; Uses the PIC12F675 (PIC12F629 should work too)
;
; IR command sequence for AF & shutter release :
; - starting pulse 2250us (IR on) OR: 2ms on
; - pause 27600us (IR off) 28ms off
; - 650us pulse 0.5ms on
; - pause 13750us 1.5ms off
; - 575us pulse 0.5ms on
; - pause 3350us 3.5ms off
; - pulse 650us 0.5ms on
; - pause 63msec 60ms off pause
; - repeat the above sequence one time
;
; The IR on-pulses need to be gated/modulated with 40kHz,
; i.e. on for 12.5us off for 12.5us
;
; The PIC runs on its 4MHz internal oscillator, so one
; instruction cycle takes 1.0us (1/4th of clock)
;
;==============================================

list p=12f675
include "P12F675.INC"
radix dec

; config:
; !MCLR pin off, no code-protect, watchdog off
; internal 4MHz clock with no output (for debug: _INTRC_OSC_CLKOUT,
; scope 1MHz signal on pin 3)
; power-up timer (72ms) on (important for power
; switch debounce!)
; brownout detect on (for additional power switch debounce, but, you
; might also disable this to conserve power)

__CONFIG _MCLRE_OFF & _INTRC_OSC_NOCLKOUT & _CP_OFF & _CPD_OFF & _WDT_OFF & _BODEN_ON & _PWRTE_ON

;------------- ISR VECTORS

org 0x000 ; startup
goto main
org 0x004 ; interrupt service
retfie



;------------- VARS : variables into file register bank

cblock 0x20 ; (bank 0 0x20-0x5f are free for use)
pulsecntr ; 0x20 counter for main pulses (pulselen = 25us * pulsecounter)
waitcntr ; 0x21 counter for pauses (pauselen = 25us * waitcntr * pulsecntr)
waittmp ; 0x22 temporary storage for waitcntr
maincntr ; 0x23 how many times the sequence has been sent
endc


LED_BIT equ 2 ; IR LED placed on pin 5 (GP2)

;------------- FUNCTIONS
;
; Function doLedToggling
;
; IR LED toggler, toggle once at 40kHz i.e. with 25us period
;
; Input: W contains counter (>0) with the number of toggles
; to perform
; Return: nothing
; Time: W*25us + 2us
;
doLedToggling
movwf pulsecntr ; store argument W into pulsecounter

doLedToggLoop
; ON for 13us
bsf GPIO,LED_BIT ; 1/13us GPx high to enable IR LED
nop ; 2/13us just use NOPs instead of complicated loop,
nop ; might even be a bit less powerhungry
nop
nop ; 5/13us
nop
nop
nop
nop
nop ; 10/13us
nop
nop
nop ; 13/13us

; OFF for 12us total
bcf GPIO,LED_BIT ; 1/12us GPx low to disable IR LED
nop ; 2/12us
nop
nop
nop ; 5/12us
nop
nop
nop
nop ; 9/12us
decfsz pulsecntr,F ; 10/12us (or +2us on exit)
goto doLedToggLoop ; 11&12/12us (+2us)
return ; (+2us)

;
; Function do25usPauses
;
; Do a longer pause, duration is approximately in multiples of 25us
;
; Input: W contains outer counter ('pulsecounter'), >0
; waitcntr contains inner counter, >0
;
; Return: nothing
; Time: (25us*waitcntr + 3us)*W + 4us
;
do25usPauses
movwf pulsecntr ; store argument W into pulsecounter
movf waitcntr,W ; load waitcntr argument to W
movwf waittmp ; place waitcntr into actual temp counter
do25outer
do25inner ; delay for 25us
nop
nop
nop
nop
nop ; 5us
nop
nop
nop
nop
nop ; 10us
nop
nop
nop
nop
nop ; 15us
nop
nop
nop
nop
nop ; 20us
nop
nop ; 22us
decfsz waittmp,F ; +1us (+2us on end)
goto do25inner ; +2us
movwf waittmp ; put back waitcntr into actual counter
; (also +1us on end so condition check always takes 3us)

decfsz pulsecntr,F
goto do25outer

return

;------------- MAIN

main
clrwdt

; init GPIO pins (PIC12F675 - disable analog inputs)
bcf STATUS,RP0 ; bank 0 (GPIO)
clrf GPIO ; init GPIO state to 0
movlw 07h ; GP<0:2> to digital IO
movwf CMCON ; comparator off
bsf STATUS,RP0 ; bank 1 (ANSEL,TRISIO)
clrf ANSEL ; digital IO only, no analog
clrf TRISIO ; all pins as output

; read the oscillator calibration data (datasheet, example 9-1)
; (part of last mem localtion 0x3FF, is for example 0x34B4)
bsf STATUS, RP0 ; bank 1 (OSCCAL)
call 3FFh ; get cal value
movwf OSCCAL ; calibrate

; initialize for entire sequence
bcf STATUS,RP0 ; bank 0 (GPIO)
initOneFullSeq
movlw 2 ; send same sequence twice
movwf maincntr

performSequences
decfsz maincntr,W ; if maincntr==1, do a longer pause
goto doOneSeq ; skip pause, send directly
; long pause of 63000us between first and second time sending
; (25us*waitcntr + 3us)*W + 4us : (25*15+3)*167+4=63130us
movlw 15
movwf waitcntr
movlw 167
call do25usPauses

; send the sequence
; ON 2250us = 90 * 25us
doOneSeq
movlw 90
call doLedToggling
; Off 27600us-(ON call 3us + w/f 3us + OFF call 2us)=27592us
; (25us*waitcntr + 3us)*W + 4us : (25*15+3)*73+4=27598
movlw 15
movwf waitcntr
movlw 73
call do25usPauses
; ON 650us = 26 * 25us
movlw 26
call doLedToggling
; Off 1375us-(3us+3us+2us)=1367us : (25*18+3)*3+4=1363
movlw 18
movwf waitcntr
movlw 3
call do25usPauses
; ON 575us = 21 * 25us
movlw 21
call doLedToggling
; Off 3350us-(3us+3us+2us)=3342us : (25*2+3)*63+4=3343
movlw 2
movwf waitcntr
movlw 63
call do25usPauses
; ON 650us = 26 * 25us
movlw 26
call doLedToggling
decfsz maincntr,F
goto performSequences

; to completely stop:
sleep
; or, to run in continuos shooting mode, do
; first a quite long pause...
;movlw 20
;movwf waitcntr
;movlw 167
;call do25usPauses
; ...and then restart
;goto initOneFullSeq

end