We're developing a new version of Spresense e-violin.
From this version, we try to automatically tune the strings.
As a trial, we attached a single DC motor to pull one string. We also attached piezo pickup, connected to Spresense. The sampled sound is FFTed and the estimated frequency is used to adjust the tension of the string.
In near future, we expect to control four motors by this 3D-printed motor box.
There are some LEGO-connectable microcomputer board cases publicly available. The black box in the photo is one of my favorite Raspberry Pi cases. However, there are almost no LEGO cases for batteries!
Therefore, we created a mobile battery case for “Cheero IoT” which is popular for geeks.