Dear All,
I got this problem,
i programmed an arduino uno for a simple mp3 playback using DFPLAYER MP3 Module.
it worked fine on computer.
but once i connect 9v battery to the arduino instead of computer USB .
i can only hear noise .
what could be the problem
??
When you say connecting 9V to the arduino, is it just the supply?
I know nothing about the library you are using but is there anything in your program that communicates via the USB? Would explain why it isn't working when removed.
it turned to be caused by the arduino it self,
seems it doesnt regulate the voltage efficiently .
so i powered the module by 6 volts and 5 volts externally and it worked
also make sure you have a resistor on the RX of the module. It doesn't like 5v.
Arduino Project: MP3 player using Arduino and DFPlayer mini MP3 player module at about 1:40
Also, I found out that some of the datasheet has errors. I can not find the link where I read it, but I have attached the sketch from the link. It may be helpful to you as well.