Converting a Newton Keyboard to USB

Deutsche Version

Below, I describe how to convert an Apple Newton keyboard to connect to a computer via USB. Normally, the keyboard connects to an Apple Newton device using an 8-pin mini-DIN plug and can only be used with it.

This is a very simple conversion that even inexperienced tinkerers can manage. If you prefer a more polished approach, the procedure can be adjusted accordingly.

The main challenge is not converting to a USB cable, but rather the fact that the keyboard does not send ASCII codes, but proprietary codes understood only by the Newton. Therefore, a small adapter is needed, which is very easy to build. The circuit board costs about €10, and a mini-DIN cable even less.

I relied on the following websites and summarized the necessary steps here. By the way, I wrote this guide entirely using the Newton keyboard on an iPad.

Downloads

Instructions for building the adapter:

https://jimandnoreen.com/?p=259

Arduino IDE (for programming the Teensy board):

https://www.arduino.cc/en/software/

Teensyduino (Add-on for Arduino IDE for controlling the Teensy board):

https://www.pjrc.com/teensy/td_download.html

Teensy Loader (program for actual communication with the Teensy board for programming):

https://www.pjrc.com/teensy/loader.html

Apple Newton Keyboard to USB Converter (script for programming the Teensy board):

https://jimandnoreen.com/?page_id=185

Required Materials

Teensy 2.0 board (other models might work, but the 2.0 board is sufficient). Note: the board must be designed for 5V!
Short mini-DIN 8 cable with a female socket (the male plug is not needed). The cable should be as thin and flexible as possible.
Mini-USB cable with USB-A or USB-C at the other end, for programming the board and later connecting the keyboard to the computer.
Soldering iron with a fine tip
Multimeter for added safety

Soldering Cables to the Teensy Board

Cut the socket with about 10 cm of cable. Alternatively, you can buy just a socket, but soldering will likely be more complex.
Strip about 3 to 4 cm of the cable to expose the fine wires.
Only three wires are needed: ground (on the metal ring of the socket), signal (on pin 8), and power (on pin 2). Good cables use the following colors (please verify with a multimeter):

Brown for power (pin 2)

Purple for signal (pin 8)

Bare wire for ground

Cut off the unnecessary wires.
Slightly strip the ends of the colored wires and solder them to the Teensy board as follows:

Brown to VCC (first connection on the top right next to the USB socket)

Purple to D2 (fourth connection from the bottom left)

Cover the bare wire with heat shrink tubing or similar and solder it to GND (first connection on the top left).

No additional soldering is required.

Programming the Teensy Board

Download and install the Arduino IDE: https://www.arduino.cc/en/software/
Download and install the Teensy Loader: https://www.pjrc.com/teensy/loader.html
Download the "Apple Newton Keyboard to USB Converter" script: https://jimandnoreen.com/?page_id=185
Compress the "Newtonkeyboard" folder into a ZIP file.
Install the "Teensyduino" extension. In Arduino IDE settings, add this URL to "Additional Board Manager URLs":

https://www.pjrc.com/teensy/package_teensy_index.json

In the program's left panel, search for "Teensy" in the Board Manager and install the module.
Connect the Teensy board to the computer using the mini-USB cable. Note that not all USB cables work! Some only provide power. A blinking LED should appear on the board (even with incompatible cables).
Connect the keyboard to the Teensy board.
In the "Tools" menu, set "USB Type" to "Keyboard + Mouse + Joystick."
Under "Tools" ➔ "Board," select "Teensy 2.0."
Under "Tools" ➔ "Port," the Teensy board should appear.
In "Sketch" ➔ "Include Library" ➔ "Add .ZIP library," load the "Newtonkeyboard" ZIP file.
Press the tiny button on the board. The LED should stop blinking.

Upload the script to the Teensy. Errors will be shown in the console — often due to incorrect port settings or USB Type configuration. Retry if needed.
Once programmed successfully, the keyboard is ready for immediate use and should be recognized by the computer.

Installing the Adapter into the Keyboard

Unscrew the keyboard and carefully lift the top cover. Avoid breaking small plastic tabs and disconnecting the ribbon cables or silver ground wire.
Twist the original black keyboard cable tightly and store it in the lower casing.
Connect the Teensy board with the mini-DIN socket to the original keyboard cable and place it inside the keyboard.
Lead the mini-USB cable through the small hole at the back of the keyboard.

Carefully reassemble the keyboard. If it warps slightly, adjust the internal cables towards the back where there is more space. Ensure the Teensy board does not contact the keyboard's inner metal cover to avoid electrical issues.

This is my quick-and-dirty solution, requiring minimal effort and preserving the keyboard's original condition since the original cable remains intact and can be reused if needed.

For more customizable connectivity, you could enlarge the small hole at the back to fit the Teensy USB port, allowing any mini-USB cable to be connected without an attached cable. The Teensy board would just need to be securely fixed inside.

However, my described solution suffices for me. Since I have a second Newton keyboard, I can use one for my Newton and the modified one for modern computers.

One issue I've had with the keyboard since purchasing it is its firm keypress feel and loudness, making it unsuitable for quiet environments like libraries. Otherwise, it is light, compact, and durable.

The only key that doesn’t work after modification is the top-left one with the degree and circumflex symbols. It’s not essential, but the script might be adjustable to assign a function like the Escape key, which the Newton keyboard lacks.