DTMF keypad

dtmf.py

"""
GUI keypad that plays DTMF (Dual-tone multi-frequency) signals.
https://en.wikipedia.org/wiki/Dual-tone_multi-frequency_signaling
"""

import sys
from functools import partial
from string import ascii_uppercase
from threading import Thread, Event

import pyaudio
import numpy as np

from PyQt5.QtWidgets import QApplication, QGridLayout, QPushButton, QWidget
from PyQt5.QtGui import QFont
from PyQt5.QtCore import Qt


# map between keyboard values and button text
KEYS = {
    int(Qt.Key_0): "0",
    int(Qt.Key_1): "1",
    int(Qt.Key_2): "2",
    int(Qt.Key_3): "3",
    int(Qt.Key_4): "4",
    int(Qt.Key_5): "5",
    int(Qt.Key_6): "6",
    int(Qt.Key_7): "7",
    int(Qt.Key_8): "8",
    int(Qt.Key_9): "9",
    int(Qt.Key_A): "A",
    int(Qt.Key_B): "B",
    int(Qt.Key_C): "C",
    int(Qt.Key_D): "D",
    int(Qt.Key_Asterisk): "*",
    int(Qt.Key_NumberSign): "#",
}

# map between button text and dual tone frequencies
FREQUENCIES = {
    "1": [697, 1209],
    "2": [697, 1336],
    "3": [697, 1477],
    "A": [697, 1633],
    "4": [770, 1209],
    "5": [770, 1336],
    "6": [770, 1477],
    "B": [770, 1633],
    "7": [852, 1209],
    "8": [852, 1336],
    "9": [852, 1477],
    "C": [852, 1633],
    "*": [941, 1209],
    "0": [941, 1336],
    "#": [941, 1477],
    "D": [941, 1633],
}

SR = 44100  # output sample rate

class KeyPad(QWidget):
    def __init__(self):
        super().__init__()

        self.setWindowTitle("DTMF keypad")

        # grid layout
        self._layout = QGridLayout()

        self.keys_pressed = []

        self.add_buttons()

        self.setLayout(self._layout)

        # open audio output
        self._pa = pyaudio.PyAudio()
        self._chunk = 1024
        self._playing = Event()
        self._playing.clear()

        self.show()

    def add_buttons(self):
        # add buttons to keypad
        self.buttons = {}

        self.buttons["1"] = QPushButton("1")
        self.buttons["2"] = QPushButton("2")
        self.buttons["3"] = QPushButton("3")
        self.buttons["A"] = QPushButton("A")

        self.buttons["4"] = QPushButton("4")
        self.buttons["5"] = QPushButton("5")
        self.buttons["6"] = QPushButton("6")
        self.buttons["B"] = QPushButton("B")

        self.buttons["7"] = QPushButton("7")
        self.buttons["8"] = QPushButton("8")
        self.buttons["9"] = QPushButton("9")
        self.buttons["C"] = QPushButton("C")

        self.buttons["*"] = QPushButton("*")
        self.buttons["0"] = QPushButton("0")
        self.buttons["#"] = QPushButton("#")
        self.buttons["D"] = QPushButton("D")

        # key pad shape
        shape = (4, 4)

        # list of current tone frequencies to play
        self._freqs = []

        for i, key in enumerate(self.buttons):
            self.buttons[key].setFixedSize(64, 64)
            self.buttons[key].setFont(QFont("Arial", 24, QFont.Bold))

            if key in ascii_uppercase:
                self.buttons[key].setStyleSheet("background-color: #ff0000")
            elif not key.isdigit():
                self.buttons[key].setStyleSheet("background-color: #00ff00")

            # add frequencies on button click
            self.buttons[key].pressed.connect(partial(self._add_freqs, FREQUENCIES[key]))
            
            # remove frequencies when button released
            self.buttons[key].released.connect(partial(self._remove_freqs, FREQUENCIES[key]))

            pos = np.unravel_index(i, shape)
            self._layout.addWidget(self.buttons[key], pos[0], pos[1])

    def _add_freqs(self, freqs):
        """
        Add tone frequencies.
        """
        
        start_audio = False
        if len(self._freqs) == 0:
            start_audio = True

        self._freqs.append(freqs)

        if start_audio:
            # start audio output thread
            self._playing.set()

            # open audio stream
            self._stream = self._pa.open(
                format=pyaudio.paFloat32,  # 32-bit float
                channels=1,  # mono channel
                rate=SR,
                output=True,
                frames_per_buffer=self._chunk,
            )

            self._playing_thread = Thread(target=self.play_tones, daemon=True)
            self._playing_thread.start()

    def _remove_freqs(self, freqs):
        """
        Remove tone frequencies.
        """

        self._freqs.remove(freqs)

        if len(self._freqs) == 0:
            # end audio output thread
            self._playing.clear()

    def keyPressEvent(self, event):
        if not event.isAutoRepeat():
            for key in KEYS:
                if int(event.key()) == key:
                    if FREQUENCIES[KEYS[key]] not in self._freqs:
                        self._add_freqs(FREQUENCIES[KEYS[key]])
                    
                        self.buttons[KEYS[key]].setDown(True)
                        break

    def keyReleaseEvent(self, event):
        if not event.isAutoRepeat():
            for key in KEYS:
                if int(event.key()) == key:
                    if FREQUENCIES[KEYS[key]] in self._freqs:
                        self._remove_freqs(FREQUENCIES[KEYS[key]])

                        self.buttons[KEYS[key]].setDown(False)
                        break

    def closeEvent(self, event):
        # stop thread and close pyAudio stream
        self._playing.clear()

        try:
            self._stream.close()
        except:
            pass

        self._pa.terminate()

    def play_tones(self):
        t0 = 0
        dt = 1 / SR
        deltat = self._chunk * dt
        amp = 1 / 16  # set amplitude so that total cannot go above 1

        while self._playing.is_set():
            times = np.arange(t0, t0 + deltat, dt)
            tones = np.zeros_like(times, dtype=np.float32)

            for f in np.unique(np.array(self._freqs).flatten()):
                tones += (amp * np.sin(2 * np.pi * f * times)).astype(np.float32)

            self._stream.write(tones.tobytes())

            t0 += deltat

        self._stream.close()


app = QApplication([])
app.setStyle("Fusion")  # explicitly use "Fusion" style sheet rather than default https://stackoverflow.com/a/75075364/1862861
keypad = KeyPad()

sys.exit(app.exec())