Adafruit Feather 32u4 FONA, Руководство пользователя

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Power supplies
You have a lot of power supply options here! We bring out the BAT pin, which is tied
to the lipoly JST connector, as well as USB which is the +5V from USB if connected.
We also have the 3V pin which has the output from the 3.3V regulator. We use a
500mA peak AP2112. While you can get 500mA from it, you can't do it continuously
from 5V as it will overheat the regulator. It's fine for, say, powering an ESP8266 WiFi
chip or XBee radio though, since the current draw is 'spiky' & sporadic. Note that the
regulator doesn't power the cellular module, that's directly powered from VBAT
Measuring Battery
If you're running off of a battery, chances are you wanna know what the voltage is at!
That way you can tell when the battery needs recharging. Lipoly batteries are 'maxed
out' at 4.2V and stick around 3.7V for much of the battery life, then slowly sink down
to 3.2V or so before the protection circuitry cuts it off. By measuring the voltage you
can quickly tell when you're heading below 3.7V
Other Feather's have a resistor divider to read the battery voltage. We decided to skip
this and instead let you read the battery voltage via the cellular module using the AT+
CBC command, which will give you the battery voltage in millivolts
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
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