Building a One-Handed Keyboard for Accessible Coding

Kian Ryan is a consultant and software engineer, which means that he spends a lot of time typing. A couple of years ago, he suffered an injury to his left shoulder the reduces his strength. He’ll need an operation to address that, but the operation will take his left arm out of commission for several months while he recovers. Losing his ability to type would be catastrophic in his line of work, so he set out to build a one-handed keyboard for accessible typing.

I recently had a medical procedure that made my own left hand unusable for a few days, which is a big deal for a writer like myself. I simply had to take time off work, but that won’t be an option for Ryan because the recovery will last several months. He needed a solution that would let him continue working while recovering.

He investigated the one-handed typing options that were out there, but wasn’t satisfied with any of them. Chorded keyboards (like those used by stenographers), for example, have an extremely steep learning curve that would be excessive for a situation that is only temporary. Then he came across FrogPad, which is similar but relies on layers of key maps based on letter frequency. Some letters are far more common than others, so those go on the top layers. This keeps the number of keys down with as few layer-shifts as possible.

Ryan’s custom keyboard, inspired by the FrogBad, utilizes half of a Lily58 keyboard. One half of the split keyboard provides 24 keys in a relatively traditional staggered layout, plus another five that the thumb can reach. It monitors the keyboard matrix with a Pro Micro running QMK firmware.

Because this has QMK, Ryan was able to configure a custom layered key map similar to the FrogPad’s. It has some dedicated number and control keys (very useful for a programmer), with 15 keys containing alpha characters, punctuation, and so on across several layers. Relegendable key caps let Ryan show information about the characters on each layer.

But, of course, looking at the keyboard while typing would be very inefficient. So Ryan turned to some old friends to build some typing proficiency with his new keyboard. He took advantage of typing training games (like many of us used as children), such as Mario Teaches Typing, to get familiar with the unusual keyboard layout.

Now Ryan has all the tools he needs to stay productive while recovering from his operation.