ev3-dc 0.9.8.1

EV3 direct commands

Use python3 to program your LEGO Mindstorms EV3. The program runs on the local host and sends direct commands to the EV3 device. It communicates via bluetooth, WiFi or USB. I wrote a blog about this code.

There is no need to boot the EV3 device from an SD Card or manipulate its software. You can use it as it is, the EV3 is designed to execute commands which come from outside.

Installation

python3 -m pip install --user ev3_dc

Examples

Writing and sending direct commands

This program communicates via USB with an EV3 device and plays a tone with a frequency of 440 Hz for a duration of 1 sec.

import ev3_dc as ev3

my_ev3 = ev3.EV3(protocol=ev3.USB)
my_ev3.verbosity = 1
ops = b''.join((
    ev3.opSound,
    ev3.TONE,
    ev3.LCX(1),  # VOLUME
    ev3.LCX(440),  # FREQUENCY
    ev3.LCX(1000),  # DURATION
))
my_ev3.send_direct_cmd(ops)

The output shows the direct command, which was sent to the EV3 device:

11:48:31.188008 Sent 0x|0E:00|2A:00|80|00:00|94:01:01:82:B8:01:82:E8:03|

Subclasses of EV3 with comfortable APIs

Method play_tone of class Jukebox also plays tones:

import ev3_dc as ev3

jukebox = ev3.Jukebox(protocol=ev3.BLUETOOTH, host='00:16:53:42:2B:99')
jukebox.verbosity = 1
jukebox.play_tone("a'", duration=1)

This program does the very same thing via Bluetooth! Before you can run it, you need to pair the two devices (the computer, that executes the program and the EV3 brick) and replace the MAC-address 00:16:53:42:2B:99 by the one of your EV3. The output:

11:55:11.324701 Sent 0x|0E:00|2A:00|80|00:00|94:01:01:82:B8:01:82:E8:03|

Independent Tasks

Specialized classes (e.g. class Jukebox) provide factory methods, which return a thread_task.Task <https://thread_task.readthedocs.io/en/latest/>. Thread tasks allow to start, stop and continue independent tasks.

import ev3_dc as ev3

jukebox = ev3.Jukebox(protocol=ev3.WIFI)
antemn = jukebox.song(ev3.EU_ANTEMN)

antemn.start()

This program plays the EU antemn. Before you can execute it, you need to connect both devices (the computer, that runs the program and the EV3 brick) with the same LAN (local area network), the EV3 brick must be connected via WiFi. If you don’t own a WiFi dongle, modify the protocol and select ev3.BLUETOOTH or ev3.USB.

Some remarks:

• Method song() returns a thread_task.Task object, which can be started, stopped and continued. It plays tones and changes the LED-colors.

• Starting a thread task does not block the program nor does it block the EV3 brick. It runs in the background and allows to do additional things parallel.

• Alternatively, you can start a thread task without mutlithreading by antemn.start(thread=False). This makes it behave like any normal callable.

Specialized Subclasses handle Sensors and Motors

Specialized subclasses of class as EV3), like Touch, Infrared, Ultrasonic, Color, Motor, or TwoWheelVehicle handle motors and sensors. You can use multiple of these objects parallel and all them can share a single physical EV3 device. You can also build complex robots with more than one EV3 device and control the robot easily by a single python program.

import ev3_dc as ev3

with ev3.Touch(ev3.PORT_1, protocol=ev3.USB) as touch_1:
    touch_4 = ev3.Touch(ev3.PORT_4, ev3_obj=touch_1)
    for touch in touch_1, touch_4:
        print(str(touch) + ':', end=' ')
        print('touched' if touch.touched else 'not touched')

Some remarks:

• Class EV3 and all its subclasses support the with statement.

• touch_4 uses the connection of touch_1. This is done by setting keyword argument ev3_obj=touch_1.

• If more than a single EV3 device ist connected via USB, this program will fail. For this case use keyword argument host (e.g. ev3.Touch(ev3.PORT_1, protocol=ev3.USB, host='00:16:53:42:2B:99')) to identify the device (for protocol BLUETOOTH keyword argument host is mandatory).

Read ev3_dc.readthedocs.io for more details.