Sound¶

Sound is a subclass of FileSystem. It provides higher order methods to play tones and sound files.

Play a Tone¶

Method tone() of class Sound plays tones with given frequencies. Connect your EV3 brick and your computer with an USB cable, then start this program:

import ev3_dc as ev3

with ev3.Sound(protocol=ev3.USB) as sound:
    sound.verbosity = 1
    sound.tone(250, duration=1, volume=100)

This plays a tone with frequency 250 Hz for one second at maximum volume. If no duration is given, method tone() plays the tone unlimited. If no volume is given it takes the volume, which can be set as a property of class Sound. If neither was set, it takes the volume from the EV3 device. The frequency must be in a range of 250 - 10.000 Hz, the volume must be in a range of 1 - 100.

The output:

13:01:25.162280 Sent 0x|0F:00|2B:00|00|00:00|94:01:81:64:82:FA:00:82:E8:03|
13:01:25.168008 Recv 0x|03:00|2B:00|02|

Play a Sound File¶

Robot sound files are a special pulse code modulation format for audio signals. The single channel signal has a sample rate of 8 kHz and an 8 bit resolution. This blog describes, how to add the header information and create robot sound files. Some sound files can be found on the EV3 device. Method play_sound() allows to play these sound files.

Connect your EV3 brick and your computer via Bluetooth, replace the MAC-address by the one of your EV3 brick, then start this program:

import ev3_dc as ev3
from time import sleep

hugo = ev3.Sound(protocol=ev3.BLUETOOTH, host='00:16:53:42:2B:99', volume=100)
hugo.verbosity = 1

hugo.play_sound(
    './ui/DownloadSucces.rsf',
    repeat=True
)

sleep(5)

hugo.stop_sound()

Some remarks:

The program plays a sound file repeatedly and stops the sound after 5 sec. This is exactly, what program Playing Sound Files repeatedly does.

The timing is done by the program.

It needs to call method stop_sound() to stop the playing, otherwise it would last forever.

The output:

13:45:30.663648 Sent 0x|1E:00|2A:00|80|00:00|94:03:81:64:84:2E:2F:75:69:2F:44:6F:77:6E:6C:6F:61:64:53:75:63:63:65:73:00|
13:45:35.669587 Sent 0x|07:00|2B:00|80|00:00|94:00|

Play a Sound File as a Thread Task¶

thread_task objects allow to define the timing beforehand, when the thread task is created. Starting thread tasks allows to do multiple things parallel.

Connect your EV3 brick and your computer via Bluetooth, replace the MAC-address by the one of your EV3 brick, then start this program:

import ev3_dc as ev3

hugo = ev3.Sound(protocol=ev3.BLUETOOTH, host='00:16:53:42:2B:99', volume=100)
hugo.verbosity = 1

t_sound = hugo.sound(
    './ui/DownloadSucces.rsf',
    duration=5,
    repeat=True
)

t_sound.start()

Some remarks:

method sound() returns a thread task object, we name it t_sound.

t_sound can be started, stopped, continued and restarted. We only start it.

t_sound runs in the background. If you add some more commands to this program, you will realize, they are executed parallel to t_sound.

the timing is done inside the thread task object.

stopping the sound also is done by the task object.

thread task objects encapsulate program logik behind a simple public API.

The output:

14:06:40.170520 Sent 0x|1E:00|2A:00|80|00:00|94:03:81:64:84:2E:2F:75:69:2F:44:6F:77:6E:6C:6F:61:64:53:75:63:63:65:73:00|
14:06:45.170841 Sent 0x|07:00|2B:00|80|00:00|94:00|

Play a local Sound File¶

If you combine method load_file() from class FileSystem() with the above described functionality, you can also play local sound files.

Find the location of LEGO’s sound files, which in my case was: …/Program Files (x86)/LEGO Software/LEGO MINDSTORMS EV3 Home Edition/Resources/BrickResources/Retail/Sounds/files (I copied this directory to a location with a shorter path). Modify the program by replacing the file location. Take an USB cable and connect your EV3 brick with your computer then start the following program.

import ev3_dc as ev3

with ev3.Sound(protocol=ev3.USB, volume=20) as hugo:
    hugo.sound(
        '../Sound/Expressions/Laughing 2.rsf',
        local=True
    ).start(thread=False)
print('all done')

Some remarks:

keyword argument local makes the distinction between local sound files and sound files on the EV3 device. In this case, the sound file exists in the file system of the machine, which runs the program and the relative path is from the directory, where this python program is located.

Starting a Thread Task with thread=False lets it behave traditional, it does its actions and your program continues with execution, when they are done.