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BREAKING - analogWriteRange 8-bit default (#7456)

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Matching standard Arduino cores, make the default analogWrite() take
values from 0...255.  Users can always use the analogWriteRange() call
to change to a different setup.

Add a `analogWriteResolution` which takes a number of bits and sets
the range from 0...(1<<bits)-1, part of the standard Arduino API.

Remove the PWMRANGE define.  It's non-standard and not generally valid
(i.e. it's fixed at 1024 of 256, but the real range varies depending on
what you last set).

Also add note about the change and how to fix pre 3.0 applications.

Fixes #2895
This commit is contained in:
Earle F. Philhower, III
2020-07-28 17:39:38 -07:00
committed by GitHub
parent 33083861c8
commit a679869155
3 changed files with 28 additions and 8 deletions
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18
doc/reference.rst
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@ -102,9 +102,19 @@ Analog output
``analogWrite(pin, value)`` enables software PWM on the given pin. PWM
may be used on pins 0 to 16. Call ``analogWrite(pin, 0)`` to disable PWM
on the pin. ``value`` may be in range from 0 to ``PWMRANGE``, which is
equal to 1023 by default. PWM range may be changed by calling
``analogWriteRange(new_range)``.
on the pin.
``value`` may be in range from 0 to 255 (which is the Arduino default).
PWM range may be changed by calling ``analogWriteRange(new_range)`` or
``analogWriteResolution(bits)``. ``new_range`` may be from 15...65535
or ``bits`` may be from 4...16.
**NOTE:** The default ``analogWrite`` range was 1023 in releases before
3.0, but this lead to incompatibility with external libraries which
depended on the Arduino core default of 256. Existing applications which
rely on the prior 1023 value may add a call to ``analogWriteRange(1023)``
to their ``setup()`` routine to retrurn to their old behavior. Applications
which already were calling ``analogWriteRange`` need no change.
PWM frequency is 1kHz by default. Call
``analogWriteFreq(new_frequency)`` to change the frequency. Valid values
@ -113,7 +123,7 @@ are from 100Hz up to 40000Hz.
The ESP doesn't have hardware PWM, so the implementation is by software.
With one PWM output at 40KHz, the CPU is already rather loaded. The more
PWM outputs used, and the higher their frequency, the closer you get to
the CPU limits, and the less CPU cycles are available for sketch execution.
the CPU limits, and the fewer CPU cycles are available for sketch execution.
Timing and delays
-----------------