1. Open the scale
2. Rest your finger on the trackpad
3. While mainting finger contact, put your object on the trackpad
4. Try and put as little pressure on the trackpad while still maintaining contact. This is the weight of your object
That is, the pressure sensors only work if it detects capacitance, so you need to be touching the track pad (but not too much!!) while weighing something.
A tiny bit of hardwired dedicated logic integrated into the camera module would be more than adequate to do this - just gating of either the digital I/O or the power to the camera, and a pulse-stretcher so the LED goes on for at least a few seconds each time to prevent an attack by rapidly flicking the camera logic on and off.
A similar circuit for the microphone with a different-coloured physical LED - not just a software-controlled dot on the screen - would be a good idea too.
Speaking of use cases, I started this project with the idea of making a flexible parser for chord symbols. In the process of solving this problem, I wrote some general-purpose utilities, which eventually took form of this library. I'm making it public in the hope that it will be useful to others who use Lua for music and audio programming.
I haven't yet implemented the functions related to scales. I'm still thinking about their relation to chords and how to express it in the library's API.
Parsing chords from notes is more difficult, as are most parsing tasks.