Spurious signals on the next channel


I’m a new user of Logic Analyser.
For each capture, I have spurious signals on the next channel. Example: for a capture on channel 0, I have for each falling edge another falling edge on channel 1 whereas there is no signal on channel 1.
The 2 GND pins of the Logic Analyser are connected to the GND of the circuit.

Do you know what happens? Thank you in advance.

I send a capture:

This can be a tough one. You see, there are multiple possibilities. Unfortunately when you’re talking about fast signals you are also talking about signals that can jump through thin air and induct a corresponding signal on adjacent wires. So, it’s possible that the wires on your Saleae are close enough together that signals in one induce signals in others. Sometimes it helps to fan out your wires as much as possible and keep them separated. Another possibility is that this same basic thing is happening on your device under test. One way to test this is to remove the lead from channel 0 and see if you are still getting the pulses on channel 1. If so then the call is coming from within the house! In that case you have to debug your device. If it goes away then probably the Saleae inputs are too sensitive and you have to either filter the glitches or keep the wires farther apart.

When signals don’t look as I expect I often turn on analog capture for the problematic inputs. Often the trouble is the input voltage is near the digital detection threshold for the input, or edges are slow or noisy. Even if you can’t see fast edges or pulses in the analog capture it can often help just to see what the voltage levels are.

Note that the analyzer currently filters the analog data so it is hard to determine where the actual samples are and when the sample rate is low compared to the sampled data the smoothing provided by the filter can be very confusing. Saleae are going to fix this, aren’t you Saleae?

@Collin and @P.Jaquiery thanks for jumping in with your thoughts on the potential sources of the crosstalk that @MatthieuW31 seems to be experiencing.

@P.Jaquiery It’s not officially on the immediate roadmap right now, but this is certainly on our todo list for after we tackle higher priority features/bugs at the moment. This is mainly due to the limitation in team size and prioritization. It’s good to get reminders like this from time to time, so keep em coming. I agree that this feature is a “must-have” and not a “nice-to-have.”

I just linked your comment to the idea post we are tracking for this:

Hello, thank you for these answers. I didn’t have any time to make other tests, I’ll do it soon!

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