Port indexing & PWM for LED fade

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.

Code:

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

Re: Port indexing & PWM for LED fade

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.

Code:

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

Re: Port indexing & PWM for LED fade

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.

Re: Port indexing & PWM for LED fade

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…

Re: Port indexing & PWM for LED fade

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

Re: Port indexing & PWM for LED fade

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

This works

Code:

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!

Code:

; 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

Re: Port indexing & PWM for LED fade

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:

Code:

#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

Re: Port indexing & PWM for LED fade

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

Re: Port indexing & PWM for LED fade

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

Re: Port indexing & PWM for LED fade

Just a comment on logic:

Code:

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

Robert