Convert an IBM Thinkpad 380ED Keyboard and Trackpoint to USB

Older Thinkpad keyboards have full size keys that feel much better than the “chicklet” keys on modern laptops. A nice feature of these keyboards is the trackpoint eraser head that takes a lot less space than a touchpad. Newer Thinkpad keyboards have a built in circuit that converts the trackpoint resistive strain gauges to PS/2 but older Thinkpads, like the 380ED, rely on circuitry external to the keyboard to do the conversion. This project will develop that circuitry so that a Teensy 3.2 can detect the voltage change with it’s A to D converter. The keyboard key matrix will also be scanned by the Teensy in order to implement a composite USB keyboard and mouse device. For more details, see https://hackaday.io/project/171439-ibm-thinkpad-380ed-keyboardtrackpoint-to-usb#menu-description