User`s guide
One seven segment digit consist of 7+1
LEDs which are arranged in a specic
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 simultaneously.
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 – RD7 pins. Make sure to disconnect
other peripherals from the interface lines
in order not to interfere with signal/data
integrity.
1 2 3 4 5 6 7 8
O
N
SW4
1
2
4
5 6
7
9
8
10
3
b
ac
d
e
f
g
dp
cc
1
2
4
5
6
7
9
8
10
3
b
ac
d
e
f
g
dp
cc
1
2
4
5
6
7
9
8
10
3
b
ac
d
e
f
g
dp
cc
1
2
4
5
6
7
9
8
10
3
b
ac
d
e
f
g
dp
cc
COM0
COM1
COM2
COM3
R81 470
R82 470
R83 470
R84 470
R85 470
R86 470
R87 470
R88 470
Q1
BC846
Q2
BC846
Q3
BC846
Q4
BC846
R28
10K
R29
10K
R30
10K
R31
10K
COM3
COM0
COM1
COM2
DIS0
DIS1
DIS2
DIS3
RA1
RA3
RA2
RA0
DIS3
DIS0
DIS1
DIS2
seg e
seg d
seg c
seg dp
seg b
seg a
seg f
seg g
RD7
RD6
RD4
RD3
RD2
RD1
RD0
RD5
seg a
seg b
seg f
seg g
seg dp
seg c
seg d
seg e
seg a
seg b
seg f
seg g
seg dp
seg c
seg d
seg e
seg a
seg b
seg f
seg g
seg dp
seg c
seg d
seg e
seg a
seg b
seg f
seg g
seg dp
seg c
seg d
seg e
DATA BUS
Figure 14-2: 4-digit 7-segment display schematic
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
displays