Touch¶

Touch is a subclass of EV3. You can use it to read values from a single touch sensor without any knowledge of direct command syntax.

To use multiple touch sensors, you can create multiple instances of class Touch.

Asking for the current state¶

Property touched is of type bool and tells, if the sensor currently is touched.

Connect your EV3 device with your local network via WiFi and make sure, it’s the only EV3 devices in the network. Connect a touch sensor (it may be an EV3-Touch or a NXT-Touch) with PORT 1, then start this program.

import ev3_dc as ev3

with ev3.Touch(ev3.PORT_1, protocol=ev3.WIFI) as my_touch:
    print(str(my_touch) + ':', end=' ')
    print('touched' if my_touch.touched else 'not touched')

Some remarks:

You already know, how to modify the program, when using protocols Bluetooth or USB.

As the output line shows, the class knows it’s sensor type.

Run the program multiple times with touched and not touched sensor.

Test what happens, when no sensor is connected to PORT 1.

Test what happens, when another sensor type is connected to PORT 1.

Switch on verbosity and you will see the communication data.

Multiple instances of class Touch¶

Connect an additional touch sensor (again it may be an EV3-Touch or a NXT-Touch) with PORT 4, then start this program.

import ev3_dc as ev3

with ev3.Touch(ev3.PORT_1, protocol=ev3.WIFI) as touch_left:
    touch_right = ev3.Touch(ev3.PORT_4, ev3_obj=touch_left)
    print(str(touch_left) + ':', end=' ')
    print('touched' if touch_left.touched else 'not touched')
    print(str(touch_right) + ':', end=' ')
    print('touched' if touch_right.touched else 'not touched')

Some remarks:

Both touch sensors share the same EV3 device. Therefore only the first instance is initialized with keyword argument protocol. The second instance is initialized with keyword argument ev3_obj instead.

touch_left owns the connection, touch_right is its joint user.

A single EV3 device controls up to four sensors and additionally up to four motors. You will deal with more than two objects, when you make use of EV3’s full capacity.

Both sensors are handled independently, therefore the communication is not optimized. The request of both sensors’ state could have been done in a single direct command, but here it needs two instead.

Bump-Mode¶

Touch sensors provide two modes, touch and bump (see sections Touch mode of the Touch Sensor and Bump mode of the Touch Sensor). The touch-mode is, what we have seen above: the sensor replies it’s current state. The bump-mode counts the number of bumps since the last sensor clearing.

Connect your EV3 device with your local network via WiFi. Replace the MAC-address by the one of your EV3 brick, connect a touch sensor (it may be an EV3-Touch or a NXT-Touch) with PORT 1, then start this program.

import ev3_dc as ev3
from time import sleep

my_touch = ev3.Touch(
        ev3.PORT_1,
        protocol=ev3.WIFI,
        host='00:16:53:42:2B:99'
)

print('\n' + 'countdown ...' + '\n')
for n in range(10, 0, -1):
    print('\r' + f'{n:2d} ', end='', flush=True)
    sleep(1)

print('\r' + '** go ** ', end='', flush=True)

my_touch.bumps = 0
sleep(5)

print('\r' + 'number of bumps:', my_touch.bumps)

Some remarks:

This program counts the number of bumps for a timespan of 5 sec.

To prevent jumping the start, the sensor clearing is done at the end of the countdown.

Instead of setting property bumps = 0, you alternatively can call method clear().

Compare the version above with the manually coded direct commands from section Bump mode of the Touch Sensor and you will realize the handiness of sensor classes.