Sensor classes

Dedicated sensor classes

These classes derive from ev3dev2.sensor.Sensor and provide helper functions specific to the corresponding sensor type. Each provides sensible property accessors for the main functionality of the sensor.

Touch Sensor

class ev3dev2.sensor.lego.TouchSensor(address=None, name_pattern='sensor*', name_exact=False, **kwargs)

Bases: ev3dev2.sensor.Sensor

Touch Sensor

MODE_TOUCH = 'TOUCH'

Button state

is_pressed

A boolean indicating whether the current touch sensor is being pressed.

wait_for_pressed(timeout_ms=None, sleep_ms=10)

Wait for the touch sensor to be pressed down.

wait_for_released(timeout_ms=None, sleep_ms=10)

Wait for the touch sensor to be released.

wait_for_bump(timeout_ms=None, sleep_ms=10)

Wait for the touch sensor to be pressed down and then released. Both actions must happen within timeout_ms.

Color Sensor

class ev3dev2.sensor.lego.ColorSensor(address=None, name_pattern='sensor*', name_exact=False, **kwargs)

Bases: ev3dev2.sensor.Sensor

LEGO EV3 color sensor.

MODE_COL_REFLECT = 'COL-REFLECT'

Reflected light. Red LED on.

MODE_COL_AMBIENT = 'COL-AMBIENT'

Ambient light. Blue LEDs on.

MODE_COL_COLOR = 'COL-COLOR'

Color. All LEDs rapidly cycling, appears white.

MODE_REF_RAW = 'REF-RAW'

Raw reflected. Red LED on

MODE_RGB_RAW = 'RGB-RAW'

Raw Color Components. All LEDs rapidly cycling, appears white.

COLOR_NOCOLOR = 0

No color.

COLOR_BLACK = 1

Black color.

COLOR_BLUE = 2

Blue color.

COLOR_GREEN = 3

Green color.

COLOR_YELLOW = 4

Yellow color.

COLOR_RED = 5

Red color.

COLOR_WHITE = 6

White color.

COLOR_BROWN = 7

Brown color.

reflected_light_intensity

Reflected light intensity as a percentage (0 to 100). Light on sensor is red.

ambient_light_intensity

Ambient light intensity, as a percentage (0 to 100). Light on sensor is dimly lit blue.

color
Color detected by the sensor, categorized by overall value.
  • 0: No color
  • 1: Black
  • 2: Blue
  • 3: Green
  • 4: Yellow
  • 5: Red
  • 6: White
  • 7: Brown
color_name

Returns NoColor, Black, Blue, etc

raw

Red, green, and blue components of the detected color, as a tuple.

Officially in the range 0-1020 but the values returned will never be that high. We do not yet know why the values returned are low, but pointing the color sensor at a well lit sheet of white paper will return values in the 250-400 range.

If this is an issue, check out the rgb() and calibrate_white() methods.

calibrate_white()

The RGB raw values are on a scale of 0-1020 but you never see a value anywhere close to 1020. This function is designed to be called when the sensor is placed over a white object in order to figure out what are the maximum RGB values the robot can expect to see. We will use these maximum values to scale future raw values to a 0-255 range in rgb().

If you never call this function red_max, green_max, and blue_max will use a default value of 300. This default was selected by measuring the RGB values of a white sheet of paper in a well lit room.

Note that there are several variables that influence the maximum RGB values detected by the color sensor - the distance of the color sensor to the white object - the amount of light in the room - shadows that the robot casts on the sensor

rgb

Same as raw() but RGB values are scaled to 0-255

lab

Return colors in Lab color space

hsv

HSV: Hue, Saturation, Value H: position in the spectrum S: color saturation (“purity”) V: color brightness

hls

HLS: Hue, Luminance, Saturation H: position in the spectrum L: color lightness S: color saturation

red

Red component of the detected color, in the range 0-1020.

green

Green component of the detected color, in the range 0-1020.

blue

Blue component of the detected color, in the range 0-1020.

Ultrasonic Sensor

class ev3dev2.sensor.lego.UltrasonicSensor(address=None, name_pattern='sensor*', name_exact=False, **kwargs)

Bases: ev3dev2.sensor.Sensor

LEGO EV3 ultrasonic sensor.

MODE_US_DIST_CM = 'US-DIST-CM'

Continuous measurement in centimeters.

MODE_US_DIST_IN = 'US-DIST-IN'

Continuous measurement in inches.

MODE_US_LISTEN = 'US-LISTEN'

Listen.

MODE_US_SI_CM = 'US-SI-CM'

Single measurement in centimeters.

MODE_US_SI_IN = 'US-SI-IN'

Single measurement in inches.

distance_centimeters_continuous

Measurement of the distance detected by the sensor, in centimeters.

The sensor will continue to take measurements so they are available for future reads.

Prefer using the equivalent UltrasonicSensor.distance_centimeters() property.

distance_centimeters_ping

Measurement of the distance detected by the sensor, in centimeters.

The sensor will take a single measurement then stop broadcasting.

If you use this property too frequently (e.g. every 100msec), the sensor will sometimes lock up and writing to the mode attribute will return an error. A delay of 250msec between each usage seems sufficient to keep the sensor from locking up.

distance_centimeters

Measurement of the distance detected by the sensor, in centimeters.

Equivalent to UltrasonicSensor.distance_centimeters_continuous().

distance_inches_continuous

Measurement of the distance detected by the sensor, in inches.

The sensor will continue to take measurements so they are available for future reads.

Prefer using the equivalent UltrasonicSensor.distance_inches() property.

distance_inches_ping

Measurement of the distance detected by the sensor, in inches.

The sensor will take a single measurement then stop broadcasting.

If you use this property too frequently (e.g. every 100msec), the sensor will sometimes lock up and writing to the mode attribute will return an error. A delay of 250msec between each usage seems sufficient to keep the sensor from locking up.

distance_inches

Measurement of the distance detected by the sensor, in inches.

Equivalent to UltrasonicSensor.distance_inches_continuous().

other_sensor_present

Boolean indicating whether another ultrasonic sensor could be heard nearby.

Gyro Sensor

class ev3dev2.sensor.lego.GyroSensor(address=None, name_pattern='sensor*', name_exact=False, **kwargs)

Bases: ev3dev2.sensor.Sensor

LEGO EV3 gyro sensor.

MODE_GYRO_ANG = 'GYRO-ANG'

Angle

MODE_GYRO_RATE = 'GYRO-RATE'

Rotational speed

MODE_GYRO_FAS = 'GYRO-FAS'

Raw sensor value

MODE_GYRO_G_A = 'GYRO-G&A'

Angle and rotational speed

MODE_GYRO_CAL = 'GYRO-CAL'

Calibration ???

angle

The number of degrees that the sensor has been rotated since it was put into this mode.

rate

The rate at which the sensor is rotating, in degrees/second.

angle_and_rate

Angle (degrees) and Rotational Speed (degrees/second).

wait_until_angle_changed_by(delta, direction_sensitive=False)

Wait until angle has changed by specified amount.

If direction_sensitive is True we will wait until angle has changed by delta and with the correct sign.

If direction_sensitive is False (default) we will wait until angle has changed by delta in either direction.

Infrared Sensor

class ev3dev2.sensor.lego.InfraredSensor(address=None, name_pattern='sensor*', name_exact=False, **kwargs)

Bases: ev3dev2.sensor.Sensor, ev3dev2.button.ButtonBase

LEGO EV3 infrared sensor.

MODE_IR_PROX = 'IR-PROX'

Proximity

MODE_IR_SEEK = 'IR-SEEK'

IR Seeker

MODE_IR_REMOTE = 'IR-REMOTE'

IR Remote Control

MODE_IR_REM_A = 'IR-REM-A'

IR Remote Control. State of the buttons is coded in binary

MODE_IR_CAL = 'IR-CAL'

Calibration ???

on_channel1_top_left = None

Handler for top-left button events on channel 1. See InfraredSensor.process().

on_channel1_bottom_left = None

Handler for bottom-left button events on channel 1. See InfraredSensor.process().

on_channel1_top_right = None

Handler for top-right button events on channel 1. See InfraredSensor.process().

on_channel1_bottom_right = None

Handler for bottom-right button events on channel 1. See InfraredSensor.process().

on_channel1_beacon = None

Handler for beacon button events on channel 1. See InfraredSensor.process().

on_channel2_top_left = None

Handler for top-left button events on channel 2. See InfraredSensor.process().

on_channel2_bottom_left = None

Handler for bottom-left button events on channel 2. See InfraredSensor.process().

on_channel2_top_right = None

Handler for top-right button events on channel 2. See InfraredSensor.process().

on_channel2_bottom_right = None

Handler for bottom-right button events on channel 2. See InfraredSensor.process().

on_channel2_beacon = None

Handler for beacon button events on channel 2. See InfraredSensor.process().

on_channel3_top_left = None

Handler for top-left button events on channel 3. See InfraredSensor.process().

on_channel3_bottom_left = None

Handler for bottom-left button events on channel 3. See InfraredSensor.process().

on_channel3_top_right = None

Handler for top-right button events on channel 3. See InfraredSensor.process().

on_channel3_bottom_right = None

Handler for bottom-right button events on channel 3. See InfraredSensor.process().

on_channel3_beacon = None

Handler for beacon button events on channel 3. See InfraredSensor.process().

on_channel4_top_left = None

Handler for top-left button events on channel 4. See InfraredSensor.process().

on_channel4_bottom_left = None

Handler for bottom-left button events on channel 4. See InfraredSensor.process().

on_channel4_top_right = None

Handler for top-right button events on channel 4. See InfraredSensor.process().

on_channel4_bottom_right = None

Handler for bottom-right button events on channel 4. See InfraredSensor.process().

on_channel4_beacon = None

Handler for beacon button events on channel 4. See InfraredSensor.process().

proximity

An estimate of the distance between the sensor and objects in front of it, as a percentage. 100% is approximately 70cm/27in.

heading(channel=1)

Returns heading (-25, 25) to the beacon on the given channel.

distance(channel=1)

Returns distance (0, 100) to the beacon on the given channel. Returns None when beacon is not found.

heading_and_distance(channel=1)

Returns heading and distance to the beacon on the given channel as a tuple.

top_left(channel=1)

Checks if top_left button is pressed.

bottom_left(channel=1)

Checks if bottom_left button is pressed.

top_right(channel=1)

Checks if top_right button is pressed.

bottom_right(channel=1)

Checks if bottom_right button is pressed.

beacon(channel=1)

Checks if beacon button is pressed.

buttons_pressed(channel=1)

Returns list of currently pressed buttons.

Note that the sensor can only identify up to two buttons pressed at once.

process()

Check for currenly pressed buttons. If the new state differs from the old state, call the appropriate button event handlers.

To use the on_channel1_top_left, etc handlers your program would do something like:

def top_left_channel_1_action(state):
    print("top left on channel 1: %s" % state)

def bottom_right_channel_4_action(state):
    print("bottom right on channel 4: %s" % state)

ir = InfraredSensor()
ir.on_channel1_top_left = top_left_channel_1_action
ir.on_channel4_bottom_right = bottom_right_channel_4_action

while True:
    ir.process()
    time.sleep(0.01)

Sound Sensor

class ev3dev2.sensor.lego.SoundSensor(address=None, name_pattern='sensor*', name_exact=False, **kwargs)

Bases: ev3dev2.sensor.Sensor

LEGO NXT Sound Sensor

MODE_DB = 'DB'

Sound pressure level. Flat weighting

MODE_DBA = 'DBA'

Sound pressure level. A weighting

sound_pressure

A measurement of the measured sound pressure level, as a percent. Uses a flat weighting.

sound_pressure_low

A measurement of the measured sound pressure level, as a percent. Uses A-weighting, which focuses on levels up to 55 dB.

Light Sensor

class ev3dev2.sensor.lego.LightSensor(address=None, name_pattern='sensor*', name_exact=False, **kwargs)

Bases: ev3dev2.sensor.Sensor

LEGO NXT Light Sensor

MODE_REFLECT = 'REFLECT'

Reflected light. LED on

MODE_AMBIENT = 'AMBIENT'

Ambient light. LED off

reflected_light_intensity

A measurement of the reflected light intensity, as a percentage.

ambient_light_intensity

A measurement of the ambient light intensity, as a percentage.

Base “Sensor”

This is the base class all the other sensor classes are derived from. You generally want to use one of the other classes instead, but if your sensor doesn’t have a dedicated class, this is will let you interface with it as a generic device.

class ev3dev2.sensor.Sensor(address=None, name_pattern='sensor*', name_exact=False, **kwargs)

The sensor class provides a uniform interface for using most of the sensors available for the EV3.

address

Returns the name of the port that the sensor is connected to, e.g. ev3:in1. I2C sensors also include the I2C address (decimal), e.g. ev3:in1:i2c8.

command

Sends a command to the sensor.

commands

Returns a list of the valid commands for the sensor. Returns -EOPNOTSUPP if no commands are supported.

decimals

Returns the number of decimal places for the values in the value<N> attributes of the current mode.

driver_name

Returns the name of the sensor device/driver. See the list of [supported sensors] for a complete list of drivers.

mode

Returns the current mode. Writing one of the values returned by modes sets the sensor to that mode.

modes

Returns a list of the valid modes for the sensor.

num_values

Returns the number of value<N> attributes that will return a valid value for the current mode.

units

Returns the units of the measured value for the current mode. May return empty string

value(n=0)

Returns the value or values measured by the sensor. Check num_values to see how many values there are. Values with N >= num_values will return an error. The values are fixed point numbers, so check decimals to see if you need to divide to get the actual value.

bin_data_format

Returns the format of the values in bin_data for the current mode. Possible values are:

  • u8: Unsigned 8-bit integer (byte)
  • s8: Signed 8-bit integer (sbyte)
  • u16: Unsigned 16-bit integer (ushort)
  • s16: Signed 16-bit integer (short)
  • s16_be: Signed 16-bit integer, big endian
  • s32: Signed 32-bit integer (int)
  • float: IEEE 754 32-bit floating point (float)
bin_data(fmt=None)

Returns the unscaled raw values in the value<N> attributes as raw byte array. Use bin_data_format, num_values and the individual sensor documentation to determine how to interpret the data.

Use fmt to unpack the raw bytes into a struct.

Example:

>>> from ev3dev2.sensor.lego import InfraredSensor
>>> ir = InfraredSensor()
>>> ir.value()
28
>>> ir.bin_data('<b')
(28,)