Java - GPS Bricklet – Tinkerforge

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# Java - GPS Bricklet

This is the description of the Java API bindings for the GPS Bricklet. General information and technical specifications for the GPS 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.BrickletGPS;
    import com.tinkerforge.IPConnection;

    public class ExampleSimple {
        private static final String HOST = "localhost";
        private static final int PORT = 4223;
        private static final String UID = "ABC"; // 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 commnents below
        public static void main(String args[]) throws Exception {
            IPConnection ipcon = new IPConnection(); // Create IP connection
            BrickletGPS gps = new BrickletGPS(UID, ipcon); // Create device object

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

            // Get current coordinates
            BrickletGPS.Coordinates coords = gps.getCoordinates(); // Can throw com.tinkerforge.TimeoutException

            System.out.println("Latitude: " + coords.latitude/1000000.0 + "° " + coords.ns);
            System.out.println("Longitude: " + coords.longitude/1000000.0 + "° " + coords.ew);

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

### Callback

Download (ExampleCallback.java)

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    import com.tinkerforge.BrickletGPS;
    import com.tinkerforge.IPConnection;

    public class ExampleCallback {
        private static final String HOST = "localhost";
        private static final int PORT = 4223;
        private static final String UID = "ABC"; // 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 commnents below
        public static void main(String args[]) throws Exception {
            IPConnection ipcon = new IPConnection(); // Create IP connection
            BrickletGPS gps = new BrickletGPS(UID, ipcon); // Create device object

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

            // Set Period for coordinates callback to 1s (1000ms)
            // Note: The current callback is only called every second if the
            //       coordinates have changed since the last call!
            gps.setCoordinatesCallbackPeriod(1000);

            // Add and implement coordinates listener (called if coordinates change)
            gps.addCoordinatesListener(new BrickletGPS.CoordinatesListener() {
                public void coordinates(long latitude, char ns, long longitude, char ew,
                                        int pdop, int hdop, int vdop, int epe) {
                    System.out.println("Latitude: " + latitude/1000000.0 + "° " + ns);
                    System.out.println("Longitude: " + longitude/1000000.0 + "° " + ew);
                }
            });

            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 `BrickletGPS`(String uid, IPConnection ipcon)

  Creates an object with the unique device ID `uid`:

      BrickletGPS gps = new BrickletGPS("YOUR_DEVICE_UID", ipcon);

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

public BrickletGPS.Coordinates `getCoordinates`()

  Returns the GPS coordinates. Latitude and longitude are given in the `DD.dddddd°` format, the value 57123468 means 57.123468°. The parameter `ns` and `ew` are the cardinal directions for latitude and longitude. Possible values for `ns` and `ew` are 'N', 'S', 'E' and 'W' (north, south, east and west).

  PDOP, HDOP and VDOP are the dilution of precision (DOP) values. They specify the additional multiplicative effect of GPS satellite geometry on GPS precision. See here for more information. The values are give in hundredths.

  EPE is the "Estimated Position Error". The EPE is given in cm. This is not the absolute maximum error, it is the error with a specific confidence. See here for more information.

  This data is only valid if there is currently a fix as indicated by `getStatus()`.

  The returned object has the public member variables `long latitude`, `char ns`, `long longitude`, `char ew`, `int pdop`, `int hdop`, `int vdop` and `int epe`.

public BrickletGPS.Status `getStatus`()

  Returns the current fix status, the number of satellites that are in view and the number of satellites that are currently used.

  Possible fix status values can be:

  Value | Description
  --- | ---
  1 | No Fix, `getCoordinates()` and `getAltitude()` return invalid data
  2 | 2D Fix, only `getCoordinates()` returns valid data
  3 | 3D Fix, `getCoordinates()` and `getAltitude()` return valid data

  There is also a blue LED on the Bricklet that indicates the fix status.

  The following constants are available for this function:

  - BrickletGPS.FIX_NO_FIX = 1
  - BrickletGPS.FIX_2D_FIX = 2
  - BrickletGPS.FIX_3D_FIX = 3

  The returned object has the public member variables `short fix`, `short satellitesView` and `short satellitesUsed`.

public BrickletGPS.Altitude `getAltitude`()

  Returns the current altitude and corresponding geoidal separation.

  Both values are given in cm.

  This data is only valid if there is currently a fix as indicated by `getStatus()`.

  The returned object has the public member variables `long altitude` and `long geoidalSeparation`.

public BrickletGPS.Motion `getMotion`()

  Returns the current course and speed. Course is given in hundredths degree and speed is given in hundredths km/h. A course of 0° means the Bricklet is traveling north bound and 90° means it is traveling east bound.

  Please note that this only returns useful values if an actual movement is present.

  This data is only valid if there is currently a fix as indicated by `getStatus()`.

  The returned object has the public member variables `long course` and `long speed`.

public BrickletGPS.DateTime `getDateTime`()

  Returns the current date and time. The date is given in the format `ddmmyy` and the time is given in the format `hhmmss.sss`. For example, 140713 means 14.05.13 as date and 195923568 means 19:59:23.568 as time.

  The returned object has the public member variables `long date` and `long time`.

### Advanced Functions

public void `restart`(short restartType)

  Restarts the GPS Bricklet, the following restart types are available:

  Value | Description
  --- | ---
  0 | Hot start (use all available data in the NV store)
  1 | Warm start (don't use ephemeris at restart)
  2 | Cold start (don't use time, position, almanacs and ephemeris at restart)
  3 | Factory reset (clear all system/user configurations at restart)

  The following constants are available for this function:

  - BrickletGPS.RESTART_TYPE_HOT_START = 0
  - BrickletGPS.RESTART_TYPE_WARM_START = 1
  - BrickletGPS.RESTART_TYPE_COLD_START = 2
  - BrickletGPS.RESTART_TYPE_FACTORY_RESET = 3

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:

  - BrickletGPS.FUNCTION_RESTART = 6
  - BrickletGPS.FUNCTION_SET_COORDINATES_CALLBACK_PERIOD = 7
  - BrickletGPS.FUNCTION_SET_STATUS_CALLBACK_PERIOD = 9
  - BrickletGPS.FUNCTION_SET_ALTITUDE_CALLBACK_PERIOD = 11
  - BrickletGPS.FUNCTION_SET_MOTION_CALLBACK_PERIOD = 13
  - BrickletGPS.FUNCTION_SET_DATE_TIME_CALLBACK_PERIOD = 15

public void `setResponseExpectedAll`(boolean responseExpected)

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

public BrickletGPS.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 `setCoordinatesCallbackPeriod`(long period)

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

  `CoordinatesListener` is only triggered if the coordinates changed since the last triggering.

  The default value is 0.

public long `getCoordinatesCallbackPeriod`()

  Returns the period as set by `setCoordinatesCallbackPeriod()`.

public void `setStatusCallbackPeriod`(long period)

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

  `StatusListener` is only triggered if the status changed since the last triggering.

  The default value is 0.

public long `getStatusCallbackPeriod`()

  Returns the period as set by `setStatusCallbackPeriod()`.

public void `setAltitudeCallbackPeriod`(long period)

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

  `AltitudeListener` is only triggered if the altitude changed since the last triggering.

  The default value is 0.

public long `getAltitudeCallbackPeriod`()

  Returns the period as set by `setAltitudeCallbackPeriod()`.

public void `setMotionCallbackPeriod`(long period)

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

  `MotionListener` is only triggered if the motion changed since the last triggering.

  The default value is 0.

public long `getMotionCallbackPeriod`()

  Returns the period as set by `setMotionCallbackPeriod()`.

public void `setDateTimeCallbackPeriod`(long period)

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

  `DateTimeListener` is only triggered if the date or time changed since the last triggering.

  The default value is 0.

public long `getDateTimeCallbackPeriod`()

  Returns the period as set by `setDateTimeCallbackPeriod()`.

### 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 BrickletGPS.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 `BrickletGPS.CoordinatesListener`()

  This listener can be added with the `addCoordinatesListener()` function. An added listener can be removed with the `removeCoordinatesListener()` function.

  public void `coordinates`(long latitude, char ns, long longitude, char ew, int pdop, int hdop, int vdop, int epe)

    This listener is triggered periodically with the period that is set by `setCoordinatesCallbackPeriod()`. The parameters are the same as for `getCoordinates()`.

    `CoordinatesListener` is only triggered if the coordinates changed since the last triggering and if there is currently a fix as indicated by `getStatus()`.

public class `BrickletGPS.StatusListener`()

  This listener can be added with the `addStatusListener()` function. An added listener can be removed with the `removeStatusListener()` function.

  public void `status`(short fix, short satellitesView, short satellitesUsed)

    This listener is triggered periodically with the period that is set by `setStatusCallbackPeriod()`. The parameters are the same as for `getStatus()`.

    `StatusListener` is only triggered if the status changed since the last triggering.

    The following constants are available for this function:

    - BrickletGPS.FIX_NO_FIX = 1
    - BrickletGPS.FIX_2D_FIX = 2
    - BrickletGPS.FIX_3D_FIX = 3

public class `BrickletGPS.AltitudeListener`()

  This listener can be added with the `addAltitudeListener()` function. An added listener can be removed with the `removeAltitudeListener()` function.

  public void `altitude`(long altitude, long geoidalSeparation)

    This listener is triggered periodically with the period that is set by `setAltitudeCallbackPeriod()`. The parameters are the same as for `getAltitude()`.

    `AltitudeListener` is only triggered if the altitude changed since the last triggering and if there is currently a fix as indicated by `getStatus()`.

public class `BrickletGPS.MotionListener`()

  This listener can be added with the `addMotionListener()` function. An added listener can be removed with the `removeMotionListener()` function.

  public void `motion`(long course, long speed)

    This listener is triggered periodically with the period that is set by `setMotionCallbackPeriod()`. The parameters are the same as for `getMotion()`.

    `MotionListener` is only triggered if the motion changed since the last triggering and if there is currently a fix as indicated by `getStatus()`.

public class `BrickletGPS.DateTimeListener`()

  This listener can be added with the `addDateTimeListener()` function. An added listener can be removed with the `removeDateTimeListener()` function.

  public void `dateTime`(long date, long time)

    This listener is triggered periodically with the period that is set by `setDateTimeCallbackPeriod()`. The parameters are the same as for `getDateTime()`.

    `DateTimeListener` is only triggered if the date or time changed since the last triggering.

### Constants

public static final int `BrickletGPS.DEVICE_IDENTIFIER`

  This constant is used to identify a GPS 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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