I've created and maintaining an Android library that implements user-space driver for common USB to serial converters https://github.com/felHR85/UsbSerial https

I've created and maintaining an Android library that implements user-space driver for common USB to serial converters https://github.com/felHR85/UsbSerial https://github.com/felHR85/UsbSerial (Nothing fancy compared with what others are posting here but it has been my little proud). I estimate that I've earned around 3 - 4 k€ in 6 years because of this project mostly from: - Freelancing in projects related. - Paid version of an Android app that uses the library - Free version of the same app with ads - Donations Obviously I have a proper job but I've been able to learn a lot because of this side project. I would do it again