Java - LED Strip Bricklet

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

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

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

        // Set first 10 LEDs to green
        short[] r = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
        short[] g = {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 0, 0, 0, 0, 0, 0};
        short[] b = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
        ledStrip.setRGBValues(0, (short)10, r, g, b);

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

Callback

Download (ExampleCallback.java)

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import com.tinkerforge.BrickletLEDStrip;
import com.tinkerforge.IPConnection;

public class ExampleCallback {
    private static final String HOST = "localhost";
    private static final int PORT = 4223;
    private static final String UID = "XYZ"; // Change to your UID
    private static final int NUM_LEDS = 16;
    private static int rIndex = 0;
    private static short[] r = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
    private static short[] g = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
    private static short[] b = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
    
    // 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
        final BrickletLEDStrip ledStrip = new BrickletLEDStrip(UID, ipcon); // Create device object

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

        // Frame rendered callback, is called when a new frame was rendered
        // We increase the index of one blue LED with every frame
        ledStrip.addFrameRenderedListener(new BrickletLEDStrip.FrameRenderedListener() {
            public void frameRendered(int length) {
                b[rIndex] = 0;
                if(rIndex == NUM_LEDS-1) {
                    rIndex = 0;
                } else {
                    rIndex++;
                }
                b[rIndex] = 255;

                // Set new data for next render cycle
                try {
                    ledStrip.setRGBValues(0, (short)NUM_LEDS, r, g, b);
                } catch(Exception e) {
                    System.out.println(e);
                }
            }
        });

        // Set frame duration to 50ms (20 frames per second)
        ledStrip.setFrameDuration(50);

        // Set initial rgb values to get started
        ledStrip.setRGBValues(0, (short)NUM_LEDS, r, g, b);

        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 BrickletLEDStrip(String uid, IPConnection ipcon)

Creates an object with the unique device ID uid:

BrickletLEDStrip ledStrip = new BrickletLEDStrip("YOUR_DEVICE_UID", ipcon);

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

public void setRGBValues(int index, short length, short[] r, short[] g, short[] b)

Sets the rgb values for the LEDs with the given length starting from index.

The maximum length is 16, the index goes from 0 to 319 and the rgb values have 8 bits each.

Example: If you set

  • index to 5,
  • length to 3,
  • r to [255, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
  • g to [0, 255, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0] and
  • b to [0, 0, 255, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]

the LED with index 5 will be red, 6 will be green and 7 will be blue.

Note

Depending on the LED circuitry colors can be permuted.

The colors will be transfered to actual LEDs when the next frame duration ends, see setFrameDuration().

Generic approach:

  • Set the frame duration to a value that represents the number of frames per second you want to achieve.
  • Set all of the LED colors for one frame.
  • Wait for the FrameRenderedListener listener.
  • Set all of the LED colors for next frame.
  • Wait for the FrameRenderedListener listener.
  • and so on.

This approach ensures that you can change the LED colors with a fixed frame rate.

The actual number of controllable LEDs depends on the number of free Bricklet ports. See here for more information. A call of setRGBValues() with index + length above the bounds is ignored completely.

public BrickletLEDStrip.RGBValues getRGBValues(int index, short length)

Returns the rgb with the given length starting from the given index.

The values are the last values that were set by setRGBValues().

The returned object has the public member variables short[] r, short[] g and short[] b.

public void setFrameDuration(int duration)

Sets the frame duration in ms.

Example: If you want to achieve 20 frames per second, you should set the frame duration to 50ms (50ms * 20 = 1 second).

For an explanation of the general approach see setRGBValues().

Default value: 100ms (10 frames per second).

public int getFrameDuration()

Returns the frame duration as set by setFrameDuration().

public int getSupplyVoltage()

Returns the current supply voltage of the LEDs. The voltage is given in mV.

public void setClockFrequency(long frequency)

Sets the frequency of the clock in Hz. The range is 10000Hz (10kHz) up to 2000000Hz (2MHz).

The Bricklet will choose the nearest achievable frequency, which may be off by a few Hz. You can get the exact frequency that is used by calling getClockFrequency().

If you have problems with flickering LEDs, they may be bits flipping. You can fix this by either making the connection between the LEDs and the Bricklet shorter or by reducing the frequency.

With a decreasing frequency your maximum frames per second will decrease too.

The default value is 1.66MHz.

Note

The frequency in firmware version 2.0.0 is fixed at 2MHz.

New in version 2.0.1 (Plugin).

public long getClockFrequency()

Returns the currently used clock frequency as set by setClockFrequency().

New in version 2.0.1 (Plugin).

public void setChipType(int chip)

Sets the type of the led driver chip. We currently support the chips

  • WS2801 (chip = 2801),
  • WS2811 (chip = 2811) and
  • WS2812 (chip = 2812).

The WS2812 is sometimes also called "NeoPixel", a name coined by Adafruit.

The default value is WS2801 (chip = 2801).

The following constants are available for this function:

  • BrickletLEDStrip.CHIP_TYPE_WS2801 = 2801
  • BrickletLEDStrip.CHIP_TYPE_WS2811 = 2811
  • BrickletLEDStrip.CHIP_TYPE_WS2812 = 2812

New in version 2.0.2 (Plugin).

public int getChipType()

Returns the currently used chip type as set by setChipType().

The following constants are available for this function:

  • BrickletLEDStrip.CHIP_TYPE_WS2801 = 2801
  • BrickletLEDStrip.CHIP_TYPE_WS2811 = 2811
  • BrickletLEDStrip.CHIP_TYPE_WS2812 = 2812

New in version 2.0.2 (Plugin).

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 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:

  • BrickletLEDStrip.FUNCTION_SET_RGB_VALUES = 1
  • BrickletLEDStrip.FUNCTION_SET_FRAME_DURATION = 3
  • BrickletLEDStrip.FUNCTION_SET_CLOCK_FREQUENCY = 7
  • BrickletLEDStrip.FUNCTION_SET_CHIP_TYPE = 9
public void setResponseExpectedAll(boolean responseExpected)

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

public BrickletLEDStrip.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.

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 BrickletLEDStrip.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 BrickletLEDStrip.FrameRenderedListener()

This listener can be added with the addFrameRenderedListener() function. An added listener can be removed with the removeFrameRenderedListener() function.

public void frameRendered(int length)

This listener is triggered directly after a new frame is rendered.

You should send the data for the next frame directly after this listener was triggered.

For an explanation of the general approach see setRGBValues().

Constants

public static final int BrickletLEDStrip.DEVICE_IDENTIFIER

This constant is used to identify a LED Strip 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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