紅外遙控的例程--AVR單片機

include "1200def.inc"
.device AT90S1200
.equ INPUT  =2 PD2
.equ SYS_ADDR =0 The system address
.def S =R0
.def inttemp =R1
.def ref1 =R2
.def ref2 =R3
.def temp =R16
.def timerL =R17
.def timerH =R16
.def system =R19
.def command =R20
.def bitcnt =R21
cseg
.org 0
rjmp reset

;********************************************************************
;* "TIM0_OVF" - Timer/counter overflow interrupt handler
;*
;* The overflow interrupt increments the "timerL" and "timerH"
;* every 64us and 16,384us.
;*
;* Number of words: 7
;* Number of cycles: 6 + reti
;* Low registers used: 1
;* High registers used: 3
;* Pointers used: 0
;********************************************************************
.org OVF0addr
TIM0_OVF: in S,sreg
  inc timerL  Updated every 64us
  inc inttemp
  brne TIM0_OVF_exit

  inc timerH

TIM0_OVF_exit: out sreg,S
  reti



;********************************************************************
;* Example program
;*
;* Initializes timer, ports and interrupts.
;*
;* Calls "detect" in an endless loop and puts the result out on
;* port B.
;*
;* Number of words: 16
;* Low registers used: 0
;* High registers used: 3
;* Pointers used: 0
;********************************************************************

reset:  ldi   temp,low(RAMEND) Initialize stackpointer
  out SPL,temp   
  ldi   temp,high(RAMEND)  Commented out since 1200 does not hae SRAM
  out SPH,temp
 
  ldi temp,1  Timer/Counter 0 clocked at CK
  out TCCR0,temp

  ldi temp,1<<TOIE0 Enable Timer0 overflow interrupt
  out TIMSK,temp

  ser temp  PORTB as output
  out DDRB,temp

  sei   Enable gobal iterrupt


main:  rcall detect  Call RC5 detect routine

  cpi system,SYS_ADDR Respponds only at the specified address
  brne release

  andi command,0x3F Remove control bit
  out PORTB,command

  rjmp main


release: clr command  Clear PORTB
  out PORTB,command
  rjmp main



;********************************************************************
;* "detect" - RC5 decode routine
;*
;* This subroutine decodes the RC5 bit stream applied on PORTD
;* pin "INPUT". 
;*
;* If successe: The command and system address are
;*  returned in "command" and "system".
;*  Bit 6 of "command" holds the toggle bit.
;*
;* If failed:  $FF in both "system" and "command"
;*
;* Crystal frequency is 4MHz
;*
;* Number of words: 72
;* Low registers used:  3
;* High registers used:  6
;* Pointers used:  0
;********************************************************************
detect:  clr inttemp
  clr timerH

detect1: clr timerL

detect2: cpi timerH,8 If line not idle within 131ms
  brlo dl1
  rjmp fault    then exit

dl1:  cpi timerL,55 If line low for 3.5ms
  brge start1     then wait for start bit

  sbis PIND,INPUT If line is
  rjmp detect1     low  - jump to detect1
  rjmp detect2     high - jump to detect2


start1:  cpi timerH,8 If no start bit detected
  brge fault  within 130ms then exit

  sbic PIND,INPUT Wait for start bit
  rjmp start1


  clr timerL  Measure length of start bit
  
start2:  cpi timerL,17 If startbit longer than 1.1ms,
  brge fault     exit

  sbis PIND,INPUT
  rjmp start2
     Positive edge of 1st start bit

  mov temp,timerL timer is 1/2 bit time
  clr timerL

  mov ref1,temp
  lsr ref1
  mov ref2,ref1
  add ref1,temp ref1 = 3/4 bit time
  lsl temp
  add ref2,temp ref2 = 5/4 bit time


start3:  cp timerL,ref1 If high periode St2 > 3/4 bit time
  brge fault     exit

  sbic PIND,INPUT Wait for falling edge start bit 2
  rjmp start3

  clr timerL
  ldi bitcnt,12 Receive 12 bits
  clr command
  clr system


sample:  cp timerL,ref1 Sample INPUT at 1/4 bit time
  brlo sample

  sbic PIND,INPUT
  rjmp bit_is_a_1 Jump if line high


bit_is_a_0: clc   Store a '0'
  rol command
  rol system

     Synchronize timing
bit_is_a_0a: cp timerL,ref2 If no edge within 3/4 bit time
  brge fault     exit
  sbis PIND,INPUT Wait for rising edge
  rjmp bit_is_a_0a in the middle of the bit

  clr timerL
  rjmp nextbit

bit_is_a_1: sec   Store a '1'
  rol command
  rol system
     Synchronize timing
bit_is_a_1a: cp timerL,ref2 If no edge within 3/4 bit time
  brge fault     exit
  sbic PIND,INPUT Wait for falling edge
  rjmp bit_is_a_1a in the middle of the bit

  clr timerL

nextbit: dec bitcnt  If bitcnt > 0
  brne sample     get next bit


;All bits sucessfully received!
  mov temp,command Place system bits in "system"
  rol temp
  rol system
  rol temp
  rol system

  bst system,5 Move toggle bit
  bld command,6 to "command"

     Clear remaining bits
  andi command,0b01111111
  andi system,0x1F

  ret