Needed firmware is here https://docs.m5stack.com/#/en/module/faces_keyboard?id=easyloader

It's simple, fill in the code from the example, hold the magnet to the M5stickC and you will see that the readings will change significantly! The magnet is needed strong enough, because The sensor is far away in the device.

I'm find this project, and in get date from Hall sensor, using MicroPython and M5 libs:
https://m5stack.hackster.io/Max-Lavrov/hall-sensor-and-temperature-sensor-in-esp32-934ba8