Strangw results when using PWM command

[malc-c]

Steve,

I tried that and it still just ramps up and doesn't seem to want to jump to the down label

@ __CONFIG _INTRC_OSC_NOCLKOUT & _WDT_ON & _PWRTE_ON & _MCLRE_OFF & _BODEN_ON

TRISIO.0 = 0   'Set GPIO.0 to output.
ANSEL.0 = 0    'Set GPIO.0 to digital		
GPIO.0 = 0
CMCON = 7 ' PortA Digital inputs
VRCON = 0        ' Voltage reference disabled
OPTION_REG.7 =    0


led var GPIO.0
i var byte
getout var bit

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

if Getout=1 then goto down

down:
for i = 254 to 1 step -1                                            
    Pwm GPIO.0,i,1
    if i=2 then 
        i=1
        GetOut=0
        endif
   next i

if Getout=0 then goto main

[malc-c]

Steve,

I've also tried the following, which seems to flash the LED rather than ramp down in brighness

for i = 254 to 1 step-1                                             
    Pwm GPIO.0,i,1
    if i=2 then 
        i=1
        GetOut=1
        endif
   next i

if Getout=1 then goto down

I can't for the life of me work out what's wrong...

[Acetronics2]

Hi, Malc

I had just forgotten it was for your famous Dr Who's light ...

so, it could not work properly with such a soft ...

There was a thread you've already started about that ... you didn't find anything usable in it ???

http://www.picbasic.co.uk/forum/show...1754#post21754

I'll try to make a search ...

Alain

Seems the HPWM module of the 16F628a you saw was doing the job ... but may be the "slow PWM" thread from Darrel could help here !!! or use a 12F683 ...

[malc-c]

Alain,

Yes this is to do with the "Dr Who" thread in a way. I started a new one as the matters raised in that thread (ie the fact you need to mod the inc files) resolved it.

What I can't understand was that I had used a 12F675 and the for next loops with the pwm command to successfully produce a pulsating LED for my mates project. I sent this off to him but he found that he needed to drive a bulb as the LED didn't give him the brightness he needed. I informed him that he could just used a FET and how to use a zenenr diode etc to produce 5v from a 12v battery, however he has never done any electronics, and may of fried the PIC. I then loaded up the PBP program but for some reason it stops running the down loop of the code.. anyway.. I've sent off the PCB so hopefully he hasn't fried his original PIC and he can simply drop that in and get filming

Thanks guys

[mister_e]

with the existing stuff, try this one

@ __CONFIG _INTRC_OSC_NOCLKOUT & _WDT_ON & _PWRTE_ON & _MCLRE_OFF & _BODEN_ON

ANSEL.0  = 0 ' Set GPIO.0 to digital		
CMCON    = 7 ' PortA Digital inputs
VRCON    = 0 ' Voltage reference disabled
TRISIO.0 = 0 ' Set GPIO.0 to output.
GPIO.0   = 0 ' 

LED    var GPIO.0
I      var byte
GetOut var bit

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

    if Getout=1 then down
    goto main

down:
    getout=0
    for i = 254 to 1 step -1                                            
        Pwm GPIO.0,i,1
        if i=2 then 
            i=1
            GetOut=1
            endif
       next i
    
    if Getout=1 then main
    goto down

and to make something usefull with the GetOut flag, use the following. Tested and work at treat. OK i'd modified the hardware assignement to fit to one of my already build board here

@ __CONFIG _INTRC_OSC_NOCLKOUT & _WDT_ON & _PWRTE_ON & _MCLRE_OFF & _BODEN_ON

ANSEL  = 0      ' Set GPIO.0 to digital		
CMCON  = 7      ' PortA Digital inputs
VRCON  = 0      ' Voltage reference disabled
TRISIO = $0F    ' gpio<3:0> : Input
                ' gpio<5:4> : Output

GPIO   = 0      ' clear all outputs

LED    var GPIO.5
PB     var GPIO.0
I      var byte
GetOut var bit

Pause 50        ' oscillator settle time...
OPTION_REG.7 =0 ' enable internal pull-up
WPU = 1         ' enable pull-up on GPIO.0 only

main:
    for i = 1 to 254                                             
        Pwm led,i,1
        if pb=0 then 
            i=254
            GetOut=1
            endif
       next i
    
    if Getout=1 then 
       while pb=0 : wend 
       pause 50
       GETOUT=0
       goto down
       endif
    goto main

down:
    for i = 254 to 1 step -1                                            
        Pwm led,i,1
        if pb=0 then 
            i=1
            GetOut=1
            endif
       next i
    
    if Getout=1 then 
       while pb=0 : wend 
       pause 50    
       GETOUT=0
       GOTO main
       ENDIF
    goto down

HTH

[malc-c]

Steve,

Thanks once again for all you help. I had given up and wrapped up the board to post it to my mate, however I took it out of the jiffy bag and gave it one last try...

I copied and pasted the code in your last post (the first program) and tried that. It compiled fine and loaded into the PIC, however the code does exactly the same as all other attempts. ie it ramps (for want of a better word) up the brightness to full, and then goes off, then repeats the same. It still doesn't ramp down from full brightness to low like it should - I've tried different PICs so it rules out that as being the cause.

I think I'll call it a day on this.. thanks again for your help

[mister_e]

That's really strange... it's working here using the first code of my previous message.

Ramp-up, ramp-down in an endless loop... mmm.

I suspect a hardware problem but damn it's not a really complicated hardware, i removed all the usual capacitor around, nothing on all other i/o, simple LED+300 ohm resistor... work fine. if i raise down the psu voltage... it's working from 2.5V. so uneless your Vdd rail is below or really noisy causing a RESET... i don't see why it shouldn't work.

[malc-c]

Steve,

Rest assured your code works fine.. I've just breadboarded the PIC and it works, yet in the PCB ot only wants to ramp up ????? - strange !!

I would of thought that if there was something wrong with the PCB I made (like a short) then the thing would not work full stop ! The board uses a 5.1 zenner to provide the supply to the PIC, and the output simply from GPIO 0 drives the gate of the FET and the LED - why it ramps up and not down I don't know ?

Thanks mate.. don't waste any more of your time... I've attached the schematic just in case someone might see whats the issue ?