I've wanted to experiment with interfacing the 96boardsHiKey (8-core, 64-bit ARM development computer) to some devices, but the 2mm 40-pin header is difficult to bring out to a breadboard (except by individual wires). I designed a simple adapter board and had some produced by the awesome OSH Park prototype PCB fabbing service. The boards are back, and I've been assembling a few of them for testing.
The adapter has a 40-pin 2mm male connector that plugs into the 96boards "low-speed" (LS) female header. It brings those signals to a 40-pin 0.1"/2.54mm header that can be used with an insulation displacement connector (IDC) on a ribbon cable. The other end of the ribbon cable can then be connected to a standard solderless breadboard using an adapter (most of the 40-pin IDC-to-breadboard adapters used with the Raspberry Pi A+/B+/2 should work -- for example, the AdaFruit Pi Cobbler Plus (straight) or T Cobbler Plus (T-shaped), KEYES SMP0047 from dx.com (U-shaped - not checked), or a 40-pin IDC Ribbon Breakout from Creatron in Toronto (straight) -- obviously, the pinouts from the 96boards connector will be different, so ignore or rewrite the pin labels on the adapter board). Update: Watch out for breadboard adapters that connect pins together -- e.g., that are designed for use with a Pi and connect together Ground or Supply pins, which will have different functions on 96boards LS connector. (I found a T-style adapter from DX.com that has this issue).
These first-try "Alpha 1" boards are not ideal -- they're bigger than they need to be, the board occludes one of the 96boards mounting holes, and the routing is wonky (I let the autorouter do its thing, and ended up with a couple of unnecessary vias and some wild traces). Nonetheless, the board seems to do what it was intended to do. I'm going to work on a second-generation design, but it may be a little while before I get around to it.
If you're interested in using this design, it's licensed under CC-BY-SA and can be downloaded or ordered from the OSH Park sharing site.
You can use this with the 2mm (96boards LS) and 2.5mm (IDC) connectors on the same side of the board, or on opposite sides of the board.
If you place them on the same side of the board (see the populated PCB with no cable attached in the photo -- though the IDC socket should be rotated 180 degrees), the pin numbering on the IDC cable will match the 96boards pin numbering. However, the IDC connector will be really tight to the edge of the board -- you may want to slightly angle the IDC header when you solder it on.
If you place them on the opposite sides of the board (the adapter plugged into the HiKey in the photo), the even and odd numbered pins will be swapped (1<->2, 3<->4).
One final note -- these should work fine with other 96boards devices that comply with the Consumer Edition specification -- and hopefully, it won't be long before the DragonBoard 410c is available so we can test this theory!
(The board in the photo is in one of the very basic acrylic cases I built for the HiKeys).