OBJECTIVE:
 To interface seven-segment to the AVR trainer.
REFERENCES:
 Mazidi and Naimi, “The AVR Microcontroller and Embedded Systems,” Chapters 4, 6, and
Section 17-3.
MATERIALS:





AVR trainer
Atmel Studio or any other AVR assembler
Two 7-segments
Two transistors
Two resistors
ACTIVITY 1
a) Connect a common cathode 7-segment directly to PORTD.
AVR
PORTx.0
PORTx.1
PORTx.2
PORTx.3
PORTx.4
PORTx.5
PORTx.6
PORTx.7
A
B
C
D
E
F
G
DP
Common
Cathod
100
b) Write the following program in the AVR Studio and then build and download it to the
trainer board. This program displays 7 on the 7-segment.
LDI
OUT
LDI
OUT
HERE: RJMP
R20, 0xFF
DDRD, R20
R20, 0b00000111
PORTD, R20
HERE
ACTIVITY 2
Modify the previous program to display 9 on the 7-segment.
ACTIVITY 3
Using look-up table write a subroutine that displays the contents of R21 on the 7-segment.
ACTIVITY 4 (ADVANCED)
a) Now connect two 7-segments to the same port of AVR, as shown below.
PORTx.0
PORTx.1
PORTx.2
PORTx.3
PORTx.4
PORTx.5
PORTx.6
PORTx.7
AVR
A
B
C
D
E
F
G
DP
A
B
C
D
E
F
G
DP
Common Cathod
Common
Cathod
PORTB.0
PORTB.1
100
100
b) Display 23 by scanning on the 7-segments.
…
L1:
LDI
CALL
LDI
OUT
CALL
R20,2
DISPLAY_ON_7SEGMENT
R16,0x01
PORTB, R16
DELAY_10ms
;wait for a while
LDI
R20,3
CALL
DISPLAY_ON_7SEGMENT
LDI
R16,0x02
OUT
PORTB, R16
CALL
DELAY_10ms
;wait for a while
RJMP L1