Updated draft schematic and created PCB design for the main control board using the latest PCB-etching lessons learned. This board will be fabricated in-house. See 03010-002 Kicad project.
Created draft schematic for the main control board. See 03010-002 Kicad project. 
Created SVG for laser cutting & engraving simplified ruler. See project CAD directory. 
After brainstorming follow-on math manipulatives with the client, we are launching a prototype effort for a manipulative involving ruler measurements. As was learned on xMM1, moving parts and a tactile input device make the manipulative very engaging for the children. This manipulative will consist of a box with an exposed sliding piece of plastic that the children will need to measure. The plastic slide will be connected to a rack and pinion so it can be driven by a servo to expose different lengths of plastic to be measured. The children will need to place a ruler against the box, and to make sure they line up the ruler correctly with the start of the plastic slide, there will be a reed switch that detects that and shows a green status LED. When the measurement is made, the child will be able to select the value (in half-inch increments) using a pegboard, by putting a peg with a magnet into the corresponding marked circular slot. The different values can be connected to a series of resistors to be able to detect the voltage value with a single ADC pin, versus having to waste a lot of GPIO pins. If the rack and pinion approach does not work due to space limitations, a servo-controlled paper scroll can be used instead.