Port indexing & PWM for LED fade

[MOUNTAIN747]

Greatings! I have stated a new project working with PWM and fading LEDs. All is going well until I tried to combine two simple test routines. The first two routines work fine. When I tried to use port indexing with PWM it failed. Can anyone point out my error or does the PWM command have limitations on pin discriptions? Manual says it can be a variable or pin discription, e.g. PortB.0 Is there another way to do this?

PIC16f886, PBP 2.6, using LAB X2 board.
;Cycle through PortB to fade ON then fade OFF eight LEDs in sequence.

Symbol Port_Pin=PortB  
    Avar    var byte  
    Duty    var byte            
    Cycle   var byte

;more stuff in here 
   
;--[ LED fade ON and fade OFF   ]---------  works fine!
FadeTest:     
    cycle=4    ;cycle is number of cycles of pulse    
    for Duty=0 to 100 step 1
        pwm led1,Duty,cycle
        next Duty
     cycle=1    ;cycle is number of cycles of pulse
     for Duty=100 to 0 step -2
        pwm led1,Duty,cycle
        next Duty
        low led1     ;end of routine
    pause 1000
    goto FadeTest

;--[  PortB indexing LEDs       ]--------------  works fine!
IndexTest:   
    for Avar=0 to 7
       Port_Pin.0[Avar]=1
       pause 250
       Port_Pin.0[Avar]=0
       pause 250
    next
    goto IndexTest

;--[  FireFlies routine         ]-------------------  FAILED
FireFlies:
    for Avar=0 to 7        
        cycle=4            
        for Duty=0 to 220 step 1
            pwm Port_Pin.0[Avar],Duty,cycle
            next Duty
        cycle=1            
        for Duty=220 to 0 step -2
            pwm Port_Pin.0[Avar],Duty,cycle
            next Duty
            low Port_Pin.0[Avar]     ;end of routine
    Next Avar     
        goto FireFlies

Comments please, Thanks.
Wayne

[Art]

Looks good to me if the addressing works with PWM.
What happens if you only try to PWM a single LED when you address it that way.. same thing?


I've read about the trick to address pins, what if you knock them into a declared array first,
and then aliased each one, I wonder what that would do.

pins[8] var byte
portb.0 var pins[0]
portb.1 var pins[1]
portb.2 var pins[2]…


Then cycle "pins" in the PWN command
for selected = 0 to 7
pins[selected] = value
next selected

[Art]

but my comment is, software PWM command (not HPWM) is a dead end.

How about starting with a constant loop that counts from zero to something,
or a hardware counter, then look at that counter each cycle of your program,
and determining which LEDs to turn on or off based on their own preset on/off counters.

Then you can vary the counters, and you're not limited to a single simultaneous PWM channel.

[MOUNTAIN747]

Art, Thanks for your reply. PWM with a single LED or port (LED1 var PortB.1) or single port (PortB.1) will work with PWM however I have been unable to get indexing to work with the PWM in any shape, form, or fashion. Some LED will light up but will not be the one you addressed. I think the problem must be within the PWM command structure. It will not recognize the indexing as a port location. I tried several versions of your suggestion of array declaration, no luck. I think indexing in some form should work but I have not figured it out yet. I have the routine working with Select Case approach but an indexing method would reduce the code considerably. Work continues…

[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

[richard]

a quick read through the old pb2.6c book (page 30 in my edition) indicates the pin number is a hangover from the old basic stamp
pin chips 0-7 8-15
8 gpio
14 porta portc
18 portb porta
28 portb portc

remember that if you can

[MOUNTAIN747]

Yep! The manual says a constant of 0 -15. It just didn’t say that it starts on PortB.0 and continues into PortC.0 and then it confuses things by talking about PortA.0. the old basic stamp thing is just fine with me. No indexing needed, no fancy port descriptions, just a constants or variables of 0 – 15. Easy to cycle through or set up for Random enables. Why do I always complicate things! thanks guys for your comments.

Wayne

[Demon]

Just a comment on logic:

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

Robert