The first generation of senor boards were a great proof-of-concept, but they had a few problems. For one, they were big. It’s easier and cheaper to make small cases. Second, the pin headers weren’t round, nor were the mounting holes perfectly on-grid. Third, the mounting holes were some weird size that was smaller than even a 4-40 screw. The silkscreen didn’t also didn’t come out legibly, which made things difficult when plugging in wires.
Long story short, there were a lot of improvements to be made. To get around the limitations of Eagle, [Evan] drew up the second generation of boards in KiCAD, taking advantage of the human-editable XML file format to lay out parts like the screw holes and terminals with precision that would have been difficult to obtain using only grid snapping. KiCAD also allow the use of the TopoR auto-router, which generated the sweet looking organic traces.
The new motes also omit the LED on the XBee disable pin. This pin is pulled high to tell the XBee to sleep, so having the LED on it wasted 5mA or so during the phase when we would be trying to *save* power. We chose different resistors for all the other LEDs, which saved a few more mA.
Overall, the MKII design is quite nice and we’ll be using these motes as the basis for some upcoming aquarium monitoring projects.
Tune in next time for a build of the test stand that will be used to program future MKII mote boards! 
-Michael
Read more for a tip on programming ATmega328/P chips with AVRdude and Arduino
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