Potentiometers ground issue(?) when audio out socket isn't used

[donutshoes]

I made this oscilloscope device using the Daisy Seed. There’s a thread about its development here (click through to see code):

Is an Audio In OLED oscilloscope possible?

Here’s the final mark 1 build! [DaisyScope mark 1] Surprised myself by figuring out how to implement horizontal scaling, other knob is vertical scaling. There’s one last thing that I can’t figure out though. If there isn’t a stereo plug plugged into the output, and if it doesn’t then lead to a stereo input, then the pots behave as if there’s grounding issues. AGND and DGND are bridged, and the audio jacks and OLED screen work fine regardless. I’d like it to be fully functioning ev…

All that’s on it is audio in and out sockets, an OLED screen, and two potentiometers for adjusting the horizontal and vertical scale of the oscilloscope. The audio I/O is just meant to be a bypass, but I also intended for the device to be used with input only. However, when the output socket is not being used the potentiometers behave in a manner consistent with ground issues (such as a fault between AGND and DGND). Here is a video of the problem in action (no sound):

daisy seed potentiometer issues

When I unplug the output cable, the potentiometer positions are “ignored”. Also, when the sleeve/ground of the output socket is disconnected, same problem. If at least one of the stereo split cables on my output cable is plugged into my mixer it works (even if the mixer is unpowered), but it doesn’t work if both are removed. Additionally, it doesn’t work if say, headphones are plugged into the output.

Everything also works fine if the input socket is not used, as long as the output socket is.

One last thing as I was trying to measure values while testing. Weirdly, regardless of configuration, Serial seems unable to read the potentiometer values. Even if the configuration is “right” and the potentiometers work correctly in practice, Serial.println(knob) only reads out “194” (or “192” in the case of the other knob).

Here is a rudimentary wiring diagram of my device:

[tele_player]

Just to confirm - are you using stereo jacks? NOT shorting jacks?

[donutshoes]

I’m using stereo jacks, these ones to be specific https://www.amazon.com/gp/product/B01C3RFHDC/

[donutshoes]

RESOLVED:

As as similar issue was brought up by another dev, I revisited my device and I’m embarrassed to admit that the reason I was having this issue is that my actual device’s wiring did not match the wiring in my diagram above. Fixing the discrepancy fixed my device and it now works as I intended.

(To be totally transparent, though again I’m super embarrassed about it, I wired the ground to Pin 1 instead of Pin 40 by accident. I must have been tired or something, idk how I messed up that bad)

Anyone else having similar problems should A) triple check that their wiring is correct, or B) troubleshoot your hardware, I suppose?

[Takumi_Ogata]

Thank you for revisiting and letting us know about the resolution. Really appreciate it!

And great seeing you around! I remember following that oscilloscope thread.
Hope you have been doing well