These changes add the ability to intialize a speaker instance to use a
PWM pin instead of a standard GPIO pin in order to emit sounds.
The current GPIO functionality is fairly constrained by the
implementation -- it only permits playing cerain hardcoded "notes".
The PWM support allows one to emit specific frequencies (currently
between 50-32Khz) using a PWM pin. Of course, you may still be
constrained by the limits of your PWM hardware in the end.
There are a few new functions provided to support this PWM mode. To
use the PWM mode of speaker, use the speaker_init_pwm() initialization
routine instead of speaker_init() (for C). For C++ and the SWIG
languages, pass "true" as the second argument to the constructor to
enable PWM mode. The default is "false", to match current default
behavior (GPIO).
Functions that are not related to a given mode (GPIO vs. PWM) will do
nothing if not usable in that mode.
Signed-off-by: Jon Trulson <jtrulson@ics.com>
