I discovered thi wonderful book when it was only expensive and hardbound. Now the author has made every chapter of the book available in PDF format - FREE! This book is readable, with a minimum of extraneous (not useful to a maker) math. My most recent insight from this book is that, for slow-changing data, a moving-average filter is most suitable. This is easily implemented on most microcontrollers.
The Scientist and Engineer's Guide to Digital Signal Processing
Makerdon is a Mastodon instance focused on Makers, Open Source Hardware (OSHW) and STEM/STEAM. Free and Open Source Software (FOSS) is a likely topic as well. If you're interested in making things, allowing others to build on your work, and/or teaching others about making things, you might like this instance.