The 7 segment display
is found in many displays such as microwaves or fancy toaster ovens
and occasionally in non cooking devices. It is just 7 LEDs that have
been combined into one case to make a convenient device for displaying
numbers and some letters. The display is shown on the left. The pinout
of the display is on the right.
Figure 2.6. 7 Segmen
3.1. Writing a character to single
This version is a common anode version.
That means that the positive leg of each LED is connected to a common
point. Each LED has a negative leg that is connected to one of the pins
of the device. To make it work you need to connect pin common to 5 volts
trough driver transistor. Then to make each segment light up, connect
the ground pin for that led to ground. A resistor is required to limit
the current. Rather than using a resistor from each LED to ground, you
can just use one resistor from Vcc to pin 3 to limit the current.
Figure 2.8. Driving 7 Segmen common anoda
Build the circuit as shown in figure 2.8. As you seen on figure 2.8.
P2.0 is connected to driver transistor, and each pin of 7 segmen is
connected to P0.0 trough P0.6. Remember, that all we want to do with
this lesson is write a number 1 to 7 segmen.
In this step, you must tipe the assembly program to make your 7 segmen
shown a number on 7 segmen, we assume that you have already known the
editor, we used MIDE-51 to edit the program.
org 0h start: mov P2,#11111001b; send high logic to a and b segmen
clr P0.0 ; send current to 7 segment
sjmp start ; jump forever
Safe your assembly program above, and name it with 7seg1.asm (for example)
Compile the program that you have been save by using MIDE-51, see the
Step 4th Download your hex file ( 7seg1.hex ) into the microcontroller
by using Microcontroller ATMEL ISP software, see the instruction.After
download this hex file you'll see the action of the 7 segmen( of course
if your cable connection and your program are corrected ).