EV3 Brick

The EV3 brick represents the heart and the brain of every robot. After inserting the battery on its bottom and a microSD card with our customized, Debian-based ev3dev operating system, you may start programming it with Python. While there are a lot of external accessories like motors and sensors, you will probably also use some of its basic functions.

brick

Specifications

CPU

300MHz TI Sitara AM1808 (ARM9 core)

RAM

64MB

LCD

178x128 pixels, monochrome

I/O

microSD slot, Bluetooth, USB host/slave, 4 in- and output ports each

In- and Outputs

brick overview

Inputs 1 to 4 and outputs A to D are located on both smaller sides of the brick. The inputs are exclusively used to connect sensors to the brick, and the outputs to connect motors.

Right next to the outputs you can find a Mini USB connector labeled PC. You can connect the brick to a computer using a cable. The connection is handled as a network connection, so it appears the same as if you would have established a WiFi or a Bluetooth connection.

On one side of the brick you will also find a microSD slot and a full size USB port to which you may connect additional accessories, like a WiFi stick.


Display Unit

The EV3 brick has a monochrome LCD display. After turning on the brick, the display shows a menu to browse files and devices, to set up a connection with a computer, or to see the specification of the battery and the brick. It is also used to show text or images as an output of a program running on the brick.

>>> import ev3dev.ev3 as ev3
>>> screen = ev3.Screen()
>>> screen.draw.text((0,0), 'Hello World!')
>>> screen.draw.rectangle((10,10,60,20), fill='black')
>>> screen.update() # Applies all changes to the display

If you want to take a screenshot of the current display output you can capture the content of the framebuffer as follows:

$ fbgrab dump.png

Controls

Below the display, in the center of the brick, are the main controls for navigating through menus. Within lies a button to turn on the unit. The separate button on the left hand corner is to leave a menu. When pressed in the main screen, it also prompts a dialog for power off or reboot of the brick.

main menu shutdown

Example 1: Callback for single button

>>> import ev3dev.ev3 as ev3
>>> from time import sleep
>>>
>>> def up_callback(state):
>>>     print('Up button pressed' if state else 'Up button released')
>>>
>>> btn = ev3.Button()
>>> btn.on_up = up_callback
>>>
>>> while True:
>>>     btn.process() # Loop internal button states and execute callbacks defined
>>>     sleep(0.250)
>>>

Example 2: Listen to any button

>>> import ev3dev.ev3 as ev3
>>> from time import sleep
>>>
>>> btn = ev3.Button()
>>>if btn.any():
>>>     # Execute something here
>>>

Audio Output

The EV3 brick supports various types of direct audio output, as it comes with a built-in speaker. No matter if you want your robot to speak, beep, play some melodies, or even be a one-man band and play Beethoven’s Symphony No. 9, please respect your neighbors and control the volume with the command line utility alsamixer.

alsamixer
>>> import ev3dev.ev3 as ev3
>>> ev3.Sound.beep() # beep
>>> ev3.Sound.tone([(200, 100, 100), (500, 200)]) # list of (frequency (Hz), duration (ms), delay to next (ms)) tuples
>>> ev3.Sound.speak('Hey there!') # speak given text