This Feather adapter rearranges the pins of a Teensy 3.x to give you the same shape and pinout for our Feathers. We've tested our FeatherWings so far and all are drop-in compatible. It's a great way to take advantage of the Feather ecosystem. Give your Teensy a stepper/DC motor driver, GPS, LED matrix or OLED add-on with ease. With the space left over, we even added in a 500mA LiPoly charger that automatically charges over USB and will switch over to the LiPo when USB is unplugged. There's also a 100K resistor divider for monitoring the battery voltage connected to A7.