I've had to put this project on hold the last few months due to work. In the meantime, I've had some time to consider where I want this project to go.

The Freescale KL27Z no longer seems like a good option. According to this conversation it sounds like FRDM-KL43Z support in mbed is stuck in limbo. I have no definite plans for producing TBD, so it wouldn't be eligible to be an online toolchain platform. I need mbed to have an existing platform compatible with the KL27Z in the online IDE, and I was hoping that the FRDM-KL43Z would be it. To make matters worse, I found that Linux has the same access control restrictions on USB HID devices as other classes, so the convenience advantage of HID on Windows doesn't extend to Linux.

And so the current TBD hardware is dead.

But TBD is not. Stay tuned.