This is a way to take a Microsoft ergonomic bluetooth keyboard, and make it into a hard-wired keyboard running QMK.
The keyboard is known under several different names: Mobile Bluetooth 5000, Mobile 6000, Sculpt mobile, and Asus rebranded
I had a stack of them,since they're cheap on ebay, travel well, and are just ergo enough.
The ribbon cable is 1mm pitch, which is hard to hand solder. I bought a cheap set of "pitch adapter" boards https://www.amazon.com/Double-Sided-0-4mm-1-0-Adapter-60mmx38mm/dp/B00OK42118
Cut the original ribbon cable sockets off the bluetooth board using a razor, they're hard to desolder. They're also allow the cable to be inserted on top or bottom.
If I was going to do it again, I'd make the MCU connection come out the top of the keyboard and avoid the wires dangling out the bottom.
As I was debugging the matrix, I started to get random failures. In desparation I tried a second MCU, but had the same problems. It turns out that the ribbon cable connections can get worn. Shave a half millimeter off the end of the ribbon cable & the errors go away.
My method for discovering the matrix was to set up a KEYMAP macro that included all pins. See MATRIX_TESTING_KEYMAP if you need it. Then set up a keymap that has all printable symbols in the first 4 rows. test each key & record output. Then switch the printable symbols to the bottom 4 rows & repeat. This was enough to show the matrix.
The full original keymap for the sculpt is
A B C D E F G H --->
0 b n m , . /
1 g h "
2 7 8 9 0 Del PgUp
3 p [ ] \
4 y u i o
5 ~ - += j k l ; 5
6 a s d q w e, Up left
7 F7 F8 F9 F10 F11 F12 f
-----> I J K L M N O P Q R
0 Caps FN
1 Vol+ mute Rctl vol- pgdn LCTL
2 Rshift LShift
3 Ralt LAlt
4 LGUI
5 6 bakspc 1 2 3 4 F4 F5 F6
6 Down right spc F1 F2 F3 tab
7 r t z x c v enter Esc
This works with 18 cols + 8 rows on a Teensy++, or Arm based Teensy.
The Astar mini has all pins exposed , so you can do 18x8 If you want a speaker, LEDs &etc, you'll need to free up a pin. I recommend joining columns R and L to the same pin.
Building - add ASTAR=1 to the compile line or leave out for teensy2++