Datasheet

Run the sketch and open up your Arduino Serial console. If there's a problem you'll get a failure to set the volume

initially

If it's OK, you can send multiple +'s and -'s to increase or decrease the volume. The volume can go down to 0 or up to

63 (which is 29dB of gain)

return;

if (thevol > 63) thevol = 63;

if (thevol < 0) thevol = 0;

setvolume(thevol);

}