Arduino.java

//  Copyright 2017-2018 Pavitra, All rights reserved
//  Released under the Apache License, Version 2.0
//  http://www.apache.org/licenses/LICENSE-2.0

package com.pavitra;

import android.content.Context;
import android.util.Log;

import com.physicaloid.lib.*;

import com.google.appinventor.components.annotations.*;
import com.google.appinventor.components.runtime.*;
import com.google.appinventor.components.common.*;

import java.io.UnsupportedEncodingException;

@DesignerComponent(version = 6,
    description = "Arduino USB Serial Extension by Pavitra.",
    category = ComponentCategory.EXTENSION,
    nonVisible = true,
    iconName = "images/extension.png")
@SimpleObject(external = true)
@UsesLibraries(libraries = "physicaloid.jar")
public class Arduino extends AndroidNonvisibleComponent implements Component {
    private static final String LOG_TAG = "Arduino USB Serial Extension";

    private Context context;

    Physicaloid mPhysicaloid;

    private int baudRate = 9600;

    public Arduino(ComponentContainer container) {
        super(container.$form());
        context = container.$context();
        Log.d(LOG_TAG, "Created");
    }

    @SimpleFunction
    public void Initialize() {
        mPhysicaloid = new Physicaloid(context);
        Log.d(LOG_TAG, "Initialized");
    }

    @SimpleFunction
    public boolean Open() {
        Log.d(LOG_TAG, "Opening connection");
        return mPhysicaloid.open();
    }

    @SimpleFunction
    public boolean Close() {
        Log.d(LOG_TAG, "Closing connection");
        return mPhysicaloid.close();
    }

    @SimpleFunction(description = "Default baud rate is 9600 bps")
    public void BaudRate(int baudRate) {
        this.baudRate = baudRate;
        mPhysicaloid.setBaudrate(baudRate);
        Log.d(LOG_TAG, "Baud Rate: " + baudRate);
    }

    @SimpleFunction(description = "Read from Serial")
    public void Read() {
        byte[] buf = new byte[256];
        boolean success = true;
        String data = "";

        if (mPhysicaloid.read(buf) > 0) {
            try {
                data = new String(buf, "UTF-8");
            } catch (UnsupportedEncodingException e) {
                success = false;
                Log.e(LOG_TAG, e.getMessage());
            }
        } else {
            success = false;
        }
        
        AfterRead(success, data);
    }

    @SimpleFunction(description = "Write Data to Serial")
    public void Write(String writeData) {
        if (!writeData.isEmpty()) {
            byte[] buf = writeData.getBytes();
            mPhysicaloid.write(buf);
        }
    }

    @SimpleFunction
    public boolean IsOpened() {
        return mPhysicaloid.isOpened();
    }

    @SimpleEvent
    public void AfterRead(boolean success, String data) {
        EventDispatcher.dispatchEvent(this, "AfterRead", success, data);
    }
}

Library JAR: https://cdn.instructables.com/ORIG/FNM/9MXQ/IJUCPKBD/FNM9MXQIJUCPKBD.jar
(from http://www.instructables.com/id/Arduin-Adroid-USB-Serial-Communication/)

Hey, Trying to work on kodular with arduino but I don't get prompt to ask access to usb for serial.
Anything I miss?