SerialPipe

Serial-based communication pipe for WLED devices. Communicates over USB serial, sending and receiving newline-delimited JSON.

Implements the WledPipe interface.

Package

robowled.wledpipe.SerialPipe

Constructor

SerialPipe(SerialPort.Port usbPort, int baudRate)

Creates a SerialPipe connected to a WLED device via USB serial.

Parameters:

Parameter Type Description
usbPort SerialPort.Port The WPILib serial port (e.g., SerialPort.Port.kUSB)
baudRate int The baud rate for serial communication (e.g., 115200)

Example:

import robowled.wledpipe.SerialPipe;
import edu.wpi.first.wpilibj.SerialPort;

// Create a serial connection on USB port at 115200 baud
SerialPipe wled = new SerialPipe(SerialPort.Port.kUSB, 115200);

Available Ports:

Port Description
SerialPort.Port.kUSB Primary USB port on roboRIO
SerialPort.Port.kUSB1 Secondary USB port
SerialPort.Port.kUSB2 Tertiary USB port
SerialPort.Port.kMXP MXP expansion port serial
SerialPort.Port.kOnboard Onboard RS-232 port

Methods

All methods are defined by the WledPipe interface.

sendGson(JsonElement json)

Sends a Gson JsonElement as JSON over the serial port, followed by a newline.

Parameters:

Parameter Type Description
json JsonElement The Gson JSON element to send

Throws: Exception if sending fails

Example:

import com.google.gson.JsonObject;

// Build a JSON command using Gson
JsonObject command = new JsonObject();
command.addProperty("on", true);
command.addProperty("bri", 255);

wled.sendGson(command);
// Sends: {"on":true,"bri":255}\n

sendString(String str)

Sends a raw string over the serial port.

Parameters:

Parameter Type Description
str String The string to send

Throws: Exception if sending fails

Example:

// Send a raw JSON command
wled.sendString("{\"ps\":1}\n");

// Activate an effect
wled.sendString("{\"seg\":[{\"fx\":42}]}\n");

tryReadString()

Non-blocking read operation. Call periodically to check for incoming data. Returns a complete line when available.

Returns: String - A complete line (without newline), or null if no complete line is available

Throws: Exception if reading fails

Example:

// In a periodic method
@Override
public void periodic() {
    try {
        String response = wled.tryReadString();
        if (response != null) {
            System.out.println("WLED response: " + response);
        }
    } catch (Exception e) {
        // Handle error
    }
}

tryReadGson()

Non-blocking read that parses the response as a Gson JsonElement.

Returns: JsonElement - A parsed JSON element, or null if no complete line is available

Throws: Exception if reading or parsing fails

Example:

import com.google.gson.JsonElement;
import com.google.gson.JsonObject;

// In a periodic method
@Override
public void periodic() {
    try {
        JsonElement response = wled.tryReadGson();
        if (response != null && response.isJsonObject()) {
            JsonObject state = response.getAsJsonObject();
            boolean isOn = state.get("on").getAsBoolean();
            int brightness = state.get("bri").getAsInt();
            System.out.println("WLED on=" + isOn + ", bri=" + brightness);
        }
    } catch (Exception e) {
        // Handle error
    }
}

Complete Example

import robowled.wledpipe.SerialPipe;
import edu.wpi.first.wpilibj.SerialPort;
import edu.wpi.first.wpilibj2.command.SubsystemBase;

public class LedSubsystem extends SubsystemBase {
    private final SerialPipe wled;

    public LedSubsystem() {
        wled = new SerialPipe(SerialPort.Port.kUSB, 115200);
    }

    public void setPreset(int presetNumber) {
        try {
            wled.sendString("{\"ps\":" + presetNumber + "}\n");
        } catch (Exception e) {
            System.err.println("Failed to set preset: " + e.getMessage());
        }
    }

    public void setColor(int r, int g, int b) {
        try {
            String json = String.format(
                "{\"seg\":[{\"col\":[[%d,%d,%d]]}]}\n", r, g, b);
            wled.sendString(json);
        } catch (Exception e) {
            System.err.println("Failed to set color: " + e.getMessage());
        }
    }

    public void setBrightness(int brightness) {
        try {
            wled.sendString("{\"bri\":" + brightness + "}\n");
        } catch (Exception e) {
            System.err.println("Failed to set brightness: " + e.getMessage());
        }
    }

    @Override
    public void periodic() {
        try {
            String response = wled.tryReadString();
            if (response != null) {
                // Process any responses from WLED
            }
        } catch (Exception e) {
            // Silently ignore read errors in periodic
        }
    }
}

See Also