The logic frame is the heart of the OSWatch. The logic frame consists of 4 main parts, a 3D printed plastic frame, an 8mhz microduino core+, a Bluegiga BLE112, and a pololu power regulator.
The power regulator is mainly a protective measure, and may potentially be omitted, although I strongly advise against it without further testing. It insures that all electronics get a clean 3v3 signal. It also offers a layer of protection in case something (such as a short) goes wrong. Replacing a power regulator is much easier than the BLE112 & microduino.
The logic frame also represents the hardest wiring / soldering you will have to do. I would suggest placing a fresh beer in the cooler as a reward when you complete the logic frame. The logic frame will accomplish the following wiring connections:
connect programming port to the microduino
connect the programming port to the ble112
connect power / ground to the power regulator
provide regulated power to the ble112 & microduino
connect the serial connection between the microduino & ble112
connect event lines from the ble112 to the microduino
Before we begin wiring, we have some physical placement / prep to do.
1.) Trim headers from 8mhz Microduino Core+
To be optimal with space, we use headerless modules. Well, Microduino doesn't sell headerless versions so we have to remove them. Trim as much plastic & metal away as possible (without bending or damaging the board). You may need to do several trim passes. Then, use a soldering iron to remove what is left of the copper headers in combination with a solder sucker. Be patient, and do not overuse the soldering iron. Too much heat can damage the board (or de-solder important parts!) I keep a finger on the board, and if it starts to get to hot, I let it cool down.
2.) using flux, lay down a layer of solder on the BLE112
Before placing the BLE112, you should add a base layer of solder. (it's much easier to do this before placing the module!) Be ready to use a lot of flux here. Flux helps the solder stick to only copper / solder. Flux will enable you to minimize accidental solder joints on the board. You can eyeball all connections, and / or use a continuity tester (most multimeters have this) to check for neighbor shorts. Also, be careful not to solder a copper point to the metal shield on top of the BLE112. It is connected to ground!
3.) Place 3 modules into logic frame
each module should fit snugly in place. You may need to sand / file and printing imperfections. Use superglue sparingly in small points when adding each module. All three are placed face down into the frame itself, so the majority of your wiring is done underneath.
4.) Build programming port connection
The programming port provides a easy connection to program both the Microduino and the BLE112. Both modules share a power and ground feed, requiring a total of 8 incoming lines. The BLE112 reset line will also connect to the Microduino, allowing the Microduino to reset the BLE112. This represents one of the major upgrades of the MKII. The combination of both programming ports greatly simplifies certain elements of the watch. Before we attach it, we will build the port. The plastic wraps that hold the port connections can simply be glued together in a line. I happened to have 2 4X ports, and used those, but you can just as easily glue 8 1X port plastic housing together. (Those come with many jumpers)
Before you insert the wires into the plastic housing, trim about 2 - 3 mm of plastic from the top. The housing plastic should juse expose the copper jumper connections (See pictures).
5.) Attach the physical port connection
The plastic port housing needs to be glued fairly auccurately. Use the assembled watch base to align it. You want the plastic housing bottom to be flush with the bottom of the base housing gap. apply a drop or two of superglue between the plastic housing and the point of contact on the logic frame. (Also, make sure you pass through the 4 center wires through the gap as pictured.) Once the drops of glue have dried, and you can confirm the alignment, place the watch top on (not pictured) and verify that it still fits. Once you are confedent the alignment is correct, take the frame out gently, and add reinforcing amounts of glue. This is a flex point which takes some force when connecting or disconnecting programming wires.
You may want to save this for later. Below is a reference for all programming pins and their eventual connection endpoints:
View = Pins North, looking down into holes
Updated June 3, 2014