Started working on 7 segment display

7_segment_display/Makefile

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+BINARY=segment
+
+AS=avr-as
+LD=avr-ld
+OBJCOPY=avr-objcopy
+AVRDUDE=avrdude
+
+AVRDUDE_CONFIG=/etc/avrdude.conf
+
+TTY=/dev/ttyACM0
+
+ARCH=atmega328p
+
+build:
+	$(AS) -g -mmcu=$(ARCH) -o $(BINARY).o $(BINARY).s
+	$(LD) -o $(BINARY).elf $(BINARY).o
+	$(OBJCOPY) -O ihex -R .eeprom $(BINARY).elf $(BINARY).hex	
+
+upload:
+	$(AVRDUDE) -C $(AVRDUDE_CONFIG) -p $(ARCH) -c arduino -P $(TTY) -b 115200 -D -U flash:w:$(BINARY).hex:i
+
+run: build upload
+	
+clean:
+	ls | grep $(BINARY) | grep -v *.s | xargs rm -f --

7_segment_display/segment.s

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+; For function calling conventions I will stick to this one:
+; http://www.nongnu.org/avr-libc/user-manual/FAQ.html
+; (see 'Function call conventions')
+
+.equ RAMEND, 0x08FF
+
+.equ SREG, 0x3F
+.equ SPL,  0x3D
+.equ SPH,  0x3E
+
+; This memory mappings can be found in iom328p.h header file.
+
+.equ PORTD, 0x0B
+.equ DDRD,  0x0A
+
+.org 0x0000
+
+    rjmp INIT
+
+INIT:
+
+    ; Description:
+    ; -----------
+    ;
+    ;  Reset the system status in SREG, initialize the stack using SPL and 
+    ;  SPH and set output PINs on PORTB. We need 7 output PINs for the 7 
+    ;  segment display so we  will use DIGITAL PINs 0-6.
+
+    clr r16
+    out SREG, r16
+
+    ldi r16, lo8(RAMEND)
+    out SPL, r16
+
+    ldi r16, hi8(RAMEND)
+    out SPH, r16
+
+    ldi r16, 0x7F 
+    out DDRD, r16
+
+LOOP:
+
+    ; Description:
+    ; -----------
+    ; 
+    ;  COUNTER will implement a loop that counts from 0 to 9 and calls the ENCODE
+    ;  subroutine to translate the binary number into a 7 segment displayable
+    ;  number. After the subroutine is finished, WAIT will be called because we
+    ;  want some delay between the numbers.
+
+    clr r16
+
+COUNTER:
+
+    mov r24, r16
+    call ENCODE
+
+    call WAIT
+
+    inc r16
+    cpi r16, 0x0A
+    brne COUNTER
+     
+    rjmp LOOP
+
+ENCODE:
+
+    ret
+
+WAIT:
+
+    ret