Mp3 Verplank Diagram

Mp3 Video

Mp3 Source Code

Mp3 State Diagram

Aim: 

To design an mp3 player which is different in a certain aspect from conventional ones. Given the time and material constraints during the quarter, I wanted to end up with a project which distinguished itself on the basis of a certain feature such that the feature could turn out to be the selling point to consumers. Hence, after looking at a number of players in the market my thoughts turned to the need for a hands-free device such that one does not need to push a button or be in the vicinity of the player to change a song each time. The thought behind it is similar to that of controlling a TV by a remote, but in this case the remote is your hand in that you just need to swipe it over the mp3 to change the song. 

Potential Uses:

The design is aimed at every age group and the applications listed below could appeal to anyone

1) The user is not close enough to the mp3 and is just too lazy to get up and change the song, would rather change it with a simple hand movement

2) Hands are not in the best position to push the mp3 button, e.g. talking on the phone, dirty hands while eating etc..

Components:

1) IR sensor (bottom left) to detect spikes in signal readings corresponding to a hand moving over the sensor, if the reading is above a certain threshold (positive reading) switches to the next song. If the reading is positive waits for 500ms before checking again else the sensor will be activated multiple times for just one hand swipe due to the sensor being polled every clock cycle

2) Nokia graphical LCD display (top left), displays a marker next to the current song as well as a list of songs

3) Audio Decoder and Audio jack (right side of the board)

4) MicroSD card to store songs

5) Potentiometer (top right) - to change the volume

6) Pause and Play buttons (bottom).

NOTE: - No interrupts were required for the buttons or the sensor given that polling the line for a signal is quite fast and can be checked on every cycle.

Mp3 Prototype:

Implementation Notes:

1) The biggest challenge was getting the IR sensor to work correctly in different settings. For example the readings in the lab tend to be much lower compared to when you take it out into the sun, hence caution must be exercised when setting the threshold to find signal spikes corresponding to hand movements else one might encounter a lot of false signals.

2) Also one needs to be careful when initializing the FatFs and the mp3 libraries, the order of initialization sometimes plays an important role, else the code doesn't run even though it seems fine. Look at the posted code to see the best way to initialize all the components in the setup function.

Possible Extensions:

Given more time these are some of the ideas that I have in mind

1) Add an FM radio so that users have both options of listening to their own music as well as radio stations

2) Add the ability for users to mix two songs (using 2 audio decoders), this was my original design, but the available components were not suited for this application. Also some research would need to be done on how mixing is carried out in hardware/software.

3) Improving on the physical design in terms of a better casing, as well as fine tuning the operation of the IR sensor to be accurate in almost any setting.