Arduino sketch to control XY-V17B MP3 module in UART mode.
Notes: for anyone's interest, I solved some noise issues by connecting the speakers's ground "-" terminal to the closest possible point of the XY-V17B GND pin. Also don't leave any audio channel unconnected (L and R), if you want a single speaker connect both channels to the same "+" terminal of the speaker.
David Sanz Kirbis December 2019
Using definitions and some code from Peter Barsznic: https://github.com/electron1979/Arduino_XY-V17B_mp3_wav_player/blob/master/XY-V17B.ino