Java - Distance US Bricklet

This is the description of the Java API bindings for the Distance US Bricklet. General information and technical specifications for the Distance US Bricklet are summarized in its hardware description.

An installation guide for the Java API bindings is part of their general description.

Examples

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

Simple

Download (ExampleSimple.java)

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import com.tinkerforge.IPConnection;
import com.tinkerforge.BrickletDistanceUS;

public class ExampleSimple {
    private static final String HOST = "localhost";
    private static final int PORT = 4223;

    // Change XYZ to the UID of your Distance US Bricklet
    private static final String UID = "XYZ";

    // Note: To make the example code cleaner we do not handle exceptions. Exceptions
    //       you might normally want to catch are described in the documentation
    public static void main(String args[]) throws Exception {
        IPConnection ipcon = new IPConnection(); // Create IP connection
        BrickletDistanceUS dus = new BrickletDistanceUS(UID, ipcon); // Create device object

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

        // Get current distance value
        int distance = dus.getDistanceValue(); // Can throw com.tinkerforge.TimeoutException
        System.out.println("Distance Value: " + distance);

        System.out.println("Press key to exit"); System.in.read();
        ipcon.disconnect();
    }
}

Callback

Download (ExampleCallback.java)

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import com.tinkerforge.IPConnection;
import com.tinkerforge.BrickletDistanceUS;

public class ExampleCallback {
    private static final String HOST = "localhost";
    private static final int PORT = 4223;

    // Change XYZ to the UID of your Distance US Bricklet
    private static final String UID = "XYZ";

    // Note: To make the example code cleaner we do not handle exceptions. Exceptions
    //       you might normally want to catch are described in the documentation
    public static void main(String args[]) throws Exception {
        IPConnection ipcon = new IPConnection(); // Create IP connection
        BrickletDistanceUS dus = new BrickletDistanceUS(UID, ipcon); // Create device object

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

        // Add distance value listener
        dus.addDistanceListener(new BrickletDistanceUS.DistanceListener() {
            public void distance(int distance) {
                System.out.println("Distance Value: " + distance);
            }
        });

        // Set period for distance value callback to 0.2s (200ms)
        // Note: The distance value callback is only called every 0.2 seconds
        //       if the distance value has changed since the last call!
        dus.setDistanceCallbackPeriod(200);

        System.out.println("Press key to exit"); System.in.read();
        ipcon.disconnect();
    }
}

Threshold

Download (ExampleThreshold.java)

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import com.tinkerforge.IPConnection;
import com.tinkerforge.BrickletDistanceUS;

public class ExampleThreshold {
    private static final String HOST = "localhost";
    private static final int PORT = 4223;

    // Change XYZ to the UID of your Distance US Bricklet
    private static final String UID = "XYZ";

    // Note: To make the example code cleaner we do not handle exceptions. Exceptions
    //       you might normally want to catch are described in the documentation
    public static void main(String args[]) throws Exception {
        IPConnection ipcon = new IPConnection(); // Create IP connection
        BrickletDistanceUS dus = new BrickletDistanceUS(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)
        dus.setDebouncePeriod(10000);

        // Add distance value reached listener
        dus.addDistanceReachedListener(new BrickletDistanceUS.DistanceReachedListener() {
            public void distanceReached(int distance) {
                System.out.println("Distance Value: " + distance);
            }
        });

        // Configure threshold for distance value "smaller than 200"
        dus.setDistanceCallbackThreshold('<', 200, 0);

        System.out.println("Press key to exit"); System.in.read();
        ipcon.disconnect();
    }
}

API

Generally, every method of the Java bindings that returns a value can throw a 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 unplugs the device). However, if a wireless connection is used, timeouts will occur if the distance to the device gets too big.

Beside the TimeoutException there is also a NotConnectedException that is thrown if a method needs to communicate with the device while the IP Connection is not connected.

Since Java does not support multiple return values and return by reference is not possible for primitive types, we use small classes that only consist of member variables. The member variables of the returned objects are described in the corresponding method descriptions.

The package for all Brick/Bricklet bindings and the IP Connection is com.tinkerforge.*

All methods listed below are thread-safe.

Basic Functions

public class BrickletDistanceUS(String uid, IPConnection ipcon)

Creates an object with the unique device ID uid:

BrickletDistanceUS distanceUS = new BrickletDistanceUS("YOUR_DEVICE_UID", ipcon);

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

public int getDistanceValue()

Returns the current distance value measured by the sensor. The value has a range of 0 to 4095. A small value corresponds to a small distance, a big value corresponds to a big distance. The relation between the measured distance value and the actual distance is affected by the 5V supply voltage (deviations in the supply voltage result in deviations in the distance values) and is non-linear (resolution is bigger at close range).

If you want to get the distance value periodically, it is recommended to use the DistanceListener listener and set the period with setDistanceCallbackPeriod().

Advanced Functions

public void setMovingAverage(short average)

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

Setting the length to 0 will turn the averaging completely off. With less averaging, there is more noise on the data.

The range for the averaging is 0-100.

The default value is 20.

public short getMovingAverage()

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

public short[] 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 boolean getResponseExpected(short 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 listener 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(short functionId, boolean 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 listener 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:

  • BrickletDistanceUS.FUNCTION_SET_DISTANCE_CALLBACK_PERIOD = 2
  • BrickletDistanceUS.FUNCTION_SET_DISTANCE_CALLBACK_THRESHOLD = 4
  • BrickletDistanceUS.FUNCTION_SET_DEBOUNCE_PERIOD = 6
  • BrickletDistanceUS.FUNCTION_SET_MOVING_AVERAGE = 10
public void setResponseExpectedAll(boolean responseExpected)

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

public BrickletDistanceUS.Identity getIdentity()

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.

The returned object has the public member variables String uid, String connectedUid, char position, short[] hardwareVersion, short[] firmwareVersion and int deviceIdentifier.

Listener Configuration Functions

public void setDistanceCallbackPeriod(long period)

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

Der DistanceListener listener is only triggered if the distance value has changed since the last triggering.

The default value is 0.

public long getDistanceCallbackPeriod()

Returns the period as set by setDistanceCallbackPeriod().

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

Sets the thresholds for the DistanceReachedListener listener.

The following options are possible:

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

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

The following constants are available for this function:

  • BrickletDistanceUS.THRESHOLD_OPTION_OFF = 'x'
  • BrickletDistanceUS.THRESHOLD_OPTION_OUTSIDE = 'o'
  • BrickletDistanceUS.THRESHOLD_OPTION_INSIDE = 'i'
  • BrickletDistanceUS.THRESHOLD_OPTION_SMALLER = '<'
  • BrickletDistanceUS.THRESHOLD_OPTION_GREATER = '>'
public BrickletDistanceUS.DistanceCallbackThreshold getDistanceCallbackThreshold()

Returns the threshold as set by setDistanceCallbackThreshold().

The following constants are available for this function:

  • BrickletDistanceUS.THRESHOLD_OPTION_OFF = 'x'
  • BrickletDistanceUS.THRESHOLD_OPTION_OUTSIDE = 'o'
  • BrickletDistanceUS.THRESHOLD_OPTION_INSIDE = 'i'
  • BrickletDistanceUS.THRESHOLD_OPTION_SMALLER = '<'
  • BrickletDistanceUS.THRESHOLD_OPTION_GREATER = '>'

The returned object has the public member variables char option, int min and int max.

public void setDebouncePeriod(long debounce)

Sets the period in ms with which the threshold listeners

are triggered, if the thresholds

keep being reached.

The default value is 100.

public long getDebouncePeriod()

Returns the debounce period as set by setDebouncePeriod().

Listeners

Listeners can be registered to receive time critical or recurring data from the device. The registration is done with "add*Listener" functions of the device object.

The parameter is a listener class object, for example:

device.addExampleListener(new BrickletDistanceUS.ExampleListener() {
    public void property(int value) {
        System.out.println("Value: " + value);
    }
});

The available listener classes with inherent methods to be overwritten are described below. It is possible to add several listeners and to remove them with the corresponding "remove*Listener" function.

Note

Using listeners 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 class BrickletDistanceUS.DistanceListener()

This listener can be added with the addDistanceListener() function. An added listener can be removed with the removeDistanceListener() function.

public void distance(int distance)

This listener is triggered periodically with the period that is set by setDistanceCallbackPeriod(). The parameter is the distance value of the sensor.

The DistanceListener listener is only triggered if the distance value has changed since the last triggering.

public class BrickletDistanceUS.DistanceReachedListener()

This listener can be added with the addDistanceReachedListener() function. An added listener can be removed with the removeDistanceReachedListener() function.

public void distanceReached(int distance)

This listener is triggered when the threshold as set by setDistanceCallbackThreshold() is reached. The parameter is the distance value of the sensor.

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

Constants

public static final int BrickletDistanceUS.DEVICE_IDENTIFIER

This constant is used to identify a Distance US Bricklet.

The getIdentity() function and the EnumerateListener listener of the IP Connection have a deviceIdentifier parameter to specify the Brick's or Bricklet's type.

public static final String BrickletDistanceUS.DEVICE_DISPLAY_NAME

This constant represents the human readable name of a Distance US Bricklet.