Java - Segment Display 4x7 Bricklet

This is the description of the Java API bindings for the Segment Display 4x7 Bricklet. General information and technical specifications for the Segment Display 4x7 Bricklet are summarized in its hardware description.

An installation guide for the Java API bindings is part of their general description.


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


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import com.tinkerforge.IPConnection;
import com.tinkerforge.BrickletSegmentDisplay4x7;

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

    // Change XYZ to the UID of your Segment Display 4x7 Bricklet
    private static final String UID = "XYZ";
    private static final byte[] DIGITS = {0x3f,0x06,0x5b,0x4f,
                                          0x39,0x5e,0x79,0x71}; // 0~9,A,b,C,d,E,F

    // 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
        BrickletSegmentDisplay4x7 sd =
          new BrickletSegmentDisplay4x7(UID, ipcon); // Create device object

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

        // Write "4223" to the display with full brightness without colon
        short[] segments = {DIGITS[4], DIGITS[2], DIGITS[2], DIGITS[3]};
        sd.setSegments(segments, (short)7, false);

        System.out.println("Press key to exit");;


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 BrickletSegmentDisplay4x7(String uid, IPConnection ipcon)

Creates an object with the unique device ID uid:

BrickletSegmentDisplay4x7 segmentDisplay4x7 = new BrickletSegmentDisplay4x7("YOUR_DEVICE_UID", ipcon);

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

public void setSegments(short[] segments, short brightness, boolean colon)

The 7-segment display can be set with bitmaps. Every bit controls one segment:

Bit order of one segment

For example to set a "5" you would want to activate segments 0, 2, 3, 5 and 6. This is represented by the number 0b01101101 = 0x6d = 109.

The brightness can be set between 0 (dark) and 7 (bright). The colon parameter turns the colon of the display on or off.

public BrickletSegmentDisplay4x7.Segments getSegments()

Returns the segment, brightness and color data as set by setSegments().

The returned object has the public member variables short[] segments, short brightness and boolean colon.

Advanced Functions

public void startCounter(short valueFrom, short valueTo, short increment, long length)

Starts a counter with the from value that counts to the to value with the each step incremented by increment. The length of the increment is given in ms.

Example: If you set from to 0, to to 100, increment to 1 and length to 1000, a counter that goes from 0 to 100 with one second pause between each increment will be started.

The maximum values for from, to and increment is 9999, the minimum value is -999.

Using a negative increment allows to count backwards.

You can stop the counter at every time by calling setSegments().

public int getCounterValue()

Returns the counter value that is currently shown on the display.

If there is no counter running a 0 will be returned.

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:

  • BrickletSegmentDisplay4x7.FUNCTION_SET_SEGMENTS = 1
  • BrickletSegmentDisplay4x7.FUNCTION_START_COUNTER = 3
public void setResponseExpectedAll(boolean responseExpected)

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

public BrickletSegmentDisplay4x7.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 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 BrickletSegmentDisplay4x7.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.


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 BrickletSegmentDisplay4x7.CounterFinishedListener()

This listener can be added with the addCounterFinishedListener() function. An added listener can be removed with the removeCounterFinishedListener() function.

public void counterFinished()

This listener is triggered when the counter (see startCounter()) is finished.


public static final int BrickletSegmentDisplay4x7.DEVICE_IDENTIFIER

This constant is used to identify a Segment Display 4x7 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 BrickletSegmentDisplay4x7.DEVICE_DISPLAY_NAME

This constant represents the human readable name of a Segment Display 4x7 Bricklet.