I'm trying to find the code that will allow me to play music from the mp3 and to control the volume. I have the mp3 that has only 4 pins (rx, tx, vcc, and gnd). Thank you!
Did you try any of the numerous code examples that are out there, and if so what's the result?
And where can we find the data sheet?
Here's the datasheet: http://geekmatic.in.ua/pdf/Catalex_MP3_board.pdf
How can I send you the Arduino file because it is a very long code?
Start with your minimum example.
I.e. the code that you use to test the player by itself.
Read the sticky for details on how to post properly.