Visual Basic .NET - Load Cell Bricklet

This is the description of the Visual Basic .NET API bindings for the Load Cell Bricklet. General information and technical specifications for the Load Cell 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 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 Load Cell Bricklet

    Sub Main()
        Dim ipcon As New IPConnection() ' Create IP connection
        Dim lc As New BrickletLoadCell(UID, ipcon) ' Create device object

        ipcon.Connect(HOST, PORT) ' Connect to brickd
        ' Don't use device before ipcon is connected

        ' Get current weight
        Dim weight As Integer = lc.GetWeight()
        Console.WriteLine("Weight: " + weight.ToString() + " g")

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

Callback

Download (ExampleCallback.vb)

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Imports System
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 Load Cell Bricklet

    ' Callback subroutine for weight callback
    Sub WeightCB(ByVal sender As BrickletLoadCell, ByVal weight As Integer)
        Console.WriteLine("Weight: " + weight.ToString() + " g")
    End Sub

    Sub Main()
        Dim ipcon As New IPConnection() ' Create IP connection
        Dim lc As New BrickletLoadCell(UID, ipcon) ' Create device object

        ipcon.Connect(HOST, PORT) ' Connect to brickd
        ' Don't use device before ipcon is connected

        ' Register weight callback to subroutine WeightCB
        AddHandler lc.WeightCallback, AddressOf WeightCB

        ' Set period for weight callback to 1s (1000ms)
        ' Note: The weight callback is only called every second
        '       if the weight has changed since the last call!
        lc.SetWeightCallbackPeriod(1000)

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

Threshold

Download (ExampleThreshold.vb)

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Imports System
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 Load Cell Bricklet

    ' Callback subroutine for weight reached callback
    Sub WeightReachedCB(ByVal sender As BrickletLoadCell, ByVal weight As Integer)
        Console.WriteLine("Weight: " + weight.ToString() + " g")
    End Sub

    Sub Main()
        Dim ipcon As New IPConnection() ' Create IP connection
        Dim lc As New BrickletLoadCell(UID, ipcon) ' Create device object

        ipcon.Connect(HOST, PORT) ' Connect to brickd
        ' Don't use device before ipcon is connected

        ' Get threshold callbacks with a debounce time of 1 second (1000ms)
        lc.SetDebouncePeriod(1000)

        ' Register weight reached callback to subroutine WeightReachedCB
        AddHandler lc.WeightReachedCallback, AddressOf WeightReachedCB

        ' Configure threshold for weight "greater than 200 g"
        lc.SetWeightCallbackThreshold(">"C, 200, 0)

        Console.WriteLine("Press key to exit")
        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 BrickletLoadCell(ByVal uid As String, ByVal ipcon As IPConnection)

Creates an object with the unique device ID uid:

Dim loadCell As New BrickletLoadCell("YOUR_DEVICE_UID", ipcon)

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

Function BrickletLoadCell.GetWeight() As Integer
Returns:
  • weight – Type: Integer, Range: [-231 to 231 - 1]

Returns the currently measured weight in grams.

If you want to get the weight periodically, it is recommended to use the WeightCallback callback and set the period with SetWeightCallbackPeriod().

Sub BrickletLoadCell.LEDOn()

Turns the LED on.

Sub BrickletLoadCell.LEDOff()

Turns the LED off.

Function BrickletLoadCell.IsLEDOn() As Boolean
Returns:
  • on – Type: Boolean

Returns true if the led is on, false otherwise.

Sub BrickletLoadCell.Tare()

Sets the currently measured weight as tare weight.

Advanced Functions

Sub BrickletLoadCell.SetMovingAverage(ByVal average As Byte)
Parameters:
  • average – Type: Byte, Range: [0 to 255]

Sets the length of a moving averaging for the weight value.

Setting the length to 1 will turn the averaging off. With less averaging, there is more noise on the data.

The range for the averaging is 1-40.

The default value is 4.

Function BrickletLoadCell.GetMovingAverage() As Byte
Returns:
  • average – Type: Byte, Range: [0 to 255]

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

Sub BrickletLoadCell.Calibrate(ByVal weight As Long)
Parameters:
  • weight – Type: Long, Range: [0 to 232 - 1]

To calibrate your Load Cell Bricklet you have to

  • empty the scale and call this function with 0 and
  • add a known weight to the scale and call this function with the weight in grams.

The calibration is saved in the EEPROM of the Bricklet and only needs to be done once.

We recommend to use the Brick Viewer for calibration, you don't need to call this function in your source code.

Sub BrickletLoadCell.SetConfiguration(ByVal rate As Byte, ByVal gain As Byte)
Parameters:
  • rate – Type: Byte, Range: See constants
  • gain – Type: Byte, Range: See constants

The measurement rate and gain are configurable.

The rate can be either 10Hz or 80Hz. A faster rate will produce more noise. It is additionally possible to add a moving average (see SetMovingAverage()) to the measurements.

The gain can be 128x, 64x or 32x. It represents a measurement range of ±20mV, ±40mV and ±80mV respectively. The Load Cell Bricklet uses an excitation voltage of 5V and most load cells use an output of 2mV/V. That means the voltage range is ±15mV for most load cells (i.e. gain of 128x is best). If you don't know what all of this means you should keep it at 128x, it will most likely be correct.

The configuration is saved in the EEPROM of the Bricklet and only needs to be done once.

We recommend to use the Brick Viewer for configuration, you don't need to call this function in your source code.

The default rate is 10Hz and the default gain is 128x.

The following constants are available for this function:

For rate:

  • BrickletLoadCell.RATE_10HZ = 0
  • BrickletLoadCell.RATE_80HZ = 1

For gain:

  • BrickletLoadCell.GAIN_128X = 0
  • BrickletLoadCell.GAIN_64X = 1
  • BrickletLoadCell.GAIN_32X = 2
Sub BrickletLoadCell.GetConfiguration(ByRef rate As Byte, ByRef gain As Byte)
Output Parameters:
  • rate – Type: Byte, Range: See constants
  • gain – Type: Byte, Range: See constants

Returns the configuration as set by SetConfiguration().

The following constants are available for this function:

For rate:

  • BrickletLoadCell.RATE_10HZ = 0
  • BrickletLoadCell.RATE_80HZ = 1

For gain:

  • BrickletLoadCell.GAIN_128X = 0
  • BrickletLoadCell.GAIN_64X = 1
  • BrickletLoadCell.GAIN_32X = 2
Function BrickletLoadCell.GetAPIVersion() As Byte()
Returns:
  • apiVersion – Type: Byte Array, Length: 3, Range: [0 to 255]

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 BrickletLoadCell.GetResponseExpected(ByVal functionId As Byte) As Boolean
Parameters:
  • functionId – Type: Byte, Range: See constants
Returns:
  • responseExpected – Type: 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.

The following constants are available for this function:

For functionId:

  • BrickletLoadCell.FUNCTION_SET_WEIGHT_CALLBACK_PERIOD = 2
  • BrickletLoadCell.FUNCTION_SET_WEIGHT_CALLBACK_THRESHOLD = 4
  • BrickletLoadCell.FUNCTION_SET_DEBOUNCE_PERIOD = 6
  • BrickletLoadCell.FUNCTION_SET_MOVING_AVERAGE = 8
  • BrickletLoadCell.FUNCTION_LED_ON = 10
  • BrickletLoadCell.FUNCTION_LED_OFF = 11
  • BrickletLoadCell.FUNCTION_CALIBRATE = 13
  • BrickletLoadCell.FUNCTION_TARE = 14
  • BrickletLoadCell.FUNCTION_SET_CONFIGURATION = 15
Sub BrickletLoadCell.SetResponseExpected(ByVal functionId As Byte, ByVal responseExpected As Boolean)
Parameters:
  • functionId – Type: Byte, Range: See constants
  • responseExpected – Type: 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 constants are available for this function:

For functionId:

  • BrickletLoadCell.FUNCTION_SET_WEIGHT_CALLBACK_PERIOD = 2
  • BrickletLoadCell.FUNCTION_SET_WEIGHT_CALLBACK_THRESHOLD = 4
  • BrickletLoadCell.FUNCTION_SET_DEBOUNCE_PERIOD = 6
  • BrickletLoadCell.FUNCTION_SET_MOVING_AVERAGE = 8
  • BrickletLoadCell.FUNCTION_LED_ON = 10
  • BrickletLoadCell.FUNCTION_LED_OFF = 11
  • BrickletLoadCell.FUNCTION_CALIBRATE = 13
  • BrickletLoadCell.FUNCTION_TARE = 14
  • BrickletLoadCell.FUNCTION_SET_CONFIGURATION = 15
Sub BrickletLoadCell.SetResponseExpectedAll(ByVal responseExpected As Boolean)
Parameters:
  • responseExpected – Type: Boolean

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

Sub BrickletLoadCell.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)
Output Parameters:
  • uid – Type: String, Length: up to 8
  • connectedUid – Type: String, Length: up to 8
  • position – Type: Char
  • hardwareVersion – Type: Byte Array, Length: 3, Range: [0 to 255]
  • firmwareVersion – Type: Byte Array, Length: 3, Range: [0 to 255]
  • deviceIdentifier – Type: Integer, Range: [0 to 216 - 1]

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 BrickletLoadCell.SetWeightCallbackPeriod(ByVal period As Long)
Parameters:
  • period – Type: Long, Unit: 1 ms, Range: [0 to 232 - 1], Default: 0

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

The WeightCallback callback is only triggered if the weight has changed since the last triggering.

Function BrickletLoadCell.GetWeightCallbackPeriod() As Long
Returns:
  • period – Type: Long, Unit: 1 ms, Range: [0 to 232 - 1], Default: 0

Returns the period as set by SetWeightCallbackPeriod().

Sub BrickletLoadCell.SetWeightCallbackThreshold(ByVal option As Char, ByVal min As Integer, ByVal max As Integer)
Parameters:
  • option – Type: Char, Range: See constants, Default: "x"C
  • min – Type: Integer, Range: [-231 to 231 - 1]
  • max – Type: Integer, Range: [-231 to 231 - 1]

Sets the thresholds for the WeightReachedCallback callback.

The following options are possible:

Option Description
'x' Callback is turned off
'o' Callback is triggered when the weight is outside the min and max values
'i' Callback is triggered when the weight is inside the min and max values
'<' Callback is triggered when the weight is smaller than the min value (max is ignored)
'>' Callback is triggered when the weight is greater than the min value (max is ignored)

The default value is ('x', 0, 0).

The following constants are available for this function:

For option:

  • BrickletLoadCell.THRESHOLD_OPTION_OFF = "x"C
  • BrickletLoadCell.THRESHOLD_OPTION_OUTSIDE = "o"C
  • BrickletLoadCell.THRESHOLD_OPTION_INSIDE = "i"C
  • BrickletLoadCell.THRESHOLD_OPTION_SMALLER = "<"C
  • BrickletLoadCell.THRESHOLD_OPTION_GREATER = ">"C
Sub BrickletLoadCell.GetWeightCallbackThreshold(ByRef option As Char, ByRef min As Integer, ByRef max As Integer)
Output Parameters:
  • option – Type: Char, Range: See constants, Default: "x"C
  • min – Type: Integer, Range: [-231 to 231 - 1]
  • max – Type: Integer, Range: [-231 to 231 - 1]

Returns the threshold as set by SetWeightCallbackThreshold().

The following constants are available for this function:

For option:

  • BrickletLoadCell.THRESHOLD_OPTION_OFF = "x"C
  • BrickletLoadCell.THRESHOLD_OPTION_OUTSIDE = "o"C
  • BrickletLoadCell.THRESHOLD_OPTION_INSIDE = "i"C
  • BrickletLoadCell.THRESHOLD_OPTION_SMALLER = "<"C
  • BrickletLoadCell.THRESHOLD_OPTION_GREATER = ">"C
Sub BrickletLoadCell.SetDebouncePeriod(ByVal debounce As Long)
Parameters:
  • debounce – Type: Long, Unit: 1 ms, Range: [0 to 232 - 1], Default: 100

Sets the period with which the threshold callback

is triggered, if the threshold

keeps being reached.

Function BrickletLoadCell.GetDebouncePeriod() As Long
Returns:
  • debounce – Type: Long, Unit: 1 ms, Range: [0 to 232 - 1], Default: 100

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

AddHandler loadCell.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 BrickletLoadCell.WeightCallback(ByVal sender As BrickletLoadCell, ByVal weight As Integer)
Callback Parameters:
  • sender – Type: BrickletLoadCell
  • weight – Type: Integer, Range: [-231 to 231 - 1]

This callback is triggered periodically with the period that is set by SetWeightCallbackPeriod(). The parameter is the weight as measured by the load cell.

The WeightCallback callback is only triggered if the weight has changed since the last triggering.

Event BrickletLoadCell.WeightReachedCallback(ByVal sender As BrickletLoadCell, ByVal weight As Integer)
Callback Parameters:
  • sender – Type: BrickletLoadCell
  • weight – Type: Integer, Range: [-231 to 231 - 1]

This callback is triggered when the threshold as set by SetWeightCallbackThreshold() is reached. The parameter is the weight as measured by the load cell.

If the threshold keeps being reached, the callback is triggered periodically with the period as set by SetDebouncePeriod().

Constants

Const BrickletLoadCell.DEVICE_IDENTIFIER

This constant is used to identify a Load Cell Bricklet.

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

Const BrickletLoadCell.DEVICE_DISPLAY_NAME

This constant represents the human readable name of a Load Cell Bricklet.