Recently I purchased an inexpensive usb based oscilloscope to help me do some low level electronics debugging. Owning an oscilloscope is so cool I just had to tell everyone about it! And the price of these USB-based oscilloscopes are in range of many hobbiests. Now I'm kicking myself for not buying one of these years ago.
The above screen shot shows the output of an ATTINY13A microcontroller (similar to what the ardupilot uses for their fail safe / manual override circuit.) My test code reads a PWM signal in (via an interrupt service routine) and generates a new signal out on a different pin that mirrors the input signal. I can see exactly what is going on with both the input and the output pins using my cool new oscope.
I'm learning as I go (just like everyone else) but I thought it would be fun to share my experience in a bit more detail and hopefully encourage some people here to also take the plunge. I have many more details and screen shots posted at my personal blog here: