Source code for gpiozero.tones

# vim: set fileencoding=utf-8:
#
# GPIO Zero: a library for controlling the Raspberry Pi's GPIO pins
#
# Copyright (c) 2019 Dave Jones <dave@waveform.org.uk>
# Copyright (c) 2019 Ben Nuttall <ben@bennuttall.com>
#
# SPDX-License-Identifier: BSD-3-Clause

import re
import warnings
from math import log2

from .exc import AmbiguousTone


[docs]class Tone(float): """ Represents a frequency of sound in a variety of musical notations. :class:`Tone` class can be used with the :class:`~gpiozero.TonalBuzzer` class to easily represent musical tones. The class can be constructed in a variety of ways. For example as a straight frequency in `Hz`_ (which is the internal storage format), as an integer MIDI note, or as a string representation of a musical note. All the following constructors are equivalent ways to construct the typical tuning note, `concert A`_ at 440Hz, which is MIDI note #69: >>> from gpiozero.tones import Tone >>> Tone(440.0) >>> Tone(69) >>> Tone('A4') If you do not want the constructor to guess which format you are using (there is some ambiguity between frequencies and MIDI notes at the bottom end of the frequencies, from 128Hz down), you can use one of the explicit constructors, :meth:`from_frequency`, :meth:`from_midi`, or :meth:`from_note`, or you can specify a keyword argument when constructing:: >>> Tone.from_frequency(440) >>> Tone.from_midi(69) >>> Tone.from_note('A4') >>> Tone(frequency=440) >>> Tone(midi=69) >>> Tone(note='A4') Several attributes are provided to permit conversion to any of the supported construction formats: :attr:`frequency`, :attr:`midi`, and :attr:`note`. Methods are provided to step :meth:`up` or :meth:`down` to adjacent MIDI notes. .. warning:: Currently :class:`Tone` derives from :class:`float` and can be used as a floating point number in most circumstances (addition, subtraction, etc). This part of the API is not yet considered "stable"; i.e. we may decide to enhance / change this behaviour in future versions. .. _Hz: https://en.wikipedia.org/wiki/Hertz .. _concert A: https://en.wikipedia.org/wiki/Concert_pitch """ tones = 'CCDDEFFGGAAB' semitones = { '♭': -1, 'b': -1, '♮': 0, '': 0, '♯': 1, '#': 1, } regex = re.compile( r'(?P<note>[A-G])' r'(?P<semi>[{semitones}]?)' r'(?P<octave>[0-9])'.format(semitones=''.join(semitones.keys()))) def __new__(cls, value=None, *, frequency=None, midi=None, note=None): n = sum(1 for arg in (value, frequency, midi, note) if arg is not None) if n != 1: raise TypeError('must specify a value, frequency, midi number, ' 'or note') if note is not None: return cls.from_note(note) elif midi is not None: return cls.from_midi(midi) elif frequency is not None: return cls.from_frequency(frequency) else: if isinstance(value, (int, float)): if 0 <= value < 128: if value > 0: warnings.warn( AmbiguousTone( "Ambiguous tone specification; assuming you " "want a MIDI note. To suppress this warning " "use, e.g. Tone(midi=60), or to obtain a " "frequency instead use, e.g. Tone(frequency=" "60)")) return cls.from_midi(value) else: return cls.from_frequency(value) elif isinstance(value, (bytes, str)): return cls.from_note(value) else: return cls.from_frequency(value) def __str__(self): return self.note def __repr__(self): try: midi = self.midi except ValueError: midi = '' else: midi = ' midi={midi!r}'.format(midi=midi) try: note = self.note except ValueError: note = '' else: note = ' note={note!r}'.format(note=note) return "<Tone{note}{midi} frequency={self.frequency:.2f}Hz>".format( note=note, midi=midi, self=self)
[docs] @classmethod def from_midi(cls, midi_note): """ Construct a :class:`Tone` from a MIDI note, which must be an integer in the range 0 to 127. For reference, A4 (`concert A`_ typically used for tuning) is MIDI note #69. .. _concert A: https://en.wikipedia.org/wiki/Concert_pitch """ midi = int(midi_note) if 0 <= midi_note < 128: A4_midi = 69 A4_freq = 440 return cls.from_frequency(A4_freq * 2 ** ((midi - A4_midi) / 12)) raise ValueError('invalid MIDI note: {midi!r}'.format(midi=midi))
[docs] @classmethod def from_note(cls, note): """ Construct a :class:`Tone` from a musical note which must consist of a capital letter A through G, followed by an optional semi-tone modifier ("b" for flat, "#" for sharp, or their Unicode equivalents), followed by an octave number (0 through 9). For example `concert A`_, the typical tuning note at 440Hz, would be represented as "A4". One semi-tone above this would be "A#4" or alternatively "Bb4". Unicode representations of sharp and flat are also accepted. """ if isinstance(note, bytes): note = note.decode('ascii') if isinstance(note, str): match = Tone.regex.match(note) if match: octave = int(match.group('octave')) + 1 return cls.from_midi( Tone.tones.index(match.group('note')) + Tone.semitones[match.group('semi')] + octave * 12) raise ValueError( 'invalid note specification: {note!r}'.format(note=note))
[docs] @classmethod def from_frequency(cls, freq): """ Construct a :class:`Tone` from a frequency specified in `Hz`_ which must be a positive floating-point value in the range 0 < freq <= 20000. .. _Hz: https://en.wikipedia.org/wiki/Hertz """ if 0 < freq <= 20000: return super().__new__(cls, freq) raise ValueError('invalid frequency: {freq:.2f}'.format(freq=freq))
@property def frequency(self): """ Return the frequency of the tone in `Hz`_. .. _Hz: https://en.wikipedia.org/wiki/Hertz """ return float(self) @property def midi(self): """ Return the (nearest) MIDI note to the tone's frequency. This will be an integer number in the range 0 to 127. If the frequency is outside the range represented by MIDI notes (which is approximately 8Hz to 12.5KHz) :exc:`ValueError` exception will be raised. """ result = int(round(12 * log2(self.frequency / 440) + 69)) if 0 <= result < 128: return result raise ValueError( '{self.frequency:f} is outside the MIDI note range'.format( self=self)) @property def note(self): """ Return the (nearest) note to the tone's frequency. This will be a string in the form accepted by :meth:`from_note`. If the frequency is outside the range represented by this format ("A0" is approximately 27.5Hz, and "G9" is approximately 12.5Khz) a :exc:`ValueError` exception will be raised. """ offset = self.midi - 60 # self.midi - A4_midi + Tone.tones.index('A') index = offset % 12 # offset % len(Tone.tones) octave = 4 + offset // 12 if 0 <= octave <= 9: return ( Tone.tones[index] + ('#' if Tone.tones[index] == Tone.tones[index - 1] else '') + str(octave) ) raise ValueError( '{self.frequency:f} is outside the notation range'.format( self=self))
[docs] def up(self, n=1): """ Return the :class:`Tone` *n* semi-tones above this frequency (*n* defaults to 1). """ return Tone.from_midi(self.midi + n)
[docs] def down(self, n=1): """ Return the :class:`Tone` *n* semi-tones below this frequency (*n* defaults to 1). """ return Tone.from_midi(self.midi - n)