>         a) do I have 5 volts on the pins where it should be?
>         b) is my crystal oscillating?
>         c) is my port pin toggling?
>         d) is there any data coming in on the serial port line?

If you're really only interested in only that level of data, a simple,
cheap logic probe may suffice.  Mine has high/low pitch beeping for logic
1/0, so I don't even have to look at it while poking it around the pins
on a board, and you can get to where you know what some typical waveforms
(like serial I/O or ICSP data) "sound like" as they pulse back and forth.

--
Steve Willoughby     | "It is our choices... that show what we truly
<steve@alchemy.com>  | are, far more than our abilities."
                     |     --Albus Dumbledore, in Harry Potter and the
                     |            Chamber of Secrets, by J. K. Rowling

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