files. Before loading the USB Flash
drive with the audio files, each file
was renamed from the original
name of the song to the
xxxxxxxx.MP3 ASCII string as
described earlier.
Since both interrupts and a data
rate of 115,200 baud were required,
it was necessary to use the micro’s
only UART for communication with
the DLP-RFID1 RFID reader. This
meant that serial communication
with the VMUSIC1 module would
have to be done via software (not
via a UART), which was not a
problem since we only needed a
rate of 9600 baud and no interrupts.
In fact, if this system did not use
the RFID reader with its high data
rate requirement, we could have
eliminated the crystal from the
design altogether and used the
microcontroller’s internal 8 MHz
oscillator instead.
I added a serial LCD display to
be able to see the name of the audio
file being played and an LED that
was turned on to indicate when the
micro was out of Sleep Mode,
requesting an RFID tag to trigger a
song selection. In fact, all that is
really needed to make the VMUSIC1
play music is four pins from a small
microcontroller and a five-volt power
supply.
Conclusion
If you want to be able to say “I
designed my own MP3 player”
then yes, this platform could be
used as the starting point. After all,
all that’s needed to implement a
player is some form of storage for
the audio files, a power source, an
(optional) LCD display, and a few
buttons for song selection.
However, with a little imagination,
the VMUSIC1 module opens
up a world of possibilities from
interactive talking robots to adding
voice or music to ANYTHING that
has a microcontroller.
So, put on your thinking cap,
grab your microphone, and start
creating audio files. The VMUSIC1
module will handle the hard part of
audio playback for you. NV
66
March 2007
