Add README

Author: matthijskooijman

README.md

@@ -0,0 +1,27 @@
+Interface board firmware
+------------------------
+This repository contains the source code for the firmware running on the
+3devo interface board. This board is part of the 3devo Filament Extruder
+and since version 1.3 includes an attiny841 microcontroller to handle
+powering up the display and reading the hopper sensor.
+
+To compile this firmware, the
+[ATTinyCore](https://github.com/SpenceKonde/ATTinyCore/blob/master/Installation.md)
+core and [Arduino-3devo](https://github.com/3devo/Arduino-3devo) board
+description files need to be installed into the `hardware` subdirectory
+of your Arduino sketchbook (these two are also included as submodules in
+this repository, so if you configure the Arduino IDE Sketchbook path to
+point to this repository, they should also be loaded as needed). Then
+select "3devo Interfaceboard" in the IDE and compile the firmware.
+
+A compiled version of this firmware is normally included in the Filament
+Extruder's main firmware, and uploaded on every startup through a
+[bootloader](https://github.com/3devo/AtTinyBootloader) running on the
+microcontroller.
+
+License
+-------
+This firmware contains a TWI implementation taken from
+[bootloader-attiny](https://github.com/modulolabs/bootloader-attiny)
+written by Erin Tomson. All code in this repository  is licensed under
+the GPL, version 3. See the LICENSE file for the full license.