[sdiy] cute hand held scopes on eBay

[Richie Burnett]

Hi Tom, and all.

> I quite like the fact that my own digital scope just puts linear sections 
> between samples. It makes it obvious that I'm zoomed in to the limit of 
> the data, and that I shouldn't go making assumptions about what's 
> inbetween those few points. Dot mode does this too, but the display isn't 
> so clear.

My point regarding the sinc-interpolation is that it is technically the 
correct way to display a continuous waveform in between the discrete sample 
points.  Assuming the signal in question has been properly band-limited 
before being sampled (by front-end analogue anti-aliasing filter), then 
sinc-interpolation actually reconstructs the original continuous-time signal 
from the discrete sample points.

> If I had a beautiful-looking sinc-interpolated image to look at, I might 
> well start confusing it with reality, and I definitely wouldn't be able to 
> tell where the actual datapoints were.
> Tastes differ, I guess.

It's not confusing anything for reality, it is reality.  Done properly sinc 
interpolation will show you the original band-limited signal by drawing a 
continuous smooth line through the sample points.

The thing is that sinc-interpolation isn't actually that hard to do.  It is 
just post-processing of the sampled data before it is displayed on the 
screen.  That's why I think that it is a shame that the ARM DSO product is 
let down in this final step of displaying the captured data!

-Richie,