One seven segment digit consist of 7+1
LEDs which are arranged in a specific
formation which can be used to represent
digits from 0 to 9 and even some letters.
One additional LED is used for marking
the decimal dot, in case you want to write
a decimal point in the desired segment.
EasyPIC
™
v7 contains four of these digits
put together to form 4 digit 7 segment
display. Driving such a display is done
using
multiplexing techniques.
Data
lines are shared between segments, and
therefore the same segment LEDs in
each digit are connected in parallel. Each
digit has it’s
unique digit select line
,
which is used to enable the digit
to which the data is currently being
sent. By multiplexing data through all
four segments fast enough, you create
an illusion that all four segments are
in operation simoutaneously. This is
possible because human eye has a
slower reaction time than the mention
changes. This way you can represent
numbers in decimal or hexadecimal
form. Eight data lines that are common
for all the digits are connected to
PORTD, and digit select lines are
connected to RA0–RA3 lines on the
microcontroller sockets.
To enable digit select lines for the 4-digit
7-segment display you have to turn
on
SW4.1
,
SW4.2
,
SW4.3
and
SW4.4
switches. Digit select lines are connected
to
RA0 – RA3
pins on the microcontroller
sockets, while data lines are connected
to
RD0 – RD8
pins. For proper operation
of the display, make sure that you do not
place additional boards on mentioned lines
which can interfere with logic levels used
in your application.
Q4
BC846
R28
10K
DIS3
Q3
BC846
R29
10K
DIS2
Q2
BC846
R30
10K
DIS1
Q1
BC846
R31
10K
DIS0
8
8
8
SEG E
SEG D
SEG C
SEG DP
SEG B
SEG A
SEG F
SEG G
DIS3
7 SEG DISP
8
cc
e
d
c
dp
b
a
f
g
R81-R88
8x470
SEG A
SEG B
SEG C
SEG D
SEG E
SEG F
SEG G
SEG DP
RD0
RD1
RD2
RD3
RD4
RD5
RD6
RD7
1
2
3
4
5
7
6
8
SEG E
SEG D
SEG C
SEG DP
SEG B
SEG A
SEG F
SEG G
DIS2
7 SEG DISP
cc
e
d
c
dp
b
a
f
g
1
2
3
4
5
7
6
8
SEG E
SEG D
SEG C
SEG DP
SEG B
SEG A
SEG F
SEG G
DIS1
7 SEG DISP
cc
e
d
c
dp
b
a
f
g
1
2
3
4
5
7
6
8
SEG E
SEG D
SEG C
SEG DP
SEG B
SEG A
SEG F
SEG G
DIS0
7 SEG DISP
cc
e
d
c
dp
b
a
f
g
1
2
3
4
5
7
6
8
ON
LCD-GLCD BPWM
DIS3
DIS2
DIS1
DIS0
LCD-GLCD BCK
EEPROM-SCL
EEPROM-SDA
RC2
VCC-5V
RC3
RC4
RA0
RA1
RA2
RA3
SW4
DIP SW 8
16
15
14
13
12
11
10
9
1
2
3
4
5
6
7
8
D
AT
A BUS
Figure 14-2: 4-digit 7-segment display schematics
Figure 14-1: Turn on switches
1 through 4 on SW4 to enable
4-digit 7-seg display
Enabling the display
4 digit
7-seg display
page 27
displa
ys
