The goal of this project is simple:
- Play MP3 songs, from a micro-SD card, randomly, forever.
This project requires three pieces of hardware:
- An Arduino-board.
- A sparkfun MP3 Player Shield - such as this official product.
- Or a cheap clone, such as this one I actually purchased.
- A set of headphones.
Assembly is trivial:
- Plug the two boards together.
- They only fit one way :)
- Insert your headphones.
- Insert your pre-prepared SD-card.
You'll need to format your card carefully, such that it can be read by the onboard card-reader. In short this means you must use a RAW block-device, not a partitioned one, and you must format it as FAT16, or FAT32. (Because of that you will also be restricted to DOS-style 8.3 filenames.)
In my case I ran this:root@deagol:~# mkdosfs -F16 /dev/sdX -I mkfs.fat 3.0.27 (2014-11-12) root@deagol:~# mount /dev/sdX /mnt root@deagol:~# cp /tmp/*.mp3 /mnt root@deagol:~# ls /mnt/*.mp3 /mnt/track001.mp3 /mnt/track002.mp3 /mnt/track003.mp3 root@deagol:~# umount /mnt
You'll notice I explicitly didn't create a partition. I just used the raw block-device.
A lot of the existing MP3-player projects will tell you to use filenames of the form
trackNNN.mp3, and warn you that only 999 files are supported. That's because the API for playback allows you to write the following to play the file named
In this project we read the filenames from the card, and play then regardless of what they are - via a different API function (
blah.playMP3(filename);). So long as you avoid UTF-8, and use filenames that honour the 8.3 format you're fine.
The code for this project has pretty much already been written for us! What we need to do is clone the appropriate library to our local Arduino development-host, then we can merely load the examples for the functionality we need.
Clone the repository:deagol ~ $ git clone https://github.com/mpflaga/Sparkfun-MP3-Player-Shield-Arduino-Library.git Cloning into 'Sparkfun-MP3-Player-Shield-Arduino-Library'... remote: Counting objects: 3303, done. remote: Total 3303 (delta 0), reused 0 (delta 0), pack-reused 3303 Receiving objects: 100% (3303/3303), 3.13 MiB | 1.26 MiB/s, done. Resolving deltas: 100% (2158/2158), done. Checking connectivity... done. deagol ~ $
Now we need to move the libraries into the correct location:deagol ~ $ mkdir -p Arduino/libraries/ || true deagol ~ $ mv Sparkfun-MP3-Player-Shield-Arduino-Library/SdFat/ ~/Arduino/libraries/ deagol ~ $ mv Sparkfun-MP3-Player-Shield-Arduino-Library/SFEMP3Shield/ ~/Arduino/libraries/
Once that is done you can open your Arduino development-environment and load the examples. There are two sets of examples - one for the SD card-reader, and one for the player. I'd suggest starting with the former.
Click on the Menu-item "
File | Examples | SdFat | SdInfo". This will load a program which will dump details about your SD-card. Compile it and upload to your board, then open the serial-console.
Once you've entered a dummy-keystroke you'll see output like this:init time: 14 ms Card type: SDHC Manufacturer ID: 0X3 OEM ID: SD Product: SU04G Version: 8.0 Serial number: 271253504 Manufacturing date: 9/2010 cardSize: 3965.19 MB (MB = 1,000,000 bytes) flashEraseSize: 128 blocks eraseSingleBlock: true SD Partition Table part,boot,type,start,length 1,0X0,0X0,0,0 2,0X0,0X0,0,0 3,0X0,0X0,0,0 4,0X0,0X0,0,0 Volume is FAT16 blocksPerCluster: 128 clusterCount: 60499 freeClusters: 60340 freeSpace: 3954.44 MB (MB = 1,000,000 bytes) fatStartBlock: 1 fatCount: 2 blocksPerFat: 256 rootDirStart: 513 dataStartBlock: 513 Data area is not aligned on flash erase boundaries! Download and use formatter from www.sdcard.org/consumer!
To do something more useful, playing files, load another example. This time we choose "
File | Examples | SFEMP3Shield | Examples | MP3Shield_Library_Demo.ino". Once loaded change the serial speed from:Serial.begin(115200);
At that point you can see a menu on your serial console, which will let you control the audio.
Our Random Player
Taking code from the samples seen above I've put together the following application, which picks a random file from the SD-card, plays it, then repeats forever.
The complete code reads as follows:
- Because randomness is non-perfect you might find track 6 plays 100 times in a row.
- Keep track of the most recent track(s) and avoid repeating them immediately.
- This will fail if you only have a small number of files though, because all tracks will be recent.
- Wire up an IR-based controller.
- Wire up an LCD display for showing the currently-playing song.