This adds an initial specification of the machine.PWM class, to provide a
way to generate PWM output that is portable across the different ports.
Such functionality may already be available in one way or another (eg
through a Timer object), but because configuring PWM via a Timer is very
port-specific, and because it's a common thing to do, it's beneficial to
have a top-level construct for it.
The specification in this commit aims to provide core functionality in a
minimal way. It also somewhat matches most existing ad-hoc implementations
of machine.PWM.
See discussion in #2283 and #4237.
Signed-off-by: Damien George <damien@micropython.org>
The machine.sleep() function can be misleading because it clashes with
time.sleep() which has quite different semantics. So change it to
machine.lightsleep() which shows that it is closer in behaviour to
machine.deepsleep().
Also, add an optional argument to these two sleep functions to specify a
maximum time to sleep for. This is a common operation and underlying
hardware usually has a special way of performing this operation.
The existing machine.sleep() function will remain for backwards
compatibility purposes, and it can simply be an alias for
machine.lightsleep() without arguments. The behaviour will be the same.
The machine module should be standard across all ports so should have the
same set of classes in the docs. A special warning is added to the top of
the machine.SD class because it is not standardised and only available on
the cc3200 port.
The list starts with the simplest functionality - GPIO, proceeds to
communication interfaces (UART, SPI, I2C), the to time(r) related
things, then everything else.
machine.time_pulse_us() is intended to provide very fine timing, including
while working with signal bursts, where each transition is tracked in row.
Throwing and handling an exception may take too much time and "signal loss".
So instead, in case of a timeout, just return negative value. Cases of
timeout while waiting for initial signal stabilization, and during actual
timing, are recognized.
The documentation is updated accordingly, and rewritten somewhat to clarify
the function behavior.
machine.POWER_ON is renamed to machine.PWRON_RESET to match other
reset-cause constants that all end in _RESET. The cc3200 port keeps a
legacy definition of POWER_ON for backwards compatibility.
Damien George
Howard Lovatt
Jason Neal
Thorsten von Eicken
Nicko van Someren
Damien George
Paul Sokolovsky
Mike Causer
danicampora