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https://github.com/geky/hcplayer

Hardcoded wave player for MBED devices
https://github.com/geky/hcplayer

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Hardcoded wave player for MBED devices

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README 

        
Hardcoded Player

================



Ever wanted a program that exists for the sole purpose of playing a single

sound clip over and over again on any MBED device that has a DAC with

absolutely no bells or whistles?

Then this is the program you're looking for.



How to use

----------

Assuming you have an mbed development environment set up, then creating your

hardcoded player is a simple 3 step process. If not then feel free to follow

the wonderful getting started guide over [here](https://docs.mbed.com/docs/getting-started-mbed-os/en/latest/).



1. Convert your audio into a wave file that will fit on your device. For this

I used the wonderful [pydub](http://pydub.com/) library, but feel free to use

any tool to get a 8-bit mono 8000hz wave file.



``` bash

$ ./decode.py music.mp3 music.wav

    

```



2. Dump the wave file into a C file for compilation. Don't worry if your wave file

still doesn't fit, you can specify an offset/size in bytes.

``` bash

$ ./dump.py light.wav data.h 4000 200000

```



3. Now all that's left is to compile and flash your hardcode player!

``` bash

$ make all flash

```



If you get an error like `cannot move location counter backwards`, don't worry, this

just means your file is still too big! Just try triming it down a bit.



Example

-------

Here's the program running on a [K64F](https://developer.mbed.org/platforms/FRDM-K64F/).

Doesn't it look like it sounds just like you imagine?



![hcplayer](hcplayer.jpg)



Why?

----

Originally the idea was to create a little music player that you could connect to speakers

and send music remotely. There have been several times I've found myself with a group of

people who all want to have music playing. The only current solution is for someone to contribute

their computer and takes requests. I figured it'd be easy to throw some code on a microcontroller

and make a cheap music player.



Long story short, I flat out underestimated audio. Decoding compressed audio requires more 

computational power than these guys can muster, and uncompressed audio is exactly what it sounds

like: uncompressed, and far too big to fit on these little guys.



Of course, these issues can both be fixed with more hardware. Adding external memory would allow full

uncompressed songs to be stored on the device and streamed as needed. An easier solution would be

a full MP3 and AAC decoder such as [this one](https://www.sparkfun.com/products/12660?gclid=CM6wm4rTp8oCFQoKaQod190PlQ) which would even be compatible with the K64F's headers.



Live and learn, you will probably need specialized hardware to play arbitrary audio directly.

Nonetheless, it's still perfectly possible to play _hardcoded_ audio directly. So now instead of

fighting over the audio cord, everyone can listen to 25 seconds of wonderful minimal-fidelity music!