Shell - Laser Range Finder Bricklet

This is the description of the Shell 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 Shell API bindings is part of their general description.

Examples

The example code below is Public Domain (CC0 1.0).

Simple

Download (example-simple.sh)

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#!/bin/sh
# Connects to localhost:4223 by default, use --host and --port to change this

uid=XYZ # Change XYZ to the UID of your Laser Range Finder Bricklet

# Turn laser on and wait 250ms for very first measurement to be ready
tinkerforge call laser-range-finder-bricklet $uid enable-laser
sleep 0.25

# Get current distance
tinkerforge call laser-range-finder-bricklet $uid get-distance

tinkerforge call laser-range-finder-bricklet $uid disable-laser # Turn laser off

Callback

Download (example-callback.sh)

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#!/bin/sh
# Connects to localhost:4223 by default, use --host and --port to change this

uid=XYZ # Change XYZ to the UID of your Laser Range Finder Bricklet

# Turn laser on and wait 250ms for very first measurement to be ready
tinkerforge call laser-range-finder-bricklet $uid enable-laser
sleep 0.25

# Handle incoming distance callbacks
tinkerforge dispatch laser-range-finder-bricklet $uid 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!
tinkerforge call laser-range-finder-bricklet $uid set-distance-callback-period 200

echo "Press key to exit"; read dummy

tinkerforge call laser-range-finder-bricklet $uid disable-laser # Turn laser off

kill -- -$$ # Stop callback dispatch in background

Threshold

Download (example-threshold.sh)

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#!/bin/sh
# Connects to localhost:4223 by default, use --host and --port to change this

uid=XYZ # Change XYZ to the UID of your Laser Range Finder Bricklet

# Turn laser on and wait 250ms for very first measurement to be ready
tinkerforge call laser-range-finder-bricklet $uid enable-laser
sleep 0.25

# Get threshold callbacks with a debounce time of 10 seconds (10000ms)
tinkerforge call laser-range-finder-bricklet $uid set-debounce-period 10000

# Handle incoming distance reached callbacks
tinkerforge dispatch laser-range-finder-bricklet $uid distance-reached &

# Configure threshold for distance "greater than 20 cm"
tinkerforge call laser-range-finder-bricklet $uid set-distance-callback-threshold threshold-option-greater 20 0

echo "Press key to exit"; read dummy

tinkerforge call laser-range-finder-bricklet $uid disable-laser # Turn laser off

kill -- -$$ # Stop callback dispatch in background

API

Possible exit codes for all tinkerforge commands are:

  • 1: interrupted (ctrl+c)
  • 2: syntax error
  • 21: Python 2.5 or newer is required
  • 22: Python argparse module is missing
  • 23: socket error
  • 24: other exception
  • 25: invalid placeholder in format string
  • 26: authentication error
  • 201: timeout occurred
  • 209: invalid argument value
  • 210: function is not supported
  • 211: unknown error

Command Structure

The common options of the call and dispatch commands are documented here. The specific command structure is shown below.

tinkerforge call laser-range-finder-bricklet [<option>..] <uid> <function> [<argument>..]
Parameters:
  • <uid> -- string
  • <function> -- string

The call command is used to call a function of the Laser Range Finder Bricklet. It can take several options:

  • --help shows help for the specific call command and exits
  • --list-functions shows a list of known functions of the Laser Range Finder Bricklet and exits
tinkerforge dispatch laser-range-finder-bricklet [<option>..] <uid> <callback>
Parameters:
  • <uid> -- string
  • <callback> -- string

The dispatch command is used to dispatch a callback of the Laser Range Finder Bricklet. It can take several options:

  • --help shows help for the specific dispatch command and exits
  • --list-callbacks shows a list of known callbacks of the Laser Range Finder Bricklet and exits
tinkerforge call laser-range-finder-bricklet <uid> <function> [<option>..] [<argument>..]
Parameters:
  • <uid> -- string
  • <function> -- string

The <function> to be called can take different options depending of its kind. All functions can take the following options:

  • --help shows help for the specific function and exits

Getter functions can take the following options:

  • --execute <command> shell command line to execute for each incoming response (see section about output formatting for details)

Setter functions can take the following options:

  • --expect-response requests response and waits for it

The --expect-response option for setter functions allows to detect timeouts and other error conditions calls of setters as well. The device will then send a response for this purpose. If this option is not given for a setter function then no response is send and errors are silently ignored, because they cannot be detected.

tinkerforge dispatch laser-range-finder-bricklet <uid> <callback> [<option>..]
Parameters:
  • <uid> -- string
  • <callback> -- string

The <callback> to be dispatched can take several options:

  • --help shows help for the specific callback and exits
  • --execute <command> shell command line to execute for each incoming response (see section about output formatting for details)

Basic Functions

tinkerforge call laser-range-finder-bricklet <uid> get-distance
Output:
  • distance -- int

Returns the measured distance. The value has a range of 0 to 4000 and is given in cm.

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 distance callback and set the period with set-distance-callback-period.

tinkerforge call laser-range-finder-bricklet <uid> get-velocity
Output:
  • velocity -- int

Returns the measured velocity. The value has a range of -12800 to 12700 and is given in 1/100 m/s.

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 velocity callback and set the period with set-velocity-callback-period.

tinkerforge call laser-range-finder-bricklet <uid> set-mode <mode>
Parameters:
  • <mode> -- int (has symbols)
Output:

no output

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:

  • 0: Distance is measured with resolution 1.0 cm and range 0-400 cm
  • 1: Velocity is measured with resolution 0.1 m/s and range is 0-12.7 m/s
  • 2: Velocity is measured with resolution 0.25 m/s and range is 0-31.75 m/s
  • 3: Velocity is measured with resolution 0.5 m/s and range is 0-63.5 m/s
  • 4: Velocity is measured with resolution 1.0 m/s and range is 0-127 m/s

The default mode is 0 (distance is measured).

The following symbols are available for this function:

  • mode-distance = 0, for <mode>
  • mode-velocity-max-13ms = 1, for <mode>
  • mode-velocity-max-32ms = 2, for <mode>
  • mode-velocity-max-64ms = 3, for <mode>
  • mode-velocity-max-127ms = 4, for <mode>
tinkerforge call laser-range-finder-bricklet <uid> get-mode
Output:
  • mode -- int (has symbols)

Returns the mode as set by set-mode.

The following symbols are available for this function:

  • mode-distance = 0, for mode
  • mode-velocity-max-13ms = 1, for mode
  • mode-velocity-max-32ms = 2, for mode
  • mode-velocity-max-64ms = 3, for mode
  • mode-velocity-max-127ms = 4, for mode
tinkerforge call laser-range-finder-bricklet <uid> enable-laser
Output:no output

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.

tinkerforge call laser-range-finder-bricklet <uid> disable-laser
Output:no output

Deactivates the laser of the LIDAR.

tinkerforge call laser-range-finder-bricklet <uid> is-laser-enabled
Output:
  • laser-enabled -- bool

Returns true if the laser is enabled, false otherwise.

tinkerforge call laser-range-finder-bricklet <uid> set-configuration <acquisition-count> <enable-quick-termination> <threshold-value> <measurement-frequency>
Parameters:
  • <acquisition-count> -- int
  • <enable-quick-termination> -- bool
  • <threshold-value> -- int
  • <measurement-frequency> -- int
Output:

no output

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 Aquisition 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 in Hz 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).

The default values for Acquisition Count, Enable Quick Termination, Threshold Value and Measurement Frequency are 128, false, 0 and 0.

New in version 2.0.3 (Plugin).

tinkerforge call laser-range-finder-bricklet <uid> get-configuration
Output:
  • acquisition-count -- int
  • enable-quick-termination -- bool
  • threshold-value -- int
  • measurement-frequency -- int

Returns the configuration as set by set-configuration.

New in version 2.0.3 (Plugin).

Advanced Functions

tinkerforge call laser-range-finder-bricklet <uid> set-moving-average <distance-average-length> <velocity-average-length>
Parameters:
  • <distance-average-length> -- int
  • <velocity-average-length> -- int
Output:

no output

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.

The range for the averaging is 0-30.

The default value is 10.

tinkerforge call laser-range-finder-bricklet <uid> get-moving-average
Output:
  • distance-average-length -- int
  • velocity-average-length -- int

Returns the length moving average as set by set-moving-average.

tinkerforge call laser-range-finder-bricklet <uid> get-sensor-hardware-version
Output:
  • version -- int (has symbols)

Returns the LIDAR-Lite hardware version.

The following symbols are available for this function:

  • version-1 = 1, for version
  • version-3 = 3, for version

New in version 2.0.3 (Plugin).

tinkerforge call laser-range-finder-bricklet <uid> get-identity
Output:
  • uid -- string
  • connected-uid -- string
  • position -- char
  • hardware-version -- int,int,int
  • firmware-version -- int,int,int
  • device-identifier -- int (has symbols)

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' or 'd'.

The device identifier numbers can be found here

Callback Configuration Functions

tinkerforge call laser-range-finder-bricklet <uid> set-distance-callback-period <period>
Parameters:
  • <period> -- int
Output:

no output

Sets the period in ms with which the distance callback is triggered periodically. A value of 0 turns the callback off.

The distance callback is only triggered if the distance value has changed since the last triggering.

The default value is 0.

tinkerforge call laser-range-finder-bricklet <uid> get-distance-callback-period
Output:
  • period -- int

Returns the period as set by set-distance-callback-period.

tinkerforge call laser-range-finder-bricklet <uid> set-velocity-callback-period <period>
Parameters:
  • <period> -- int
Output:

no output

Sets the period in ms with which the velocity callback is triggered periodically. A value of 0 turns the callback off.

The velocity callback is only triggered if the velocity value has changed since the last triggering.

The default value is 0.

tinkerforge call laser-range-finder-bricklet <uid> get-velocity-callback-period
Output:
  • period -- int

Returns the period as set by set-velocity-callback-period.

tinkerforge call laser-range-finder-bricklet <uid> set-distance-callback-threshold <option> <min> <max>
Parameters:
  • <option> -- char (has symbols)
  • <min> -- int
  • <max> -- int
Output:

no output

Sets the thresholds for the 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 default value is ('x', 0, 0).

The following symbols are available for this function:

  • threshold-option-off = x, for <option>
  • threshold-option-outside = o, for <option>
  • threshold-option-inside = i, for <option>
  • threshold-option-smaller = <, for <option>
  • threshold-option-greater = >, for <option>
tinkerforge call laser-range-finder-bricklet <uid> get-distance-callback-threshold
Output:
  • option -- char (has symbols)
  • min -- int
  • max -- int

Returns the threshold as set by set-distance-callback-threshold.

The following symbols are available for this function:

  • threshold-option-off = x, for option
  • threshold-option-outside = o, for option
  • threshold-option-inside = i, for option
  • threshold-option-smaller = <, for option
  • threshold-option-greater = >, for option
tinkerforge call laser-range-finder-bricklet <uid> set-velocity-callback-threshold <option> <min> <max>
Parameters:
  • <option> -- char (has symbols)
  • <min> -- int
  • <max> -- int
Output:

no output

Sets the thresholds for the 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 default value is ('x', 0, 0).

The following symbols are available for this function:

  • threshold-option-off = x, for <option>
  • threshold-option-outside = o, for <option>
  • threshold-option-inside = i, for <option>
  • threshold-option-smaller = <, for <option>
  • threshold-option-greater = >, for <option>
tinkerforge call laser-range-finder-bricklet <uid> get-velocity-callback-threshold
Output:
  • option -- char (has symbols)
  • min -- int
  • max -- int

Returns the threshold as set by set-velocity-callback-threshold.

The following symbols are available for this function:

  • threshold-option-off = x, for option
  • threshold-option-outside = o, for option
  • threshold-option-inside = i, for option
  • threshold-option-smaller = <, for option
  • threshold-option-greater = >, for option
tinkerforge call laser-range-finder-bricklet <uid> set-debounce-period <debounce>
Parameters:
  • <debounce> -- int
Output:

no output

Sets the period in ms with which the threshold callbacks

are triggered, if the thresholds

keep being reached.

The default value is 100.

tinkerforge call laser-range-finder-bricklet <uid> get-debounce-period
Output:
  • debounce -- int

Returns the debounce period as set by set-debounce-period.

Callbacks

Callbacks can be used to receive time critical or recurring data from the device:

tinkerforge dispatch laser-range-finder-bricklet <uid> example

The available callbacks 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.

tinkerforge dispatch laser-range-finder-bricklet <uid> distance
Output:
  • distance -- int

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 distance callback is only triggered if the distance value has changed since the last triggering.

tinkerforge dispatch laser-range-finder-bricklet <uid> velocity
Output:
  • velocity -- int

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 velocity callback is only triggered if the velocity has changed since the last triggering.

tinkerforge dispatch laser-range-finder-bricklet <uid> distance-reached
Output:
  • distance -- int

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.

tinkerforge dispatch laser-range-finder-bricklet <uid> velocity-reached
Output:
  • velocity -- int

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.