;
; Packard Bell Infrared Remote receiver
;
; Copyright (C) 2000-1 Tom Parker   (tom-hc11@wiresncode.com)
; Portions Copyright (C) 2000 Paul Stoffregen (paul@pjrc.com)
;
; This program is free software; you can redistribute it and/or
; modify it under the terms of the GNU General Public License
; as published by the Free Software Foundation; either version 2
; of the License, or (at your option) any later version.
;
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
; GNU General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with this program; if not, write to the Free Software
; Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
;
; Author's note: This is free software, for commerical use I would
; appreciate some recognition though.  If you are using this and like
; it send me some email or a postcard.  Code changes for inclusion
; are also welcome.
;
; Tom Parker, PO Box 2165, Fitzroy, VIC, 3065, AUSTRALIA (tom@wiresncode.com)
;

.include "pbir.h"

;
;---------------------------------------------------------
; 
; 
;-*                *------------------*       *-------*               *-------*
; |                |                  |       |       |               |       |
; |                |                  |       |       |               |       |
; *----------------*                  *-------*       *---------------*       *---
; ^                                   ^               ^                       ^
; |             preamble              |      zero     |              one      |
;
;
minpre = 0x3080			;Minimum preamble length
maxpre = 0x3100 		;Maximum preamble length
minzero = 0x03f0		;Minimum zero pulse length
maxzero = 0x0430		;Maximum zero pulse length
minone = 0x07f0			;Minimum one pulse length
maxone = 0x0830			;Maximum one pulse length

; typical sequence
;
; 30 A0 
; 04 0F 04 0F 03 F9 04 10 08 22 03 FB 04 25 03 F8 08 12 08 0D 08 21 08 11 04 0E 08 23 07 FB 
; 08 20 08 13 04 0C 04 0E 08 0F 03 FC 04 10 04 0D 04 11 04 0E 07 FB 08 22 04 0E 08 10 08 23
;---------------------------------------------------------;
	.module pbir_asm
	.area	code (REL)
;
;Initialisation
;
pbir_init:
	mov	irmesg+0, #0
	mov	irmesg+1, #0
	mov	irbitcnt, #0
	mov	ircode, #0xff
	clr	irprefound
	ret

;
;save current timer & enable interrupts
;
pbir_start:
	mov	irtimersample+0, th0
	mov	irtimersample+1, tl0
	ret

;
;interrupt service routine
;
pbir_isr:
	clr	ex0
	push	acc
	clr	rs1			;register bank 1
	setb	rs0
	clr	tr0
	mov	r6, th0			;save new timer sample
	mov	r7, tl0
	setb	tr0
	mov	a, r6
	mov	r4, a
	mov	a, r7			;subtract lsb from previous
	clr	c
	subb	a, irtimersample+1
	jnc	i0noborrow
	dec	r4			;borrow from msb
i0noborrow:
	mov	r5, a
	mov	a, r4			;subtract msb from previous
	clr	c
	subb	a, irtimersample+0
	mov	r4, a
	mov	irtimersample+0, r6
	mov	irtimersample+1, r7
i0zmsbmax:
	add	a, #255 - (maxzero >> 8)
	jc	i0omsbmax                ;check zero msb maximum
	inc	a
	jnz	i0zmsbmin
	mov	a, r5			;check lsb maximum
	add	a, #255 - (maxzero & 0x00ff)
	jc	i0omsbmax
i0zmsbmin:
	mov	a, r4
	add	a, #255 - (minzero >> 8) + 1
	jnc	i0invalid		;check msb minimum
	jnz	i0zerofound
	mov	a, r5			;check lsb minimum
	clr	c
	subb	a, #(minzero & 0x00ff)
	jc	i0invalid
i0zerofound:
	jnb	irprefound, i0invalid
	clr	c
	sjmp	i0datafound
i0invalid:
	clr	irprefound
	ajmp	i0done
i0omsbmax:
	mov	a, r4
	add	a, #255 - (maxone >> 8)
	jc	i0pmsbmax                ;check zero msb maximum
	inc	a
	jnz	i0omsbmin
	mov	a, r5			;check lsb maximum
	add	a, #255 - (maxone & 0x00ff)
	jc	i0pmsbmax
i0omsbmin:
	mov	a, r4
	add	a, #255 - (minone >> 8) + 1
	jnc	i0invalid		;check msb minimum
	jnz	i0onefound
	mov	a, r5			;check lsb minimum
	clr	c
	subb	a, #(minone & 0x00ff)
	jc	i0invalid
i0onefound:
	jnb	irprefound, i0invalid
	setb	c
i0datafound:
	mov	a, irmesg+0
	rlc	a
	mov	irmesg+0, a
	mov	a, irmesg+1
	rlc	a
	mov	irmesg+1, a
	dec	irbitcnt
	mov	a, irbitcnt
	jz	i0mesg			;whole mesg?
	cjne	a, #16, i0done		;first 2 bytes?
	mov	a, irmesg+1		;check for control ID
	cjne	a, #0x08, i0invalid
	mov	a, irmesg+0
	cjne	a, #0xf7, i0invalid
	sjmp	i0done
i0mesg:
	mov	a, ircode		;check previous mesg was received
	cjne	a, #0xff, i0invalid
	mov	a, irmesg+0		;check new mesg
	xrl	a, #0xff
	cjne	a, irmesg+1, i0invalid
	mov	ircode, a
	clr	irprefound	
	sjmp	i0done
i0pmsbmax:
	mov	a, r4
	add	a, #255 - (maxpre >> 8)
	jc	i0invalid                ;check msb maximum
	inc	a
	jnz	i0pmsbmin
	mov	a, r5			;check lsb maximum
	add	a, #255 - (maxpre & 0x00ff)
	jc	i0invalid
i0pmsbmin:
	mov	a, r4
	add	a, #255 - (minpre >> 8) + 1
	jnc	i0invalid		;check msb minimum
	jnz	i0prefound
	mov	a, r5			;check lsb minimum
	clr	c
	subb	a, #(minpre & 0x00ff)
	jc	i0invalid
i0prefound:
	setb	irprefound		;flag preamble and clear message buffer
	mov	irmesg+0, #0
	mov	irmesg+1, #0
	mov	irbitcnt, #32
i0done:
	pop	acc
	setb	ex0
	clr	rs1			;register bank 0
	clr	rs0
	reti