214 lines
6.6 KiB
Python
214 lines
6.6 KiB
Python
# SPDX-FileCopyrightText: 2021 Melissa LeBlanc-Williams for Adafruit Industries
|
|
#
|
|
# SPDX-License-Identifier: MIT
|
|
"""PWMOut Class for NXP LPC4330"""
|
|
|
|
from greatfet import GreatFET
|
|
|
|
try:
|
|
from microcontroller.pin import pwmOuts
|
|
except ImportError:
|
|
raise RuntimeError("No PWM outputs defined for this board") from ImportError
|
|
|
|
|
|
# pylint: disable=unnecessary-pass
|
|
class PWMError(IOError):
|
|
"""Base class for PWM errors."""
|
|
|
|
pass
|
|
|
|
|
|
# pylint: enable=unnecessary-pass
|
|
class PWMOut:
|
|
"""Pulse Width Modulation Output Class"""
|
|
|
|
MAX_CYCLE_LEVEL = 1024
|
|
|
|
def __init__(self, pin, *, frequency=750, duty_cycle=0, variable_frequency=False):
|
|
"""This class makes use of the GreatFET One's Pattern Generator to create a
|
|
Simulated Pulse width modulation. The way that the Pattern Generator works is that
|
|
takes a pattern in the form of bytes and will repeat the output. The trick to simulate
|
|
PWM is to generate the correct byte pattern for the correct channel.
|
|
|
|
Args:
|
|
pin (Pin): CircuitPython Pin object to output to
|
|
duty_cycle (int) : The fraction of each pulse which is high. 16-bit
|
|
frequency (int) : target frequency in Hertz (32-bit)
|
|
|
|
Returns:
|
|
PWMOut: PWMOut object.
|
|
|
|
Raises:
|
|
PWMError: if an I/O or OS error occurs.
|
|
TypeError: if `channel` or `pin` types are invalid.
|
|
ValueError: if PWM channel does not exist.
|
|
"""
|
|
self._gf = GreatFET()
|
|
|
|
if variable_frequency:
|
|
raise NotImplementedError("Variable Frequency is not currently supported.")
|
|
|
|
self._pattern = None
|
|
self._channel = None
|
|
self._enable = False
|
|
self._frequency = 500
|
|
self._duty_cycle = 0
|
|
self._open(pin, duty_cycle, frequency)
|
|
|
|
def __enter__(self):
|
|
return self
|
|
|
|
def __exit__(self, t, value, traceback):
|
|
self.deinit()
|
|
|
|
def _open(self, pin, duty=0, freq=500):
|
|
self._channel = None
|
|
for pwmpair in pwmOuts:
|
|
if pwmpair[1] == pin:
|
|
self._channel = pwmpair[0]
|
|
|
|
self._pin = pin
|
|
if self._channel is None:
|
|
raise RuntimeError("No PWM channel found for this Pin")
|
|
|
|
# set duty
|
|
self.duty_cycle = duty
|
|
|
|
# set frequency
|
|
self.frequency = freq
|
|
|
|
self._set_enabled(True)
|
|
|
|
def deinit(self):
|
|
"""Deinit the GreatFET One PWM."""
|
|
# pylint: disable=broad-except
|
|
try:
|
|
if self._channel is not None:
|
|
# self.duty_cycle = 0
|
|
self._set_enabled(False)
|
|
except Exception as e:
|
|
# due to a race condition for which I have not yet been
|
|
# able to find the root cause, deinit() often fails
|
|
# but it does not effect future usage of the pwm pin
|
|
print(
|
|
"warning: failed to deinitialize pwm pin {0} due to: {1}\n".format(
|
|
self._channel, type(e).__name__
|
|
)
|
|
)
|
|
finally:
|
|
self._pattern = None
|
|
self._channel = None
|
|
# pylint: enable=broad-except
|
|
|
|
def _is_deinited(self):
|
|
if self._pattern is None:
|
|
raise ValueError(
|
|
"Object has been deinitialize and can no longer "
|
|
"be used. Create a new object."
|
|
)
|
|
|
|
# Mutable properties
|
|
|
|
def _get_period(self):
|
|
return 1.0 / self._get_frequency()
|
|
|
|
def _set_period(self, period):
|
|
"""Get or set the PWM's output period in seconds.
|
|
|
|
Raises:
|
|
PWMError: if an I/O or OS error occurs.
|
|
TypeError: if value type is not int or float.
|
|
|
|
:type: int, float
|
|
"""
|
|
if not isinstance(period, (int, float)):
|
|
raise TypeError("Invalid period type, should be int or float.")
|
|
|
|
self._set_frequency(1.0 / period)
|
|
|
|
period = property(_get_period, _set_period)
|
|
|
|
def _get_duty_cycle(self):
|
|
"""Get or set the PWM's output duty cycle as a ratio from 0.0 to 1.0.
|
|
|
|
Raises:
|
|
PWMError: if an I/O or OS error occurs.
|
|
TypeError: if value type is not int or float.
|
|
ValueError: if value is out of bounds of 0.0 to 1.0.
|
|
|
|
:type: int, float
|
|
"""
|
|
return self._duty_cycle
|
|
|
|
def _set_duty_cycle(self, duty_cycle):
|
|
if not isinstance(duty_cycle, (int, float)):
|
|
raise TypeError("Invalid duty cycle type, should be int or float.")
|
|
|
|
# convert from 16-bit
|
|
if isinstance(duty_cycle, int):
|
|
duty_cycle /= 65535.0
|
|
if not 0.0 <= duty_cycle <= 1.0:
|
|
raise ValueError("Invalid duty cycle value, should be between 0.0 and 1.0.")
|
|
|
|
# Generate a pattern for 1024 samples of the duty cycle
|
|
pattern = [(1 << self._channel)] * round(PWMOut.MAX_CYCLE_LEVEL * duty_cycle)
|
|
pattern += [(0 << self._channel)] * round(
|
|
PWMOut.MAX_CYCLE_LEVEL * (1.0 - duty_cycle)
|
|
)
|
|
|
|
self._pattern = pattern
|
|
self._duty_cycle = duty_cycle
|
|
if self._enable:
|
|
self._set_enabled(True)
|
|
|
|
duty_cycle = property(_get_duty_cycle, _set_duty_cycle)
|
|
|
|
def _get_frequency(self):
|
|
return self._frequency
|
|
|
|
def _set_frequency(self, frequency):
|
|
"""Get or set the PWM's output frequency in Hertz.
|
|
|
|
Raises:
|
|
PWMError: if an I/O or OS error occurs.
|
|
TypeError: if value type is not int or float.
|
|
|
|
:type: int, float
|
|
"""
|
|
if not isinstance(frequency, (int, float)):
|
|
raise TypeError("Invalid frequency type, should be int or float.")
|
|
|
|
# We are sending 1024 samples per second already
|
|
self._gf.pattern_generator.set_sample_rate(frequency * len(self._pattern))
|
|
self._frequency = frequency
|
|
|
|
frequency = property(_get_frequency, _set_frequency)
|
|
|
|
def _get_enabled(self):
|
|
enabled = self._enable
|
|
|
|
if enabled == "1":
|
|
return True
|
|
if enabled == "0":
|
|
return False
|
|
|
|
raise PWMError(None, 'Unknown enabled value: "%s"' % enabled)
|
|
|
|
def _set_enabled(self, value):
|
|
"""Get or set the PWM's output enabled state.
|
|
|
|
Raises:
|
|
PWMError: if an I/O or OS error occurs.
|
|
TypeError: if value type is not bool.
|
|
|
|
:type: bool
|
|
"""
|
|
if not isinstance(value, bool):
|
|
raise TypeError("Invalid enabled type, should be string.")
|
|
self._enable = value
|
|
if self._gf:
|
|
if self._enable:
|
|
if self._pattern:
|
|
self._gf.pattern_generator.scan_out_pattern(self._pattern)
|
|
else:
|
|
self._gf.pattern_generator.stop()
|