So, after coming back from vacations, and with the new Pro Tinket arrived, it was time to test my assumptions. It looks like it's gonna work just fine for simple data logging. As a refresher, here's the idea

Sample every 50ms, and keep the sum of forces applied to the sensor (for a completely still object, that should be 1g). Measure the max-min within every 20 samples (1 second), and flag each second as active or inactive.

My research so far shows that when sitting or standing, very few seconds are flagged as active (the ones where you pick up a glass to drink whater, for example), and the majority of seconds are flagged as active when walking.

So, just to take this further, i moved the circuit to use the newly-arrived Pro Trinket. I've also added the LiPo charging circuit to un-tether myself from the computer, and slightly modified the code to log data on an SD on top of sending them over Serial. Since we only log 1 byte (active/inactive) per second - well, 2 including the newline - there is plenty of space in the SD. My main concern is battery life, which i'm also going to test in this iteration.

Here's a video of the current iteration. Can't wait to try it out this Monday at work. The LEDs are there just for me to be able to know that this thing is working, and to add a couple of drain to stress the battery a bit.

Goal: Gather data of 1 day including walking, standing, and sitting. Evaluate battery life. Settle on final algorithm to discern between stages.

Next Target: The next iteration should include the final algorithm, and some kind of notice for the user when they need to start working, so it should be the first functional prototype. Next goal should be to settle on the final notification type (as much as i'd like to add electroshock, it will be hard to convince others at work to wear this, not to mention battery life!), and work on power-saving.