Redefining HPWM as output

[Acetronics2]

Hi,

I think if you simply issue the command at the frequency you've been using, but at a 0% duty cycle, it will be solid OFF. If you issue the command with a 100% duty cycle (255 if 8-bit) it will be solid ON.

Does anybody see any problem with this approach?

Regards,

Hi, Picnaut

this approach runs perfectly well, and it is recommended by Melabs itself ...as I use HPWM for R/C E-motors , I just clear CCP1CON when I'm not really really sure a glitch could give a false value to duty cycle. ( never saw it ...but i'm sure !!! )

Alain

[peterdeco1]

Thank you Everybody. Bruce, I did the CCP1CON = 0 thing in place of my "zero frequency" command and it works like a charm.

[picnaut]

Bruce's approach sounds better to me.
It probably uses less code than issuing the HPWM command again also.

Cheers.

[Bruce]

Here's a simple test to show the effects of disabling the hardware PWM module, or using a zero duty-cycle or freq with HPWM.

Hook an LED up to your CCP out pin.

CCP output pin ---|>|----/\/\/\/\----GND

SYMBOL PIN = PORTC.2 ' Define whatever pin on your PIC is CCP out here

    HPWM 1,127,2000
    PAUSE 8000
    CCP1CON = 0 ' Test once with this, then comment it out
    'HPWM 1,0,0  ' Now test with this un-commented
    
WAITUP: 
    HIGH PIN
    PAUSE 500
    LOW PIN
    PAUSE 500
    GOTO WAITUP

On a 16F876A, the LED never toggles with HPWM 1,0,0. It does once the hardware PWM module is disabled with CCP1CON = 0. I'm curious if it works either way on other PIC's.

[picnaut]

Hi Bruce,

Try it again, but this time leave the frequency at 2000 (only the duty cycle is 0). See if it toggles then.
I'm curious (and no where near a PIC right now).

Cheers!

[picnaut]

Hi Bruce,

Also, maybe put a 500ms delay right after the "WAITUP" label. Otherwise, if PIN goes low, it will immediately go high again and you won't catch it.


Cheers!

[Bruce]

Works the same until CCP1CON = 0.

Another delay isn't really necessary since it never toggles the LED to begin with.

[Stump]

I find that setting duty to 0 allows the pin to float
and that can cause a fet to turn on.
I add a weak pull down resistor to the pin used
or set the output to low when duty=0