ESP32 Peculiar Readout on Power Supply

Development Boards ESP32
1

I have the SparkFun Thing Plus Connected via USB and lately I have to force the ground pin to oscilloscope ground to get true ground, otherwise I end up having no power to any of my peripherals.

When I measure the voltage across each pin and have the Digilent Analog Discovery 2 set to DC coupling and each grounding clip on the BNC oscilloscope probes I use are connected together, I end up with this result. The difference between the power and ground is less than 0.5V when both the scope and microcontroller are plugged in via USB. As soon as I connect a jumper wire between the grounding clips and ground on my test circuit, the system works as expected. I have yet to see this having been produced anywhere before, but I seem to encounter it on this board.

Something peculiar with SparkFun Thing Plus ESP32.png
Something peculiar with SparkFun Thing Plus ESP32.png1916×922 108 KB

Here is the current setup. The red wire is connected to the 3V3 pin and the black wire is connected to GND. The capacitor going between them is the bypass capacitor of 1000uF. The red wire is powering a charge pump circuit used for providing rails used for opamps in the circuit that filter and amplify the two DAC signals and feed into a speaker.

IMG_20210920_165657191 (1).jpg
IMG_20210920_165657191 (1).jpg4608×3456 1.3 MB

2

This is the speaker circuit (minus the speakers). The speakers connect to the potentiometers. When the speakers are connected no sound is produced until the ground clips (mentioned above) of the Analog Discovery 2 are connected to the ground line.

SpeakerCircuit.jpg
SpeakerCircuit.jpg4340×1925 3.39 MB

3

Sounds like either a bad USB cable or something is going on with the USB ports on your computer.

4

hmm well they are cheap USB cables I picked up in the store… will try with the lipo battery to see what I get. I am also powering both the Thing Plus and the Analog Discovery 2 through an unpowered hub