. These assurances arc designed to
make the specincadons of the project more complete and fo make our task easier. (In
other words, we have been given the parameters ior what we are to do.)