And now, turn off Sinc and this Gibbs phenomenon disappear (because it is not in real input signal and produced by Sinc interpolation. And in these cases Sinc do not reconstruct true input signal right (even in theory it can not, rules are included in theory) . (Gibbs "ear" is not error, it is Sinc interpolation normal "feature" specially if input signal violate rules))
The wobble on screen isn't just the Gibbs phenomenon, it's mostly ringing from looking at an Arduino pin through a crappy piece of breadboard wire.
I can turn sinc on/off and there's
some difference on screen. It's most visible in the preshoot, here's a couple of captures:
Maybe you've accidentally hit on the reason why Rigol decided to enable the "sinc on/off" button when you get to the extremes, ie. to see how much Gibbs is on screen.
And, yes, Wolfie, we know it's not truly "off" - no reconstruction at all would display a horrible mess on screen.
There's a pretty curve on screen so they must be doing a
different reconstruction (ie. not sin(x)/x) that produces a nice display but minimizes the Gibbs Effect.
I think we might
finally be getting to the bottom of the Rigol "sinc" mystery (and why there's no truly "raw" data available).
Edit: Just for completeness, here's the same pulse with only 2 channels enabled on the 'scope. The sin(x)/x button is disabled now (no longer needed - we have twice as many samples available so Gibbs phenomenon isn't a problem).