自动化专业毕业英文及翻译

2021年1月25日发(作者：草种)

英文原文

LED Display Screen Design and Proteus Simulation
Based on Single-Chip Microcomputer
Abstract
—

This
paper
designs
a
LED
display
system
controlled
by
AT89C52
MCU
(Microcomputer Controller
Unit).
The
AT89C52 controls
the external circuit
formed
by
74HC154
and
used
to
control
the
real
time
display.
Language
C
is
applied
to
compile
program
in
KeiluVision3
programming
environment.
The
display
system
is
simulated through Proteus software. In Proteus environment, the schematic diagram is
drawn.
Through stimulation,
it achieves real-time display, static display and dynamic
display
of
Chinese
characters.
It
has
switch
keys
to
change
display
state
of
details.
Through
the
actual
simulation,
the
biggest
controllable
screen
size
of
the
AT89C52

MCU
is
64×
32.
The
AT89C52
controls
the
entire
screen
display

of
Chinese
characters of 16×
16 dot
matrix, a total of eight characters.
And
the key
function can
be extended.
Keywords-LED display; AT89C52; Proteus; dynamic scanning
I. INTRODUCTION
Energy- saving
issue attracts every
one’s attention.
Thus the
products
that
focus
on
energy
conservation
get
more
recognition.
LED
(Light
Emitting
Diode-LED)
display
produced
in
the
1970s
when
it
was
simply
used
to
display
number
and
text.
With
the
diversification
of
Led
colors
and


enhancement
of
brightness,
full
color
outdoors LED display became a reality at the end of the 20th century. The LED of our
country
appeared
in
the
1970s
and
its
industrial
production
inthe
1980s.
The
development
of
information
and
advertising


industry
brings
about
the
emergence
of LED display screen.

LED display screens are mainly used in advertising window,
train
stations,
banks
and
other
places.
It
gets
more
and
more
widely
used.
Its
own
characteristics
could
make
it
occupy
a
market
in
the
display
screen
industry
in
the
future.
In
the
design
of
LED
display,
the
hardest
part
is
hardware
debug.
In
order
to
solve
the
signal
interference,
insufficient
solder
in
hardware
connection,
component
damage
and
a
series
of
debugging
problems,
the
EDA
(Electronic
Design

Automation-EDA)
utility
software
Proteus
that
the
UK

Labcenter
electronics
company
researched
can
be
used
to
realize
the
entire
hardware
system
schematic
drawing and simulation[1].
Proteus
simulation
environment
includes
ISIS
and
ARES.
In
the
ISIS
environment, electronic circuit can be directly stimulated
in the stage of schematic. It
also
provides
virtual


machines,
simulation
of
the
input
signal
which
makes
a
convenient
simulation.
ARES
is
mainly
used
for
PCB
(Printed
Circuit
Board-PCB)
design.
The
device
library
provides
schematic
device
and
its
package.
It
can
design
printed circuit board in this environment.
Proteus
simulation
system
currently
supports
MCU
(Micro
Controller

1

Unit-MCU)
with
ARM7,
8051/52
series,
AVRseries,
PIC
10/12/16/18
series,
HC11
series
and
the
MSP430[2].
It
can
observe
the
direct
result
of
hardware
debug
with
proteus
simulation.
It
has
the
characters
such
as
intuitive,
convenient,
cost
savings,
high efficiency and so on.

II. THE DESIGN OF LED DISPLAY
LED display system
is
formed by MCU,
LED screen

display circuit, external
circuit
and
the
program
for
control
the
system.
LED
screen
display
circuit
includes
LED
panel
and
the
driving
circuit
of
row
and
column.
The
external
function
circuit
includes
key
controlling
circuit
and
real-time
clock
circuit.
Display
function
can
be
achieved
as
follows:
numbers,
characters,
Chinese
characters,
static
display
of
monochrome
pictures,
and
dynamic
display.
Dynamic
display
includes
the
whole
display content
moving
up and
left. The shift
method
is controlled by keys, and also
by automatic cycle.
The system of real-time clock display provides seconds,
minutes,
hours,
day,
date,
month,
and
year
information.
The
overall
block
diagramof
LED
display screen is shown in Fig. 1.


III. HARDWARE DESIGN OF LED DISPLAY
A. Design of Row Driving Circuit
The
core
of
LED
display
system
is
the
control
circuit.
The
control
circuit
includes driving circuit, clock circuit and the smallest MCU system which consists of
AT89C52
MCU,
Crystal
oscillator
circuit
and
reset
circuit.
Row
driving
chip
is
74HC154,
4-to-16
line
decoder/
demultiplexer,
active
LOW
outputs.
P2.0~P2.3
port
of
AT89C52
connect
to
A0~A3
of
74HC154
decoder.
According
to
the
operating
principle
of
the
decoder,
when
the
MCU
system
controls
its
P2
port
output
0x00~0x0F, the 74HC154 respectively output
LOW
level
from Y0
to Y15.
And then
the
first
line to the sixteenth
line of display screen
is selected.
The P2.4 port of MCU
connects
to
the
first
74HC154
decoder’s
(1~16
line
controller)
enable
pins,

meanwhile
connects
to
the
second
one
enable
pins
(17~32
line
controller)
through

2

inverters. That realizes line scanning method. When scanning from the first line to the
sixteenth
line,
the
P2.4
port’s
output
is
jump
from
0
to
1.
And
enable
the

second
74HC154: the seventeenth line is output. This method achieves scan of low-half LED
display. The row driving circuit diagram is shown in Fig. 2.

B. Design of Column Driving Circuit
P1.0~P1.2
ports
of
MCU
are
used
to
control
the
column
driving
chip
MC74HC595. 74HC595
is shift register
with an 8- bit serial
in, serial or parallel out
with output
latches 3 states. Its control clock and
shift clock are separate that brings
convenience for controlling. Each character is composed by dot matrix of 16 rows and
16 columns: each character of
national standard Chinese character
library
is represent
by
256
dots


matrix
[3].
The
font
software
generates
code
of
dot
matrix
which
is
hexadecimal
number
of
8
bit
a
group.
In
this
design
row
scan
is
used,
so
the
horizontal
font
code
is
taken.
Using
74HC595
to
control
the
column
data
send
out.
When using 74HC595 to control each characters code display, P1.0 port of MCU will
send 8 bit serial
data
from the
first column
to the eighth column,
which
is
high after
the
previous
low
in
this
transmission.
P1.2
port
of
MCU
outputs
shift
clock.
When
P1.0 port outputs a bit data, the electrical
level of P1.2 port changes
from
low to
high
once, then the content of shift register 74HC595 will
move one bit
from the
high to
the
low
once.

When
the
ninth
bit
data
is
sent
to
SDI
port
of
74HC595,
the
74HC595’s SDO port will serially output the first bit in the
shift register to the eighth
bit of
the
next 74HC595 chip,
and the
new
incoming data
is sent to
the eighth
in
the
first
chip.
After
the
end
of
the
data
preparation
from
the
1st
column
to
the
64th
column, P1.1 port
generates a rising
edge pulse
which sends to
the
LCHCLK port of
74HC595.
Firstly
putting
74HC595
chip
in
cascade
connection,
then
connecting
the
parallel
output
clock
pins
in
series
and
these
clock
pins
are
controlled
by
P1.1
port.
Therefore, when the output clock is
valid, every 74HC595’s column data output at the
same time. Then to achieve displays this whole row by selecting the homologous row.

3

Continuing
to do
the steps,
it can
realize a row scan.
As
long as the entire
screen of
the scan rate is


highe


than 50 times per seconds, people could see static images.
The 74HC595 column driving circuit is shown in Fig. 3

C. Design of Functional Circuit
Besides
the
above
function,
the
design
also
has
real
time
display
and
the
key
function
to
switch
the
display
modes.
P3.0~P3.3
ports
individually
connect
to
four
buttons
which
control
static
display,
moving
up
display,
moving
left
display
and
automatic cycle display. The automatic cycle display
is
from
the static,
moving
up to
moving
left
circle
shows.
The
function
is
realized
by
programming
of
key
scan.
DS1302 chip
is
used
to control real time clock.
The timeinformation such as second,
minute,
hour, day, date,
month, and
year
is displayed
in
LED display screen.
A 3.6V
button
battery
is
connected
to
the
eighth
pin
of
DS1302,
which
ensures
DS1302
continuous operation
while
LED display
system does
not
work
[4].
Three data
wires
are used to control


DS1302 in order to achieve synchronous serial communication.

The
P3.6
port
of
MCU
controls
serial
clock
SCLK
pin,
P3.7
port
controls
the
DS1302’s
REST/
RST
pin,
and
P3.5
connects

to
data
line
I/O.
According
to
the
operating principle of
DS1302, MCU reads and
writes the data, then sends to display
in LED panel. The function circuit and the MCU system

diagram are shown in Fig4.

4


IV. SOFTWARE DESIGN
Using
C
language
to
write
the
program,
the
program
is
compiled
in
Keil
uVision3
development
environment.
The
program
uses
modular
design,
which
is
as
follows:
time
delay
function,
74HC595
performance
function,
DS1302
control

function,
data
display
function
and
the
main
function.
The
modular
design
of
LED
display program is convenient for writing and changing.




Fig.5
is
the
main
function
block
diagram.
It
mainly
realizes
the
overall
initialization,
DS1302
initialization
and
key
scan.
When
the
main
function
is
programmed, sub
function should be placed before the
main
function, or declared
in
advance.
Key
scan
includes
four
function
keys,
which
respectively
accomplish
the

5