Strangw results when using PWM command

[malc-c]

I've written a simple program to pulse a LED on GPIO.0 of a 12F675, which worked fine. However I didn't save the file, and so I started from scratch again this morning.. but I'm experiencing some strange behaviour.

This is the main body of the code:

led var GPIO.0

i var byte

up:
For i = 1 to 254                                                  
Pwm GPIO.0,i,1
if i = 254 then goto down
next i

down:
for i = 254 to 1 step-1
pwm GPIO.0,i,1
if i = 1 then goto main
next i

As you can see its a simple FOR/NEXT loop, that, should i reach a set value, goto either up or down section.

However when programmed, the LED ramps up in brightness but then fails to ramp down. I've tried remming out the up section and all that happens is that the LED flashes fast (as if i is not reducing by the step-1 command)

;up:
For i = 255 to 1 step-1                                                 
Pwm GPIO.0,i,1
;if i = 254 then goto down
next i

;down:
;for i = 254 to 1 step-1
;pwm GPIO.0,i,1
;if i = 1 then goto main
;next i

Its as if the PWM command or the step-1 statement is not being observed. And what's bugging me is I know it can be done as it worked before (the chip is now in cornwall so I can't read back the HEX !)

Comments anyone please !

[malc-c]

This is really strange.. its as though the "IF" in the "IF i = 245" is being ignored.

I've just tried the following and it simply ramps up the LED to full brightness, over and over again, with out any pause ! (ie its the same as not having the pause statement there)

Main:
For i = 1 to 254                                                 
Pwm GPIO.0,i,1
if i = 254 then pause 500
if i = 254 then down
next i

[malc-c]

Now this is getting silly !

Main:
for i = 1 to 254                                             
Pwm GPIO.0,i,1
if i=253 then goto down
next i

down:
high gpio.0 
pause 1000
low gpio.0
goto main

The above test even fails... it simple runs the main loop and doesn't branch off to the down routine !


EDIT:

As does the following

Main:
for i = 1 to 254                                             
Pwm GPIO.0,i,1
if i=253 then t=1
if t=1 then goto down
next i

This is doing my head in

[Acetronics2]

Hi, Malc

Try this ... and do not forget I/Os and clock defining ...

DEFINE OSCCAL_1K 1

ADCON0 = 0
ANSEL = 0

' Define YOUR I/Os Here !!! TRISIO = % ?????1

led var GPIO.0

i var byte

up:
For i = 1 to 254
Pwm GPIO.0,i,1
next i

for i = 254 to 1 step-1
pwm GPIO.0,i,1
next i

GOTO up

END

Alain

[mister_e]

DEFINE OSCCAL_1K 1

ADCON0 = 0
ANSEL = 0

' Define YOUR I/Os Here !!! TRISIO = % ?????1

The define OSCCAL have nothing usefull to do there
Same for ADCON0 as it's the POR default.. but i agree could be safer

Add CMCON=7 as it's a 12F675 and it have internal comparator multiplexed with GP.0

Main:
for i = 1 to 254
Pwm GPIO.0,i,1
if i=253 then goto down
next i

Bad programming method IMHO, i always prefer to validate the Loop condition before getout and if usefull, set a flag wich say i interrupt the loop... something like

Main:
for i = 1 to 254                                             
    Pwm GPIO.0,i,1
    if i=253 then 
        i=254
        GetOut=1
        endif
   next i

if Getout then DoSomething

In your case, the main problem is most the analog stuff

[malc-c]

Alain, thank for the reply, but that still has the same effect, ie the LED ramps up in brightness, but doesn't ramp down.

Steve,
I never said my coding was tidy

However isn't

Main:
for i = 1 to 254                                             
    Pwm GPIO.0,i,1
    if i=253 then 
        i=254
        GetOut=1
        endif
   next i

if Getout then DoSomething

The same thing as

Main:
for i = 1 to 254                                             
Pwm GPIO.0,i,1
if i=253 then t=1
if t=1 then goto down
next i

in a round about way ? where the condition is replaced with t in my case ?

The thing that is also bugging me if that whilst the loop to increase the brightness works, the one to decrease it doesn't ???

Let me go away and try Steve's suggestion and see if I get any further.

Thanks as always for your inputs