LabVIEW - Load Cell Bricklet

This is the description of the LabVIEW 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 LabVIEW API bindings is part of their general description.

API

Generally, every method of the LabVIEW bindings that outputs a value can report a Tinkerforge.TimeoutException. This error gets reported if the device did not respond. If a cable based connection is used, it is unlikely that this exception gets thrown (assuming nobody plugs the device out). However, if a wireless connection is used, timeouts will occur if the distance to the device gets too big.

The namespace for all Brick/Bricklet bindings and the IPConnection is Tinkerforge.*.

Basic Functions

BrickletLoadCell(uid, ipcon) → loadCell
Input:
  • uid – Type: String
  • ipcon – Type: .NET Refnum (IPConnection)
Output:
  • loadCell – Type: .NET Refnum (BrickletLoadCell)

Creates an object with the unique device ID uid. This object can then be used after the IP Connection is connected (see examples above).

BrickletLoadCell.GetWeight() → weight
Output:
  • weight – Type: Int32, 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().

BrickletLoadCell.LEDOn()

Turns the LED on.

BrickletLoadCell.LEDOff()

Turns the LED off.

BrickletLoadCell.IsLEDOn() → on
Output:
  • on – Type: Boolean

Returns true if the led is on, false otherwise.

BrickletLoadCell.Tare()

Sets the currently measured weight as tare weight.

Advanced Functions

BrickletLoadCell.SetMovingAverage(average)
Input:
  • 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.

BrickletLoadCell.GetMovingAverage() → average
Output:
  • average – Type: Byte, Range: [0 to 255]

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

BrickletLoadCell.Calibrate(weight)
Input:
  • weight – Type: Int64, 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.

BrickletLoadCell.SetConfiguration(rate, gain)
Input:
  • 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
BrickletLoadCell.GetConfiguration() → rate, gain
Output:
  • 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
BrickletLoadCell.GetAPIVersion() → apiVersion
Output:
  • apiVersion – Type: Byte[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.

BrickletLoadCell.GetResponseExpected(functionId) → responseExpected
Input:
  • functionId – Type: Byte, Range: See constants
Output:
  • 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
BrickletLoadCell.SetResponseExpected(functionId, responseExpected)
Input:
  • 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
BrickletLoadCell.SetResponseExpectedAll(responseExpected)
Input:
  • responseExpected – Type: Boolean

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

BrickletLoadCell.GetIdentity() → uid, connectedUid, position, hardwareVersion, firmwareVersion, deviceIdentifier
Output:
  • uid – Type: String, Length: up to 8
  • connectedUid – Type: String, Length: up to 8
  • position – Type: Char
  • hardwareVersion – Type: Byte[3], Range: [0 to 255]
  • firmwareVersion – Type: Byte[3], Range: [0 to 255]
  • deviceIdentifier – Type: Int32, 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

BrickletLoadCell.SetWeightCallbackPeriod(period)
Input:
  • period – Type: Int64, 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.

BrickletLoadCell.GetWeightCallbackPeriod() → period
Output:
  • period – Type: Int64, Unit: 1 ms, Range: [0 to 232 - 1], Default: 0

Returns the period as set by SetWeightCallbackPeriod().

BrickletLoadCell.SetWeightCallbackThreshold(option, min, max)
Input:
  • option – Type: Char, Range: See constants, Default: "x"
  • min – Type: Int32, Range: [-231 to 231 - 1]
  • max – Type: Int32, 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"
  • BrickletLoadCell.THRESHOLD_OPTION_OUTSIDE = "o"
  • BrickletLoadCell.THRESHOLD_OPTION_INSIDE = "i"
  • BrickletLoadCell.THRESHOLD_OPTION_SMALLER = "<"
  • BrickletLoadCell.THRESHOLD_OPTION_GREATER = ">"
BrickletLoadCell.GetWeightCallbackThreshold() → option, min, max
Output:
  • option – Type: Char, Range: See constants, Default: "x"
  • min – Type: Int32, Range: [-231 to 231 - 1]
  • max – Type: Int32, 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"
  • BrickletLoadCell.THRESHOLD_OPTION_OUTSIDE = "o"
  • BrickletLoadCell.THRESHOLD_OPTION_INSIDE = "i"
  • BrickletLoadCell.THRESHOLD_OPTION_SMALLER = "<"
  • BrickletLoadCell.THRESHOLD_OPTION_GREATER = ">"
BrickletLoadCell.SetDebouncePeriod(debounce)
Input:
  • debounce – Type: Int64, 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.

BrickletLoadCell.GetDebouncePeriod() → debounce
Output:
  • debounce – Type: Int64, 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 function to a callback property of the device object. 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 → sender, weight
Callback Output:
  • sender – Type: .NET Refnum (BrickletLoadCell)
  • weight – Type: Int32, 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 → sender, weight
Callback Output:
  • sender – Type: .NET Refnum (BrickletLoadCell)
  • weight – Type: Int32, 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

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.

BrickletLoadCell.DEVICE_DISPLAY_NAME

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