Neurolab data transfer – Establishing serial communication between Arduino and Android

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  • Post category:FOSSASIA

In the development process of the Neurolab Android, we needed an Arduino-Android connection for transfer of data from datasets which included String and float data type values. In this blog post, I will show you how to establish a serial communication channel between

Android and Arduino through USB cable through which we can transmit data bidirectionally.



  1. Android Phone
  2. Arduino (theoretically from any type, but I’ll be using Arduino Uno)
  3. USB 2.0 Cable Type A/B (for Arduino)
  4. OTG Cable (On The Go)
  5. Normal USB Cable (for transferring the data from Android Studio to your phone)


  1. Android Studio
  2. Arduino IDE

Wiring and Setup

Wiring must be established in the following way:

                                                                                 Figure: Android-Arduino Setup

Working on the Android Side

We would be using the UsbSerial Library by felHR85 for establishing serial


1. Adding the dependency:

a) Add the following line of code to your app level build.gradle file.

implementation "com.github.felHR85:UsbSerial:$rootProject.usbSerialLibraryVersion"

Note: The ‘usbSerialLibraryVersion’ may change from time to time. Please keep your project with the latest library version. Updates can be found here.

b) Add jitpack to your file.

allprojects {
   repositories {
       maven { url "" }

2. Working with Arduino:

We need to program the Arduino to send and receive data. We achieve that with the help of Arduino IDE as mentioned above. Verify, compile and upload a sketch to the Arduino for sending and receiving data. If you are a complete beginner in Arduino programming, there are example sketches for this same purpose. Load an example sketch from under the communication segment and choose the serial communication sketch. Here, we will be working with a simple sketch for the Arduino such that it simply echoes whatever it receives on the serial port. Here is sketch code:

// the setup routine runs once when you press reset:
void setup() {
  // initialize serial communication at 9600 bits per second:

// the loop routine runs over and over again forever:
void loop() {
  char incomingByte;
   // If there is a data stored in the serial receive buffer, read it and print it to the serial port as human-readable ASCII text.
    incomingByte =;

Feel free to compile and upload it to your own Arduino.

2. Working with Android:

  1. Firstly, we need an USBManager instance initialized with the system service – ‘USB_SERVICE’. This needs to be done in an Activity (preferably main) so that this instance can be passed to the Communication Handler class, which we are going to create next.
  2. Now, we will be working with a class for handling the serial communications with our Android device and the Arduino board. We would pass the USBManager instance to this class wherein work will be done with that to find the USBDevice and USBDeviceConnection

Starting with, we need to search for any attached Arduino devices to the Android device. We create a method for this and use the ‘getDevicesList’ callback to achieve this in the following way:

public void searchForArduinoDevice(Context context) {
        HashMap usbDevices = usbManager.getDeviceList();

        if (!usbDevices.isEmpty()) {
            boolean keep = true;
            for (Object object : usbDevices.entrySet()) {
                Map.Entry<String, UsbDevice> entry = (Map.Entry<String, UsbDevice>) object;
                device = entry.getValue();

                int deviceVID = device.getVendorId();
                if (deviceVID == ARDUINO_DEVICE_ID) { //Arduino Vendor ID = 0x2341
                    PendingIntent pi = PendingIntent.getBroadcast(context, 0,
                            new Intent(ACTION_USB_PERMISSION), 0);
                    usbManager.requestPermission(device, pi);
                    keep = false;
                } else {
                    connection = null;
                    device = null;
                if (!keep)

c. Now, in the Activity where we will be testing or intend to work with the serial connection, we check for the usb permission in a broadcast receiver which is registered in the onCreate method of the activity along with an Intent Filter. The Intent filter has the usp permission as an action added to it.

usbCommunicationHandler = USBCommunicationHandler.getInstance(this, NeuroLab.getUsbManager());

        deviceConnector = new DeviceConnector(NeuroLab.getUsbManager());

        IntentFilter intentFilter = new IntentFilter();
        registerReceiver(broadcastReceiver, intentFilter);

d. In the onReceive callback of the broadcast receiver, if the usb permission is granted, we initialize the serial connection with a baud rate for our Arduino device. In this initialization method, we get the connection and serial port of the connected Arduino to the Android device with which we can work. The method is implemented in the following way:

public boolean initializeSerialConnection(int baudRate) {
        connection = usbManager.openDevice(device);
        serialPort = UsbSerialDevice.createUsbSerialDevice(device, connection);
        if (serialPort != null) {
            if ( { 
            } else {
                Log.d("SERIAL", "PORT NOT OPEN");
                return false;
        } else {
            Log.d("SERIAL", "PORT IS NULL");
            return false;
        return true;

e. Now, with this ‘serialPort’ we can read data from the Arduino in the UsbReadCallback callback from the USBSerialInterface. The data is read in the form of array of bytes. This read data can be used to carry out the various functionalities we want to achieve.

With the above steps we can establish a serial connection between Android and Arduino, transmit data from Arduino to Android device for processing.

The whole working source code of the Neurolab Android project can be found here:

Thanks for taking the time to read this blog. Hope it was able to make some good contributions to your knowledge base.



Tags: FOSSASIA, Neurolab, GSOC19, Open-source, Arduino, Serial terminal

Continue Reading Neurolab data transfer – Establishing serial communication between Arduino and Android

Implementing pagination with Retrofit in Eventyay Attendee

Pagination (Paging) is a common and powerful technique in Android Development when making HTTP requests or fetching data from the database. Eventyay Attendee has found many situations where data binding comes in as a great solution for our network calls with Retrofit. Let’s take a look at this technique.

  • Problems without Pagination in Android Development
  • Implementing Pagination with Kotlin with Retrofit
  • Results and GIF
  • Conclusions


Making HTTP requests to fetch data from the API is a basic work in any kind of application. With the mobile application, network data usage management is an important factor that affects the loading performance of the app. Without paging, all of the data are fetched even though most of them are not displayed on the screen. Pagination is a technique to load all the data in pages of limited items, which is much more efficient


Step 1:  Set up dependency in build.gradle

// Paging
implementation "androidx.paging:paging-runtime:$paging_version"
implementation "androidx.paging:paging-rxjava2:$paging_version"

Step 2:  Set up retrofit to fetch events from the API

fun searchEventsPaged(
   @Query("sort") sort: String,
   @Query("filter") eventName: String,
   @Query("page[number]") page: Int,
   @Query("page[size]") pageSize: Int = 5
): Single<List<Event>>

Step 3: Set up the DataSource

DataSource is a base class for loading data in the paging library from Android. In Eventyay, we use PageKeyedDataSource. It will fetch the data based on the number of pages and items per page with our default parameters. With PageKeyedDataSource, three main functions loadInitial(), loadBefore(), loadAfter() are used to to load each chunks of data.

class EventsDataSource(
   private val eventService: EventService,
   private val compositeDisposable: CompositeDisposable,
   private val query: String?,
   private val mutableProgress: MutableLiveData<Boolean>

) : PageKeyedDataSource<Int, Event>() {
   override fun loadInitial(
       params: LoadInitialParams<Int>,
       callback: LoadInitialCallback<Int, Event>
   ) {
       createObservable(1, 2, callback, null)

   override fun loadAfter(params: LoadParams<Int>, callback: LoadCallback<Int, Event>) {
       val page = params.key
       createObservable(page, page + 1, null, callback)

   override fun loadBefore(params: LoadParams<Int>, callback: LoadCallback<Int, Event>) {
       val page = params.key
       createObservable(page, page - 1, null, callback)

   private fun createObservable(
       requestedPage: Int,
       adjacentPage: Int,
       initialCallback: LoadInitialCallback<Int, Event>?,
       callback: LoadCallback<Int, Event>?
   ) {
       compositeDisposable +=
           eventService.getEventsByLocationPaged(query, requestedPage)
               .subscribe({ response ->
                   if (response.isEmpty()) mutableProgress.value = false
                   initialCallback?.onResult(response, null, adjacentPage)
                   callback?.onResult(response, adjacentPage)
               }, { error ->
                   Timber.e(error, "Fail on fetching page of events")

Step 4: Set up the Data Source Factory

DataSourceFactory is the class responsible for creating DataSource object so that we can create PagedList (A type of List used for paging) for events.

class EventsDataSourceFactory(
   private val compositeDisposable: CompositeDisposable,
   private val eventService: EventService,
   private val query: String?,
   private val mutableProgress: MutableLiveData<Boolean>
) : DataSource.Factory<Int, Event>() {
   override fun create(): DataSource<Int, Event> {
       return EventsDataSource(eventService, compositeDisposable, query, mutableProgress)

Step 5: Adapt the current change to the ViewModel. 

Previously, events fetched in List<Event> Object are now should be turned into PagedList<Event>.

sourceFactory = EventsDataSourceFactory(
val eventPagedList = RxPagedListBuilder(sourceFactory, config)

compositeDisposable += eventPagedList
   .doOnSubscribe {
       mutableProgress.value = true
       val currentPagedEvents = mutablePagedEvents.value
       if (currentPagedEvents == null) {
           mutablePagedEvents.value = it
       } else {
           mutablePagedEvents.value = currentPagedEvents
   }, {
       Timber.e(it, "Error fetching events")
       mutableMessage.value = resource.getString(R.string.error_fetching_events_message)

Step 6: Turn ListAdapter into PagedListAdapter

PageListAdapter is basically the same ListAdapter to update the UI of the events item but specifically used for Pagination. In here, List objects can also be null.

class EventsListAdapter : PagedListAdapter<Event, EventViewHolder>(EventsDiffCallback()) {

   var onEventClick: EventClickListener? = null
   var onFavFabClick: FavoriteFabClickListener? = null
   var onHashtagClick: EventHashTagClickListener? = null

   override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): EventViewHolder {
       val binding = ItemCardEventsBinding.inflate(LayoutInflater.from(parent.context), parent, false)
       return EventViewHolder(binding)

   override fun onBindViewHolder(holder: EventViewHolder, position: Int) {
       val event = getItem(position)
       if (event != null)
           holder.apply {
               bind(event, position)
               eventClickListener = onEventClick
               favFabClickListener = onFavFabClick
               hashTagClickListAdapter = onHashtagClick

    * The function to call when the adapter has to be cleared of items
   fun clear() {



Databinding is the way to go when working with a complex UI in Android Development. This helps reducing boilerplate code and to increase the readability of the code and the performance of the UI. One problem with data-binding is that sometimes, it is pretty hard to debug with unhelpful log messages. Hopefully, you can empower your UI in your project now with data-binding. 

Pagination is the way to go for fetching items from the API and making infinite scrolling. This helps reduce network usage and improve the performance of Android applications. And that’s it. I hope you can make your application more powerful with pagination. 


Open Event Codebase:


Google Codelab:

Continue Reading Implementing pagination with Retrofit in Eventyay Attendee

Dialog Component in SUSI.AI

Dialog Component in SUSI.AI is rendered in App.js to remove code redundancy. Redux is integrated in the Dialog component which allows us to open/close the dialog from any component by altering the modal states. This implementation allows us to get rid of the need of having dialog component in different components.

Redux Code

There are two actions and reducers which control the dialog component. Default state of isModalOpen is false and modalType is an empty string. To open a dialog modal the action openModal is dispatched, which sets isModalOpen to true and the modalType. To close a dialog modal the action closeModal is dispatched, which sets isModalOpen to default state i.e. false.

import { handleActions } from 'redux-actions';
import actionTypes from '../actionTypes';

const defaultState = {
 modalProps: {
   isModalOpen: false,
   modalType: '',

export default handleActions(
   [actionTypes.UI_OPEN_MODAL](state, { payload }) {
     return {
       modalProps: {
         isModalOpen: true,
   [actionTypes.UI_CLOSE_MODAL](state) {
     return {
       modalProps: defaultState.modalProps,

Shared Dialog Component

Dialog Modal can be opened from any component by dispatching an action. 

To open a Dialog Modal: this.props.actions.openModal({modalType: [modal name]});

To close a Dialog Modal: this.props.actions.closeModal();

Shared Dialog Component has a DialogData object which contains objects with two main properties : Dialog component and Dialog size. Other props can also be passed along with these two properties such as fullScreen. Dialog Content of different Dialogs are present in their respective folders. Each Dialog Content has a Title, Content and Actions.Different Dialog types present are:

  1. Confirm Delete with Input: This dialog modal is used when a user deletes account, device and skill. 
  2. Confirm Dialog: This dialog modal is used where confirmation is required from the user/admin such as on changing skill status, on password reset,etc.
  3. Share Dialog: This dialog modal opens up when the share icon is clicked in the chat.
  4. Standard Action Dialog: This dialog modal opens up on restore skill, delete feedback, system settings and bot.
  5. Tour Dialog: This dialog modal opens up SUSI.AI tour.

To add a new Dialog to DialogSection, the steps are:

  1. Import the Dialog Content Component
  2. Add the Dialog Component to DialogData object in the following manner:
const DialogData = {
[dialog componet name]: { Component : [imported dialog component name], size : [size of the Dialog Component]},

Code (Reduced)

const DialogData = {
  login: { Component: Login, size: 'sm' },
const DialogSection = props => {
 const {
   modalProps: { isModalOpen, modalType, ...otherProps },
 } = props;

 const getDialog = () => {
   if (isModalOpen) {
     return DialogData[modalType];
   return DialogData.noComponent;

 const { size, Component, fullScreen = false } = getDialog();

return (
      open={isModalOpen || !visited}
      onClose={isModalOpen ? actions.closeModal : actions.setVisited}
       {Component ? <Component {...otherProps} /> : null}

In conclusion, having a shared dialog component reduces redundant code and allows to have a similar Dialog UI across the repo. Also having one component managing all the dialogs removes the possibility of  two dialogs being fired up at once.


Continue Reading Dialog Component in SUSI.AI

My Devices in SUSI.AI

In this blog I’ll be explaining how to view, edit and delete connected devices from SUSI.AI webclient. To connect a device open up the SUSI.AI android app, and fill the details accordingly. Device can also be connected by logging in to your raspberry pi. Once the devices is connected you can edit, delete and access specific features for the device from the web client.

My Devices

All the connected devices can be viewed in My Devices tab in the Dashboard. In this tab all the devices connected to your account are listed in a table along with their locations on the map. Each device table row has three action buttons – view, edit and delete. Clicking on the view button takes to device specific page. Clicking on the edit button makes the fields name and room editable in table row. Clicking on the delete button opens a confirm with input dialog. Device can be deleted by entering the device name and clicking on delete.

To fetch all the device getUserDevices action is dispatched on component mounting which sets the reducer state devices in settings reducer. initialiseDevices function is called after all the devices are fetched from the server. This function creates an array of objects of devices with name, room, macId, latitude, longitude and location.

 componentDidMount() {
   const { accessToken, actions } = this.props;
   if (accessToken) {
       .then(({ payload }) => {
           loading: false,
           emptyText: 'You do not have any devices connected yet!',
       .catch(error => {
           loading: false,
           emptyText: 'Some error occurred while fetching the devices!',
   document.title =
     'My Devices - SUSI.AI - Open Source Artificial Intelligence for Personal  Assistants, Robots, Help Desks and Chatbots';
 initialiseDevices = () => {
   const { devices } = this.props;
   if (devices) {
     let devicesData = [];
     let deviceIds = Object.keys(devices);
     let invalidLocationDevices = 0;
     deviceIds.forEach(eachDevice => {
       const {
         geolocation: { latitude, longitude },
       } = devices[eachDevice];
       let deviceObj = {
         macId: eachDevice,
         deviceName: name,
         location: `${latitude}, ${longitude}`,
       if (
         deviceObj.latitude === 'Latitude not available.' ||
         deviceObj.longitude === 'Longitude not available.'
       ) {
         deviceObj.location = 'Not found';
       } else {
         deviceObj.latitude = parseFloat(latitude);
         deviceObj.longitude = parseFloat(longitude);

Device Page

Clicking on the view icon button in my devices redirects to mydevices/:macId. This page consists of device information in tabular format, local configuration settings and location of the device on the map. User can edit and delete the device from actions present in table. Local configuration settings can be accessed only if the user is logged in the local server.

Edit Device

To edit a device click on the edit icon button in the actions column of the table. The name and room field become editable.On changing the values handleChange function is called which updates the devicesData state. Clicking on the tick icon saves the new details by calling the onDeviceSave function. This function class the addUserDevice api which takes in the new device details.

startEditing = rowIndex => {
   this.setState({ editIdx: rowIndex });
 handleChange = (e, fieldName, rowIndex) => {
   const value =;
   let data = this.state.devicesData;
     devicesData:, index) =>
       index === rowIndex ? { ...row, [fieldName]: value } : row,

 handleDeviceSave = rowIndex => {
     editIdx: -1,
   const deviceData = this.state.devicesData[rowIndex];
   addUserDevice({ ...deviceData })
     .then(payload => {})
     .catch(error => {

Delete Device

To delete a device click on the delete icon button under the actions column in the table. Clicking on the delete device button opens up the confirm with input dialog modal. Type in the name of the device and click on delete. Clicking on delete calls the handeRemoveDevice function which calls the removeUserDevice api which takes in the macId. On deleting the device user is redirected to the My Devices in Dashboard.

 handleRemoveConfirmation = () => {
     modalType: 'deleteDevice',
     name: this.state.devicesData[0].deviceName,
     handleConfirm: this.handleRemoveDevice,
     handleClose: this.props.actions.closeModal,
 handleRemoveDevice = () => {
   const macId = this.macId;
   removeUserDevice({ macId })
     .then(payload => {
     .catch(error => {

In conclusion, My Devices tab in dashboard helps you manage the devices connected with your account along with specific device configuration. Now the users can edit, view and delete their connected devices.


Continue Reading My Devices in SUSI.AI

Tax Information on Public Ticket Page

  • Post author:
  • Post category:FOSSASIA

This blog post will elaborate on how Tax Information is being displayed on the public page of an event. In current implementation, the user gets to know the total tax inclusive amount only after he/she decides to place an order but no such information was given to them on the public ticket page itself.

Order summary example in eventyay

Example : In initial implementation, the user gets to know that the order is of only $120 and no information is given about the additional 30% being charged and taking the total to $156.

To tackle this issue, I added two hybrid components to the ticket object to handle the two tax cases : 

  • Inclusion in the price : In European and Asian Countries , the tax amount is included in the ticket price itself. For this case, I created the following parameter to store the tax amount included in gross amount.
// app/models/ticket.js
includedTaxAmount: computed('', '', function() {
  const taxType = this.event.get('tax.isTaxIncludedInPrice');
  if (taxType) {
    const taxRate = this.event.get('tax.rate');
    return ((taxRate * this.price) / (100 + taxRate)).toFixed(2);
  return 0;
  • Added on the ticket price : In basic US tax policy, the tax amount is added on top of the ticket price. For such cases I have added a new attribute to ticket model which calculates the total amount payable for that particular ticket with tax inclusion
// app/models/ticket.js
ticketPriceWithTax: computed('', '', function() {
  let taxType = this.event.get('tax.isTaxIncludedInPrice');
  if (!taxType) {
    return ((1 + this.event.get('tax.rate') / 100) * this.price).toFixed(2);
  return this.price;

Now, the public ticket page has to be edited accordingly. The design I decided to follow is inspired by eventbrite itself : 

Eventbrite specimen of the proposed implementation

For this implementation, I modified the ticket list template to accommodate the changes in the following way : 

// app/components/public/ticket-list.hbs
td id="{{}}_price">
{{currency-symbol eventCurrency}} {{format-number ticket.price}}
if (and taxInfo (not-eq ticket.type 'free'))}}
if showTaxIncludedMessage}}
small class="ui gray-text small">
      {{t 'includes'}} {{currency-symbol eventCurrency}} {{format-number ticket.includedTaxAmount}}
small class="ui gray-text small">
      + {{currency-symbol eventCurrency}} {{format-number (sub ticket.ticketPriceWithTax ticket.price)}}
small class="ui gray-text tiny aligned right">({{}})</small>
Tax amount is included in ticket price

Hence making the new public ticket list display to look like this in case of tax amount inclusion and additional charge as follows

Tax amount is charged over the base price

Discount Code application cases:

In the cases when a user applies the discount code, the ticket price need to be updated, hence, the tax applied has to be updated accordingly. I achieved this by updating the two computed properties of the ticket model on each togglePromotionalCode and applyPromotionalCode action. When a promotional code is applied, the appropriate attribute is updated according to the discount offered.

// app/components/public/ticket-list.js
tickets.forEach(ticket => {
let ticketPrice = ticket.get('price');
let taxRate = ticket.get('');
let discount = discountType === 'amount' ? Math.min(ticketPrice, discountValue) : ticketPrice * (discountValue / 100);
ticket.set('discount', discount);
if (taxRate && !this.showTaxIncludedMessage) {
  let ticketPriceWithTax = (ticketPrice - * (1 + taxRate / 100);
  ticket.set('ticketPriceWithTax', ticketPriceWithTax);
} else if (taxRate && this.showTaxIncludedMessage) {
  let includedTaxAmount = (taxRate * (ticketPrice - discount)) / (100 + taxRate);
  ticket.set('includedTaxAmount', includedTaxAmount);

Similarly, on toggling the discount code off, the ticket’s computed properties are set back to their initial value using the same formula kept during the time of initialization which has been achieved in the following manner.

// app/components/public/ticket-list.js
this.discountedTickets.forEach(ticket => {
let taxRate = ticket.get('');
let ticketPrice = ticket.get('price');
if (taxRate && !this.showTaxIncludedMessage) {
  let ticketPriceWithTax = ticketPrice * (1 + taxRate / 100);
  ticket.set('ticketPriceWithTax', ticketPriceWithTax);
} else if (taxRate && this.showTaxIncludedMessage) {
  let includedTaxAmount = (taxRate * ticketPrice) / (100 + taxRate);
  ticket.set('includedTaxAmount', includedTaxAmount);
ticket.set('discount', 0);

This particular change makes sure that the tax amount is calculated properly as per the discounted amount and thus eliminates the possibility of overcharging the attendee.

Tax recalculation for discounted tickets

In conclusion, this feature has been implemented keeping in mind the consumer’s interest in using the Open Event Frontend and the ease of tax application on the public level with minimum required network requests.


Related Work and Code Repository

Continue Reading Tax Information on Public Ticket Page

Data Binding with Kotlin in Eventyay Attendee

Databinding is a common and powerful technique in Android Development. Eventyay Attendee has found many situations where data binding comes in as a great solution for our complex UI. Let’s take a look at this technique.

  • Problems without data binding in Android Development
  • Implementing Databinding with Kotlin inside Fragment
  • Implementing Databinding with Kotlin inside RecyclerView/Adapter
  • Results and GIF
  • Conclusions


Getting the data and fetching it to the UI is a basic work in any kind of application. With Android Development, the most common way to do is it to call function like .setText(), isVisible = True/False,.. in your fragment. This can create many long boilerplate codes inside Android classes. Databinding removes them and moves to the UI classes (XML).


Step 1: Enabling data binding in the project build.gradle

android {
   dataBinding {
       enabled = true

Step 2: Wrap the current layout with <layout></layout> tag. Inside that, put <data></data> to indicate any variables needed for data binding. For example, this code here display an event variable for our fragment about event details:

<layout xmlns:android=""


           type="org.fossasia.openevent.general.event.Event" />


Step 3: Bind your data in the XML file and create a Binding Adapter class for better usage

With the setup above, you can start binding your data with “@{<data code here>}”

   tools:text="Open Source Meetup" />

Sometimes, to bind our data normally we need to use a complex function, then creating Binding Adapter class really helps. For example, Eventyay Attendee heavily uses Picasso function to fetch image to ImageView:

fun setEventImage(imageView: ImageView, url: String?) {
   app:layout_constraintTop_toBottomOf="@id/alreadyRegisteredLayout" />

Step 4: Finalize data binding setup in Android classes. We can create a binding variable. The binding root will serve as the root node of the layout. Whenever data is needed to be bind, set the data variable stated to that binding variable and call function executePendingBingdings()

private lateinit var rootView: View
private lateinit var binding: FragmentEventBinding
binding = DataBindingUtil.inflate(inflater, R.layout.fragment_event, container, false)
rootView = binding.root
binding.event = event


  • In the example mentioned above, the name of the binding variable class is auto-generated based on the name of XML file + “Binding”. For example, the XML name was fragment_event so the DataBinding classes generated name is FragmentEventBinding.
  • The data binding class is only generated only after compiling the project.
  • Sometimes, compiling the project fails because of some problems due to data binding without any clear log messages, then that’s probably because of error when binding your data in XML class. For example, we encounter a problem when changing the value in Attendee data class from firstname to firstName but XML doesn’t follow the update. So make sure you bind your data correctly
   android:text="@{attendee.firstname + ` ` + attendee.lastname}"
   tools:text="@string/name_preview" />


Databinding is the way to go when working with a complex UI in Android Development. This helps reducing boilerplate code and to increase the readability of the code and the performance of the UI. One problem with data binding is that sometimes, it is pretty hard to debug with an unhelpful log message. Hopefully, you can empower your UI in your project now with data binding.  


Eventyay Attendee Android Codebase:

Eventyay Attendee Android PR: #1961 – feat: Set up data binding for Recycler/Adapter


Google Codelab:

Continue Reading Data Binding with Kotlin in Eventyay Attendee

How to fix undetected Arduino boards in Android

  • Post author:
  • Post category:FOSSASIA

In the development process of the Neurolab Android app, we needed an Arduino-Android connection. This blog explains how to  establish the connection and getting the Arduino board detected in my Android device

Context-connecting the board and getting it detected

Arduino boards are primarily programmed from the Desktop using the Arduino IDE, but they are not limited to the former. Android devices can be used to program the circuit boards using an application named Arduinodroid.

Arduino is basically a platform for building various types of electronic projects and the best part about it is that, it is open-sourced. Arduino, the company has got two products The physical programmable circuit board (often referred to as a microcontroller). 

Examples of Arduino circuit boards – UNO, UNO CH340G, Mega, etc. Find more here.

Connecting the board and getting it detected

Arduino boards are primarily programmed from the Desktop using the Arduino IDE, but they are not limited to the former. Android devices can be used to program the circuit boards using an application named Arduinodroid.

In this blog, we are going to use Arduinodroid app for establishing a connection between the Arduino board and the Android device, getting the board detected in the Android phone and uploading a sketch to it.

Materials/Gadgets required:-

  1. Arduino board (UNO preferably)
  2. Arduino-USB Cable
  3. OTG Cable
  4. Android device

Now, one of the most frequent issues, while establishing a connection and getting the Arduino board detected with the Android device, is the error message of: “No Arduino boards detected” in the Arduinodroid app. There can be a few core reasons for this –

  1. Your Android mobile device isn’t USB-OTG supported – Probably because it is an old model or it might be a company/brand-specific issue.
  2. Disabled OTG Mode – Be sure to enable USB-OTG mode (only if your device has one) from the Developer options in your Android device settings.

Even after trying and making sure of these above points, if you still continue to get an error while uploading a sketch from the Arduinodroid app like this:

                                                            Figure 1: The Error Message

Follow the steps below carefully and simultaneously one after the other:

  1. Look for any external module attached to your Arduino board using jumper wires. If so, remove those connections completely and press the reset button on the Arduino circuit board. The attached modules can be one of the following: Micro SD Card module, Bluetooth module, etc.
  2. Remove pin connections, if any from the TX and RX pin-slots in the Arduino board. These pre-attached pins can cause unnecessary signal transfers which can hinder and make the actual port of Arduino board busy.
  3. Before connecting the Arduino to the Android device, go to the drop down menu in the app at the top-right corner -> Settings -> Board Type -> Arduino -> UNO
  4. Now, you need to code a sketch and make it ready for compile and upload to the circuit board. We will use a basic example sketch for this case. Feel free to try out your own custom coded Arduino sketches. Go to the drop-down menu -> Sketch -> Examples -> Basics -> AnalogReadSignal
  5. Don’t compile the sketch yet because we haven’t connected any Arduino circuit board to our Android device. So first, connect the Arduino circuit board to the Android device through the OTG cable connected to the Arduino-USB cable.
  6. You should see some LEDs lit up on the circuit board (indicates power is flowing to the board). Go ahead to compile the sketch. Click the ‘lightning’ icon on the top in the toolbar of the app. You should see the code/sketch getting compiled. Once done you should see a toast message saying “Compilation finished”. This signifies that your code/sketch has been verified by the compiler.

                                              Figure 2: Successful Compilation of sketch

This process is inevitable and there is hardly any issue while compiling a sketch.

       7. Upload the sketch: Click on the upload icon from the toolbar in the app. Upload             should start once you get a pop-up dialog like this:

                                           Figure 3: Arduino board detected successfully

Once you click Okay, the upload shall start and if your code is correct and matches the particular Arduino circuit board, you shall get a successful upload, which was not the case earlier for the error : “no Arduino boards found” on clicking the upload button.

So, that’s it then. Hope this blog adds value to your development skills and you can continue working bug free with your Android-Arduino connections.


  1. Author – Nick Gamon, Article – Have I bricked my Arduino uno problems with uploading to board, Date – Nov’16 2016, Website –
  2. Author – Arduino Products, Article – Arduino boards, Website –

3. Author – Anton Smirnov, App name – ArduinoDroid, Website –

Tags: FOSSASIA, Neurolab, GSOC19, Open-source, Arduino, Serial terminal

Continue Reading How to fix undetected Arduino boards in Android

Implementing Attendee Forms in Wizard of Open Event Frontend

  • Post author:
  • Post category:FOSSASIA

This blog post illustrates on how the order form is included in the attendee information of the Open Event Frontend form  and enabling the organizer to choosing what information to collect from the attendee apart from the mandatory data i.e. First Name, Last Name and the Email Id during the creation of event itself.

The addition of this feature required alteration in the existing wizard flow to accommodate this extra step. This new wizard flow contains the step :

  • Basic Details : Where organizer fills the basic details regarding the event.
  • Attendee Form : In this step, the organizer can choose what information he/she has to collect from the ticket buyers.
  • Sponsors : This step enables the organizer to fill in the sponsor details
  • Session and Speakers : As the name suggests, this final step enables the organizer to fill in session details to be undertaken during the event.

This essentially condensed the flow to this :

The updated wizard checklist

To implement this, the navigation needed to be altered first in the way that Forward and Previous buttons comply to the status bar steps

// app/controller/create.jsmove() {
      ['tickets', 'socialLinks', 'copyright', 'tax', 'stripeAuthorization']
move(direction) {
      direction === 'forwards' ? 'events.view.edit.sessions-speakers' : 'events.view.edit.attendee',

Once the navigation was done, I decided to add the step in the progress bar by simply including the attendees form in the event mixin.

// app/mixins/event-wizard.js
      title     : this.l10n.t('Attendee Form'),
      description : this.l10n.t('Know your audience'),
      icon     : 'list icon',
      route     : 'events.view.edit.attendee'

Now a basic layout for the wizard is prepared, all what is left is setting up the route for this step and including it in the router file. I took my inspiration for setting up the route from events/view/tickets/order-from.js and implemented it like this:

// app/routes/events/view/edit/attendee.js
import Route from '@ember/routing/route';
import CustomFormMixin from 'open-event-frontend/mixins/event-wizard';
import { A } from '@ember/array';
export default Route.extend(CustomFormMixin, {

titleToken() {
  return this.l10n.t('Attendee Form');

async model() {
  let filterOptions = [{
    name : 'form',
    op : 'eq',
    val : 'attendee'

  let data = {
    event: this.modelFor('events.view')
  data.customForms = await data.event.query('customForms', {
    filter       : filterOptions,
    sort         : 'id',
    'page[size]' : 50

  return data;
afterModel(data) {
    * Create the additional custom forms if only the compulsory forms exist.
  if (data.customForms.length === 3) {
    let customForms = A();
    for (const customForm of data.customForms ? data.customForms.toArray() : []) {

    const createdCustomForms = this.getCustomAttendeeForm(data.event);

    for (const customForm of createdCustomForms ? createdCustomForms : []) {

    data.customForms = customForms;

With the route setup and included in the router, I just need to take care of the form data and pass it to the server. Thankfully, the project was already using EventWizardMixin so all I had to do was utilize these functions (save and move) which saves the event data in the status user decides to save it in i.e. either published or draft state

// app/controllers/events/view/edit/attendee.js
import Controller from '@ember/controller';
import EventWizardMixin from 'open-event-frontend/mixins/event-wizard';

export default Controller.extend(EventWizardMixin, {
async saveForms(data) {
  for (const customForm of data.customForms ? data.customForms.toArray() : []) {
  return data;
actions: {
  async save(data) {
    try {
      await this.saveForms(data);
    } catch (error) {
  async move(direction, data) {
    try {
      await this.saveForms(data);
        direction === 'forwards' ? 'events.view.edit.sponsors' : 'events.view.edit.basic-details',
    } catch (error) {

Apart from that, the form design was already there, essentially, I reutilized the form design provided to an event organizer / co-organizer in the ticket section of the event dashboard to make it look like this form :

Basic attendee information collection

In the end, after utilizing the existing template and adding it in the route’s template, the implementation is ready for a test run!

// app/templates/events/view/edit/attendee.hbs
{{forms/wizard/attendee-step data=model move='move' save='save' isLoading=isLoading}}

This is a simple test run of how the attendees form step works as others work fine along with it!

Demonstration of new event submission workflow


Related Work and Code Repository

Continue Reading Implementing Attendee Forms in Wizard of Open Event Frontend

Dependency Injection with Kotlin Koin in Eventyay Attendee

Eventyay Attendee Android app contains a lot of shared components between classes that should be reused. Dependency Injection with Koin really comes in as a great problem solver.

Dependency Injection is a common design pattern used in various projects, especially with Android Development. In short, dependency injection helps to create/provide instances to the dependent class, and share it among other classes.

  • Why using Koin?
  • Process of setting up Koin in the application
  • Results
  • Conclusion
  • Resources

Let’s get into the details


Before Koin, dependency injection in Android Development was mainly used with other support libraries like Dagger or Guice. Koin is a lightweight alternative that was developed for Kotlin developers. Here are some of the major things that Koin can do for your project:

  • Modularizing your project by declaring modules
  • Injecting class instances into Android classes
  • Injecting class instance by the constructor
  • Supporting with Android Architecture Component and Kotlin
  • Testing easily


Adding the dependencies to build.gradle

// Koin
implementation "org.koin:koin-android:$koin_version"
implementation "org.koin:koin-androidx-scope:$koin_version"
implementation "org.koin:koin-androidx-viewmodel:$koin_version"

Create a folder to manage all the dependent classes.

Inside this Modules class, we define modules and create “dependency” class instances/singletons that can be reused or injected. For Eventyay Attendee, we define 5 modules: commonModule, apiModule, viewModelModule, networkModule, databaseModule. This saves a lot of time as we can make changes like adding/removing/editing the dependency in one place.

Let’s take a look at what is inside some of the modules:


val databaseModule = module {

   single {
 , "open_event_database")

   factory {
       val database: OpenEventDatabase = get()

   factory {
       val database: OpenEventDatabase = get()


val commonModule = module {
   single { Preference() }
   single { Network() }
   single { Resource() }
   factory { MutableConnectionLiveData() }
   factory<LocationService> { LocationServiceImpl(androidContext()) }


val apiModule = module {
   single {
       val retrofit: Retrofit = get()
   single {
       val retrofit: Retrofit = get()


single {
   val connectTimeout = 15 // 15s
   val readTimeout = 15 // 15s

   val builder = OkHttpClient().newBuilder()
       .connectTimeout(connectTimeout.toLong(), TimeUnit.SECONDS)
       .readTimeout(readTimeout.toLong(), TimeUnit.SECONDS)

   if (BuildConfig.DEBUG) {
       val httpLoggingInterceptor = HttpLoggingInterceptor().apply { level = HttpLoggingInterceptor.Level.BODY }

single {
   val baseUrl = BuildConfig.DEFAULT_BASE_URL
   val objectMapper: ObjectMapper = get()
   val onlineApiResourceConverter = ResourceConverter(


As described in the code, Koin support single for creating a singleton object, factory for creating a new instance every time an object is injected.

With all the modules created, it is really simple to get Koin running in the project with the function startKoin() and a few lines of code. We use it inside the application class:

startKoin {
   androidContext([email protected])

Injecting created instances defined in the modules can be used in two way, directly inside a constructor or injecting into Android classes.  

Here is an example of dependency injection to the constructor that we used for a ViewModel class and injecting that ViewModel class into the Fragment:

class EventsViewModel(
   private val eventService: EventService,
   private val preference: Preference,
   private val resource: Resource,
   private val mutableConnectionLiveData: MutableConnectionLiveData,
   private val config: PagedList.Config,
   private val authHolder: AuthHolder
) : ViewModel() {
class EventsFragment : Fragment(), BottomIconDoubleClick {
   private val eventsViewModel by viewModel<EventsViewModel>()
   private val startupViewModel by viewModel<StartupViewModel>()

For testing, it is also really easy with support library from Koin.

fun testDependencies() {
   koinApplication {
       modules(listOf(commonModule, apiModule, databaseModule, networkModule, viewModelModule))


Koin is really easy to use and integrate into Kotlin Android project. Apart from some of the basic functionalities mention above, Koin also supports other helpful features like Scoping or Logging with well-written documentation and examples. Even though it is only developed a short time ago, Koin has proved to be a great use in the Android community. So the more complicated your project is, the more likely it is that dependency injection with Koin will be a good idea.



Eventyay Attendee Android Codebase:

Continue Reading Dependency Injection with Kotlin Koin in Eventyay Attendee

Announcing the FOSSASIA Codeheat Winners 2018/19

We are very proud to announce our Grand Prize Winners and Finalist Winners of Codeheat 2018/2019.

Codeheat participants not only solved a stunning number of issues in FOSSASIA’s projects, reviewed pull requests, shared scrums, and wrote blog posts, but most importantly they encouraged and helped each other and collaborated across borders and cultures. More than 700 developers from 18 countries participated in the contest supported by 37 mentors. Over 2000 pull requests were merged. Thank you all for this amazing achievement!

With so many outstanding developers participating it was extremely difficult to decide the Grand Prize and Finalist Winners of the contest. Our winners stand out in particular as they contributed to FOSSASIA projects on a continuously high level following our Best Practices.

Each of the Grand Prize Winners is awarded a travel grant to join us at the FOSSASIA Summit in Singapore in March where they receive the official Codeheat award, and meet with mentors and FOSSASIA developers. Other Finalist Winners will receive travel support vouchers to go to a Free and Open Source Software event of their choice.

Congratulations to our Grand Prize Winners, Finalist Winners, and all of the participants who spent the last few of months learning, sharing and contributing to Free and Open Source Projects. Well-done! We are truly impressed by your work, your progress and advancement. The winners are (in alphabetical order):

Grand Prize Winners

Aakash S. Mallik
Harshit Khandelwal
Shubham Gupta

Finalist Winners

Aditya Srivastava
Samagra Gupta
Shridhar Goel
Shubham Kumar
Pranav Kulshrestha
Raj Vaibhav Dubey
Yogesh Sharma

About Codeheat

Codeheat is a contest that the FOSSASIA organization is honored to run every year. We saw immense growth this year in participants and the depth of contributions.

Thank you Mentors and Supporters

Our 40+ mentors and many project developers, the heart and soul of Codeheat, are the reason the contest thrives. Mentors volunteer their time to help participants become open source contributors. Mentors spend hundreds of hours during answering questions, reviewing submitted code, and welcoming the new developers to project. Codeheat would not be possible without their patience and tireless efforts. Learn more about this year’s mentors on the Codeheat website.

Certificate of Participation

Participating developers, mentors and the FOSSASIA admin team learnt so much and it was an amazing and enriching experience and we believe the learnings are the main take-away of the program. We hope to see everyone continuing their contributions, sharing what they have learnt with others and to seize the opportunity to develop their code profile with FOSSASIA. We want to work together with the Open Tech community to improve people’s lives and create a better world for all. As a participating developer or mentor, you will receive your certificate over the upcoming weeks. Thank you!

More Links

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