Datasheet

The above shows the Micro USB jack (left), Lipoly JST jack (top left), as well as the 3.3V regulator and changeover

diode (just to the right of the JST jack) and the Lipoly charging circuitry (right below the regulator).

There's also a CHG LED next to the USB jack, which will light up while the battery is charging. This LED might also

flicker if the battery is not connected.

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 low-dropout regulator. While you can get 500mA from it, you can't do it continuously

from 5V as it will overheat the regulator. We use this to power the ESP8266 which can draw spikes of 250+mA

(although its not continuous).

You should be able to budget about 250mA current available from the regulator, which will leave plenty for the WiFi

module.

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