/*

  Motion sensor program in AVR assembly.
  See motion.S for code.

*/

asm-motion-sensor.ino

diagram.json

#define __SFR_OFFSET 0

#include "avr/io.h"

.global main

main:
  sbi   DDRB, 5     ; Set PB5 as output

motion:
  sbic  PINB, 5
  sbi   PINB, 5
  sbic  PIND, 7
  jmp   light
  jmp   motion

light:
  sbis  PINB, 5
  sbi   PINB, 5     ; Toggle PINB
  ldi   r25, hi8(14000)
  ldi   r24, lo8(14000)
  call  delay_ms
  jmp   motion

delay_ms:
  ; Delay about (r25:r24)*ms. Clobbers r30, and r31.
  ; One millisecond is about 16000 cycles at 16MHz.
  ; The inner loop takes 4 cycles, so we repeat it 3000 times
  ldi   r31, hi8(3000)
  ldi   r30, lo8(3000)
1:
  sbiw    r30, 1
  brne    1b
  sbiw    r24, 1
  brne    delay_ms
  ret