Added Iris node documentation

electrical/documents/nodes/files/.gitignore

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+# We want board documentation photos in here, 
+# so we'll allow specific files in this subdirectory
+!*.jpg
+!*.png

electrical/documents/nodes/iris.md

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+# IRIS Node
+
+![Iris](files/iris.jpg)
+
+![Iris Render](files/iris_render.png)
+
+Designed by [Nick McComb](www.nickmccomb.net) for OSURC Mars Rover.
+
+
+## Summary
+
+Made for MR1718 as part of the OSU Robotics Club.
+
+Enables a single USB port to act as 10 RS485 Transceivers, receive inputs from an S.BUS style RC receiver, and interface with a few switches. Input power is 24V (self powered, no power is drawn from the USB connection). Features a Teensy 3.2 microcontroller.
+
+This design is entirely Open Source and is available on CircuitMaker, see below for a link to the file.
+
+This is a 4-layer design.
+
+### Bill of Materials
+
+[Bill of Materials V1](
+https://docs.google.com/spreadsheets/d/1TkVeK_GaS78QLqv8NcE_QGGE-NSj-3agn10lKnISSjQ/edit?usp=sharing
+)
+
+#### Design files
+
+[MR1718 IRIS](https://workspace.circuitmaker.com/Projects/Details/Nick-McComb/OSURC-Mars-Rover-2017-2018-Iris-Board)
+
+### Downloads
+
+[Schematic V1](files/iris-v1-schematic.pdf)
+[Step V1](files/iris.step)