In late 2015, I found this post (In Chinese), the author 3dg12 developed a kit which re-use Thinkpad keyboards for Bluetooth LE 4.0 or 2.4GHz USB dongle connection. It supports wide range of Thinkpad keyboards, T43 and older keyboards use the "bigger" version of the connector and T60 and newer use the smaller version connector. I ordered several kits immediately. I have to say it's an amazing design, that I am still using them right now. Until now (May 2020), the author provided a few upgrades, both software and hardware. I ordered every version of them. 2nd version has very slightly upgrade, it put the LED indicators to the back of the board. While the 3rd version added a feature to "wake up by any key". It's very useful.
The kit comes with a main board with nRF51822 as controller and RF transceiver, a conversion board that converts Thinkpad Keyboard connector to the main board connector, a ribbon cable connects these two boards and a USB dongle.
The FW upgrade and configuration can only be done via USB dongle, so buy one even if you use plan to use BLE only.
Since I purchase it from the US, battery is not be able to ship international. I re-used a old cellphone battery.
The down side of this kit is I have to build the enclosure of the keyboard. I have 3 designs since I got the kit.
Bottom part of X60 laptop.
I board a for-part-only thinkpad X60 off ebay for $20, it's still of good shape but got a cracked LCD and bad motherboard which I don't care. I removed all the parts inside, to keep bottom cases and keyboard only. It's very comfortable with full size palm rest.
The keyboard inside SK8855 is actually the same keyboard as Thinkpad T420. SK8855 use a converter to convert it to USB. Two modifications are made to get it working with 3dg12's kit.
- Add a power button. SK8855 removed the power key on the keyboard, but I need it to power the keyboard on and off with the kit. So I bought a power key from ebay for $2, and drilled a hole to install it. It fits perfectly.
- Drilled 3 holes for LED indicators.
It looks like this:
I have it in my office. It has the first version of the main board. I might consider to replace it with a 3rd version if I got time.
3D printed enclosure
I guess this is my last design. I am happy with everything. It's very compact, has foot stands, storage for the USB dongle and 3rd gen main board supporting wake up by any key feature. I am using it everyday. Even if I got a mechanical keyboard in the future, I will still use it as a carry-on-keyboard to bring with me all the time or during a travel.
I am happy to share the design, let me know if you want to build you own.