I love taking notes on my iPad, but the lack of tool-switching buttons on my Apple Pencil really bugs me. I get that buttons = Apple blasphemy, but I really miss the ability to jump into eraser or lasso mode without moving my pencil from the line I'm writing.
I decided to hack a PS/2 10-key number pad into a programmable Bluetooth macro pad. I'll have dedicated "eraser", "pen", "highligher", and "lasso" keys, as well as a pair of undo/redo and pen grow/shrink buttons.
I've just begun this project -- still waiting for the parts to arrive! -- but I figured I'd live-blog the process here so that y'all can learn from any pitfalls I encounter along the way.
A no-name 500mAh 1S lithium-polymer battery from Amazon.
A Sparkfun Artemis Nano microcontroller.
The microcontroller is really powerful for its size. According to the manufacturer, it can even run TensorFlow Lite models for voice recognition, etc. I chose it because it had several must-haves: native Bluetooth LE support, native Li-Po battery management, and was small enough to stuff into the case of the keypad.
I think I set a new speedrun record in the Smoke% category. Less than half a minute after unboxing the controller, I plugged in the Li-Po and immediately smelled burning silicon.
My thought process went something like this:
The Artemis Nano's got a JST socket. The battery's got a JST plug. Should work.
Turns out all the fancy one-way keying on the socket doesn't do jack-shit if the plug is crimped backwards.
Lesson number one: NEVER TRUST THE CONNECTOR.
I unplugged it fast enough that the charge controller most likely survived. I'll rewire the Li-Po tomorrow, and hope nothing else blows up.