Java - Rotary Encoder Bricklet

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

public class ExampleSimple {
    private static final String HOST = "localhost";
    private static final int PORT = 4223;

    // Change XYZ to the UID of your Rotary Encoder Bricklet
    private static final String UID = "XYZ";

    // 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
        BrickletRotaryEncoder re = new BrickletRotaryEncoder(UID, ipcon); // Create device object

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

        // Get current count without reset
        int count = re.getCount(false); // Can throw com.tinkerforge.TimeoutException
        System.out.println("Count: " + count);

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

Callback

Download (ExampleCallback.java)

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import com.tinkerforge.IPConnection;
import com.tinkerforge.BrickletRotaryEncoder;

public class ExampleCallback {
    private static final String HOST = "localhost";
    private static final int PORT = 4223;

    // Change XYZ to the UID of your Rotary Encoder Bricklet
    private static final String UID = "XYZ";

    // 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
        BrickletRotaryEncoder re = new BrickletRotaryEncoder(UID, ipcon); // Create device object

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

        // Add count listener
        re.addCountListener(new BrickletRotaryEncoder.CountListener() {
            public void count(int count) {
                System.out.println("Count: " + count);
            }
        });

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

        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 BrickletRotaryEncoder(String uid, IPConnection ipcon)

Creates an object with the unique device ID uid:

BrickletRotaryEncoder rotaryEncoder = new BrickletRotaryEncoder("YOUR_DEVICE_UID", ipcon);

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

public int getCount(boolean reset)

Returns the current count of the encoder. If you set reset to true, the count is set back to 0 directly after the current count is read.

The encoder has 24 steps per rotation

Turning the encoder to the left decrements the counter, so a negative count is possible.

public boolean isPressed()

Returns true if the button is pressed and false otherwise.

It is recommended to use the PressedListener and ReleasedListener listeners to handle the button.

Advanced Functions

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.

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:

  • BrickletRotaryEncoder.FUNCTION_SET_COUNT_CALLBACK_PERIOD = 2
  • BrickletRotaryEncoder.FUNCTION_SET_COUNT_CALLBACK_THRESHOLD = 4
  • BrickletRotaryEncoder.FUNCTION_SET_DEBOUNCE_PERIOD = 6
public void setResponseExpectedAll(boolean responseExpected)

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

public BrickletRotaryEncoder.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 setCountCallbackPeriod(long period)

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

The CountListener listener is only triggered if the count has changed since the last triggering.

The default value is 0.

public long getCountCallbackPeriod()

Returns the period as set by setCountCallbackPeriod().

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

Sets the thresholds for the CountReachedListener listener.

The following options are possible:

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

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

The following constants are available for this function:

  • BrickletRotaryEncoder.THRESHOLD_OPTION_OFF = 'x'
  • BrickletRotaryEncoder.THRESHOLD_OPTION_OUTSIDE = 'o'
  • BrickletRotaryEncoder.THRESHOLD_OPTION_INSIDE = 'i'
  • BrickletRotaryEncoder.THRESHOLD_OPTION_SMALLER = '<'
  • BrickletRotaryEncoder.THRESHOLD_OPTION_GREATER = '>'
public BrickletRotaryEncoder.CountCallbackThreshold getCountCallbackThreshold()

Returns the threshold as set by setCountCallbackThreshold().

The following constants are available for this function:

  • BrickletRotaryEncoder.THRESHOLD_OPTION_OFF = 'x'
  • BrickletRotaryEncoder.THRESHOLD_OPTION_OUTSIDE = 'o'
  • BrickletRotaryEncoder.THRESHOLD_OPTION_INSIDE = 'i'
  • BrickletRotaryEncoder.THRESHOLD_OPTION_SMALLER = '<'
  • BrickletRotaryEncoder.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 listener

  • CountReachedListener

is triggered, if the thresholds

keeps 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 BrickletRotaryEncoder.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 BrickletRotaryEncoder.CountListener()

This listener can be added with the addCountListener() function. An added listener can be removed with the removeCountListener() function.

public void count(int count)

This listener is triggered periodically with the period that is set by setCountCallbackPeriod(). The parameter is the count of the encoder.

The CountListener listener is only triggered if the count has changed since the last triggering.

public class BrickletRotaryEncoder.CountReachedListener()

This listener can be added with the addCountReachedListener() function. An added listener can be removed with the removeCountReachedListener() function.

public void countReached(int count)

This listener is triggered when the threshold as set by setCountCallbackThreshold() is reached. The parameter is the count of the encoder.

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

public class BrickletRotaryEncoder.PressedListener()

This listener can be added with the addPressedListener() function. An added listener can be removed with the removePressedListener() function.

public void pressed()

This listener is triggered when the button is pressed.

public class BrickletRotaryEncoder.ReleasedListener()

This listener can be added with the addReleasedListener() function. An added listener can be removed with the removeReleasedListener() function.

public void released()

This listener is triggered when the button is released.

Constants

public static final int BrickletRotaryEncoder.DEVICE_IDENTIFIER

This constant is used to identify a Rotary Encoder Bricklet.

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

public static final String BrickletRotaryEncoder.DEVICE_DISPLAY_NAME

This constant represents the human readable name of a Rotary Encoder Bricklet.