Enable Pin; Alternative Power Options - Adafruit Feather M4 Express Manual

import board
from analogio import AnalogIn
vbat_voltage = analogio.AnalogIn(board.VOLTAGE_MONITOR)
def get_voltage(pin):
return (pin.value * 3.3) / 65536 * 2
battery_voltage = get_voltage(vbat_voltage)
print("VBat voltage: {:.2f}".format(battery_voltage))

ENable pin

If you'd like to turn off the 3.3V regulator, you can do that with the EN(able) pin. Simply tie this pin to Ground and it will
disable the 3V regulator. The BAT and USB pins will still be powered

Alternative Power Options

The two primary ways for powering a feather are a 3.7/4.2V LiPo battery plugged into the JST port or a USB power
cable.
If you need other ways to power the Feather, here's what we recommend:
For permanent installations, a
reliable power
For mobile use, where you don't want a LiPoly,
If you have a higher voltage power supply,
cable's 5V and GND input
Here's what you cannot do:
Do not use alkaline or NiMH batteries and connect to the battery port - this will destroy the LiPoly charger and
there's no way to disable the charger
Do not use 7.4V RC batteries on the battery port - this will destroy the board
The Feather is not designed for external power supplies - this is a design decision to make the board compact and low
cost. It is not recommended, but technically possible:
© Adafruit Industries
5V 1A USB wall adapter
use a USB battery pack!
use a 5V buck converter
(https://adafru.it/DHu)
https://learn.adafruit.com/adafruit-feather-m4-express-atsamd51
(https://adafru.it/duP) will let you plug in a USB cable for
(https://adafru.it/e2q)
(https://adafru.it/DHs) and wire it to a USB
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