336 lines
10 KiB
Python
336 lines
10 KiB
Python
# SPDX-FileCopyrightText: 2021 Melissa LeBlanc-Williams for Adafruit Industries
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#
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# SPDX-License-Identifier: MIT
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"""
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Much code from https://github.com/vsergeev/python-periphery/blob/master/periphery/pwm.py
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Copyright (c) 2015-2016 vsergeev / Ivan (Vanya) A. Sergeev
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License: MIT
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"""
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import os
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try:
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from microcontroller.pin import pwmOuts
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except ImportError:
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raise RuntimeError("No PWM outputs defined for this board") from ImportError
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# pylint: disable=unnecessary-pass
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class PWMError(IOError):
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"""Base class for PWM errors."""
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pass
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# pylint: enable=unnecessary-pass
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class PWMOut:
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"""Pulse Width Modulation Output Class"""
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# Sysfs paths
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_sysfs_path = "/sys/class/pwm/"
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_channel_path = "pwmchip{}"
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# Channel paths
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_export_path = "export"
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_unexport_path = "unexport"
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_pin_path = "pwm-{}:{}"
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# Pin attribute paths
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_pin_period_path = "period"
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_pin_duty_cycle_path = "duty_cycle"
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_pin_polarity_path = "polarity"
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_pin_enable_path = "enable"
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def __init__(self, pin, *, frequency=500, duty_cycle=0, variable_frequency=False):
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"""Instantiate a PWM object and open the sysfs PWM corresponding to the
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specified channel and pin.
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Args:
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pin (Pin): CircuitPython Pin object to output to
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duty_cycle (int) : The fraction of each pulse which is high. 16-bit
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frequency (int) : target frequency in Hertz (32-bit)
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variable_frequency (bool) : True if the frequency will change over time
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Returns:
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PWMOut: PWMOut object.
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Raises:
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PWMError: if an I/O or OS error occurs.
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TypeError: if `channel` or `pin` types are invalid.
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ValueError: if PWM channel does not exist.
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"""
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self._pwmpin = None
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self._channel = None
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self._period = 0
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self._open(pin, duty_cycle, frequency, variable_frequency)
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def __del__(self):
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self.deinit()
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def __enter__(self):
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return self
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def __exit__(self, t, value, traceback):
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self.deinit()
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def _open(self, pin, duty=0, freq=500, variable_frequency=False):
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self._channel = None
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for pwmpair in pwmOuts:
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if pwmpair[1] == pin:
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self._channel = pwmpair[0][0]
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self._pwmpin = pwmpair[0][1]
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self._pin = pin
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if self._channel is None:
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raise RuntimeError("No PWM channel found for this Pin")
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if variable_frequency:
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print("Variable Frequency is not supported, continuing without it...")
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channel_path = os.path.join(
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self._sysfs_path, self._channel_path.format(self._channel)
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)
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if not os.path.isdir(channel_path):
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raise ValueError(
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"PWM channel does not exist, check that the required modules are loaded."
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)
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pin_path = os.path.join(
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channel_path, self._pin_path.format(self._channel, self._pwmpin)
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)
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if not os.path.isdir(pin_path):
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try:
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with open(
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os.path.join(channel_path, self._export_path), "w", encoding="utf-8"
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) as f_export:
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f_export.write("%d\n" % self._pwmpin)
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except IOError as e:
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raise PWMError(e.errno, "Exporting PWM pin: " + e.strerror) from IOError
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# Look up the period, for fast duty cycle updates
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self._period = self._get_period()
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# set frequency
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self.frequency = freq
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# set duty
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self.duty_cycle = duty
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self._set_enabled(True)
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def deinit(self):
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"""Deinit the sysfs PWM."""
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# pylint: disable=broad-except
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try:
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channel_path = os.path.join(
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self._sysfs_path, self._channel_path.format(self._channel)
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)
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if self._channel is not None:
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# self.duty_cycle = 0
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self._set_enabled(False) # make to disable before unexport
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try:
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# unexport_path = os.path.join(channel_path, self._unexport_path)
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with open(
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os.path.join(channel_path, self._unexport_path),
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"w",
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encoding="utf-8",
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) as f_unexport:
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f_unexport.write("%d\n" % self._pwmpin)
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except IOError as e:
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raise PWMError(
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e.errno, "Unexporting PWM pin: " + e.strerror
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) from IOError
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except Exception as e:
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# due to a race condition for which I have not yet been
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# able to find the root cause, deinit() often fails
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# but it does not effect future usage of the pwm pin
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print(
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"warning: failed to deinitialize pwm pin {0}:{1} due to: {2}\n".format(
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self._channel, self._pwmpin, type(e).__name__
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)
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)
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finally:
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self._channel = None
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self._pwmpin = None
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# pylint: enable=broad-except
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def _is_deinited(self):
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if self._pwmpin is None:
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raise ValueError(
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"Object has been deinitialize and can no longer "
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"be used. Create a new object."
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)
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def _write_pin_attr(self, attr, value):
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# Make sure the pin is active
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self._is_deinited()
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path = os.path.join(
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self._sysfs_path,
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self._channel_path.format(self._channel),
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self._pin_path.format(self._channel, self._pwmpin),
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attr,
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)
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with open(path, "w", encoding="utf-8") as f_attr:
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f_attr.write(value + "\n")
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def _read_pin_attr(self, attr):
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# Make sure the pin is active
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self._is_deinited()
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path = os.path.join(
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self._sysfs_path,
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self._channel_path.format(self._channel),
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self._pin_path.format(self._channel, self._pwmpin),
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attr,
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)
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with open(path, "r", encoding="utf-8") as f_attr:
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return f_attr.read().strip()
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# Mutable properties
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def _get_period(self):
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period_ns = self._read_pin_attr(self._pin_period_path)
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try:
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period_ns = int(period_ns)
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except ValueError:
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raise PWMError(
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None, 'Unknown period value: "%s"' % period_ns
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) from ValueError
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# Convert period from nanoseconds to seconds
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period = period_ns / 1e9
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# Update our cached period
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self._period = period
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return period
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def _set_period(self, period):
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if not isinstance(period, (int, float)):
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raise TypeError("Invalid period type, should be int or float.")
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# Convert period from seconds to integer nanoseconds
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period_ns = int(period * 1e9)
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self._write_pin_attr(self._pin_period_path, "{}".format(period_ns))
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# Update our cached period
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self._period = float(period)
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period = property(_get_period, _set_period)
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"""Get or set the PWM's output period in seconds.
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Raises:
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PWMError: if an I/O or OS error occurs.
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TypeError: if value type is not int or float.
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:type: int, float
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"""
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def _get_duty_cycle(self):
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duty_cycle_ns = self._read_pin_attr(self._pin_duty_cycle_path)
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try:
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duty_cycle_ns = int(duty_cycle_ns)
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except ValueError:
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raise PWMError(
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None, 'Unknown duty cycle value: "%s"' % duty_cycle_ns
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) from ValueError
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# Convert duty cycle from nanoseconds to seconds
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duty_cycle = duty_cycle_ns / 1e9
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# Convert duty cycle to ratio from 0.0 to 1.0
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duty_cycle = duty_cycle / self._period
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# convert to 16-bit
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duty_cycle = int(duty_cycle * 65535)
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return duty_cycle
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def _set_duty_cycle(self, duty_cycle):
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if not isinstance(duty_cycle, (int, float)):
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raise TypeError("Invalid duty cycle type, should be int or float.")
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# convert from 16-bit
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duty_cycle /= 65535.0
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if not 0.0 <= duty_cycle <= 1.0:
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raise ValueError("Invalid duty cycle value, should be between 0.0 and 1.0.")
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# Convert duty cycle from ratio to seconds
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duty_cycle = duty_cycle * self._period
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# Convert duty cycle from seconds to integer nanoseconds
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duty_cycle_ns = int(duty_cycle * 1e9)
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self._write_pin_attr(self._pin_duty_cycle_path, "{}".format(duty_cycle_ns))
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duty_cycle = property(_get_duty_cycle, _set_duty_cycle)
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"""Get or set the PWM's output duty cycle as a ratio from 0.0 to 1.0.
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Raises:
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PWMError: if an I/O or OS error occurs.
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TypeError: if value type is not int or float.
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ValueError: if value is out of bounds of 0.0 to 1.0.
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:type: int, float
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"""
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def _get_frequency(self):
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return 1.0 / self._get_period()
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def _set_frequency(self, frequency):
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if not isinstance(frequency, (int, float)):
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raise TypeError("Invalid frequency type, should be int or float.")
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self._set_period(1.0 / frequency)
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frequency = property(_get_frequency, _set_frequency)
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"""Get or set the PWM's output frequency in Hertz.
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Raises:
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PWMError: if an I/O or OS error occurs.
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TypeError: if value type is not int or float.
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:type: int, float
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"""
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def _get_enabled(self):
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enabled = self._read_pin_attr(self._pin_enable_path)
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if enabled == "1":
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return True
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if enabled == "0":
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return False
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raise PWMError(None, 'Unknown enabled value: "%s"' % enabled)
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def _set_enabled(self, value):
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"""Get or set the PWM's output enabled state.
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Raises:
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PWMError: if an I/O or OS error occurs.
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TypeError: if value type is not bool.
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:type: bool
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"""
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if not isinstance(value, bool):
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raise TypeError("Invalid enabled type, should be string.")
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self._write_pin_attr(self._pin_enable_path, "1" if value else "0")
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# String representation
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def __str__(self):
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return "PWM%d, pin %s (freq=%f Hz, duty_cycle=%f%%)" % (
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self._channel,
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self._pin,
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self.frequency,
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self.duty_cycle * 100,
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)
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