>Why not? if the pic must be powered from the ac line without transformer
(no
>external psu) , and detect  voltage levels via interrupts and comparators,
>send pulses to fire triacs and keep a multiplexed display via tmr0
>interrupt, and so... i'm really more comfortable with software, but where
>trying to figure why the interrupts don't work as i expect, and check if
the
>hysteresis feed via another port is enought to make the comparator work as
i
>expect, etc, etc, a scope can show what is not working.
>
>i must confess that i make a special plug without earth, and check what i
>want in ten minutes, and fix the problem. I don't know why if i can put the
>probes of a ac powered multimeter in the line to check if i have 220V, i
>can't put the probes of a 400V oscilloscope, this is a bit extraneous to
me.

Well by all means have the PIC line powered - once you have the thing up and
running properly. For goodness sake use an isolating transformer between the
circuit under development and the incoming mains, otherwise you stand a very
good chance of looking the pictures Jinx posted in the [OT] list.

While working on the PIC itself, why not power it from a low voltage power
supply until you have it running properly? It will be a lot safer than
running it from mains level supply while working on it, even if you do have
an isolating transformer.

>I understand that this must be done in few cases and taking all the
>precautions.

Well if you ever want to get to a stage of drawing your pension, make this
ALL CASES, and always taking precautions. I would hate to try and count the
number of times I have had shocks off equipment despite taking all possible
safety precautions

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