ESP32 onliners
The ESP32 runs on 3.3V power and logic, and unless otherwise specified, GPIO pins are not 5V safe!
GENERAL
Why can I not read analog input ADC2 once WiFi is initialized?
Due to the design of the ESP32, you can only read analog inputs on ADC
Some pins are special about the ESP32 - here's a list of 'notorious’ pins to watch for!
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A2 / I34 - this pin is an input only! You can use it as an analog input so we suggest keeping it for that purpose
A3 / I39 - this pin is an input only! You can use it as an analog input so we suggest keeping it for that purpose
IO12 - this pin has an internal pulldown, and is used for booting up. We recommend not using it or if you do use it, as an output only so that nothing interferes with the pulldown when the board resets
A13 / I35 - this pin is not exposed, it is used only for measuring the voltage on the battery. The voltage is divided by 2 so be sure to double it once you've done the analog reading
ESP32 Feather Huzzah
Why does the yellow CHARGE LED blink while USB powered?
The charging circuit will flash when there is no LiPoly battery plugged in. It's harmless and doesn't mean anything. When a LiPoly battery is connect it will stabilize the charger and will stop flashing
Power
Please budget 250mA for the WROOM32 module.
While you can get 500mA total from it, you can't do it continuously from 5V as it will overheat the regulator. –
We use this to power the ESP32 which draws about 200mA continuous.
The good news is you can put the ESP32 into sleep and low-power modes much easier.