On Tuesday, September 27, 2011 6:02 PM, "Jacopo Monegato" wrote:

> know WHY this happens. I know that a lot of hum comes from switching
> power supplies (and since i come from italy, i think it has 220V hum ;)

The EMI filtering in the power supply couples the primary to the
secondary, so even though the output voltage is 12 VDC, both output
terminals have a fraction of the primary voltage impressed upon them.
This is through a network that is mostly capacitive, so the amount of
current is small. And it is from both primary wires, so it is half the
primary voltage. But the "ground" of your PIC circuit will have 100 VAC
on it, and if you have it sitting close to a workbench surface, there is
some coupling. And any PIC input that is open can interpret that
coupling as some input.
=20
> Now what i can't understand is WHY only the pwm module doesn't work....

Perhaps other things might not work also.=20

> If it's so obvious that it's not written anywhere, i am sorry ;)

Inputs that are driven beyond the supply voltage or more negative than
ground can cause unpredictable operation. And if the inputs are
floating, almost anything can drive them out of spec.

Also maybe your power supply voltage does not rise quickly enough. You
should enable PWRT and BOR.

Cheerful regards,

Bob

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