Visual Basic .NET - Laser Range Finder Bricklet

This is the description of the Visual Basic .NET 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 Visual Basic .NET API bindings is part of their general description.

Examples

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

Simple

Download (ExampleSimple.vb)

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Imports System
Imports System.Threading
Imports Tinkerforge

Module ExampleSimple
    Const HOST As String = "localhost"
    Const PORT As Integer = 4223
    Const UID As String = "XYZ" ' Change XYZ to the UID of your Laser Range Finder Bricklet

    Sub Main()
        Dim ipcon As New IPConnection() ' Create IP connection
        Dim lrf As New 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.EnableLaser()
        Thread.Sleep(250)

        ' Get current distance
        Dim distance As Integer = lrf.GetDistance()
        Console.WriteLine("Distance: " + distance.ToString() + " cm")

        Console.WriteLine("Press key to exit")
        Console.ReadLine()
        lrf.DisableLaser() ' Turn laser off
        ipcon.Disconnect()
    End Sub
End Module

Callback

Download (ExampleCallback.vb)

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Imports System
Imports System.Threading
Imports Tinkerforge

Module ExampleCallback
    Const HOST As String = "localhost"
    Const PORT As Integer = 4223
    Const UID As String = "XYZ" ' Change XYZ to the UID of your Laser Range Finder Bricklet

    ' Callback subroutine for distance callback
    Sub DistanceCB(ByVal sender As BrickletLaserRangeFinder, ByVal distance As Integer)
        Console.WriteLine("Distance: " + distance.ToString() + " cm")
    End Sub

    Sub Main()
        Dim ipcon As New IPConnection() ' Create IP connection
        Dim lrf As New 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.EnableLaser()
        Thread.Sleep(250)

        ' Register distance callback to subroutine DistanceCB
        AddHandler lrf.DistanceCallback, AddressOf DistanceCB

        ' 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.SetDistanceCallbackPeriod(200)

        Console.WriteLine("Press key to exit")
        Console.ReadLine()
        lrf.DisableLaser() ' Turn laser off
        ipcon.Disconnect()
    End Sub
End Module

Threshold

Download (ExampleThreshold.vb)

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Imports System
Imports System.Threading
Imports Tinkerforge

Module ExampleThreshold
    Const HOST As String = "localhost"
    Const PORT As Integer = 4223
    Const UID As String = "XYZ" ' Change XYZ to the UID of your Laser Range Finder Bricklet

    ' Callback subroutine for distance reached callback
    Sub DistanceReachedCB(ByVal sender As BrickletLaserRangeFinder, _
                          ByVal distance As Integer)
        Console.WriteLine("Distance: " + distance.ToString() + " cm")
    End Sub

    Sub Main()
        Dim ipcon As New IPConnection() ' Create IP connection
        Dim lrf As New 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.EnableLaser()
        Thread.Sleep(250)

        ' Get threshold callbacks with a debounce time of 10 seconds (10000ms)
        lrf.SetDebouncePeriod(10000)

        ' Register distance reached callback to subroutine DistanceReachedCB
        AddHandler lrf.DistanceReachedCallback, AddressOf DistanceReachedCB

        ' Configure threshold for distance "greater than 20 cm"
        lrf.SetDistanceCallbackThreshold(">"C, 20, 0)

        Console.WriteLine("Press key to exit")
        Console.ReadLine()
        lrf.DisableLaser() ' Turn laser off
        ipcon.Disconnect()
    End Sub
End Module

API

Since Visual Basic .NET does not support multiple return values directly, we use the ByRef keyword to return multiple values from a function.

All functions and procedures listed below are thread-safe.

Basic Functions

Class BrickletLaserRangeFinder(ByVal uid As String, ByVal ipcon As IPConnection)

Creates an object with the unique device ID uid:

Dim laserRangeFinder As New BrickletLaserRangeFinder("YOUR_DEVICE_UID", ipcon)

This object can then be used after the IP Connection is connected (see examples above).

Function BrickletLaserRangeFinder.GetDistance() As Integer

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

Sensor hardware version 1 (see GetSensorHardwareVersion()) cannot measure distance and velocity at the same time. Therefore, the distance mode has to be enabled using SetMode(). Sensor hardware version 3 can measure distance and velocity at the same time. Also the laser has to be enabled, see EnableLaser().

If you want to get the distance periodically, it is recommended to use the DistanceCallback callback and set the period with SetDistanceCallbackPeriod().

Function BrickletLaserRangeFinder.GetVelocity() As Short

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 GetSensorHardwareVersion()) cannot measure distance and velocity at the same time. Therefore, the velocity mode has to be enabled using SetMode(). 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 SetConfiguration()) is configured. Also the laser has to be enabled, see EnableLaser().

If you want to get the velocity periodically, it is recommended to use the VelocityCallback callback and set the period with SetVelocityCallbackPeriod().

Sub BrickletLaserRangeFinder.SetMode(ByVal mode As Byte)

Note

This function is only available if you have a LIDAR-Lite sensor with hardware version 1. Use SetConfiguration() for hardware version 3. You can check the sensor hardware version using GetSensorHardwareVersion().

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 constants are available for this function:

  • BrickletLaserRangeFinder.MODE_DISTANCE = 0
  • BrickletLaserRangeFinder.MODE_VELOCITY_MAX_13MS = 1
  • BrickletLaserRangeFinder.MODE_VELOCITY_MAX_32MS = 2
  • BrickletLaserRangeFinder.MODE_VELOCITY_MAX_64MS = 3
  • BrickletLaserRangeFinder.MODE_VELOCITY_MAX_127MS = 4
Function BrickletLaserRangeFinder.GetMode() As Byte

Returns the mode as set by SetMode().

The following constants are available for this function:

  • BrickletLaserRangeFinder.MODE_DISTANCE = 0
  • BrickletLaserRangeFinder.MODE_VELOCITY_MAX_13MS = 1
  • BrickletLaserRangeFinder.MODE_VELOCITY_MAX_32MS = 2
  • BrickletLaserRangeFinder.MODE_VELOCITY_MAX_64MS = 3
  • BrickletLaserRangeFinder.MODE_VELOCITY_MAX_127MS = 4
Sub BrickletLaserRangeFinder.EnableLaser()

Activates the laser of the LIDAR.

We recommend that you wait 250ms after enabling the laser before the first call of GetDistance() to ensure stable measurements.

Sub BrickletLaserRangeFinder.DisableLaser()

Deactivates the laser of the LIDAR.

Function BrickletLaserRangeFinder.IsLaserEnabled() As Boolean

Returns true if the laser is enabled, false otherwise.

Sub BrickletLaserRangeFinder.SetConfiguration(ByVal acquisitionCount As Byte, ByVal enableQuickTermination As Boolean, ByVal thresholdValue As Byte, ByVal measurementFrequency As Integer)

Note

This function is only available if you have a LIDAR-Lite sensor with hardware version 3. Use SetMode() for hardware version 1. You can check the sensor hardware version using GetSensorHardwareVersion().

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).

Sub BrickletLaserRangeFinder.GetConfiguration(ByRef acquisitionCount As Byte, ByRef enableQuickTermination As Boolean, ByRef thresholdValue As Byte, ByRef measurementFrequency As Integer)

Returns the configuration as set by SetConfiguration().

New in version 2.0.3 (Plugin).

Advanced Functions

Sub BrickletLaserRangeFinder.SetMovingAverage(ByVal distanceAverageLength As Byte, ByVal velocityAverageLength As Byte)

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.

Sub BrickletLaserRangeFinder.GetMovingAverage(ByRef distanceAverageLength As Byte, ByRef velocityAverageLength As Byte)

Returns the length moving average as set by SetMovingAverage().

Function BrickletLaserRangeFinder.GetSensorHardwareVersion() As Byte

Returns the LIDAR-Lite hardware version.

The following constants are available for this function:

  • BrickletLaserRangeFinder.VERSION_1 = 1
  • BrickletLaserRangeFinder.VERSION_3 = 3

New in version 2.0.3 (Plugin).

Function BrickletLaserRangeFinder.GetAPIVersion() As Byte()

Returns the version of the API definition (major, minor, revision) 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.

Function BrickletLaserRangeFinder.GetResponseExpected(ByVal functionId As Byte) As Boolean

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 SetResponseExpected(). 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 send and errors are silently ignored, because they cannot be detected.

See SetResponseExpected() for the list of function ID constants available for this function.

Sub BrickletLaserRangeFinder.SetResponseExpected(ByVal functionId As Byte, ByVal responseExpected As Boolean)

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 send and errors are silently ignored, because they cannot be detected.

The following function ID constants are available for this function:

  • BrickletLaserRangeFinder.FUNCTION_SET_DISTANCE_CALLBACK_PERIOD = 3
  • BrickletLaserRangeFinder.FUNCTION_SET_VELOCITY_CALLBACK_PERIOD = 5
  • BrickletLaserRangeFinder.FUNCTION_SET_DISTANCE_CALLBACK_THRESHOLD = 7
  • BrickletLaserRangeFinder.FUNCTION_SET_VELOCITY_CALLBACK_THRESHOLD = 9
  • BrickletLaserRangeFinder.FUNCTION_SET_DEBOUNCE_PERIOD = 11
  • BrickletLaserRangeFinder.FUNCTION_SET_MOVING_AVERAGE = 13
  • BrickletLaserRangeFinder.FUNCTION_SET_MODE = 15
  • BrickletLaserRangeFinder.FUNCTION_ENABLE_LASER = 17
  • BrickletLaserRangeFinder.FUNCTION_DISABLE_LASER = 18
  • BrickletLaserRangeFinder.FUNCTION_SET_CONFIGURATION = 25
Sub BrickletLaserRangeFinder.SetResponseExpectedAll(ByVal responseExpected As Boolean)

Changes the response expected flag for all setter and callback configuration functions of this device at once.

Sub BrickletLaserRangeFinder.GetIdentity(ByRef uid As String, ByRef connectedUid As String, ByRef position As Char, ByRef hardwareVersion() As Byte, ByRef firmwareVersion() As Byte, ByRef deviceIdentifier As Integer)

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. There is also a constant for the device identifier of this Bricklet.

Callback Configuration Functions

Sub BrickletLaserRangeFinder.SetDistanceCallbackPeriod(ByVal period As Long)

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

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

The default value is 0.

Function BrickletLaserRangeFinder.GetDistanceCallbackPeriod() As Long

Returns the period as set by SetDistanceCallbackPeriod().

Sub BrickletLaserRangeFinder.SetVelocityCallbackPeriod(ByVal period As Long)

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

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

The default value is 0.

Function BrickletLaserRangeFinder.GetVelocityCallbackPeriod() As Long

Returns the period as set by SetVelocityCallbackPeriod().

Sub BrickletLaserRangeFinder.SetDistanceCallbackThreshold(ByVal option As Char, ByVal min As Integer, ByVal max As Integer)

Sets the thresholds for the DistanceReachedCallback 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 constants are available for this function:

  • BrickletLaserRangeFinder.THRESHOLD_OPTION_OFF = "x"C
  • BrickletLaserRangeFinder.THRESHOLD_OPTION_OUTSIDE = "o"C
  • BrickletLaserRangeFinder.THRESHOLD_OPTION_INSIDE = "i"C
  • BrickletLaserRangeFinder.THRESHOLD_OPTION_SMALLER = "<"C
  • BrickletLaserRangeFinder.THRESHOLD_OPTION_GREATER = ">"C
Sub BrickletLaserRangeFinder.GetDistanceCallbackThreshold(ByRef option As Char, ByRef min As Integer, ByRef max As Integer)

Returns the threshold as set by SetDistanceCallbackThreshold().

The following constants are available for this function:

  • BrickletLaserRangeFinder.THRESHOLD_OPTION_OFF = "x"C
  • BrickletLaserRangeFinder.THRESHOLD_OPTION_OUTSIDE = "o"C
  • BrickletLaserRangeFinder.THRESHOLD_OPTION_INSIDE = "i"C
  • BrickletLaserRangeFinder.THRESHOLD_OPTION_SMALLER = "<"C
  • BrickletLaserRangeFinder.THRESHOLD_OPTION_GREATER = ">"C
Sub BrickletLaserRangeFinder.SetVelocityCallbackThreshold(ByVal option As Char, ByVal min As Short, ByVal max As Short)

Sets the thresholds for the VelocityReachedCallback 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 constants are available for this function:

  • BrickletLaserRangeFinder.THRESHOLD_OPTION_OFF = "x"C
  • BrickletLaserRangeFinder.THRESHOLD_OPTION_OUTSIDE = "o"C
  • BrickletLaserRangeFinder.THRESHOLD_OPTION_INSIDE = "i"C
  • BrickletLaserRangeFinder.THRESHOLD_OPTION_SMALLER = "<"C
  • BrickletLaserRangeFinder.THRESHOLD_OPTION_GREATER = ">"C
Sub BrickletLaserRangeFinder.GetVelocityCallbackThreshold(ByRef option As Char, ByRef min As Short, ByRef max As Short)

Returns the threshold as set by SetVelocityCallbackThreshold().

The following constants are available for this function:

  • BrickletLaserRangeFinder.THRESHOLD_OPTION_OFF = "x"C
  • BrickletLaserRangeFinder.THRESHOLD_OPTION_OUTSIDE = "o"C
  • BrickletLaserRangeFinder.THRESHOLD_OPTION_INSIDE = "i"C
  • BrickletLaserRangeFinder.THRESHOLD_OPTION_SMALLER = "<"C
  • BrickletLaserRangeFinder.THRESHOLD_OPTION_GREATER = ">"C
Sub BrickletLaserRangeFinder.SetDebouncePeriod(ByVal debounce As Long)

Sets the period in ms with which the threshold callbacks

are triggered, if the thresholds

keep being reached.

The default value is 100.

Function BrickletLaserRangeFinder.GetDebouncePeriod() As Long

Returns the debounce period as set by SetDebouncePeriod().

Callbacks

Callbacks can be registered to receive time critical or recurring data from the device. The registration is done by assigning a procedure to an callback property of the device object:

Sub MyCallback(ByVal sender As BrickletLaserRangeFinder, ByVal value As Short)
    Console.WriteLine("Value: {0}", value)
End Sub

AddHandler laserRangeFinder.ExampleCallback, AddressOf MyCallback

The available callback property and their 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.

Event BrickletLaserRangeFinder.DistanceCallback(ByVal sender As BrickletLaserRangeFinder, ByVal distance As Integer)

This callback is triggered periodically with the period that is set by SetDistanceCallbackPeriod(). The parameter is the distance value of the sensor.

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

Event BrickletLaserRangeFinder.VelocityCallback(ByVal sender As BrickletLaserRangeFinder, ByVal velocity As Short)

This callback is triggered periodically with the period that is set by SetVelocityCallbackPeriod(). The parameter is the velocity value of the sensor.

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

Event BrickletLaserRangeFinder.DistanceReachedCallback(ByVal sender As BrickletLaserRangeFinder, ByVal distance As Integer)

This callback is triggered when the threshold as set by SetDistanceCallbackThreshold() 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 SetDebouncePeriod().

Event BrickletLaserRangeFinder.VelocityReachedCallback(ByVal sender As BrickletLaserRangeFinder, ByVal velocity As Short)

This callback is triggered when the threshold as set by SetVelocityCallbackThreshold() 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 SetDebouncePeriod().

Constants

Const BrickletLaserRangeFinder.DEVICE_IDENTIFIER

This constant is used to identify a Laser Range Finder Bricklet.

The GetIdentity() function and the EnumerateCallback callback of the IP Connection have a deviceIdentifier parameter to specify the Brick's or Bricklet's type.

Const BrickletLaserRangeFinder.DEVICE_DISPLAY_NAME

This constant represents the human readable name of a Laser Range Finder Bricklet.