Visual Basic .NET - Laser Range Finder Bricklet

Note

This Bricklet is currently in the prototype stage and the software/hardware as well as the documentation is in an incomplete state.

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 Tinkerforge
Imports System.Threading

Module ExampleSimple
    Const HOST As String = "localhost"
    Const PORT As Integer = 4223
    Const UID As String = "XYZ" ' Change to your UID

    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 (unit is cm)
        Dim distance As Integer = lrf.GetDistance()

        System.Console.WriteLine("Distance: " + distance.ToString() + " cm")

        System.Console.WriteLine("Press key to exit")
        System.Console.ReadLine()
        ipcon.Disconnect()
    End Sub
End Module

Callback

Download (ExampleCallback.vb)

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Imports Tinkerforge
Imports System.Threading

Module ExampleCallback
    Const HOST As String = "localhost"
    Const PORT As Integer = 4223
    Const UID As String = "XYZ" ' Change to your UID

    ' Callback function for distance callback (parameter has unit cm)
    Sub DistanceCB(ByVal sender As BrickletLaserRangeFinder, ByVal distance As Integer)
        System.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)

        ' Set Period for distance callback to 1s (1000ms)
        ' Note: The distance callback is only called every second if the
        '       distance has changed since the last call!
        lrf.SetDistanceCallbackPeriod(1000)

        ' Register distance callback to function DistanceCB
        AddHandler lrf.Distance, AddressOf DistanceCB

        System.Console.WriteLine("Press key to exit")
        System.Console.ReadLine()
        ipcon.Disconnect()
    End Sub
End Module

Threshold

Download (ExampleThreshold.vb)

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Imports Tinkerforge
Imports System.Threading

Module ExampleThreshold
    Const HOST As String = "localhost"
    Const PORT As Integer = 4223
    Const UID As String = "XYZ" ' Change to your UID

    ' Callback for distance greater than 20 cm
    Sub ReachedCB(ByVal sender As BrickletLaserRangeFinder, ByVal distance As Integer)
        System.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 threshold reached callback to function ReachedCB
        AddHandler lrf.DistanceReached, AddressOf ReachedCB

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

        System.Console.WriteLine("Press key to exit")
        System.Console.ReadLine()
        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.

The Laser Range Finder Bricklet knows different modes. Distances are only measured in the distance measurement mode, see SetMode(). Also the laser has to be enabled, see EnableLaser().

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

Function BrickletLaserRangeFinder.GetVelocity() As Short

Returns the measured velocity. The value has a range of 0 to 12700 and is given in 1/100 m/s.

The Laser Range Finder Bricklet knows different modes. Velocity is only measured in the velocity measurement modes, see SetMode(). Also the laser has to be enabled, see EnableLaser().

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

Sub BrickletLaserRangeFinder.SetMode(ByVal mode As Byte)

The LIDAR 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.

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.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 and callbacks it is always disabled.

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
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 Distance callback is triggered periodically. A value of 0 turns the callback off.

Distance 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 Velocity callback is triggered periodically. A value of 0 turns the callback off.

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

AddHandler laserRangeFinder.Example, AddressOf Callback

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.Distance(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.

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

Event BrickletLaserRangeFinder.Velocity(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.

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

Event BrickletLaserRangeFinder.DistanceReached(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.VelocityReached(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.

Creative Commons Licence The content of this page is licensed under Creative Commons Attribution 3.0 Unported License.