Java - Distance US Bricklet – Tinkerforge

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# 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.BrickletDistanceUS;
    import com.tinkerforge.IPConnection;

    public class ExampleSimple {
        private static final String HOST = "localhost";
        private static final int PORT = 4223;
        private static final String UID = "XYZ"; // Change to your UID

        // 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 dir = 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 = dir.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.BrickletDistanceUS;
    import com.tinkerforge.IPConnection;

    public class ExampleCallback {
        private static final String HOST = "localhost";
        private static final int PORT = 4223;
        private static final String UID = "XYZ"; // Change to your UID

        // 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 dir = new BrickletDistanceUS(UID, ipcon); // Create device object

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

            // Set Period for distance callback to 1s (1000ms)
            // Note: The distance callback is only called every second if the
            //       distance has changed since the last call!
            dir.setDistanceCallbackPeriod(1000);

            // Add and implement distance listener (called if distance changes)
            dir.addDistanceListener(new BrickletDistanceUS.DistanceListener() {
                public void distance(int distance) {
                    System.out.println("Distance Value: " + distance);
                }
            });

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

### Threshold

Download (ExampleThreshold.java)

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

    public class ExampleThreshold {
        private static final String HOST = "localhost";
        private static final int PORT = 4223;
        private static final String UID = "XYZ"; // Change to your UID

        // 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 dir = 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)
            dir.setDebouncePeriod(10000);

            // Configure threshold for "smaller than 200"
            dir.setDistanceCallbackThreshold('<', (short)200, (short)0);

            // Add and implement distance reached listener
            // (called if distance value is smaller than 200)
            dir.addDistanceReachedListener(new BrickletDistanceUS.DistanceReachedListener() {
                public void distanceReached(int distance) {
                    System.out.println("Distance Value is smaller than 200: " + distance);
                }
            });

            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 listener `DistanceListener` 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 and listeners 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:

  - 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.

  `DistanceListener` 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, short min, short 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`, `short min` and `short max`.

public void `setDebouncePeriod`(long debounce)

  Sets the period in ms with which the threshold listeners

  - `DistanceReachedListener`,

  are triggered, if the thresholds

  - `setDistanceCallbackThreshold()`,

  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.

    `DistanceListener` 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.

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