Visual Basic .NET - Servo Brick

This is the description of the Visual Basic .NET API bindings for the Servo Brick. General information and technical specifications for the Servo Brick 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).

Configuration

Download (ExampleConfiguration.vb)

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Imports System
Imports Tinkerforge

Module ExampleConfiguration
    Const HOST As String = "localhost"
    Const PORT As Integer = 4223
    Const UID As String = "XXYYZZ" ' Change XXYYZZ to the UID of your Servo Brick

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

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

        ' Configure two servos with voltage 5.5V
        ' Servo 1: Connected to port 0, period of 19.5ms, pulse width of 1 to 2ms
        '          and operating angle -100 to 100°
        '
        ' Servo 2: Connected to port 5, period of 20ms, pulse width of 0.95
        '          to 1.95ms and operating angle -90 to 90°
        servo.SetOutputVoltage(5500)

        servo.SetDegree(0, -10000, 10000)
        servo.SetPulseWidth(0, 1000, 2000)
        servo.SetPeriod(0, 19500)
        servo.SetAcceleration(0, 1000) ' Slow acceleration
        servo.SetVelocity(0, 65535) ' Full speed

        servo.SetDegree(5, -9000, 9000)
        servo.SetPulseWidth(5, 950, 1950)
        servo.SetPeriod(5, 20000)
        servo.SetAcceleration(5, 65535) ' Full acceleration
        servo.SetVelocity(5, 65535) ' Full speed

        servo.SetPosition(0, 10000) ' Set to most right position
        servo.Enable(0)

        servo.SetPosition(5, -9000) ' Set to most left position
        servo.Enable(5)

        Console.WriteLine("Press key to exit")
        Console.ReadLine()
        servo.Disable(0)
        servo.Disable(5)
        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 = "XXYYZZ" ' Change XXYYZZ to the UID of your Servo Brick

    ' Use position reached callback to swing back and forth
    Sub PositionReachedCB(ByVal sender As BrickServo, ByVal servoNum As Byte, _
                          ByVal position As Short)
        If position = 9000 Then
            Console.WriteLine("Position: 90°, going to -90°")
            sender.SetPosition(servoNum, -9000)
        Else If position = -9000 Then
            Console.WriteLine("Position: -90°, going to 90°")
            sender.SetPosition(servoNum, 9000)
        Else
            ' Can only happen if another program sets position
            Console.WriteLine("Error")
        End If
    End Sub

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

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

        ' Register position reached callback to subroutine PositionReachedCB
        AddHandler servo.PositionReachedCallback, AddressOf PositionReachedCB

        ' Enable position reached callback
        servo.EnablePositionReachedCallback()

        ' Set velocity to 100°/s. This has to be smaller or equal to the
        ' maximum velocity of the servo you are using, otherwise the position
        ' reached callback will be called too early
        servo.SetVelocity(0, 10000)
        servo.SetPosition(0, 9000)
        servo.Enable(0)

        Console.WriteLine("Press key to exit")
        Console.ReadLine()
        servo.Disable(0)
        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.

Every function of the Servo Brick API that has a servo_num parameter can address a servo with the servo number (0 to 6). If it is a setter function then multiple servos can be addressed at once with a bitmask for the servos, if the highest bit is set. For example: 1 will address servo 1, (1 << 1) | (1 << 5) | (1 << 7) will address servos 1 and 5, 0xFF will address all seven servos, etc. This allows to set configurations to several servos with one function call. It is guaranteed that the changes will take effect in the same PWM period for all servos you specified in the bitmask.

Basic Functions

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

Creates an object with the unique device ID uid:

Dim servo As New BrickServo("YOUR_DEVICE_UID", ipcon)

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

Sub BrickServo.Enable(ByVal servoNum As Byte)

Enables a servo (0 to 6). If a servo is enabled, the configured position, velocity, acceleration, etc. are applied immediately.

Sub BrickServo.Disable(ByVal servoNum As Byte)

Disables a servo (0 to 6). Disabled servos are not driven at all, i.e. a disabled servo will not hold its position if a load is applied.

Function BrickServo.IsEnabled(ByVal servoNum As Byte) As Boolean

Returns true if the specified servo is enabled, false otherwise.

Sub BrickServo.SetPosition(ByVal servoNum As Byte, ByVal position As Short)

Sets the position in °/100 for the specified servo.

The default range of the position is -9000 to 9000, but it can be specified according to your servo with SetDegree().

If you want to control a linear servo or RC brushless motor controller or similar with the Servo Brick, you can also define lengths or speeds with SetDegree().

Function BrickServo.GetPosition(ByVal servoNum As Byte) As Short

Returns the position of the specified servo as set by SetPosition().

Function BrickServo.GetCurrentPosition(ByVal servoNum As Byte) As Short

Returns the current position of the specified servo. This may not be the value of SetPosition() if the servo is currently approaching a position goal.

Sub BrickServo.SetVelocity(ByVal servoNum As Byte, ByVal velocity As Integer)

Sets the maximum velocity of the specified servo in °/100s. The velocity is accelerated according to the value set by SetAcceleration().

The minimum velocity is 0 (no movement) and the maximum velocity is 65535. With a value of 65535 the position will be set immediately (no velocity).

The default value is 65535.

Function BrickServo.GetVelocity(ByVal servoNum As Byte) As Integer

Returns the velocity of the specified servo as set by SetVelocity().

Function BrickServo.GetCurrentVelocity(ByVal servoNum As Byte) As Integer

Returns the current velocity of the specified servo. This may not be the value of SetVelocity() if the servo is currently approaching a velocity goal.

Sub BrickServo.SetAcceleration(ByVal servoNum As Byte, ByVal acceleration As Integer)

Sets the acceleration of the specified servo in °/100s².

The minimum acceleration is 1 and the maximum acceleration is 65535. With a value of 65535 the velocity will be set immediately (no acceleration).

The default value is 65535.

Function BrickServo.GetAcceleration(ByVal servoNum As Byte) As Integer

Returns the acceleration for the specified servo as set by SetAcceleration().

Sub BrickServo.SetOutputVoltage(ByVal voltage As Integer)

Sets the output voltages with which the servos are driven in mV. The minimum output voltage is 2000mV and the maximum output voltage is 9000mV.

Note

We recommend that you set this value to the maximum voltage that is specified for your servo, most servos achieve their maximum force only with high voltages.

The default value is 5000.

Function BrickServo.GetOutputVoltage() As Integer

Returns the output voltage as specified by SetOutputVoltage().

Sub BrickServo.SetPulseWidth(ByVal servoNum As Byte, ByVal min As Integer, ByVal max As Integer)

Sets the minimum and maximum pulse width of the specified servo in µs.

Usually, servos are controlled with a PWM, whereby the length of the pulse controls the position of the servo. Every servo has different minimum and maximum pulse widths, these can be specified with this function.

If you have a datasheet for your servo that specifies the minimum and maximum pulse width, you should set the values accordingly. If your servo comes without any datasheet you have to find the values via trial and error.

Both values have a range from 1 to 65535 (unsigned 16-bit integer). The minimum must be smaller than the maximum.

The default values are 1000µs (1ms) and 2000µs (2ms) for minimum and maximum pulse width.

Sub BrickServo.GetPulseWidth(ByVal servoNum As Byte, ByRef min As Integer, ByRef max As Integer)

Returns the minimum and maximum pulse width for the specified servo as set by SetPulseWidth().

Sub BrickServo.SetDegree(ByVal servoNum As Byte, ByVal min As Short, ByVal max As Short)

Sets the minimum and maximum degree for the specified servo (by default given as °/100).

This only specifies the abstract values between which the minimum and maximum pulse width is scaled. For example: If you specify a pulse width of 1000µs to 2000µs and a degree range of -90° to 90°, a call of SetPosition() with 0 will result in a pulse width of 1500µs (-90° = 1000µs, 90° = 2000µs, etc.).

Possible usage:

  • The datasheet of your servo specifies a range of 200° with the middle position at 110°. In this case you can set the minimum to -9000 and the maximum to 11000.
  • You measure a range of 220° on your servo and you don't have or need a middle position. In this case you can set the minimum to 0 and the maximum to 22000.
  • You have a linear servo with a drive length of 20cm, In this case you could set the minimum to 0 and the maximum to 20000. Now you can set the Position with SetPosition() with a resolution of cm/100. Also the velocity will have a resolution of cm/100s and the acceleration will have a resolution of cm/100s².
  • You don't care about units and just want the highest possible resolution. In this case you should set the minimum to -32767 and the maximum to 32767.
  • You have a brushless motor with a maximum speed of 10000 rpm and want to control it with a RC brushless motor controller. In this case you can set the minimum to 0 and the maximum to 10000. SetPosition() now controls the rpm.

Both values have a possible range from -32767 to 32767 (signed 16-bit integer). The minimum must be smaller than the maximum.

The default values are -9000 and 9000 for the minimum and maximum degree.

Sub BrickServo.GetDegree(ByVal servoNum As Byte, ByRef min As Short, ByRef max As Short)

Returns the minimum and maximum degree for the specified servo as set by SetDegree().

Sub BrickServo.SetPeriod(ByVal servoNum As Byte, ByVal period As Integer)

Sets the period of the specified servo in µs.

Usually, servos are controlled with a PWM. Different servos expect PWMs with different periods. Most servos run well with a period of about 20ms.

If your servo comes with a datasheet that specifies a period, you should set it accordingly. If you don't have a datasheet and you have no idea what the correct period is, the default value (19.5ms) will most likely work fine.

The minimum possible period is 1µs and the maximum is 65535µs.

The default value is 19.5ms (19500µs).

Function BrickServo.GetPeriod(ByVal servoNum As Byte) As Integer

Returns the period for the specified servo as set by SetPeriod().

Function BrickServo.GetServoCurrent(ByVal servoNum As Byte) As Integer

Returns the current consumption of the specified servo in mA.

Function BrickServo.GetOverallCurrent() As Integer

Returns the current consumption of all servos together in mA.

Function BrickServo.GetStackInputVoltage() As Integer

Returns the stack input voltage in mV. The stack input voltage is the voltage that is supplied via the stack, i.e. it is given by a Step-Down or Step-Up Power Supply.

Function BrickServo.GetExternalInputVoltage() As Integer

Returns the external input voltage in mV. The external input voltage is given via the black power input connector on the Servo Brick.

If there is an external input voltage and a stack input voltage, the motors will be driven by the external input voltage. If there is only a stack voltage present, the motors will be driven by this voltage.

Warning

This means, if you have a high stack voltage and a low external voltage, the motors will be driven with the low external voltage. If you then remove the external connection, it will immediately be driven by the high stack voltage

Advanced Functions

Function BrickServo.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 BrickServo.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 BrickServo.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:

  • BrickServo.FUNCTION_ENABLE = 1
  • BrickServo.FUNCTION_DISABLE = 2
  • BrickServo.FUNCTION_SET_POSITION = 4
  • BrickServo.FUNCTION_SET_VELOCITY = 7
  • BrickServo.FUNCTION_SET_ACCELERATION = 10
  • BrickServo.FUNCTION_SET_OUTPUT_VOLTAGE = 12
  • BrickServo.FUNCTION_SET_PULSE_WIDTH = 14
  • BrickServo.FUNCTION_SET_DEGREE = 16
  • BrickServo.FUNCTION_SET_PERIOD = 18
  • BrickServo.FUNCTION_SET_MINIMUM_VOLTAGE = 24
  • BrickServo.FUNCTION_ENABLE_POSITION_REACHED_CALLBACK = 29
  • BrickServo.FUNCTION_DISABLE_POSITION_REACHED_CALLBACK = 30
  • BrickServo.FUNCTION_ENABLE_VELOCITY_REACHED_CALLBACK = 32
  • BrickServo.FUNCTION_DISABLE_VELOCITY_REACHED_CALLBACK = 33
  • BrickServo.FUNCTION_SET_SPITFP_BAUDRATE_CONFIG = 231
  • BrickServo.FUNCTION_SET_SPITFP_BAUDRATE = 234
  • BrickServo.FUNCTION_ENABLE_STATUS_LED = 238
  • BrickServo.FUNCTION_DISABLE_STATUS_LED = 239
  • BrickServo.FUNCTION_RESET = 243
Sub BrickServo.SetResponseExpectedAll(ByVal responseExpected As Boolean)

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

Sub BrickServo.SetSPITFPBaudrateConfig(ByVal enableDynamicBaudrate As Boolean, ByVal minimumDynamicBaudrate As Long)

The SPITF protocol can be used with a dynamic baudrate. If the dynamic baudrate is enabled, the Brick will try to adapt the baudrate for the communication between Bricks and Bricklets according to the amount of data that is transferred.

The baudrate will be increased exponentially if lots of data is send/received and decreased linearly if little data is send/received.

This lowers the baudrate in applications where little data is transferred (e.g. a weather station) and increases the robustness. If there is lots of data to transfer (e.g. Thermal Imaging Bricklet) it automatically increases the baudrate as needed.

In cases where some data has to transferred as fast as possible every few seconds (e.g. RS485 Bricklet with a high baudrate but small payload) you may want to turn the dynamic baudrate off to get the highest possible performance.

The maximum value of the baudrate can be set per port with the function SetSPITFPBaudrate(). If the dynamic baudrate is disabled, the baudrate as set by SetSPITFPBaudrate() will be used statically.

The minimum dynamic baudrate has a value range of 400000 to 2000000 baud.

By default dynamic baudrate is enabled and the minimum dynamic baudrate is 400000.

New in version 2.3.4 (Firmware).

Sub BrickServo.GetSPITFPBaudrateConfig(ByRef enableDynamicBaudrate As Boolean, ByRef minimumDynamicBaudrate As Long)

Returns the baudrate config, see SetSPITFPBaudrateConfig().

New in version 2.3.4 (Firmware).

Function BrickServo.GetSendTimeoutCount(ByVal communicationMethod As Byte) As Long

Returns the timeout count for the different communication methods.

The methods 0-2 are available for all Bricks, 3-7 only for Master Bricks.

This function is mostly used for debugging during development, in normal operation the counters should nearly always stay at 0.

The following constants are available for this function:

  • BrickServo.COMMUNICATION_METHOD_NONE = 0
  • BrickServo.COMMUNICATION_METHOD_USB = 1
  • BrickServo.COMMUNICATION_METHOD_SPI_STACK = 2
  • BrickServo.COMMUNICATION_METHOD_CHIBI = 3
  • BrickServo.COMMUNICATION_METHOD_RS485 = 4
  • BrickServo.COMMUNICATION_METHOD_WIFI = 5
  • BrickServo.COMMUNICATION_METHOD_ETHERNET = 6
  • BrickServo.COMMUNICATION_METHOD_WIFI_V2 = 7

New in version 2.3.2 (Firmware).

Sub BrickServo.SetSPITFPBaudrate(ByVal brickletPort As Char, ByVal baudrate As Long)

Sets the baudrate for a specific Bricklet port ('a' - 'd'). The baudrate can be in the range 400000 to 2000000.

If you want to increase the throughput of Bricklets you can increase the baudrate. If you get a high error count because of high interference (see GetSPITFPErrorCount()) you can decrease the baudrate.

If the dynamic baudrate feature is enabled, the baudrate set by this function corresponds to the maximum baudrate (see SetSPITFPBaudrateConfig()).

Regulatory testing is done with the default baudrate. If CE compatibility or similar is necessary in you applications we recommend to not change the baudrate.

The default baudrate for all ports is 1400000.

New in version 2.3.2 (Firmware).

Function BrickServo.GetSPITFPBaudrate(ByVal brickletPort As Char) As Long

Returns the baudrate for a given Bricklet port, see SetSPITFPBaudrate().

New in version 2.3.2 (Firmware).

Sub BrickServo.GetSPITFPErrorCount(ByVal brickletPort As Char, ByRef errorCountACKChecksum As Long, ByRef errorCountMessageChecksum As Long, ByRef errorCountFrame As Long, ByRef errorCountOverflow As Long)

Returns the error count for the communication between Brick and Bricklet.

The errors are divided into

  • ACK checksum errors,
  • message checksum errors,
  • framing errors and
  • overflow errors.

The errors counts are for errors that occur on the Brick side. All Bricklets have a similar function that returns the errors on the Bricklet side.

New in version 2.3.2 (Firmware).

Sub BrickServo.EnableStatusLED()

Enables the status LED.

The status LED is the blue LED next to the USB connector. If enabled is is on and it flickers if data is transfered. If disabled it is always off.

The default state is enabled.

New in version 2.3.1 (Firmware).

Sub BrickServo.DisableStatusLED()

Disables the status LED.

The status LED is the blue LED next to the USB connector. If enabled is is on and it flickers if data is transfered. If disabled it is always off.

The default state is enabled.

New in version 2.3.1 (Firmware).

Function BrickServo.IsStatusLEDEnabled() As Boolean

Returns true if the status LED is enabled, false otherwise.

New in version 2.3.1 (Firmware).

Sub BrickServo.GetProtocol1BrickletName(ByVal port As Char, ByRef protocolVersion As Byte, ByRef firmwareVersion() As Byte, ByRef name As String)

Returns the firmware and protocol version and the name of the Bricklet for a given port.

This functions sole purpose is to allow automatic flashing of v1.x.y Bricklet plugins.

Function BrickServo.GetChipTemperature() As Short

Returns the temperature in °C/10 as measured inside the microcontroller. The value returned is not the ambient temperature!

The temperature is only proportional to the real temperature and it has an accuracy of +-15%. Practically it is only useful as an indicator for temperature changes.

Sub BrickServo.Reset()

Calling this function will reset the Brick. Calling this function on a Brick inside of a stack will reset the whole stack.

After a reset you have to create new device objects, calling functions on the existing ones will result in undefined behavior!

Sub BrickServo.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 Brick is connected to, the position, the hardware and firmware version as well as the device identifier.

The position can be '0'-'8' (stack position).

The device identifier numbers can be found here. There is also a constant for the device identifier of this Brick.

Callback Configuration Functions

Sub BrickServo.SetMinimumVoltage(ByVal voltage As Integer)

Sets the minimum voltage in mV, below which the UnderVoltageCallback callback is triggered. The minimum possible value that works with the Servo Brick is 5V. You can use this function to detect the discharge of a battery that is used to drive the stepper motor. If you have a fixed power supply, you likely do not need this functionality.

The default value is 5V (5000mV).

Function BrickServo.GetMinimumVoltage() As Integer

Returns the minimum voltage as set by SetMinimumVoltage()

Sub BrickServo.EnablePositionReachedCallback()

Enables the PositionReachedCallback callback.

Default is disabled.

New in version 2.0.1 (Firmware).

Sub BrickServo.DisablePositionReachedCallback()

Disables the PositionReachedCallback callback.

Default is disabled.

New in version 2.0.1 (Firmware).

Function BrickServo.IsPositionReachedCallbackEnabled() As Boolean

Returns true if PositionReachedCallback callback is enabled, false otherwise.

New in version 2.0.1 (Firmware).

Sub BrickServo.EnableVelocityReachedCallback()

Enables the VelocityReachedCallback callback.

Default is disabled.

New in version 2.0.1 (Firmware).

Sub BrickServo.DisableVelocityReachedCallback()

Disables the VelocityReachedCallback callback.

Default is disabled.

New in version 2.0.1 (Firmware).

Function BrickServo.IsVelocityReachedCallbackEnabled() As Boolean

Returns true if VelocityReachedCallback callback is enabled, false otherwise.

New in version 2.0.1 (Firmware).

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

AddHandler servo.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 BrickServo.UnderVoltageCallback(ByVal sender As BrickServo, ByVal voltage As Integer)

This callback is triggered when the input voltage drops below the value set by SetMinimumVoltage(). The parameter is the current voltage given in mV.

Event BrickServo.PositionReachedCallback(ByVal sender As BrickServo, ByVal servoNum As Byte, ByVal position As Short)

This callback is triggered when a position set by SetPosition() is reached. If the new position matches the current position then the callback is not triggered, because the servo didn't move. The parameters are the servo and the position that is reached.

You can enable this callback with EnablePositionReachedCallback().

Note

Since we can't get any feedback from the servo, this only works if the velocity (see SetVelocity()) is set smaller or equal to the maximum velocity of the servo. Otherwise the servo will lag behind the control value and the callback will be triggered too early.

Event BrickServo.VelocityReachedCallback(ByVal sender As BrickServo, ByVal servoNum As Byte, ByVal velocity As Short)

This callback is triggered when a velocity set by SetVelocity() is reached. The parameters are the servo and the velocity that is reached.

You can enable this callback with EnableVelocityReachedCallback().

Note

Since we can't get any feedback from the servo, this only works if the acceleration (see SetAcceleration()) is set smaller or equal to the maximum acceleration of the servo. Otherwise the servo will lag behind the control value and the callback will be triggered too early.

Constants

Const BrickServo.DEVICE_IDENTIFIER

This constant is used to identify a Servo Brick.

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 BrickServo.DEVICE_DISPLAY_NAME

This constant represents the human readable name of a Servo Brick.