How to Setup IR Remote Decoder (AVR ASM)
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;*************************************************************************** ;* A P P L I C A T I O N N O T E F O R T H E A V R F A M I L Y ;* ;* Number : AVR410 ;* File Name :"rc5.asm" ;* Title :RC5 IR Remote Control Decoder ;* Date :97.08.15 ;* Version :1.0 ;* Target MCU :AT90S1200 ;* ;* DESCRIPTION ;* This Application note describes how to decode the frequently used ;* RC5 IR remote control protocol. ;* ;* The timing is adapted for 4 MHz crystal ;* ;*************************************************************************** .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 fault: ser command ;Both "command" and "system" ser system ;0xFF indicates failure ret |