“The ESP32 inside the M5Stack Core module has a built-in Hall effect sensor. But where exactly is this small piece located? Let’s measure it.
A Hall effect sensor has nothing to do with acoustic reverberation (German for reverb = hall) but is named after Edwin Hall and is used to measure magnetic fields. The output voltage of such a sensor is directly proportional to the strength of the magnetic field to which the sensor is exposed. Don’t ask me why, but the ESP32 has an integrated Hall effect sensor. This means that you can measure the presence and strength of a magnet if the magnet is in the right place above the M5Stack Core module. But where exactly is this right spot?”