Addressable LED minimal installation

[MysDevLop]

I am setting up a program to run on a Raspberry PI 4 (2G ram), written in Java. The OS image installation is from Pi4J https://pi4j.com

I need to be able to output my LED string colours to the PWM port, ideally both. I also am planning to use a multiplexor, so I need to be able to toggle the four address pins.

I have looked through your project, and I have extracted the classes which flow from the AddressableLED class:

 LEDLibrary/AddressableLED.java
 LEDLibrary/AddressableLEDBuffer.java
 LEDLibrary/AddressableLEDJNI.java
 LEDLibrary/AllianceStationID.java
 LEDLibrary/Color.java
 LEDLibrary/Color8Bit.java
 LEDLibrary/ControlWord.java
 LEDLibrary/DIOJNI.java
 LEDLibrary/DriverStationJNI.java
 LEDLibrary/FRCNetComm.java
 LEDLibrary/HAL.java
 LEDLibrary/JNIWrapper.java
 LEDLibrary/MatchInfoData.java
 LEDLibrary/MathUtil.java
 LEDLibrary/PWMConfigDataResult.java
 LEDLibrary/PWMJNI.java
 LEDLibrary/RuntimeDetector.java
 LEDLibrary/RuntimeLoader.java

And here I am stuck. Following the execution path leads me to a supposed dead end, that is an interface. There is no code to be executed, just:

public class AddressableLEDJNI extends JNIWrapper
{
  /**
   * Starts the output.
   *
   * <p>
   * The output writes continuously.
   *
   * @param handle
   *            the Addressable LED handle
   * @see "HAL_StartAddressableLEDOutput"
   */
  public static native void start( int handle );
}

Obviously it works, But I am at a loss to what I am missing.

I know that the library is there for controlling a robot, but I only need to LED strip code, and some way to toggle the multiplexor address pins.

Thanks in advance.

[Kevin-OConnor]

I do not recommend attempting to use WPILib as an example for controlling Addressable LEDs. As you've noticed, WPILib uses JNI to interface with C++ components of WPILIb, and these further interface with the closed source Network Communication module and FPGA image provided by NI for the roboRIO. The actual LED timing is handled in the FPGA. I would recommend searching for other examples closer to what you are trying to do, usually by searching the LED part number you are using + "Raspberry pi" such as "WS2812b raspberry pi".

[TheTripleV]

If you are on a Raspberry Pi, I would recommend using Python. Here's an example https://github.com/CtrlZ-FRC4096/Robot-2023-Public/blob/main/rpi/leds/robot_leds1.py

Also, have you considered just running your LEDs off of the roborio, where addressableled is supported?

[MysDevLop]

Thanks for the quick response. I don't know Python, which is why I am using Java.

The program will run for an indefinite time, so JRE startup is irrelevant. I also have a GUI written in Swing. It reads JSON from a server, processes that, then sets up an LED string.

It all works, but I just need to get to the LEDs...

[ThadHouse]

As said above, the LED code here is written for a very specific piece of hardware that is not a raspberry pi. So you’d need to look up ws2812 Java libraries that are supported on raspberry pi.

[TechplexEngineer]

From the Pi4j website you may want to examine this example: https://pi4j.com/examples/components/ledstrip/

[MysDevLop]

I have seen this, and I have managed to download the code base.

However the code snippet has several ambiguous calls. It would have been more helpful to have a complete code example which includes things like what and where does pi4j come from. final LedStrip ledStrip = new LedStrip(pi4j, pixels, 0.5);

Also, their code has a lot of warning messages which show up in Eclipse, things like generic usage which is missing parameters. Missing imports, which then have to be located in the great wide web. The referral to "Photobooth" is a broken link, nor does GitHub know about it.

Regardless, my search continues...

:-))