DIGITAL
AUDIO PROCESSING
This
is not a poor man’s iPod. It’s the real McCoy.
My digital audio player is an example of digital
audio processing in software.
There
is often a need for audio in an embedded application,
which can be controlled programmatically (by
a command on a serial port that can make the
system play a suitable tune). The block diagram
for generic embedded audio processing is shown
in Figure 1. The blocks used in the project
are highlighted.
(Click
here to enlarge) |
Figure
1—The input transducer (e.g., a microphone)
converts sound from different sources into
an analog signal. The ADC converts the analog
signal into a digital signal. The DSP system
with its resources does the processing,
and it outputs the resulting signal into
a DAC. To output sound, the DAC sends the
analog signal into the speaker or headphones. |
The
user manual for the LPC214x family of Philips
microcontrollers (section 1.3 Applications)
doesn’t list digital audio in its other applications,
but you don’t need to tell Philips what you’re
using it for. The SPI port on LPC214x microcontrollers
doesn’t support I2S mode, but that’s easy to
fix.
