Page 187 - Making PIC Microcontroller Instruments and Controllers

THE UNIVERSAL INSTRUMENT:

A BACKGROUND DISCUSSION

The Properties and Capabilities
of a Universal Instrument

Almost all the instruments we will make have some shared characteristics. What are
they and what advantages and disadvantages do we get from lhem?Whatdoes having
our instruments based on PIC microcontrollers do for us? Asking thesequestions and
unde$tanding basic concepts like these makes it easier for us to proceed with our work.
Let's look at the propertres needed in ar instrument by comparing it with an instru-
ment we are all familiar wjth; a volvohm meter or VOM. We will compare its proper-
ties and functions lo the insfuments we are designing to get a better understanding of
what we a-re trying to accomplish and how we might accomplish it.
Each instrumentcontroller must have fhe iollowing basic propefies:

I . lt must have a way to enter infomqtion lnto rhe device in a convenient manner. In
a VOM, we are Fovided with two probes that we place at various points in the cir
cuitry. In the instruments we make, we will provide comection points for the sig-
nals and pulses we are interested in reading, but more importantly we arc interested
in providing inputs that canbe programned ro influence the operation of the instru-
ment in rcaI time. Wirh a little imagination, the inslruments we create can be both
interactive and intelligert-
2. It must have some form of decision making cqability that allows it to manipulale
the jnformation sent to it, and some of lhis capability needs to be conffollab]e
(influence-able) bythe operator.In the VOM, thereis a selector switch that we use
to choose ranges and functions we will use. In our instruments, we will use the com-
puter to set the parameters within which our instrument will operate. we will be
able to progam the instrument for the task at hand as needed. For our instruments,

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