Weird signal problems using cheap oscilloscope to look at OctoWS2811 adaptor

[heyspencerb]

Hello!

I built a PCB which uses WS2812b LEDs and the Teensy 4.0 and I was having some small signal issues with LEDs randomly flashing random colors every once in a while.
To investigate I used a cheap Oscilloscope I have to measure the signal, and got this crazy result in the photo. I then checked it directly on the Octo Adaptor and got the same result. Do you think this is a problem of to inferior an oscilloscope? What is going on here? Thank you!

 

[MarkT]

You haven't said what the 'scope actually is - so how can we tell?

You don't have a x10 probe, which means the 'scope may interfere with logic signals through the capacitance and signal reflections.

 

[heyspencerb]

it is a DSO138

 

[MarkT]

it is a DSO138

200kHz analog bandwidth, possibly with some aliasing - not idea for looking at a high speed logic signal I'm afraid.

For signal integrity of a logic signal something more like 100 to 200MHz bandwidth is good, as reflections down
a few metres of cable happen in timescales of nanoseconds.

 

[OhioJim]

What happens if you change the time per division?

It looks like you are getting some aliasing of the signal, as MarkT suggested.