Sounding Off Part 4
by Gordon McComb
Creating a Custom Sound Co-processor
Discuss this article in the SERVO Magazine
forums at http://forum.servomagazine.com.
My first fascination with electronics
was sound-making gizmos. It didn’t
matter what sound: sirens, warblers,
choo-choo train effects ... you name it,
I wanted to build it. Most used a 555
timer IC, but others involved the latest
specialty sound-making chips of the
day, like the venerable Texas
Instruments SN76477 — made famous
by the Space Invaders arcade game.
but an even better method is to use a microcontroller that
is designed from the ground up to handle multiple tasks at
the same time.
In this fourth and final installment of Sounding Off,
you’ll discover how to use the Parallax Propeller
microcontroller to augment the audio generation features
of your Arduino-based robot — generate tones, synthesize
MIDI instruments, even play digitized WAV files. While the
emphasis is on sound, know the same general concepts
work for any co-processing task, such as operating motors
and reading sensors.
Getting to Know the Propeller
That was then, this is now. For the past several months, we’ve looked at ways to use the Arduino to create
sound — all the way from simple tones, to speech, MIDI,
and even MP3 playback. As capable as the Arduino is,
sound generation tasks can use up a lot of processing time.
The more cycles your robot’s brain spends on making noise,
the less time it has for driving around and avoiding
FIGURE 1. The Propeller Board of Education
(PropBOE) serves — among other things — as an
able experimenter and development board for
working with sound.
58 SERVO 06.2012