This is the description of the Python API bindings for the Laser Range Finder Bricklet. General information and technical specifications for the Laser Range Finder Bricklet are summarized in its hardware description.
An installation guide for the Python API bindings is part of their general description.
The example code below is Public Domain (CC0 1.0).
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 | #!/usr/bin/env python
# -*- coding: utf-8 -*-
HOST = "localhost"
PORT = 4223
UID = "XYZ" # Change XYZ to the UID of your Laser Range Finder Bricklet
import time
from tinkerforge.ip_connection import IPConnection
from tinkerforge.bricklet_laser_range_finder import BrickletLaserRangeFinder
if __name__ == "__main__":
ipcon = IPConnection() # Create IP connection
lrf = BrickletLaserRangeFinder(UID, ipcon) # Create device object
ipcon.connect(HOST, PORT) # Connect to brickd
# Don't use device before ipcon is connected
# Turn laser on and wait 250ms for very first measurement to be ready
lrf.enable_laser()
time.sleep(0.25)
# Get current distance
distance = lrf.get_distance()
print("Distance: " + str(distance) + " cm")
input("Press key to exit\n") # Use raw_input() in Python 2
lrf.disable_laser() # Turn laser off
ipcon.disconnect()
|
Download (example_callback.py)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 | #!/usr/bin/env python
# -*- coding: utf-8 -*-
HOST = "localhost"
PORT = 4223
UID = "XYZ" # Change XYZ to the UID of your Laser Range Finder Bricklet
import time
from tinkerforge.ip_connection import IPConnection
from tinkerforge.bricklet_laser_range_finder import BrickletLaserRangeFinder
# Callback function for distance callback
def cb_distance(distance):
print("Distance: " + str(distance) + " cm")
if __name__ == "__main__":
ipcon = IPConnection() # Create IP connection
lrf = BrickletLaserRangeFinder(UID, ipcon) # Create device object
ipcon.connect(HOST, PORT) # Connect to brickd
# Don't use device before ipcon is connected
# Turn laser on and wait 250ms for very first measurement to be ready
lrf.enable_laser()
time.sleep(0.25)
# Register distance callback to function cb_distance
lrf.register_callback(lrf.CALLBACK_DISTANCE, cb_distance)
# Set period for distance callback to 0.2s (200ms)
# Note: The distance callback is only called every 0.2 seconds
# if the distance has changed since the last call!
lrf.set_distance_callback_period(200)
input("Press key to exit\n") # Use raw_input() in Python 2
lrf.disable_laser() # Turn laser off
ipcon.disconnect()
|
Download (example_threshold.py)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 | #!/usr/bin/env python
# -*- coding: utf-8 -*-
HOST = "localhost"
PORT = 4223
UID = "XYZ" # Change XYZ to the UID of your Laser Range Finder Bricklet
import time
from tinkerforge.ip_connection import IPConnection
from tinkerforge.bricklet_laser_range_finder import BrickletLaserRangeFinder
# Callback function for distance reached callback
def cb_distance_reached(distance):
print("Distance: " + str(distance) + " cm")
if __name__ == "__main__":
ipcon = IPConnection() # Create IP connection
lrf = BrickletLaserRangeFinder(UID, ipcon) # Create device object
ipcon.connect(HOST, PORT) # Connect to brickd
# Don't use device before ipcon is connected
# Turn laser on and wait 250ms for very first measurement to be ready
lrf.enable_laser()
time.sleep(0.25)
# Get threshold callbacks with a debounce time of 10 seconds (10000ms)
lrf.set_debounce_period(10000)
# Register distance reached callback to function cb_distance_reached
lrf.register_callback(lrf.CALLBACK_DISTANCE_REACHED, cb_distance_reached)
# Configure threshold for distance "greater than 20 cm"
lrf.set_distance_callback_threshold(">", 20, 0)
input("Press key to exit\n") # Use raw_input() in Python 2
lrf.disable_laser() # Turn laser off
ipcon.disconnect()
|
Generally, every function of the Python bindings can throw an
tinkerforge.ip_connection.Error
exception that has a value
and a
description
property. value
can have different values:
All functions listed below are thread-safe.
BrickletLaserRangeFinder
(uid, ipcon)¶Parameters: |
|
---|---|
Returns: |
|
Creates an object with the unique device ID uid
:
laser_range_finder = BrickletLaserRangeFinder("YOUR_DEVICE_UID", ipcon)
This object can then be used after the IP Connection is connected.
BrickletLaserRangeFinder.
get_distance
()¶Returns: |
|
---|
Returns the measured distance.
Sensor hardware version 1 (see get_sensor_hardware_version()
) cannot
measure distance and velocity at the same time. Therefore, the distance mode
has to be enabled using set_mode()
.
Sensor hardware version 3 can measure distance and velocity at the same
time. Also the laser has to be enabled, see enable_laser()
.
If you want to get the distance periodically, it is recommended to
use the CALLBACK_DISTANCE
callback and set the period with
set_distance_callback_period()
.
BrickletLaserRangeFinder.
get_velocity
()¶Returns: |
|
---|
Returns the measured velocity.
Sensor hardware version 1 (see get_sensor_hardware_version()
) cannot
measure distance and velocity at the same time. Therefore, the velocity mode
has to be enabled using set_mode()
.
Sensor hardware version 3 can measure distance and velocity at the same
time, but the velocity measurement only produces stables results if a fixed
measurement rate (see set_configuration()
) is configured. Also the laser
has to be enabled, see enable_laser()
.
If you want to get the velocity periodically, it is recommended to
use the CALLBACK_VELOCITY
callback and set the period with
set_velocity_callback_period()
.
BrickletLaserRangeFinder.
set_mode
(mode)¶Parameters: |
|
---|---|
Returns: |
|
Note
This function is only available if you have a LIDAR-Lite sensor with hardware
version 1. Use set_configuration()
for hardware version 3. You can check
the sensor hardware version using get_sensor_hardware_version()
.
The LIDAR-Lite sensor (hardware version 1) has five different modes. One mode is for distance measurements and four modes are for velocity measurements with different ranges.
The following modes are available:
The following constants are available for this function:
For mode:
BrickletLaserRangeFinder.
get_mode
()¶Returns: |
|
---|
Returns the mode as set by set_mode()
.
The following constants are available for this function:
For mode:
BrickletLaserRangeFinder.
enable_laser
()¶Returns: |
|
---|
Activates the laser of the LIDAR.
We recommend that you wait 250ms after enabling the laser before
the first call of get_distance()
to ensure stable measurements.
BrickletLaserRangeFinder.
disable_laser
()¶Returns: |
|
---|
Deactivates the laser of the LIDAR.
BrickletLaserRangeFinder.
is_laser_enabled
()¶Returns: |
|
---|
Returns true if the laser is enabled, false otherwise.
BrickletLaserRangeFinder.
set_configuration
(acquisition_count, enable_quick_termination, threshold_value, measurement_frequency)¶Parameters: |
|
---|---|
Returns: |
|
Note
This function is only available if you have a LIDAR-Lite sensor with hardware
version 3. Use set_mode()
for hardware version 1. You can check
the sensor hardware version using get_sensor_hardware_version()
.
The Acquisition Count defines the number of times the Laser Range Finder Bricklet will integrate acquisitions to find a correlation record peak. With a higher count, the Bricklet can measure longer distances. With a lower count, the rate increases. The allowed values are 1-255.
If you set Enable Quick Termination to true, the distance measurement will be terminated early if a high peak was already detected. This means that a higher measurement rate can be achieved and long distances can be measured at the same time. However, the chance of false-positive distance measurements increases.
Normally the distance is calculated with a detection algorithm that uses peak value, signal strength and noise. You can however also define a fixed Threshold Value. Set this to a low value if you want to measure the distance to something that has very little reflection (e.g. glass) and set it to a high value if you want to measure the distance to something with a very high reflection (e.g. mirror). Set this to 0 to use the default algorithm. The other allowed values are 1-255.
Set the Measurement Frequency to force a fixed measurement rate. If set to 0, the Laser Range Finder Bricklet will use the optimal frequency according to the other configurations and the actual measured distance. Since the rate is not fixed in this case, the velocity measurement is not stable. For a stable velocity measurement you should set a fixed measurement frequency. The lower the frequency, the higher is the resolution of the calculated velocity. The allowed values are 10Hz-500Hz (and 0 to turn the fixed frequency off).
New in version 2.0.3 (Plugin).
BrickletLaserRangeFinder.
get_configuration
()¶Return Object: |
|
---|
Returns the configuration as set by set_configuration()
.
New in version 2.0.3 (Plugin).
BrickletLaserRangeFinder.
set_moving_average
(distance_average_length, velocity_average_length)¶Parameters: |
|
---|---|
Returns: |
|
Sets the length of a moving averaging for the distance and velocity.
Setting the length to 0 will turn the averaging completely off. With less averaging, there is more noise on the data.
BrickletLaserRangeFinder.
get_moving_average
()¶Return Object: |
|
---|
Returns the length moving average as set by set_moving_average()
.
BrickletLaserRangeFinder.
get_sensor_hardware_version
()¶Returns: |
|
---|
Returns the LIDAR-Lite hardware version.
The following constants are available for this function:
For version:
New in version 2.0.3 (Plugin).
BrickletLaserRangeFinder.
get_identity
()¶Return Object: |
|
---|
Returns the UID, the UID where the Bricklet is connected to, the position, the hardware and firmware version as well as the device identifier.
The position can be 'a', 'b', 'c', 'd', 'e', 'f', 'g' or 'h' (Bricklet Port). A Bricklet connected to an Isolator Bricklet is always at position 'z'.
The device identifier numbers can be found here. There is also a constant for the device identifier of this Bricklet.
BrickletLaserRangeFinder.
register_callback
(callback_id, function)¶Parameters: |
|
---|---|
Returns: |
|
Registers the given function
with the given callback_id
.
The available callback IDs with corresponding function signatures are listed below.
BrickletLaserRangeFinder.
set_distance_callback_period
(period)¶Parameters: |
|
---|---|
Returns: |
|
Sets the period with which the CALLBACK_DISTANCE
callback is triggered
periodically. A value of 0 turns the callback off.
The CALLBACK_DISTANCE
callback is only triggered if the distance value has
changed since the last triggering.
BrickletLaserRangeFinder.
get_distance_callback_period
()¶Returns: |
|
---|
Returns the period as set by set_distance_callback_period()
.
BrickletLaserRangeFinder.
set_velocity_callback_period
(period)¶Parameters: |
|
---|---|
Returns: |
|
Sets the period with which the CALLBACK_VELOCITY
callback is triggered
periodically. A value of 0 turns the callback off.
The CALLBACK_VELOCITY
callback is only triggered if the velocity value has
changed since the last triggering.
BrickletLaserRangeFinder.
get_velocity_callback_period
()¶Returns: |
|
---|
Returns the period as set by set_velocity_callback_period()
.
BrickletLaserRangeFinder.
set_distance_callback_threshold
(option, min, max)¶Parameters: |
|
---|---|
Returns: |
|
Sets the thresholds for the CALLBACK_DISTANCE_REACHED
callback.
The following options are possible:
Option | Description |
---|---|
'x' | Callback is turned off |
'o' | Callback is triggered when the distance value is outside the min and max values |
'i' | Callback is triggered when the distance value is inside the min and max values |
'<' | Callback is triggered when the distance value is smaller than the min value (max is ignored) |
'>' | Callback is triggered when the distance value is greater than the min value (max is ignored) |
The following constants are available for this function:
For option:
BrickletLaserRangeFinder.
get_distance_callback_threshold
()¶Return Object: |
|
---|
Returns the threshold as set by set_distance_callback_threshold()
.
The following constants are available for this function:
For option:
BrickletLaserRangeFinder.
set_velocity_callback_threshold
(option, min, max)¶Parameters: |
|
---|---|
Returns: |
|
Sets the thresholds for the CALLBACK_VELOCITY_REACHED
callback.
The following options are possible:
Option | Description |
---|---|
'x' | Callback is turned off |
'o' | Callback is triggered when the velocity is outside the min and max values |
'i' | Callback is triggered when the velocity is inside the min and max values |
'<' | Callback is triggered when the velocity is smaller than the min value (max is ignored) |
'>' | Callback is triggered when the velocity is greater than the min value (max is ignored) |
The following constants are available for this function:
For option:
BrickletLaserRangeFinder.
get_velocity_callback_threshold
()¶Return Object: |
|
---|
Returns the threshold as set by set_velocity_callback_threshold()
.
The following constants are available for this function:
For option:
BrickletLaserRangeFinder.
set_debounce_period
(debounce)¶Parameters: |
|
---|---|
Returns: |
|
Sets the period with which the threshold callbacks
are triggered, if the thresholds
keep being reached.
BrickletLaserRangeFinder.
get_debounce_period
()¶Returns: |
|
---|
Returns the debounce period as set by set_debounce_period()
.
Callbacks can be registered to receive
time critical or recurring data from the device. The registration is done
with the register_callback()
function of
the device object. The first parameter is the callback ID and the second
parameter the callback function:
def my_callback(param):
print(param)
laser_range_finder.register_callback(BrickletLaserRangeFinder.CALLBACK_EXAMPLE, my_callback)
The available constants with inherent number and type of parameters are described below.
Note
Using callbacks for recurring events is always preferred compared to using getters. It will use less USB bandwidth and the latency will be a lot better, since there is no round trip time.
BrickletLaserRangeFinder.
CALLBACK_DISTANCE
¶Callback Parameters: |
|
---|
This callback is triggered periodically with the period that is set by
set_distance_callback_period()
. The parameter is the distance
value of the sensor.
The CALLBACK_DISTANCE
callback is only triggered if the distance value has changed
since the last triggering.
BrickletLaserRangeFinder.
CALLBACK_VELOCITY
¶Callback Parameters: |
|
---|
This callback is triggered periodically with the period that is set by
set_velocity_callback_period()
. The parameter is the velocity
value of the sensor.
The CALLBACK_VELOCITY
callback is only triggered if the velocity has changed since
the last triggering.
BrickletLaserRangeFinder.
CALLBACK_DISTANCE_REACHED
¶Callback Parameters: |
|
---|
This callback is triggered when the threshold as set by
set_distance_callback_threshold()
is reached.
The parameter is the distance value of the sensor.
If the threshold keeps being reached, the callback is triggered periodically
with the period as set by set_debounce_period()
.
BrickletLaserRangeFinder.
CALLBACK_VELOCITY_REACHED
¶Callback Parameters: |
|
---|
This callback is triggered when the threshold as set by
set_velocity_callback_threshold()
is reached.
The parameter is the velocity value of the sensor.
If the threshold keeps being reached, the callback is triggered periodically
with the period as set by set_debounce_period()
.
Virtual functions don't communicate with the device itself, but operate only on the API bindings device object. They can be called without the corresponding IP Connection object being connected.
BrickletLaserRangeFinder.
get_api_version
()¶Return Object: |
|
---|
Returns the version of the API definition implemented by this API bindings. This is neither the release version of this API bindings nor does it tell you anything about the represented Brick or Bricklet.
BrickletLaserRangeFinder.
get_response_expected
(function_id)¶Parameters: |
|
---|---|
Returns: |
|
Returns the response expected flag for the function specified by the function ID parameter. It is true if the function is expected to send a response, false otherwise.
For getter functions this is enabled by default and cannot be disabled,
because those functions will always send a response. For callback configuration
functions it is enabled by default too, but can be disabled by
set_response_expected()
. For setter functions it is disabled by default
and can be enabled.
Enabling the response expected flag for a setter function allows to detect timeouts and other error conditions calls of this setter as well. The device will then send a response for this purpose. If this flag is disabled for a setter function then no response is sent and errors are silently ignored, because they cannot be detected.
The following constants are available for this function:
For function_id:
BrickletLaserRangeFinder.
set_response_expected
(function_id, response_expected)¶Parameters: |
|
---|---|
Returns: |
|
Changes the response expected flag of the function specified by the function ID parameter. This flag can only be changed for setter (default value: false) and callback configuration functions (default value: true). For getter functions it is always enabled.
Enabling the response expected flag for a setter function allows to detect timeouts and other error conditions calls of this setter as well. The device will then send a response for this purpose. If this flag is disabled for a setter function then no response is sent and errors are silently ignored, because they cannot be detected.
The following constants are available for this function:
For function_id:
BrickletLaserRangeFinder.
set_response_expected_all
(response_expected)¶Parameters: |
|
---|---|
Returns: |
|
Changes the response expected flag for all setter and callback configuration functions of this device at once.
BrickletLaserRangeFinder.
DEVICE_IDENTIFIER
¶This constant is used to identify a Laser Range Finder Bricklet.
The get_identity()
function and the
IPConnection.CALLBACK_ENUMERATE
callback of the IP Connection have a device_identifier
parameter to specify
the Brick's or Bricklet's type.
BrickletLaserRangeFinder.
DEVICE_DISPLAY_NAME
¶This constant represents the human readable name of a Laser Range Finder Bricklet.