MATLAB/Octave - Barometer Bricklet

This is the description of the MATLAB/Octave API bindings for the Barometer Bricklet. General information and technical specifications for the Barometer 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.BrickletBarometer;

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

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

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

    % Get current air pressure
    airPressure = b.getAirPressure();
    fprintf('Air Pressure: %g mbar\n', airPressure/1000.0);

    % Get current altitude
    altitude = b.getAltitude();
    fprintf('Altitude: %g m\n', altitude/100.0);

    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.BrickletBarometer;

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

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

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

    % Register air pressure callback to function cb_air_pressure
    set(b, 'AirPressureCallback', @(h, e) cb_air_pressure(e));

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

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

% Callback function for air pressure callback
function cb_air_pressure(e)
    fprintf('Air Pressure: %g mbar\n', e.airPressure/1000.0);
end

Threshold (MATLAB)

Download (matlab_example_threshold.m)

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function matlab_example_threshold()
    import com.tinkerforge.IPConnection;
    import com.tinkerforge.BrickletBarometer;

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

    ipcon = IPConnection(); % Create IP connection
    b = handle(BrickletBarometer(UID, ipcon), 'CallbackProperties'); % 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)
    b.setDebouncePeriod(10000);

    % Register air pressure reached callback to function cb_air_pressure_reached
    set(b, 'AirPressureReachedCallback', @(h, e) cb_air_pressure_reached(e));

    % Configure threshold for air pressure "greater than 1025 mbar"
    b.setAirPressureCallbackThreshold('>', 1025*1000, 0);

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

% Callback function for air pressure reached callback
function cb_air_pressure_reached(e)
    fprintf('Air Pressure: %g mbar\n', e.airPressure/1000.0);
    fprintf('Enjoy the potentially good weather!\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 Barometer Bricklet

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

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

    % Get current air pressure
    airPressure = b.getAirPressure();
    fprintf("Air Pressure: %g mbar\n", airPressure/1000.0);

    % Get current altitude
    altitude = b.getAltitude();
    fprintf("Altitude: %g m\n", altitude/100.0);

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

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

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

    % Register air pressure callback to function cb_air_pressure
    b.addAirPressureCallback(@cb_air_pressure);

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

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

% Callback function for air pressure callback
function cb_air_pressure(e)
    fprintf("Air Pressure: %g mbar\n", e.airPressure/1000.0);
end

Threshold (Octave)

Download (octave_example_threshold.m)

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function octave_example_threshold()
    more off;

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

    ipcon = javaObject("com.tinkerforge.IPConnection"); % Create IP connection
    b = javaObject("com.tinkerforge.BrickletBarometer", 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)
    b.setDebouncePeriod(10000);

    % Register air pressure reached callback to function cb_air_pressure_reached
    b.addAirPressureReachedCallback(@cb_air_pressure_reached);

    % Configure threshold for air pressure "greater than 1025 mbar"
    b.setAirPressureCallbackThreshold(">", 1025*1000, 0);

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

% Callback function for air pressure reached callback
function cb_air_pressure_reached(e)
    fprintf("Air Pressure: %g mbar\n", e.airPressure/1000.0);
    fprintf("Enjoy the potentially good weather!\n");
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

public class BrickletBarometer(String uid, IPConnection ipcon)

Creates an object with the unique device ID uid.

In MATLAB:

import com.tinkerforge.BrickletBarometer;

barometer = BrickletBarometer('YOUR_DEVICE_UID', ipcon);

In Octave:

barometer = java_new("com.tinkerforge.BrickletBarometer", "YOUR_DEVICE_UID", ipcon);

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

public int getAirPressure()

Returns the air pressure of the air pressure sensor. The value has a range of 10000 to 1200000 and is given in mbar/1000, i.e. a value of 1001092 means that an air pressure of 1001.092 mbar is measured.

If you want to get the air pressure periodically, it is recommended to use the AirPressureCallback callback and set the period with setAirPressureCallbackPeriod().

public int getAltitude()

Returns the relative altitude of the air pressure sensor. The value is given in cm and is calculated based on the difference between the current air pressure and the reference air pressure that can be set with setReferenceAirPressure().

If you want to get the altitude periodically, it is recommended to use the AltitudeCallback callback and set the period with setAltitudeCallbackPeriod().

public void setReferenceAirPressure(int airPressure)

Sets the reference air pressure in mbar/1000 for the altitude calculation. Valid values are between 10000 and 1200000. Setting the reference to the current air pressure results in a calculated altitude of 0cm. Passing 0 is a shortcut for passing the current air pressure as reference.

Well known reference values are the Q codes QNH and QFE used in aviation.

The default value is 1013.25mbar.

public int getReferenceAirPressure()

Returns the reference air pressure as set by setReferenceAirPressure().

Advanced Functions

public short getChipTemperature()

Returns the temperature of the air pressure sensor. The value has a range of -4000 to 8500 and is given in °C/100, i.e. a value of 2007 means that a temperature of 20.07 °C is measured.

This temperature is used internally for temperature compensation of the air pressure measurement. It is not as accurate as the temperature measured by the Temperature Bricklet or the Temperature IR Bricklet.

public void setAveraging(short movingAveragePressure, short averagePressure, short averageTemperature)

Sets the different averaging parameters. It is possible to set the length of a normal averaging for the temperature and pressure, as well as an additional length of a moving average for the pressure. The moving average is calculated from the normal averages. There is no moving average for the temperature.

The maximum length for the pressure average is 10, for the temperature average is 255 and for the moving average is 25.

Setting the all three parameters to 0 will turn the averaging completely off. If the averaging is off, there is lots of noise on the data, but the data is without delay. Thus we recommend to turn the averaging off if the Barometer Bricklet data is to be used for sensor fusion with other sensors.

The default values are 10 for the normal averages and 25 for the moving average.

New in version 2.0.1 (Plugin).

public BrickletBarometer.Averaging getAveraging()

Returns the averaging configuration as set by setAveraging().

New in version 2.0.1 (Plugin).

The returned object has the public member variables short movingAveragePressure, short averagePressure and short averageTemperature.

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 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(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 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:

  • BrickletBarometer.FUNCTION_SET_AIR_PRESSURE_CALLBACK_PERIOD = 3
  • BrickletBarometer.FUNCTION_SET_ALTITUDE_CALLBACK_PERIOD = 5
  • BrickletBarometer.FUNCTION_SET_AIR_PRESSURE_CALLBACK_THRESHOLD = 7
  • BrickletBarometer.FUNCTION_SET_ALTITUDE_CALLBACK_THRESHOLD = 9
  • BrickletBarometer.FUNCTION_SET_DEBOUNCE_PERIOD = 11
  • BrickletBarometer.FUNCTION_SET_REFERENCE_AIR_PRESSURE = 13
  • BrickletBarometer.FUNCTION_SET_AVERAGING = 20
public void setResponseExpectedAll(boolean responseExpected)

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

public BrickletBarometer.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.

Callback Configuration Functions

public void setAirPressureCallbackPeriod(long period)

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

The AirPressureCallback callback is only triggered if the air pressure has changed since the last triggering.

The default value is 0.

public long getAirPressureCallbackPeriod()

Returns the period as set by setAirPressureCallbackPeriod().

public void setAltitudeCallbackPeriod(long period)

Sets the period in ms 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 has changed since the last triggering.

The default value is 0.

public long getAltitudeCallbackPeriod()

Returns the period as set by setAltitudeCallbackPeriod().

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

Sets the thresholds for the AirPressureReachedCallback callback.

The following options are possible:

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

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

The following constants are available for this function:

  • BrickletBarometer.THRESHOLD_OPTION_OFF = 'x'
  • BrickletBarometer.THRESHOLD_OPTION_OUTSIDE = 'o'
  • BrickletBarometer.THRESHOLD_OPTION_INSIDE = 'i'
  • BrickletBarometer.THRESHOLD_OPTION_SMALLER = '<'
  • BrickletBarometer.THRESHOLD_OPTION_GREATER = '>'
public BrickletBarometer.AirPressureCallbackThreshold getAirPressureCallbackThreshold()

Returns the threshold as set by setAirPressureCallbackThreshold().

The following constants are available for this function:

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

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

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

Sets the thresholds for the AltitudeReachedCallback callback.

The following options are possible:

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

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

The following constants are available for this function:

  • BrickletBarometer.THRESHOLD_OPTION_OFF = 'x'
  • BrickletBarometer.THRESHOLD_OPTION_OUTSIDE = 'o'
  • BrickletBarometer.THRESHOLD_OPTION_INSIDE = 'i'
  • BrickletBarometer.THRESHOLD_OPTION_SMALLER = '<'
  • BrickletBarometer.THRESHOLD_OPTION_GREATER = '>'
public BrickletBarometer.AltitudeCallbackThreshold getAltitudeCallbackThreshold()

Returns the threshold as set by setAltitudeCallbackThreshold().

The following constants are available for this function:

  • BrickletBarometer.THRESHOLD_OPTION_OFF = 'x'
  • BrickletBarometer.THRESHOLD_OPTION_OUTSIDE = 'o'
  • BrickletBarometer.THRESHOLD_OPTION_INSIDE = 'i'
  • BrickletBarometer.THRESHOLD_OPTION_SMALLER = '<'
  • BrickletBarometer.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 callbacks

are triggered, if the thresholds

keep 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 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.

public callback BrickletBarometer.AirPressureCallback
Parameters:airPressure -- int

This callback is triggered periodically with the period that is set by setAirPressureCallbackPeriod(). The parameter is the air pressure of the air pressure sensor.

The AirPressureCallback callback is only triggered if the air pressure has 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 addAirPressureCallback() function. An added callback function can be removed with the removeAirPressureCallback() function.

public callback BrickletBarometer.AltitudeCallback
Parameters:altitude -- int

This callback is triggered periodically with the period that is set by setAltitudeCallbackPeriod(). The parameter is the altitude of the air pressure sensor.

The AltitudeCallback callback is only triggered if the altitude has 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 addAltitudeCallback() function. An added callback function can be removed with the removeAltitudeCallback() function.

public callback BrickletBarometer.AirPressureReachedCallback
Parameters:airPressure -- int

This callback is triggered when the threshold as set by setAirPressureCallbackThreshold() is reached. The parameter is the air pressure of the air pressure sensor.

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

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 addAirPressureReachedCallback() function. An added callback function can be removed with the removeAirPressureReachedCallback() function.

public callback BrickletBarometer.AltitudeReachedCallback
Parameters:altitude -- int

This callback is triggered when the threshold as set by setAltitudeCallbackThreshold() is reached. The parameter is the altitude of the air pressure sensor.

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

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 addAltitudeReachedCallback() function. An added callback function can be removed with the removeAltitudeReachedCallback() function.

Constants

public static final int BrickletBarometer.DEVICE_IDENTIFIER

This constant is used to identify a Barometer Bricklet.

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

public static final String BrickletBarometer.DEVICE_DISPLAY_NAME

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