I am going to rewrite all the projects for the 30 Days in Space.  I have expanded my workspace to a 2×4 sheet of plywood.  You have a Raspberry Pi with a Bi Directional Logic Converter 3.3V to 5V handling the I2C bus.   I have a row of Arduino devices connected to the I2C bus.  I will be adding more Arduino Mega 2560 and some Arduino Nano devices to this setup.

I2C page

Inventr.io has a great 30 day project called 30 Days in Space.  You are trapped on a broken space craft and need to fix it.  I bought a Hero Starter Kit last year.  Last month they have a deal on the $97 Mega Kit.  They gave you a $40 Mega 2560 unit with it.  Alex@invertr.io is working with me on this project.  

I went out and bought assorted bread boards and a box of toggle switches to build my imaginary space craft.   I decided to change the entire design around.   I put a row of bread boards in front of the Arduino devices.