Em 8/2/2011 22:27, Bob Blick escreveu:
>
> On Tue, 08 Feb 2011 23:47 +0000, "Wortinguk" wrote:
>> I have a 16F88 project in need of advise.
>> PWM output on CCP1 on RB0 drives a MOSFET to drive a motor.
>> RB0/INT interrupt is enabled (on rising edge)
>> The interrupt service routine does an adc sample of the current flowing
>> to
>> see if there is an overcurrent. (1 ohm resistor in ground side of MOSFET=
)
>> This currently drives an LED if an overcurrent.
>>
>> But cant get my head around a method to tempory collapse the PWM output
>> voltage if there is an over current condition and allow the PWM period t=
o
>> continue and re-test the current in the next interrupt. Setting RB0 =3D =
0
>> wont
>> do it.
> Hi Dave,
>
> A few things come to mind. I don't have the 16F88 datasheet in front of
> me, so any of these could be wrong. But it is worth checking out:
>
> 1.Setting TRIS for the pin that PWM is coming out from. I think TRIS is
> after the PWM circuitry so this might work.
> 2.Setting TMR2 to some number higher than PR2 and stopping it.
> 3.Setting CCPR1H to some number.
> 4.AND-ing the PWM in hardware with the pin you are driving the LED from.
> 5.Temporarily turning off PWM in CCP1CON.
> 6.Setting PR2 to 0? Or does that only work on the next cycle?
>
> Cheers,
>
> Bob


In an old project with PIC16F628, just turning off the CCP1CON left the=20
pin at the last state set by the PWM controller. Sometimes it stopped at
"1". To turn it off I needed also explicitly clearing the pin.

Isaac

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