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4.1.2 Music Player

Introduction

In project 3.1.3 Audio Module, let speaker play a song. Now we add 3 buttons to control the play/pause and volume of the music.

Required Components

In this project, we need the following components.

It’s definitely convenient to buy a whole kit, here’s the link:

Name	ITEMS IN THIS KIT	LINK
Raphael Kit	337	Raphael Kit

You can also buy them separately from the links below.

COMPONENT INTRODUCTION	PURCHASE LINK
GPIO Extension Board	BUY
Breadboard	BUY
Jumper Wires	BUY
Resistor	BUY
Audio Module and Speaker	-
Button	BUY

Schematic Diagram

T-Board Name	physical	wiringPi	BCM
GPIO17	Pin 11	0	17
GPIO18	Pin 12	1	18
GPIO27	Pin 13	2	27

Experimental Procedures

Step 1: Build the circuit.

After building the circuit according to the above diagram, then plug the audio cable into the Raspberry Pi’s 3.5mm audio jack.

Step 2: Get into the folder of the code.

cd ~/raphael-kit/python/

Step 3: Run.

python3 4.1.2_MusicPlayer.py

After the code runs, Raspberry Pi will play the my_music.mp3 file in the ~/raphael-kit/music directory.

• Button 1 pauses/play the music.

• Button 2 decreases the volume.

• Button 3 increases the volume.

If you want to upload other music files to Raspberry Pi, you can refer to Filezilla Software.

Code

Note

You can Modify/Reset/Copy/Run/Stop the code below. But before that, you need to go to source code path like raphael-kit/python. After modifying the code, you can run it directly to see the effect.

from pygame import mixer
import RPi.GPIO as GPIO
import time
import os
user = os.getlogin()
user_home = os.path.expanduser(f'~{user}')

BtnPin1 = 18
BtnPin2 = 17
BtnPin3 = 27
volume = 0.7

status = False
upPressed = False
downPressed = False
playPressed = False

def setup():
    mixer.init()
    GPIO.setmode(GPIO.BCM)
    GPIO.setup(BtnPin1, GPIO.IN, GPIO.PUD_UP)
    GPIO.setup(BtnPin2, GPIO.IN, GPIO.PUD_UP)
    GPIO.setup(BtnPin3, GPIO.IN, GPIO.PUD_UP)

def clip(x,min,max):
    if x < min:
        return min
    elif x > max:
        return max
    return x

def play(pin):
    global playPressed
    playPressed = True

def volDown(pin):
    global downPressed
    downPressed = True

def volUp(pin):
    global upPressed
    upPressed = True

def main():
    global volume, status
    global downPressed, upPressed, playPressed
    mixer.music.load(f'{user_home}/raphael-kit/music/my_music.mp3')
    mixer.music.set_volume(volume)
    mixer.music.play()
    GPIO.add_event_detect(BtnPin1, GPIO.FALLING, callback=play)
    GPIO.add_event_detect(BtnPin2, GPIO.FALLING, callback=volDown)
    GPIO.add_event_detect(BtnPin3, GPIO.FALLING, callback=volUp)
    while True:
        if upPressed:
            volume = volume + 0.1
            upPressed = False
        if downPressed:
            volume = volume - 0.1
            downPressed = False
        if playPressed:
            if status:
                mixer.music.pause()
                status = not status
            else:
                mixer.music.unpause()
                status = not status
            playPressed = False
            time.sleep(0.5)
        volume = clip(volume,0.2,1)
        mixer.music.set_volume(volume)
        time.sleep(0.1)

def destroy():
    # Release resource
    GPIO.cleanup()
    mixer.music.stop()

# If run this script directly, do:
if __name__ == '__main__':
    setup()
    try:
        main()
    # When 'Ctrl+C' is pressed, the program
    # destroy() will be  executed.
    except KeyboardInterrupt:
        destroy()

Code Explanation

from pygame import mixer

mixer.init()

Import the Mixer method in the pygame library and initialize the method.

BtnPin1 = 18
BtnPin2 = 17
BtnPin3 = 27
volume = 0.7

Define the pin ports of the three buttons and set the initial volume to 0.7.

upPressed = False
downPressed = False
playPressed = False

UpPressed, downPressed and playPressed are all interrupt flags, the corresponding task will be executed When they are True.

def clip(x,min,max):
if x < min:
    return min
elif x > max:
    return max
return x

The clip() function is used to set the upper and lower limits of input parameters.

GPIO.add_event_detect(BtnPin1, GPIO.FALLING, callback=play)
GPIO.add_event_detect(BtnPin2, GPIO.FALLING, callback=volDown)
GPIO.add_event_detect(BtnPin3, GPIO.FALLING, callback=volUp)

Set the key detection events of BtnPin1, BtnPin2 and BtnPin3.

• When BtnPin1 is pressed, the interrupt function play() is executed.

• when BtnPin2 is pressed, the interrupt function volDown() is executed.

• When BtnPin3 is pressed, the interrupt function volUp() is executed.

Phenomenon Picture