Port indexing & PWM for LED fade

[richard]

from the book :- pwm pin,duty,cycle [ it says pin can be a constant or var from 0 to 15] whwre portb.0 = 0
therefore this may work , I have not tested it

for Avar=0 to 7
cycle=4
for Duty=0 to 220 step 1
pwm Avar,Duty,cycle
next Duty
cycle=1
for Duty=220 to 0 step -2
pwm Avar,Duty,cycle
next Duty
low Avar ;end of routine

[MOUNTAIN747]

Richard, it worked, Thanks, although it raises as many questions as it answers.

This works

        for Avar= 0 to 7   
                cycle=4    ;cycle is number of cycles of pulse    
            for Duty=0 to 220 step 1
                pwm Avar,Duty,cycle
                next Duty
                cycle=2    ;cycle is number of cycles of pulse
            for Duty=220 to 0 step -2
                pwm Avar,Duty,cycle
                next Duty
                low Avar
        next Avar

This works, on PortB, why? This should work on PortA. PortB, I tought, would be 8-15.
Yes I had used ‘Symbol Port_Pin=PortB’ which would set PortB to 0-7 but now I’m not using Port_Pin in the routine. I remember there is a file somewhere that sets the port numbers but I can ‘t remember what or where it is. I may have changed the default numbering over the years. Oh well, it works and now and I’m happy. I’m surprised I had not seen an example for PWM that used this method to cycle through LEDs. Too easy! thank you both for your input!

; 16F886
@ DEVICE INTRC_OSC,MCLR_ON,BOD_OFF,WDT_OFF,LVP_OFF

define  osc 8
;------[ Set Hardware ]------------------------------------------------------
    OSCCON=$70    '$70=8MHz, $60=4MHz 
    ANSEL=$00
    ANSELH=$0    
    ADCON0=$00
    CM1CON0=0 
    CM2CON0=0
    OPTION_REG=0    ; INTOC RB0 set to interrupt on falling edge
    
	PORTA=%00000000
	PORTB=%00000000
	PORTC=%00000000     ' RAC6&7 set with Hserout command
	TRISA=%00000011      ' PORTA RA0 & RA1 input all other output
	TRISB=%00000000      ' PORTB all set to Onput
              TRISC=%00000000      ' PortC     RC7&RC6 for hserout
;--[ VARIBLES, CONSTATNS ]-------------------------------------------------
;  Symbol Port_Pin=PortB   ; To define PortB port numbers start at RB.0    
    Avar    var byte   
    Duty    var byte            
    Cycle   var byte    
;--[ Main Program ]-------------------------------------------------------------
Start:
    gosub FadeTest
     
;--[ Routine for fade on and fade off LEDs]------------------------------------
FadeTest:
        for avar = 0 to 7   
                cycle=4    ;cycle is number of cycles of pulse    
            for Duty= 0 to 220 step 1
                pwm Avar,Duty,cycle
                next Duty
                cycle=2    ;cycle is number of cycles of pulse
            for Duty= 220 to 0 step -2
                pwm Avar,Duty,cycle
                next Duty
                low Avar
        next Avar
    Return  
         end

[Archangel]

Hi All,
I tried this just the way it's published to no avail, but did manage to make it work after tinkering a bit. I used a PIC Demo board featuring a PIC16F690 and the 4 LEDs on Port C as follows:

#CONFIG
    __CONFIG _INTRC_OSC_NOCLKOUT & _WDT_ON & _PWRTE_ON & _MCLRE_ON & _WDT_ON

#ENDCONFIG
DEFINE OSC 4
TRISA = 0
TRISB = 0
TRISC = 0



;------[ Set Hardware ]------------------------------------------------------
    OSCCON=$70    '$70=8MHz, $60=4MHz 
    ANSEL=$00
    ANSELH=$0    
    ADCON0=$00
    CM1CON0=0 
    CM2CON0=0
   
    
	PORTA=%00000000
	PORTB=%00000000
	PORTC=%00000000     ' RAC6&7 set with Hserout command
	
	TRISA=%00000011      ' PORTA RA0 & RA1 input all other output
	TRISB=%00000000      ' PORTB all set to Onput
    TRISC=%00000000      ' PortC     RC7&RC6 for hserout
   
    Avar    var byte  
    Duty    var byte            
    Cycle   var byte    
;--[ Main Program ]-------------------------------------------------------------
Start:
    gosub FadeTest
goto start
     
;--[ Routine for fade on and fade off LEDs]------------------------------------
FadeTest:
        for avar = 8 to 11
        PortC = avar << 2 &%00000001 ;& OP damps a leading on signal   
                cycle=4    ;cycle is number of cycles of pulse    
            for Duty= 0 to 220 step 1
                pwm Avar,Duty,cycle
                next Duty
                cycle=3    ;cycle is number of cycles of pulse
            for Duty= 220 to 0 step -2
                pwm Avar,Duty,cycle
                next Duty
               
        next Avar
         Avar = 8
    Return  
         end

[Demon]

Just a comment on logic:

Start:
    gosub FadeTest
    goto Start   <---- missing

Robert