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Tried to read analog data from gpio, but only see a way which returns signal strength as LOW or HIGH (boolean). Couldn't find any solution in the documentation and in code references. Is it even possible for now?
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The ESP32 DEVKIT V1 DOIT board (version with 30 pins) has 15 ADC pins you can use to read analog inputs. These pins have a resolution of 12 bits, which means you can get values from 0 to 4095. To read a value in the Arduino IDE, you simply use the analogRead() function. The ESP32 ADC pins don't have a linear behavior.
In order to read analog data we need to use the following pins: VDD (power) and DGND (digital ground) to power the MCP3008 chip. We also need four "SPI" data pins: DOUT (Data Out from MCP3008), CLK (Clock pin), DIN (Data In from Raspberry Pi), and /CS (Chip Select). Finally of course, a source of analog data.
ADC in ESP32 have a maximum resolution of ADC of 12-bits and yes, the resolution of ADC is configurable with possible values include 9-bit, 10-bit, 11-bit and 12-bit. Usually, the resolution is set to 12-bit, if not changed.
The ESP32 integrates two 12-bit SAR (“Successive Approximation Register”) ADC (Analog to Digital Converters) and supports measurements on 18 channels (analog enabled pins). Some of these pins can be used to build a programmable gain amplifier which is used for the measurement of small analog signals.
Raspberry Pi 3 doesn't have analog-to-digital converter so you can only get boolean values (high/low) from its GPIO. So in order to get analog data you need to use external ADC module in your project.
EDIT: I found this interesting blogpost showing how to measure analog input on Android Things.
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