C# - Load Cell Bricklet

This is the description of the C# 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 C# API bindings is part of their general description.

Examples

The example code below is Public Domain (CC0 1.0).

Simple

Download (ExampleSimple.cs)

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using System;
using Tinkerforge;

class Example
{
    private static string HOST = "localhost";
    private static int PORT = 4223;
    private static string UID = "XYZ"; // Change XYZ to the UID of your Load Cell Bricklet

    static void Main()
    {
        IPConnection ipcon = new IPConnection(); // Create IP connection
        BrickletLoadCell lc = 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
        int weight = lc.GetWeight();
        Console.WriteLine("Weight: " + weight + " g");

        Console.WriteLine("Press enter to exit");
        Console.ReadLine();
        ipcon.Disconnect();
    }
}

Callback

Download (ExampleCallback.cs)

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using System;
using Tinkerforge;

class Example
{
    private static string HOST = "localhost";
    private static int PORT = 4223;
    private static string UID = "XYZ"; // Change XYZ to the UID of your Load Cell Bricklet

    // Callback function for weight callback
    static void WeightCB(BrickletLoadCell sender, int weight)
    {
        Console.WriteLine("Weight: " + weight + " g");
    }

    static void Main()
    {
        IPConnection ipcon = new IPConnection(); // Create IP connection
        BrickletLoadCell lc = 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 function WeightCB
        lc.WeightCallback += 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 enter to exit");
        Console.ReadLine();
        ipcon.Disconnect();
    }
}

Threshold

Download (ExampleThreshold.cs)

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using System;
using Tinkerforge;

class Example
{
    private static string HOST = "localhost";
    private static int PORT = 4223;
    private static string UID = "XYZ"; // Change XYZ to the UID of your Load Cell Bricklet

    // Callback function for weight reached callback
    static void WeightReachedCB(BrickletLoadCell sender, int weight)
    {
        Console.WriteLine("Weight: " + weight + " g");
    }

    static void Main()
    {
        IPConnection ipcon = new IPConnection(); // Create IP connection
        BrickletLoadCell lc = 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 function WeightReachedCB
        lc.WeightReachedCallback += WeightReachedCB;

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

        Console.WriteLine("Press enter to exit");
        Console.ReadLine();
        ipcon.Disconnect();
    }
}

API

Generally, every method of the C# bindings that returns a value can throw a Tinkerforge.TimeoutException. This exception gets thrown 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.

Since C# does not support multiple return values directly, we use the out keyword to return multiple values from a method.

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

All methods listed below are thread-safe.

Basic Functions

public class BrickletLoadCell(String uid, IPConnection ipcon)

Creates an object with the unique device ID uid:

BrickletLoadCell loadCell = new BrickletLoadCell("YOUR_DEVICE_UID", ipcon);

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

public int GetWeight()

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().

public void LEDOn()

Turns the LED on.

public void LEDOff()

Turns the LED off.

public bool IsLEDOn()

Returns true if the led is on, false otherwise.

public void Tare()

Sets the currently measured weight as tare weight.

Advanced Functions

public void SetMovingAverage(byte average)

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.

public byte GetMovingAverage()

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

public void Calibrate(long weight)

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.

public void SetConfiguration(byte rate, byte gain)

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:

  • BrickletLoadCell.RATE_10HZ = 0
  • BrickletLoadCell.RATE_80HZ = 1
  • BrickletLoadCell.GAIN_128X = 0
  • BrickletLoadCell.GAIN_64X = 1
  • BrickletLoadCell.GAIN_32X = 2
public void GetConfiguration(out byte rate, out byte gain)

Returns the configuration as set by SetConfiguration().

The following constants are available for this function:

  • BrickletLoadCell.RATE_10HZ = 0
  • BrickletLoadCell.RATE_80HZ = 1
  • BrickletLoadCell.GAIN_128X = 0
  • BrickletLoadCell.GAIN_64X = 1
  • BrickletLoadCell.GAIN_32X = 2
public byte[] GetAPIVersion()

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.

public bool GetResponseExpected(byte functionId)

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.

public void SetResponseExpected(byte functionId, bool responseExpected)

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:

  • 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
public void SetResponseExpectedAll(bool responseExpected)

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

public void GetIdentity(out string uid, out string connectedUid, out char position, out byte[] hardwareVersion, out byte[] firmwareVersion, out int deviceIdentifier)

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

public void SetWeightCallbackPeriod(long period)

Sets the period in ms 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.

The default value is 0.

public long GetWeightCallbackPeriod()

Returns the period as set by SetWeightCallbackPeriod().

public void SetWeightCallbackThreshold(char option, int min, int max)

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:

  • BrickletLoadCell.THRESHOLD_OPTION_OFF = 'x'
  • BrickletLoadCell.THRESHOLD_OPTION_OUTSIDE = 'o'
  • BrickletLoadCell.THRESHOLD_OPTION_INSIDE = 'i'
  • BrickletLoadCell.THRESHOLD_OPTION_SMALLER = '<'
  • BrickletLoadCell.THRESHOLD_OPTION_GREATER = '>'
public void GetWeightCallbackThreshold(out char option, out int min, out int max)

Returns the threshold as set by SetWeightCallbackThreshold().

The following constants are available for this function:

  • BrickletLoadCell.THRESHOLD_OPTION_OFF = 'x'
  • BrickletLoadCell.THRESHOLD_OPTION_OUTSIDE = 'o'
  • BrickletLoadCell.THRESHOLD_OPTION_INSIDE = 'i'
  • BrickletLoadCell.THRESHOLD_OPTION_SMALLER = '<'
  • BrickletLoadCell.THRESHOLD_OPTION_GREATER = '>'
public void SetDebouncePeriod(long debounce)

Sets the period in ms with which the threshold callback

is triggered, if the threshold

keeps being reached.

The default value is 100.

public long GetDebouncePeriod()

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 appending your callback handler to the corresponding event:

void MyCallback(BrickletLoadCell sender, int value)
{
    System.Console.WriteLine("Value: " + value);
}

loadCell.ExampleCallback += MyCallback;

The available events 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.

public event WeightCallback(BrickletLoadCell sender, int weight)

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.

public event WeightReachedCallback(BrickletLoadCell sender, int weight)

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

public int 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.

public string DEVICE_DISPLAY_NAME

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