I have a board with 16F628A running with internal osc. Also, a 32KHz xtal is
connected for basic time keeping.  It sleeps all the time and wakes up about
every 500ms and does some stuff for short time then sleeps again.  During
the awake time I turn on a led and turn it off just before going to sleep.

I have discovered that the chip does not wake up from sleep (the led does
not blink) for a while (4 seconds to 20 seconds or so) under 2 seperate
conditions:

1. If I touch (with my bare finger) to the cap that is connected to the RB7
pin of the pic (where the xtal's one pin is connected) the unit does not
wake up

Or

2. If I "breathe" on the same cap above.

Note that I do not know the exact word for what I am doing so I said
breathing.  Let's say that you want to see if your breath smeels, and you
"breathe" to your hand and smeel it.  That is what I do to the cap (except I
don't smell it afterwards).  When I did this, I was actually trying the get
something off of the pcb, and was not testing my breath.  I also did this
test right after brushing so probably this is not because of my breath! :-)

I have put this board to a test in a fridge with -16 deg C and +85 deg C
(+/- 5 deg C).  And the board still works.  Also, this behaviour has been
observed with many of the same boards and many of different kind of board.

The cap is 22pF.

Why does this happen?  Bad board design?
Has anybody else experienced this before?
How would I know this wouldn't happen after the unit is shipped?
Is this a humidity problem?  Would this problem occur again after it rains
on the unit (in IP68 box) and then there is sun right after the rain?

P.s. The unit will be in an IP68 enclosure and the problem occurred without
the enclosure, no way to test it inside the enclosure.

I am sorry for the lengthy message but I am really curious as to what is
going on here and to find out if I can take any precautions.

Best regards,

Omer

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