Visual Basic .NET - Heart Rate 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 Heart Rate Bricklet. General information and technical specifications for the Heart Rate 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

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

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

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

        ' Get current colot (in RGBC)
        Dim hrate As Short
        hrate = hr.GetHeartRate()

        System.Console.WriteLine("Heart Rate(bpm): " + hrate.ToString())

        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

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

    ' Callback function for heart rate callback (in beats per minute)
    Sub HeartRateCB(ByVal sender As BrickletHeartRate, ByVal hrate As Integer)
        System.Console.WriteLine("Heart Rate(bpm): " + hrate.ToString())
        System.Console.WriteLine("")
    End Sub

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

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

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

        ' Register heart rate callback to function HeartRateCB
        AddHandler hr.HeartRate, AddressOf HeartRateCB

        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

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

    ' Callback for heart rate reached
    Sub ReachedCB(ByVal sender As BrickletHeartRate, ByVal hrate As Integer)
        
        System.Console.WriteLine("Heart Rate(bpm): " + hrate.ToString())
        System.Console.WriteLine("")
    End Sub

    Sub Main()
        Dim ipcon As New IPConnection() ' Create IP connection
        Dim hr As New BrickletHeartRate(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 10 seconds (10000ms)
        hr.SetDebouncePeriod(10000)

        ' Register threshold reached callback to function ReachedCB
        AddHandler hr.HeartRateReached, AddressOf ReachedCB

        ' Configure threshold for heart rate values,
        ' Heart Rate  : greater than 170 beats per minute
        hr.SetHeartRateCallbackThreshold(">"C, 50, 70)

        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 BrickletHeartRate(ByVal uid As String, ByVal ipcon As IPConnection)

Creates an object with the unique device ID uid:

Dim heartRate As New BrickletHeartRate("YOUR_DEVICE_UID", ipcon)

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

Function BrickletHeartRate.GetHeartRate() As Integer

Returns the current heart rate measured.

If you want to get the heart rate periodically, it is recommended to use the callback HeartRate and set the period with SetHeartRateCallbackPeriod().

Advanced Functions

Function BrickletHeartRate.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 BrickletHeartRate.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 BrickletHeartRate.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:

  • BrickletHeartRate.FUNCTION_SET_HEART_RATE_CALLBACK_PERIOD = 2
  • BrickletHeartRate.FUNCTION_SET_HEART_RATE_CALLBACK_THRESHOLD = 4
  • BrickletHeartRate.FUNCTION_SET_DEBOUNCE_PERIOD = 6
  • BrickletHeartRate.FUNCTION_ENABLE_BEAT_STATE_CHANGED_CALLBACK = 11
  • BrickletHeartRate.FUNCTION_DISABLE_BEAT_STATE_CHANGED_CALLBACK = 12
Sub BrickletHeartRate.SetResponseExpectedAll(ByVal responseExpected As Boolean)

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

Sub BrickletHeartRate.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 BrickletHeartRate.SetHeartRateCallbackPeriod(ByVal period As Long)

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

HeartRate is only triggered if the heart rate has changed since the last triggering.

The default value is 0.

Function BrickletHeartRate.GetHeartRateCallbackPeriod() As Long

Returns the period as set by SetHeartRateCallbackPeriod().

Sub BrickletHeartRate.SetHeartRateCallbackThreshold(ByVal option As Char, ByVal min As Integer, ByVal max As Integer)

Sets the thresholds for the HeartRateReached callback.

The following options are possible:

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

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

The following constants are available for this function:

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

Returns the threshold as set by SetHeartRateCallbackThreshold().

The following constants are available for this function:

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

Sets the period in ms with which the threshold callback

is triggered, if the threshold

keeps being reached.

The default value is 100.

Function BrickletHeartRate.GetDebouncePeriod() As Long

Returns the debounce period as set by SetDebouncePeriod().

Sub BrickletHeartRate.EnableBeatStateChangedCallback()

Enables the BeatStateChanged callback.

Sub BrickletHeartRate.DisableBeatStateChangedCallback()

Disables the BeatStateChanged callback.

Function BrickletHeartRate.IsBeatStateChangedCallbackEnabled() As Boolean

Returns true if the BeatStateChanged callback is enabled.

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

AddHandler heartRate.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 BrickletHeartRate.HeartRate(ByVal sender As BrickletHeartRate, ByVal heartRate As Integer)

This callback is triggered periodically with the period that is set by SetHeartRateCallbackPeriod(). The parameter is the heart rate of the sensor.

HeartRate is only triggered if the heart rate has changed since the last triggering.

Event BrickletHeartRate.HeartRateReached(ByVal sender As BrickletHeartRate, ByVal heartRate As Integer)

This callback is triggered when the threshold as set by SetHeartRateCallbackThreshold() is reached. The parameter is the heart rate of the sensor.

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

Event BrickletHeartRate.BeatStateChanged(ByVal sender As BrickletHeartRate, ByVal state As Byte)

This callback provides the current heart beat state.It is called every time a heart beat is detected. The state can either be

  • 0 = Falling: The falling edge of a detected heart beat.
  • 1 = Rising: The rising edge of a detected heart beat.

The following constants are available for this function:

  • BrickletHeartRate.BEAT_STATE_FALLING = 0
  • BrickletHeartRate.BEAT_STATE_RISING = 1

Constants

Const BrickletHeartRate.DEVICE_IDENTIFIER

This constant is used to identify a Heart Rate 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.

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