MATLAB/Octave - GPS Bricklet

This is the description of the MATLAB/Octave 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 MATLAB/Octave API bindings is part of their general description.

Examples

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

Simple (MATLAB)

Download (matlab_example_simple.m)

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function matlab_example_simple()
    import com.tinkerforge.IPConnection;
    import com.tinkerforge.BrickletGPS;

    HOST = 'localhost';
    PORT = 4223;
    UID = 'XYZ'; % Change XYZ to the UID of your GPS Bricklet

    ipcon = IPConnection(); % Create IP connection
    gps = handle(BrickletGPS(UID, ipcon), 'CallbackProperties'); % Create device object

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

    % Get current coordinates
    coordinates = gps.getCoordinates();

    fprintf('Latitude: %g °\n', coordinates.latitude/1000000.0);
    fprintf('N/S: %s\n', coordinates.ns);
    fprintf('Longitude: %g °\n', coordinates.longitude/1000000.0);
    fprintf('E/W: %s\n', coordinates.ew);

    input('Press key to exit\n', 's');
    ipcon.disconnect();
end

Callback (MATLAB)

Download (matlab_example_callback.m)

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function matlab_example_callback()
    import com.tinkerforge.IPConnection;
    import com.tinkerforge.BrickletGPS;

    HOST = 'localhost';
    PORT = 4223;
    UID = 'XYZ'; % Change XYZ to the UID of your GPS Bricklet

    ipcon = IPConnection(); % Create IP connection
    gps = handle(BrickletGPS(UID, ipcon), 'CallbackProperties'); % Create device object

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

    % Register coordinates callback to function cb_coordinates
    set(gps, 'CoordinatesCallback', @(h, e) cb_coordinates(e));

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

    input('Press key to exit\n', 's');
    ipcon.disconnect();
end

% Callback function for coordinates callback
function cb_coordinates(e)
    fprintf('Latitude: %g °\n', e.latitude/1000000.0);
    fprintf('N/S: %s\n', e.ns);
    fprintf('Longitude: %g °\n', e.longitude/1000000.0);
    fprintf('E/W: %s\n', e.ew);
    fprintf('\n');
end

Simple (Octave)

Download (octave_example_simple.m)

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function octave_example_simple()
    more off;

    HOST = "localhost";
    PORT = 4223;
    UID = "XYZ"; % Change XYZ to the UID of your GPS Bricklet

    ipcon = javaObject("com.tinkerforge.IPConnection"); % Create IP connection
    gps = javaObject("com.tinkerforge.BrickletGPS", UID, ipcon); % Create device object

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

    % Get current coordinates
    coordinates = gps.getCoordinates();

    fprintf("Latitude: %g °\n", java2int(coordinates.latitude)/1000000.0);
    fprintf("N/S: %s\n", coordinates.ns);
    fprintf("Longitude: %g °\n", java2int(coordinates.longitude)/1000000.0);
    fprintf("E/W: %s\n", coordinates.ew);

    input("Press key to exit\n", "s");
    ipcon.disconnect();
end

function int = java2int(value)
    if compare_versions(version(), "3.8", "<=")
        int = value.intValue();
    else
        int = value;
    end
end

Callback (Octave)

Download (octave_example_callback.m)

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function octave_example_callback()
    more off;

    HOST = "localhost";
    PORT = 4223;
    UID = "XYZ"; % Change XYZ to the UID of your GPS Bricklet

    ipcon = javaObject("com.tinkerforge.IPConnection"); % Create IP connection
    gps = javaObject("com.tinkerforge.BrickletGPS", UID, ipcon); % Create device object

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

    % Register coordinates callback to function cb_coordinates
    gps.addCoordinatesCallback(@cb_coordinates);

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

    input("Press key to exit\n", "s");
    ipcon.disconnect();
end

% Callback function for coordinates callback
function cb_coordinates(e)
    fprintf("Latitude: %g °\n", java2int(e.latitude)/1000000.0);
    fprintf("N/S: %s\n", e.ns);
    fprintf("Longitude: %g °\n", java2int(e.longitude)/1000000.0);
    fprintf("E/W: %s\n", e.ew);
    fprintf("\n");
end

function int = java2int(value)
    if compare_versions(version(), "3.8", "<=")
        int = value.intValue();
    else
        int = value;
    end
end

API

Generally, every method of the MATLAB 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 the MATLAB bindings are based on Java and 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

class BrickletGPS(String uid, IPConnection ipcon)
Parameters:
  • uid – Type: String
  • ipcon – Type: IPConnection
Returns:
  • gps – Type: BrickletGPS

Creates an object with the unique device ID uid.

In MATLAB:

import com.tinkerforge.BrickletGPS;

gps = BrickletGPS('YOUR_DEVICE_UID', ipcon);

In Octave:

gps = java_new("com.tinkerforge.BrickletGPS", "YOUR_DEVICE_UID", ipcon);

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

BrickletGPS.Coordinates BrickletGPS.getCoordinates()
Return Object:
  • latitude – Type: long, Range: [0 to 232 - 1]
  • ns – Type: char
  • longitude – Type: long, Range: [0 to 232 - 1]
  • ew – Type: char
  • pdop – Type: int, Range: [0 to 216 - 1]
  • hdop – Type: int, Range: [0 to 216 - 1]
  • vdop – Type: int, Range: [0 to 216 - 1]
  • epe – Type: int, Range: [0 to 216 - 1]

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().

BrickletGPS.Status BrickletGPS.getStatus()
Return Object:
  • fix – Type: short, Range: See constants
  • satellitesView – Type: short, Range: [0 to 255]
  • satellitesUsed – Type: short, Range: [0 to 255]

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(), getAltitude() and getMotion() return invalid data
2 2D Fix, only getCoordinates() and getMotion() return valid data
3 3D Fix, getCoordinates(), getAltitude() and getMotion() 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:

For fix:

  • BrickletGPS.FIX_NO_FIX = 1
  • BrickletGPS.FIX_2D_FIX = 2
  • BrickletGPS.FIX_3D_FIX = 3
BrickletGPS.Altitude BrickletGPS.getAltitude()
Return Object:
  • altitude – Type: int, Range: [-231 to 231 - 1]
  • geoidalSeparation – Type: int, Range: [-231 to 231 - 1]

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().

BrickletGPS.Motion BrickletGPS.getMotion()
Return Object:
  • course – Type: long, Range: [0 to 232 - 1]
  • speed – Type: long, Range: [0 to 232 - 1]

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().

BrickletGPS.DateTime BrickletGPS.getDateTime()
Return Object:
  • date – Type: long, Range: [0 to 232 - 1]
  • time – Type: long, Range: [0 to 232 - 1]

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 14.07.13 as date and 195923568 means 19:59:23.568 as time.

Advanced Functions

void BrickletGPS.restart(short restartType)
Parameters:
  • restartType – Type: short, Range: See constants

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:

For restartType:

  • BrickletGPS.RESTART_TYPE_HOT_START = 0
  • BrickletGPS.RESTART_TYPE_WARM_START = 1
  • BrickletGPS.RESTART_TYPE_COLD_START = 2
  • BrickletGPS.RESTART_TYPE_FACTORY_RESET = 3
short[] BrickletGPS.getAPIVersion()
Returns:
  • apiVersion – Type: short[], Length: 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.

boolean BrickletGPS.getResponseExpected(short functionId)
Parameters:
  • functionId – Type: short, Range: See constants
Returns:
  • 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:

  • 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
void BrickletGPS.setResponseExpected(short functionId, boolean responseExpected)
Parameters:
  • functionId – Type: short, 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:

  • 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
void BrickletGPS.setResponseExpectedAll(boolean responseExpected)
Parameters:
  • responseExpected – Type: boolean

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

BrickletGPS.Identity BrickletGPS.getIdentity()
Return Object:
  • uid – Type: String, Length: up to 8
  • connectedUid – Type: String, Length: up to 8
  • position – Type: char
  • hardwareVersion – Type: short[], Length: 3, Range: [0 to 255]
  • firmwareVersion – Type: short[], Length: 3, Range: [0 to 255]
  • deviceIdentifier – Type: int, 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

void BrickletGPS.setCoordinatesCallbackPeriod(long period)
Parameters:
  • period – Type: long, Unit: 1 ms, Range: [0 to 232 - 1], Default: 0

Sets the period with which the CoordinatesCallback callback is triggered periodically. A value of 0 turns the callback off.

The CoordinatesCallback callback is only triggered if the coordinates changed since the last triggering.

long BrickletGPS.getCoordinatesCallbackPeriod()
Returns:
  • period – Type: long, Unit: 1 ms, Range: [0 to 232 - 1], Default: 0

Returns the period as set by setCoordinatesCallbackPeriod().

void BrickletGPS.setStatusCallbackPeriod(long period)
Parameters:
  • period – Type: long, Unit: 1 ms, Range: [0 to 232 - 1], Default: 0

Sets the period with which the StatusCallback callback is triggered periodically. A value of 0 turns the callback off.

The StatusCallback callback is only triggered if the status changed since the last triggering.

long BrickletGPS.getStatusCallbackPeriod()
Returns:
  • period – Type: long, Unit: 1 ms, Range: [0 to 232 - 1], Default: 0

Returns the period as set by setStatusCallbackPeriod().

void BrickletGPS.setAltitudeCallbackPeriod(long period)
Parameters:
  • period – Type: long, Unit: 1 ms, Range: [0 to 232 - 1], Default: 0

Sets the period with which the AltitudeCallback callback is triggered periodically. A value of 0 turns the callback off.

The AltitudeCallback callback is only triggered if the altitude changed since the last triggering.

long BrickletGPS.getAltitudeCallbackPeriod()
Returns:
  • period – Type: long, Unit: 1 ms, Range: [0 to 232 - 1], Default: 0

Returns the period as set by setAltitudeCallbackPeriod().

void BrickletGPS.setMotionCallbackPeriod(long period)
Parameters:
  • period – Type: long, Unit: 1 ms, Range: [0 to 232 - 1], Default: 0

Sets the period with which the MotionCallback callback is triggered periodically. A value of 0 turns the callback off.

The MotionCallback callback is only triggered if the motion changed since the last triggering.

long BrickletGPS.getMotionCallbackPeriod()
Returns:
  • period – Type: long, Unit: 1 ms, Range: [0 to 232 - 1], Default: 0

Returns the period as set by setMotionCallbackPeriod().

void BrickletGPS.setDateTimeCallbackPeriod(long period)
Parameters:
  • period – Type: long, Unit: 1 ms, Range: [0 to 232 - 1], Default: 0

Sets the period with which the DateTimeCallback callback is triggered periodically. A value of 0 turns the callback off.

The DateTimeCallback callback is only triggered if the date or time changed since the last triggering.

long BrickletGPS.getDateTimeCallbackPeriod()
Returns:
  • period – Type: long, Unit: 1 ms, Range: [0 to 232 - 1], Default: 0

Returns the period as set by setDateTimeCallbackPeriod().

Callbacks

Callbacks can be registered to receive time critical or recurring data from the device. The registration is done with "set" function of MATLAB. The parameters consist of the IP Connection object, the callback name and the callback function. For example, it looks like this in MATLAB:

function my_callback(e)
    fprintf('Parameter: %s\n', e.param);
end

set(device, 'ExampleCallback', @(h, e) my_callback(e));

Due to a difference in the Octave Java support the "set" function cannot be used in Octave. The registration is done with "add*Callback" functions of the device object. It looks like this in Octave:

function my_callback(e)
    fprintf("Parameter: %s\n", e.param);
end

device.addExampleCallback(@my_callback);

It is possible to add several callbacks and to remove them with the corresponding "remove*Callback" function.

The parameters of the callback are passed to the callback function as fields of the structure e, which is derived from the java.util.EventObject class. The available callback names with corresponding structure fields 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.

callback BrickletGPS.CoordinatesCallback
Event Object:
  • latitude – Type: long, Range: [0 to 232 - 1]
  • ns – Type: char
  • longitude – Type: long, Range: [0 to 232 - 1]
  • ew – Type: char
  • pdop – Type: int, Range: [0 to 216 - 1]
  • hdop – Type: int, Range: [0 to 216 - 1]
  • vdop – Type: int, Range: [0 to 216 - 1]
  • epe – Type: int, Range: [0 to 216 - 1]

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

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

In MATLAB the set() function can be used to register a callback function to this callback.

In Octave a callback function can be added to this callback using the addCoordinatesCallback() function. An added callback function can be removed with the removeCoordinatesCallback() function.

callback BrickletGPS.StatusCallback
Event Object:
  • fix – Type: short, Range: See constants
  • satellitesView – Type: short, Range: [0 to 255]
  • satellitesUsed – Type: short, Range: [0 to 255]

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

The StatusCallback callback is only triggered if the status changed since the last triggering.

The following constants are available for this function:

For fix:

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

In MATLAB the set() function can be used to register a callback function to this callback.

In Octave a callback function can be added to this callback using the addStatusCallback() function. An added callback function can be removed with the removeStatusCallback() function.

callback BrickletGPS.AltitudeCallback
Event Object:
  • altitude – Type: int, Range: [-231 to 231 - 1]
  • geoidalSeparation – Type: int, Range: [-231 to 231 - 1]

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

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

In MATLAB the set() function can be used to register a callback function to this callback.

In Octave a callback function can be added to this callback using the addAltitudeCallback() function. An added callback function can be removed with the removeAltitudeCallback() function.

callback BrickletGPS.MotionCallback
Event Object:
  • course – Type: long, Range: [0 to 232 - 1]
  • speed – Type: long, Range: [0 to 232 - 1]

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

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

In MATLAB the set() function can be used to register a callback function to this callback.

In Octave a callback function can be added to this callback using the addMotionCallback() function. An added callback function can be removed with the removeMotionCallback() function.

callback BrickletGPS.DateTimeCallback
Event Object:
  • date – Type: long, Range: [0 to 232 - 1]
  • time – Type: long, Range: [0 to 232 - 1]

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

The DateTimeCallback callback is only triggered if the date or time changed since the last triggering.

In MATLAB the set() function can be used to register a callback function to this callback.

In Octave a callback function can be added to this callback using the addDateTimeCallback() function. An added callback function can be removed with the removeDateTimeCallback() function.

Constants

int BrickletGPS.DEVICE_IDENTIFIER

This constant is used to identify a GPS 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.

String BrickletGPS.DEVICE_DISPLAY_NAME

This constant represents the human readable name of a GPS Bricklet.