ADC Conflicting with Camera

[logicgator]

Hi All,

Happy Thanksgiving. I am currently using the ESP32 WROOM 32D SOC and am trying to use the ADC and Camera simultaneously.
I am using esp_camera.h library to initialize an OV2640 and have xclk pins and pclk pins on GPIO32 and GPIO31. In testing, without configuring the camera, the ADC works at the expected resolution.

If the camera is configured, the ADC produces results that vary nearly .8V, which is unacceptable in terms of accuracy. I thought maybe the proximity of the ADC pin- 33, to the high-frequency camera signals were affecting it so I moved the sampling pin to gpio36, however, the same issue persists.

With no input into the GPIO ADC pin, the pin reads .4V on my scope, not sure why this is. Does anyone have any ideas on this issue? So far I have attributed it to an internal issue with the SOC such that the high frequency is on the same ADC bus line as the sampling pin. Not sure. Any help with this issue is greatly appreciated.

[becorey]

GPIO34 to 39 are input only and have no internal pull-up / pull-down resistor. They are floating, so that could explain the spurious 0.4V you are measuring.