UMLIFE 3PCS Mini MP3 Player Audio Module MP3 Voice Decode Board TF Card U Disk IO/Serial Port/AD Board DFPlayer Audio Voice Music Module for Arduino

The most BASIC function: grounding pin IO_1 or IO_2 for play next or previous. Longer ground adjusts volume fine. Haven't tried using a library to program my Arduino and ATtiny85 for specific file play yet, but need to soon. The amp function works great with speaker positive to SPK_1, and negative on SPK_2 pins for mono audio on my 4 ohm 3 amp speaker in project box. MicroSD cards hold snug in slot and haven't popped out. NO discernable/significant heat from amp chip, which was a HUGE problem with the BY8301-16P MP3 Module that these replaced. Only issue is on 1 of the modules the header pins are soldered on somewhat slanted and take some fussing to insert in breadboard, but I'm not penalizing a star for that. Will update if I have problems with the Arduino library when programming for this, but until then, I'm very pleased with this purchase

I had an existing project that uses this chip but from a different project, and it always ran fine. When I put these chips into that project, none of them worked at all. Poor quality. Save you money.

It took me awhile to get this thing up and running. Unbelievably, most wiring diagrams and test code I found online were wrong! I used this with an Arduino Pro mini 328 (functionally the same as an UNO). I could not get the hardware serial encoding to work, so I had to use software serial encoding. I could only get the software encoding to work with the library AltSoftSerial on pins 8 and 9, with 1Kohm resistors on both RX and TX pins. You also MUST use an external power supply! I could not power up the chip from the arduino USB power for whatever reason. There is a small red LED at the top of the DFPlayer, and it must be illuminated. If its not lit up that's your first problem. The speaker should be hooked up to speaker + and speaker -, not from speaker + to ground. If you want stereo sound you need to use the DAC outputs. Many people say that have to connect both grounds. It worked fine (without any noticeable noise) only using the ground near the speaker terminals, but it is smart to connect both grounds together. The way you organize your MP3 files is extremely important. It read a 32gB card formatted in FAT32 just fine. I converted all my MP3s to constant bit rate (many you download with be variable bit rate) . I don't know if this can read variable bit rate, but I didn't take that chance. If you want to play the files off the root directory, you must name the files with a 4 digit number, for example "0004.mp3". HOWEVER, if you want to use several folders to play different sounds, i.e. 30 files in folder 01, 30 files in folder 02, etc. you must name the sounds with a 3 digit number, i.e. "004.mp3" in folder "03". After getting all that figured out, its a neat little device! Only uses 2 pins and about 10% of memory. You can change the volume and a bunch of other stuff via code. I have about 100 small MP3 files on my SD card and there is no noticeable lag when playing. The sound quality and volume is pretty good for such a small chip, if you have a decent speaker (3w max) hooked up to it. WAY better than using any sort of onboard noise making on the arduino. And once you send the play commands, the DFPlayer plays it stand alone without using up too many Arduino resources. Great for any arduino sound project!

I used this device for a music player project. It worked fine for my purposes. Credit to "Richard Makes Escape Rooms" for his tips on using the serial command API. Project source, pictures and video link on my rshorton github music_box project.

As others have recently noted this unit works fine as a standalone but nothing but issues with serial communication. Tried multiple libraries on Arduino, different arduinos and versions to no avail. Even reached out to a friend who has used hundreds of these (working ones). I ordered a second batch with the same result. Ordered from another seller and those worked with no issues using the latest library from dfrobot. Product images shown on listing do not match what you get. You can see in the attached pictures what to look for. 2 stars because it works fine in stand-alone but hours of frustration trying to get these to work.