Progrsmming arduino with assembly

Projects Interfacing w/ Software on the Computer
3

You don't need to use inline, you can add standard assembly files (using the .S file extension) to your sketch in Arduino IDE.

Here's something I just cobbled together. It's the only time I've messed with assembly so I'm sure there's a better way to do this but it does work:

blink.ino:

extern "C" {
  // function prototypes
  void start();
  void blink();
}

void setup() {
  start();
}

void loop() {
  blink();
}

blink.S:

; Blink LED on PB5(Arduino Uno pin 13)
; http://forum.arduino.cc/index.php?topic=159572#msg1194604

#define __SFR_OFFSET 0
  
#include "avr/io.h"

.global start
.global blink

start:
  sbi   DDRB,5  ; Set PB5 as output
  ret

blink: 
  ldi   r20,250 ; Set the delay duration in ms. Maximum value is 255.
  call  delay_n_ms
  sbi   PORTB,5 ; Set PB5 HIGH
  ldi   r20,250
  call  delay_n_ms
  cbi   PORTB,5 ; Set PB5 LOW
  ret

delay_n_ms:
  ; Delay about r20*1ms. Destroys r20, r30, and r31.
  ; One millisecond is about 16000 cycles at 16MHz.
  ; The basic loop takes about 5 cycles, so we need about 3000 loops.
  ldi   31, 3000>>8 ; high(3000)
  ldi   30, 3000&255  ; low(3000)
delaylp:
  sbiw    r30, 1
  brne    delaylp
  subi    r20, 1
  brne    delay_n_ms
  ret

I seem to remember there was some work done on this in the last year or two so I'd recommend using a recent version of the Arduino IDE.