""" Much code from https://github.com/vsergeev/python-periphery/blob/master/periphery/pwm.py Copyright (c) 2015-2016 vsergeev / Ivan (Vanya) A. Sergeev License: MIT """ import os from time import sleep from errno import EACCES try: from microcontroller.pin import pwmOuts except ImportError: raise RuntimeError("No PWM outputs defined for this board.") from ImportError # pylint: disable=unnecessary-pass, too-many-instance-attributes class PWMError(IOError): """Base class for PWM errors.""" pass # pylint: enable=unnecessary-pass class PWMOut: """Pulse Width Modulation Output Class""" # Number of retries to check for successful PWM export on open PWM_STAT_RETRIES = 10 # Delay between check for successful PWM export on open (100ms) PWM_STAT_DELAY = 0.1 # Sysfs paths _chip_path = "pwmchip{}" _channel_path = "pwm{}" def __init__(self, pwm, *, frequency=500, duty_cycle=0, variable_frequency=False): """Instantiate a PWM object and open the sysfs PWM corresponding to the specified chip and channel. Args: pwm (str): PWM pin. frequency (int, float): target frequency in Hertz (32-bit). duty_cycle (int, float): The fraction of each pulse which is high (16-bit). variable_frequency (bool): True if the frequency will change over time. Returns: PWM: PWM object. Raises: PWMError: if an I/O or OS error occurs. TypeError: if `chip` or `channel` types are invalid. LookupError: if PWM chip does not exist. TimeoutError: if waiting for PWM export times out. """ self._chip = None self._channel = None self._period_ns = 0 self._open(pwm, frequency, duty_cycle, variable_frequency) def __del__(self): self.close() def __enter__(self): return self def __exit__(self, exc_type, exc_val, exc_tb): self.close() def _open(self, pwm, frequency, duty_cycle, variable_frequency): for pwmout in pwmOuts: if pwmout[1] == pwm: self._chip = pwmout[0][0] self._channel = pwmout[0][1] self._chip_path = os.path.join( "/sys/class/pwm", self._chip_path.format(self._chip) ) self._channel_path = os.path.join( self._chip_path, self._channel_path.format(self._channel) ) if variable_frequency: print("Variable Frequency is not supported, continuing without it...") if not os.path.isdir(self._chip_path): raise LookupError("Opening PWM: PWM chip {} not found.".format(self._chip)) if not os.path.isdir(self._channel_path): # Exporting the PWM. try: with open(os.path.join(self._chip_path, "export"), "w") as f_export: f_export.write("{:d}\n".format(self._channel)) except IOError as e: raise PWMError( e.errno, "Exporting PWM channel: " + e.strerror ) from IOError # Loop until PWM is exported exported = False for i in range(PWMOut.PWM_STAT_RETRIES): if os.path.isdir(self._channel_path): exported = True break sleep(PWMOut.PWM_STAT_DELAY) if not exported: raise TimeoutError( 'Exporting PWM: waiting for "{:s}" timed out.'.format( self._channel_path ) ) # Loop until 'period' is writable, This could take some time after # export as application of the udev rules after export is asynchronous. # Without this loop, the following properties may not be writable yet. for i in range(PWMOut.PWM_STAT_RETRIES): try: with open( os.path.join(self._channel_path, "period"), "w", ): break except IOError as e: if e.errno != EACCES or ( e.errno == EACCES and i == PWMOut.PWM_STAT_RETRIES - 1 ): raise PWMError( e.errno, "Opening PWM period: " + e.strerror ) from IOError sleep(PWMOut.PWM_STAT_DELAY) self.frequency = frequency self.duty_cycle = duty_cycle # Cache the period for fast duty cycle updates self._period_ns = self._get_period_ns() def close(self): """Close the PWM.""" if self._channel is not None: # Unexporting the PWM channel try: unexport_fd = os.open( os.path.join(self._chip_path, "unexport"), os.O_WRONLY ) os.write(unexport_fd, "{:d}\n".format(self._channel).encode()) os.close(unexport_fd) except OSError as e: raise PWMError(e.errno, "Unexporting PWM: " + e.strerror) from OSError self._chip = None self._channel = None def _write_channel_attr(self, attr, value): with open(os.path.join(self._channel_path, attr), "w") as f_attr: f_attr.write(value + "\n") def _read_channel_attr(self, attr): with open(os.path.join(self._channel_path, attr), "r") as f_attr: return f_attr.read().strip() # Methods def enable(self): """Enable the PWM output.""" self.enabled = True def disable(self): """Disable the PWM output.""" self.enabled = False # Mutable properties def _get_period(self): return float(self.period_ms) / 1000 def _set_period(self, period): if not isinstance(period, (int, float)): raise TypeError("Invalid period type, should be int.") self.period_ms = int(period * 1000) period = property(_get_period, _set_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. :type: int, float """ def _get_period_ms(self): return self.period_us / 1000 def _set_period_ms(self, period_ms): if not isinstance(period_ms, (int, float)): raise TypeError("Invalid period type, should be int or float.") self.period_us = int(period_ms * 1000) period_ms = property(_get_period_ms, _set_period_ms) """Get or set the PWM's output period in milliseconds. Raises: PWMError: if an I/O or OS error occurs. TypeError: if value type is not int. :type: int, float """ def _get_period_us(self): return self.period_ns / 1000 def _set_period_us(self, period_us): if not isinstance(period_us, int): raise TypeError("Invalid period type, should be int.") self.period_ns = int(period_us * 1000) period_us = property(_get_period_us, _set_period_us) """Get or set the PWM's output period in microseconds. Raises: PWMError: if an I/O or OS error occurs. TypeError: if value type is not int. :type: int """ def _get_period_ns(self): period_ns = self._read_channel_attr("period") try: period_ns = int(period_ns) except ValueError: raise PWMError( None, 'Unknown period value: "%s".' % period_ns ) from ValueError self._period_ns = period_ns return period_ns def _set_period_ns(self, period_ns): if not isinstance(period_ns, int): raise TypeError("Invalid period type, should be int.") self._write_channel_attr("period", str(period_ns)) # Update our cached period self._period_ns = period_ns period_ns = property(_get_period_ns, _set_period_ns) """Get or set the PWM's output period in nanoseconds. Raises: PWMError: if an I/O or OS error occurs. TypeError: if value type is not int. :type: int """ def _get_duty_cycle_ns(self): duty_cycle_ns_str = self._read_channel_attr("duty_cycle") try: duty_cycle_ns = int(duty_cycle_ns_str) except ValueError: raise PWMError( None, 'Unknown duty cycle value: "{:s}"'.format(duty_cycle_ns_str) ) from ValueError return duty_cycle_ns def _set_duty_cycle_ns(self, duty_cycle_ns): if not isinstance(duty_cycle_ns, int): raise TypeError("Invalid duty cycle type, should be int.") self._write_channel_attr("duty_cycle", str(duty_cycle_ns)) duty_cycle_ns = property(_get_duty_cycle_ns, _set_duty_cycle_ns) """Get or set the PWM's output duty cycle in nanoseconds. Raises: PWMError: if an I/O or OS error occurs. TypeError: if value type is not int. :type: int """ def _get_duty_cycle(self): return float(self.duty_cycle_ns) / self._period_ns 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.") if not 0.0 <= duty_cycle <= 1.0: raise ValueError("Invalid duty cycle value, should be between 0.0 and 1.0.") # Convert duty cycle from ratio to nanoseconds self.duty_cycle_ns = int(duty_cycle * self._period_ns) duty_cycle = property(_get_duty_cycle, _set_duty_cycle) """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 """ def _get_frequency(self): return 1.0 / self.period def _set_frequency(self, frequency): if not isinstance(frequency, (int, float)): raise TypeError("Invalid frequency type, should be int or float.") self.period = 1.0 / frequency frequency = property(_get_frequency, _set_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 """ def _get_polarity(self): return self._read_channel_attr("polarity") def _set_polarity(self, polarity): if not isinstance(polarity, str): raise TypeError("Invalid polarity type, should be str.") if polarity.lower() not in ["normal", "inversed"]: raise ValueError('Invalid polarity, can be: "normal" or "inversed".') self._write_channel_attr("polarity", polarity.lower()) polarity = property(_get_polarity, _set_polarity) """Get or set the PWM's output polarity. Can be "normal" or "inversed". Raises: PWMError: if an I/O or OS error occurs. TypeError: if value type is not str. ValueError: if value is invalid. :type: str """ def _get_enabled(self): enabled = self._read_channel_attr("enable") if enabled == "1": return True if enabled == "0": return False raise PWMError(None, 'Unknown enabled value: "{:s}"'.format(enabled)) def _set_enabled(self, value): if not isinstance(value, bool): raise TypeError("Invalid enabled type, should be bool.") self._write_channel_attr("enable", "1" if value else "0") enabled = property(_get_enabled, _set_enabled) """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 """ # String representation def __str__(self): return ( "PWM {:d}, chip {:d} (period={:f} sec, duty_cycle={:f}%," " polarity={:s}, enabled={:s})".format( self._channel, self._chip, self.period, self.duty_cycle * 100, self.polarity, str(self.enabled), ) )