Code snippets for Dumblebots AVR Assembly blog

a.txt

instruction             operand1, operand2...           ; remarks

avr_gcc_assemble.sh

avr-gcc -mmcu=atmega328P -nostdlib -g build/main.s -o build/main.o

avr_gcc_install.sh

apt-get install gcc-avr

avr_gcc_link.sh

avr-ld -o build/main.elf build/main.o

avr_gcc_objcopy.sh

avr-objcopy build/main.elf build/main.hex -O ihex

avr_gcc_preprocess.sh

avr-gcc -DF_CPU=16000000UL -mmcu=atmega328P -E main.S -o build/main.s

avr_gcc_target_help.sh

avr-gcc --target-help

avr_gcc_version.sh

avr-gcc --version

avr_size.sh

avr-size --format=avr --mcu=atmega328p build/main.elf

avrdude_info.sh

avrdude

avrdude_install.sh

apt-get install avrdude

avrdude_targets.sh

avrdude -c -h

avrdude_upload_arduino.sh

avrdude -v -p atmega328p -c arduino -P COM1 -b 19200 -U flash:w:build/main.hex:i

avrdude_upload_stk500.sh

avrdude -v -p atmega328p -c stk500 -P COM1 -b 19200 -U flash:w:build/main.hex:i

b.txt

LDI         R16, 2                                      ; load the constant 2 to register 16 
LDI         R17, 3                                      ; load the constant 3 to register 17 
ADD         R16, R17                                    ; add the values and store the sum in register 16
ANDI        R16, 1                                      ; perform logical and with constant 1 (only preserved bit 0)
ADD         R16, R16                                    ; left shift the value once (bit 0 is moved to bit 1)
SBI         _SFR_IO_ADDR (DDRB), 1                      ; put pin 1 of port B in output mode
OUT         _SFR_IO_ADDR (PORTB), R16                   ; write out the value of R16 to port B 

c.txt

; some code before the loop

LDI         R16, 5                                  ; load the constant 5 to register 16

_loopstart:
; some code within the loop
DEC         R16                                     ; decrement the value in register 16
BRNE        _loopstart                              ; if the result of the previous operation was not 0, jump to _loopstart
_loopend:

; some code after the loop

d.txt

                ; some code before the loop

                LDI         R16, 5                      ; load the constant 5 to register 16

_loopstart:     ; some code within the loop
                DEC         R16                         ; decrement the value in register 16
                BRNE        _loopstart                  ; jump to _loopstart if the previous result was not 0
_loopend:

                ; some code after the loop

e.txt

                .global _loopstart
                .global _loopend
                
                ; some code before the loop

                LDI         R16, 5                      ; load the constant 5 to register 16

_loopstart:     ; some code within the loop
                DEC         R16                         ; decrement the value in register 16
                BRNE        _loopstart                  ; jump to _loopstart if the previous result was not 0
_loopend:

                ; some code after the loop

f.txt

MSG:            .ASCII      "Hello World"
MSGEND:         .EQU        MSGLEN, (MSGEND - MSG)

g.txt

.section .data

.section .bss

.section .text
                .org        0x00

                LDI         R16, 2                      ; load the constant 2 to register 16
                LDI         R17, 3                      ; load the constant 3 to register 17
                ADD         R16, R17                    ; add the values and store the sum in register 16
                ANDI        R16, 1                      ; perform logical and with constant 1 (only preserves bit 0)
                ADD         R16, R16                    ; left shift the value once (bit 0 is moved to bit 1)
                SBI         _SFR_IO_ADDR (DDRB), 1      ; put pin 1 on port b in output mode
                OUT         _SFR_IO_ADDR (PORB), R16    ; write out the value of R16 to port B

h.txt

#include <avr/io.h>

.section .data

.section .bss

.section .text
                .org 0x00

i.txt

SBI         _SFR_IO_ADDR (DDRB), PB5

j.txt

LDI         R16, 0b00100000
LDI         R17, 0b00100000
OUT         0x24, R16

k.txt

LDI         R16, 0b00100000
LDI         R17, 0b00100000
OUT         0x04, R16

l.txt

LDI         R16, (1<<PB5)
LDI         R17, (1<<PB5)
OUT         _SFR_IO_ADDR (DDRB), R16

m.txt

LOOP:           OUT         _SFR_IO_ADDR (PORTB), R16
                EOR         R16, R17
                RJMP        LOOP

n.txt

DELAY_1S:
                ; some code to perform the delay
                RET

o.txt

                LDI         R20, 255                    ; 1 cycle (IGNORED)
LOOP:           DEC         R20                         ; 1 cycle * 255 = 255 cycles
                NOP                                     ; 1 cycle * 255 = 255 cycles
                BRNE        LOOP                        ; 2 cycles * 255 = 510 cycles
                                                        ; -1 cycle on last iteration (IGNORED)

p.txt

DELAY_1S:

                LDI         R20, 64                     ; 1 cycle * 1 = 1 cycle (IGNORED)
DELAY1:         LDI         R21, 250                    ; 1 cycle * 64 = 64 cycles
DELAY2:         LDI         R22, 250                    ; 1 cycle * 16,000 = 16,000 cycles
DELAY3:         DEC         R22                         ; 1 cycle * 4e6 = 4e6 cycles
                NOP                                     ; 1 cycle * 4e6 = 4e6 cycles
                BRNE        DELAY3                      ; 2 cycles * 4e6 = 8e6 cycles
                                                        ; -1 cycle * 16,000 = -16,000 cycles
                DEC         r21                         ; 1 cycle * 16,000 = 16,000 cycles
                BRNE        DELAY2                      ; 2 cycles * 16,000 = 32,000 cycles
                                                        ; -1 cycle * 64 = -64 cycles
                DEC         r20                         ; 1 cycle * 64 = 64 cycles
                BRNE        DELAY1                      ; 2 cycle * 64 = 128 cycles
                                                        ; -1 cycle * 64 = -64 cycles
                RET

q.txt

LOOP:           OUT         _SFR_IO_ADDR (PORTB), R16
                EOR         R16, R17
                RCALL       DELAY_1S  
                RJMP        LOOP

r.txt

#include <avr/io.h>

.section .data

.section .bss

.section .text
                .org 0x00
                LDI         R16, (1<<PB5)
                LDI         R17, (1<<PB5)
                OUT         _SFR_IO_ADDR (DDRB), R16

LOOP:           OUT         _SFR_IO_ADDR (PORTB), R16
                RCALL       DELAY_1S
                EOR         R16, R17
                RJMP        LOOP

DELAY_1S:

                LDI         R20, 64
DELAY1:         LDI         R21, 250
DELAY2:         LDI         R22, 250
DELAY3:         DEC         R22
                NOP
                BRNE        DELAY3

                DEC         r21
                BRNE        DELAY2

                DEC         r20
                BRNE        DELAY1

                RET

serial_ports_unix.sh

ls /dev/tty*