MATLAB/Octave - Hall Effect Bricklet

This is the description of the MATLAB/Octave API bindings for the Hall Effect Bricklet. General information and technical specifications for the Hall Effect 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.BrickletHallEffect;

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

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

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

    % Get current edge count without reset
    count = he.getEdgeCount(false);
    fprintf('Count: %i\n', count);

    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.BrickletHallEffect;

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

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

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

    % Register edge count callback to function cb_edge_count
    set(he, 'EdgeCountCallback', @(h, e) cb_edge_count(e));

    % Set period for edge count callback to 0.05s (50ms)
    % Note: The edge count callback is only called every 0.05 seconds
    %       if the edge count has changed since the last call!
    he.setEdgeCountCallbackPeriod(50);

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

% Callback function for edge count callback
function cb_edge_count(e)
    fprintf('Count: %i\n', e.count);
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 Hall Effect Bricklet

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

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

    % Get current edge count without reset
    count = he.getEdgeCount(false);
    fprintf("Count: %d\n", java2int(count));

    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 Hall Effect Bricklet

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

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

    % Register edge count callback to function cb_edge_count
    he.addEdgeCountCallback(@cb_edge_count);

    % Set period for edge count callback to 0.05s (50ms)
    % Note: The edge count callback is only called every 0.05 seconds
    %       if the edge count has changed since the last call!
    he.setEdgeCountCallbackPeriod(50);

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

% Callback function for edge count callback
function cb_edge_count(e)
    fprintf("Count: %d\n", java2int(e.count));
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

public class BrickletHallEffect(String uid, IPConnection ipcon)

Creates an object with the unique device ID uid.

In MATLAB:

import com.tinkerforge.BrickletHallEffect;

hallEffect = BrickletHallEffect('YOUR_DEVICE_UID', ipcon);

In Octave:

hallEffect = java_new("com.tinkerforge.BrickletHallEffect", "YOUR_DEVICE_UID", ipcon);

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

public boolean getValue()

Returns true if a magnetic field of 35 Gauss (3.5mT) or greater is detected.

public long getEdgeCount(boolean resetCounter)

Returns the current value of the edge counter. You can configure edge type (rising, falling, both) that is counted with setEdgeCountConfig().

If you set the reset counter to true, the count is set back to 0 directly after it is read.

Advanced Functions

public void setEdgeCountConfig(short edgeType, short debounce)

The edge type parameter configures if rising edges, falling edges or both are counted. Possible edge types are:

  • 0 = rising (default)
  • 1 = falling
  • 2 = both

A magnetic field of 35 Gauss (3.5mT) or greater causes a falling edge and a magnetic field of 25 Gauss (2.5mT) or smaller causes a rising edge.

If a magnet comes near the Bricklet the signal goes low (falling edge), if a magnet is removed from the vicinity the signal goes high (rising edge).

The debounce time is given in ms.

Configuring an edge counter resets its value to 0.

If you don't know what any of this means, just leave it at default. The default configuration is very likely OK for you.

Default values: 0 (edge type) and 100ms (debounce time)

The following constants are available for this function:

  • BrickletHallEffect.EDGE_TYPE_RISING = 0
  • BrickletHallEffect.EDGE_TYPE_FALLING = 1
  • BrickletHallEffect.EDGE_TYPE_BOTH = 2
public BrickletHallEffect.EdgeCountConfig getEdgeCountConfig()

Returns the edge type and debounce time as set by setEdgeCountConfig().

The following constants are available for this function:

  • BrickletHallEffect.EDGE_TYPE_RISING = 0
  • BrickletHallEffect.EDGE_TYPE_FALLING = 1
  • BrickletHallEffect.EDGE_TYPE_BOTH = 2

The returned object has the public member variables short edgeType and short debounce.

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:

  • BrickletHallEffect.FUNCTION_SET_EDGE_COUNT_CONFIG = 3
  • BrickletHallEffect.FUNCTION_SET_EDGE_INTERRUPT = 5
  • BrickletHallEffect.FUNCTION_SET_EDGE_COUNT_CALLBACK_PERIOD = 7
public void setResponseExpectedAll(boolean responseExpected)

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

public BrickletHallEffect.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 setEdgeInterrupt(long edges)

Sets the number of edges until an interrupt is invoked.

If edges is set to n, an interrupt is invoked for every n-th detected edge.

If edges is set to 0, the interrupt is disabled.

Default value is 0.

public long getEdgeInterrupt()

Returns the edges as set by setEdgeInterrupt().

public void setEdgeCountCallbackPeriod(long period)

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

The EdgeCountCallback callback is only triggered if the edge count has changed since the last triggering.

The default value is 0.

public long getEdgeCountCallbackPeriod()

Returns the period as set by setEdgeCountCallbackPeriod().

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 BrickletHallEffect.EdgeCountCallback
Parameters:
  • count -- long
  • value -- boolean

This callback is triggered periodically with the period that is set by setEdgeCountCallbackPeriod(). The parameters are the current count and the current value (see getValue() and getEdgeCount()).

The EdgeCountCallback callback is only triggered if the count or value 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 addEdgeCountCallback() function. An added callback function can be removed with the removeEdgeCountCallback() function.

Constants

public static final int BrickletHallEffect.DEVICE_IDENTIFIER

This constant is used to identify a Hall Effect 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 BrickletHallEffect.DEVICE_DISPLAY_NAME

This constant represents the human readable name of a Hall Effect Bricklet.