Hi Michele, benvenuto
the sd-card has to be formatted fat16 or fat. This means you can only use cards up to 32gb.
The structure should be:
Use the files from the repository for the folders advert and mp3.
Put your own files in the folders 01 to 99. Each folder can contain 255 mp3 files named 001.mp3, 002.mp3 up to 255.mp3.
Prepare a folder on your pc and copy it to the card in one go.
Put your sd card in the dfplayer, power everything on and put a rfid card on the reader and leave it there.
Now TONuino asks for the folder to attach to this rfid card. Navigate through the folders with the vol-up vol-down button and press play for the folder you like. TONuino says the number and starts playing the first file in the folder while navigating.
Next it asks for the mode for the selected folder. Again navigate through modes with vol-up and vol-down and press play if done.
Your card is now connected to the folder.
Repeat with other RFID-Cards for more folders.