--         file     : jpwm3.jal
--       author     : Toon Beerten
--         date     : 21-August-2005
--      purpose     : PWM-Output on 3 pins of a PIC for RGB LED
--      credits     : based upon the one-pin PWM output library of
--                    Branko Karaklajic
-- Copyright (C) 2005 Toon Beerten
--
-- This library is free software; you can redistribute it and/or
-- modify it under the terms of the GNU Library General Public
-- License as published by the Free Software Foundation; either
-- version 2 of the License, or (at your option) any later version.
--
-- This library 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
-- Library General Public License for more details.
-- 
-- You should have received a copy of the GNU Library General Public
-- License along with this library; if not, write to the
-- Free Software Foundation, Inc., 59 Temple Place - Suite 330,
-- Boston, MA  02111-1307, USA.

-- defining which pins are activated for PWM
var volatile bit PWM_outR1_pin 		is pin_b6                    -- Red
var volatile bit PWM_out_pinR1_direction  is pin_b6_direction
var volatile bit PWM_outG1_pin 		is pin_b5                    -- Green
var volatile bit PWM_out_pinG1_direction  is pin_b5_direction
var volatile bit PWM_outB1_pin 		is pin_b4                    -- Blue
var volatile bit PWM_out_pinB1_direction  is pin_b4_direction
-- end defining pins

-- PWM procedure for 3 RGB pins. First three bytes must be within 1 - 255. Not 0
procedure PWM_OUT(byte in PWMR1, byte in PWMG1,byte in PWMB1,byte in TRA) is

var byte LoPWM1         -- LoPWM : time color is high
var byte LoPWM2
var byte LoPWM3
var byte LoPWM4
var byte HiPWM1
var byte HiPWM2
var byte HiPWM3
var bit firstR1 = low   -- bits to see which colors need to be
var bit firstG1 = low   -- turned off first and second
var bit firstB1 = low
var bit secondR1 = low
var bit secondG1 = low
var bit secondB1 = low

-- "dirty" fix if some values are equal, what whould
-- cause problems in algorithm
if PWMR1 == PWMG1 & PWMR1 == PWMB1 then
    if PWMB1 > 2 then
       PWMB1 = PWMB1 - 2
       PWMG1 = PWMG1 - 1
    elsif PWMB1 <= 2 then
       PWMG1 = PWMB1 + 1
       PWMR1 = PWMR1 + 2
    end if
elsif PWMR1 == PWMG1 then
    if PWMR1 > 2  then
       PWMG1 = PWMG1 - 1
    elsif PWMR1 <= 2 then
       PWMR1 = PWMR1 + 1
    end if
elsif PWMR1 == PWMB1 then
    if PWMR1 > 2  then
       PWMB1 = PWMB1 - 1
    elsif PWMR1 <= 2 then
       PWMR1 = PWMR1 + 1
    end if
elsif PWMB1 == PWMG1 then
    if PWMB1 > 2   then
       PWMG1 = PWMG1 - 1
    elsif PWMB1 <= 2 then
       PWMG1 = PWMG1 + 1
    end if
end if

-- determine order when colors should be turned off
if PWMR1 > PWMG1 then
   if PWMG1 > PWMB1 then
      LoPWM1 =  PWMB1
      LoPWM2 =  PWMG1
      LoPWM3 =  PWMR1
      firstB1 = high
      secondG1 = high
   elsif PWMG1 < PWMB1 & PWMR1 < PWMB1 then
      LoPWM1 =  PWMG1
      LoPWM2 =  PWMR1
      LoPWM3 =  PWMB1
      firstG1 = high
      secondR1 = high
   elsif PWMG1 < PWMB1 & PWMR1 > PWMB1 then
      LoPWM1 =  PWMG1
      LoPWM2 =  PWMB1
      LoPWM3 =  PWMR1
      firstG1 = high
      secondB1 = high
   end if
elsif  PWMR1 < PWMG1 then
   if PWMG1 < PWMB1 then
      LoPWM1 =  PWMR1
      LoPWM2 =  PWMG1
      LoPWM3 =  PWMB1
      firstR1 = high
      secondG1 = high
   elsif PWMG1 > PWMB1 & PWMR1 < PWMB1 then
      LoPWM1 =  PWMR1
      LoPWM2 =  PWMB1
      LoPWM3 =  PWMG1
      firstR1 = high
      secondB1 = high
   elsif PWMG1 > PWMB1 & PWMB1 < PWMR1 then
      LoPWM1 =  PWMB1
      LoPWM2 =  PWMR1
      LoPWM3 =  PWMG1
      firstB1 = high
      secondR1 = high
   end if
end if

LoPWM4 = LoPWM3            -- make wait times relative to each other
LoPWM3 = LoPWM3 - LoPWM2
LoPWM2 = LoPWM2 - LoPWM1

-- PWM_out_pinR1_direction = output  --use if not already in main program
-- PWM_out_pinG1_direction = output
-- PWM_out_pinB1_direction = output

assembler
	
	local PWMa
	local PWMb
	local PWMtra
	local PWMend

	bsf status, status_rp0
	movlw 0b_1000_0011
	OPTION
	bcf status, status_rp0

  movf LoPWM1,W
	sublw 0xFF
        movwf HiPWM1
  movf LoPWM2,W
	sublw 0xFF
        movwf HiPWM2
  movf LoPWM3,W
	sublw 0xFF
        movwf HiPWM3

PWMa:
	bcf INTCON, intcon_t0if
	movf HiPWM1, W
	movwf TMR0
PWMb:

  -- turn all colors on
  bsf PWM_outR1_pin
  bsf PWM_outG1_pin
  bsf PWM_outB1_pin
  call PWMtra
  
 	-- turn first color off
 	btfsc firstR1          -- if firstR1 = 0 skip next line
  bcf PWM_outR1_pin
  btfsc firstG1
	bcf PWM_outG1_pin
	btfsc firstB1
  bcf PWM_outB1_pin
  -- second wait time
 	movf HiPWM2, W
	movwf TMR0
	call PWMtra
	
	-- turn second color off
	btfsc secondR1          -- if secondR1 = 0 skip next line
  bcf PWM_outR1_pin
  btfsc secondG1
	bcf PWM_outG1_pin
	btfsc secondB1
  bcf PWM_outB1_pin
 	-- third wait time
 	movf HiPWM3, W
	movwf TMR0
	call PWMtra
	
	-- turn third color off = turn all off
	bcf PWM_outR1_pin
	bcf PWM_outG1_pin
  bcf PWM_outB1_pin
	-- fourth wait time when all colors are 0
	movf LoPWM4, W
	movwf TMR0
	call PWMtra
	
	-- repeat all until TRA 0 is
	decfsz TRA,f
	goto PWMa
	goto PWMend


PWMtra:
	btfss INTCON, intcon_t0if  -- wait until overflow happens
	goto PWMtra
	bcf INTCON, intcon_t0if    -- set overflow bit back to 0
	return
	
PWMend:

end assembler

-- PWM_out_pinR1_direction = input  --use if not already in main program
-- PWM_out_pinG1_direction = input
-- PWM_out_pinB1_direction = input

end procedure