page 32
Digital signals
have
two discrete states
, which are decoded
as
high
and
low
, and interpreted as
logic 1
and
logic 0
.
Analog signals
, on the other hand, are
continuous
, and can
have any value within defined range.
A/D converters
are
specialized circuits which can convert analog signals (voltages)
into a digital representation, usually in form of an
integer
number
. The value of this number is
lineary dependent
on the
input voltage value. Most microcontrollers nowdays internally have
A/D converters connected to one or more input pins. Some of the
most important parameters of A/D converters are
conversion time
and
resolution
. Conversion time determines how fast can an analog
voltage be represented in form of a digital number. This is an important
parameter if you need fast data acquisition. The other parameter is resolution.
Resolution represents the number of discrete steps that supported voltage range
can be divided into. It determines the sensitivity of the A/D converter. Resolution is
represented in maximum number of bits that resulting number occupies. PIC18F87K22
microcontroller which comes on MCU card with the EasyPIC PRO v7
™
board has 12-bit resolution,
meaning that maximum value of conversion can be represented with 12 bits, which converted to integer is
2
12
=4096. This means that supported voltage range, for example from 0-5V, can be devided into 4096 discrete steps of
about 1.22mV.
EasyPIC PRO
™
v7 provides an interface in form of two potentiometers for simulating analog input voltages that can be routed
to any of the 10 supported analog input pins.
ADC inputs
DATA BUS
Enabling ADC inputs
In order to connect the output of the
potentiometer
P2
to
RA0
,
RA1
,
RA2
,
RA3
or
RA5
analog microcontroller inputs,
you have to place the jumper
J5
in the
desired position. If you want to connect
potentiometer
P3
to any of the
RF1 – RF5
analog microcontroller inputs, place jumper
J6
in the desired position. By moving
the potentiometer knob, you can create
voltages in range from
GND
to
VCC
.
Figure 18-1: use J5 and J6 jumpers
to connect analog input lines with
potentiometers P2 and P3
Figure 18-2:
Schematic of ADC
input
Easy
PIC PRO
v7
other modules
Summary of Contents for EasyPIC PRO v7
Page 37: ...page 37 EasyPIC PROv7 notes...
Page 38: ...page 38 EasyPIC PROv7 notes...
