Feather R3 Adapter

Breakout a feather board to Arduino R3 Layout!

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This is a feather board adapter/shield/wing. It allows you to make use of Arduino R3 layout shields and boards!

This is a project for the Adafruit Feather series of boards.  This dual purpose FeatherWing Arduino R3 adapter allows you to plug in your feather board and have the I/Os broken out to the Arduino R3 layout for use with other shields that are not available as Feather Wing shields.  You can also run it backwards too.  Meaning you could use a FeatherWing shield like a R3 shield for a different MCU!  The shield supports the standard Feather pin-out so it should be compatible with all Feathers.  It interconnects the I2C and SPI bus along with the analog and digital pins.  It also features two switches for additional configuration (mainly for the Huzzah ESP8266 Feather) and also incorporates a voltage divider for monitoring the battery.  The first switch ties, the Huzzah ESP8266 Feather, GPIO16 (wake pin) to RESET pin for use with deep sleep.  The second ties the raw battery voltage to A0 via a voltage divider with a max output of 1.0v so the battery can be read if one wishes.  Both can be switched off to free A0/GPIO16 for normal IO use.  As of right now only supports 3.3v logic.  Another version to come soon to support level switching.  


  • Make use of other shields/boards
  • Controllable battery voltage monitoring
  • Controllable reset to wake from deep sleep
  • Battery connection on shield, 3.7-4.2v batteries
  • Reset switch resets both board and shields
  • Shield power LED
  • AREF supported


  • Supports 3.3v shield powering via battery, 5v powering via usb on feather
  • Supports 5v & 3.3v MCU powering
  • Supports 3.3v logic currently
  • Digital pins 11, 12 & 13 not usable with SPI connection on ESP8266 Feather

Future Features...

  • Logic Level shifting ( supporting both 3.3v and 5v logic )
  • Disable/enable 3.3v LDO
  • Controllable power routing 


Board Schematic

sch - 297.53 kB - 12/29/2019 at 19:32



Board Layout

brd - 64.44 kB - 12/29/2019 at 19:32


  • 3 × Resistor 2 for voltage divider, one for led(depending on color)
  • 1 × Dual Switch for selecting options
  • 1 × Push button momentary switch for reset
  • 1 × LED for power indicator
  • 1 × JST-PH connector for battery connection

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bobgreenwade wrote 08/31/2020 at 14:35 point

If one uses short headers to put the Feather on top of this Shield, can one stack another Shield on top?

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Mike Pate wrote 07/05/2020 at 15:08 point

Great project and was looking for this exact solution.  I'm new to Hackaday so not sure where to obtain the details on the components (i.e. resistor values, LED, part numbers).  Also what is the purpose of the 2-position switch?

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Mark Aldritz Dela Virgen wrote 12/27/2019 at 09:38 point

Suggestion: Add a 3.3V<--->5V level shifter. The UNO uses 5V logic, and the feather uses 3.3V logic.

I want to see if this thing can work both ways. (R3+FeatherWing and Feather+Shield)

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Mitch wrote 12/27/2019 at 10:06 point

I thought about implementing that but unsure the best way to do it.  I need to think about it some more.  I planned on using 3.3v logic shields with it or at least dual logic.  

Thanks for the comment!

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bobgreenwade wrote 01/09/2020 at 00:22 point

Level shifting (and voltage shifting) will be a challenge to plan out, since it's impossible for a designer to predict which direction the board will be operating in (Feather to Arduino or Arduino to Feather), and whether there even will be 5V logic involved. For your own purposes, I think you're fine leaving it as it is; for a commercial venture, I'd recommend including the parts for all of the above, but requiring a solder jumper or some similar mechanism to make them active (it may require a pair of DPDT slide switches with a center-off position, or something even more funky).

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Ted wrote 03/24/2021 at 22:02 point

I think you could do it with something like:


It might not work for everything, but I expect it would work for most cases.

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