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an AndroidThings Playground

AndroidThings is a fairly new Internet of Things (IoT) rapid-prototyping platform developed by Google. Firebase is a Cloud Platform by Google providing, among other things, cloud persistence and functions.

Combining these two technologies is a great way to rapidly prototype new ideas.

The motivation for this project is to provide a simple but solid platform to start experimenting with AndroidThings, Firebase Database and Cloud Functions.

Please note that AndroidThings, Firebase Database and Firebase Functions are free when used for experimentation as described on the Firebase Pricing Guide. This project will describe how to create such a test account within the Firebase Cloud.

The 'use case' for this project is to have an AndroidThings platform (e.g. PICO PI) connected up to a PWM-controlled Servo. This servo can be used to actuate a real world object (e.g. unlock a door).

The FirebaseDatabase and Firebase Function code included in this project provide a webhook so one can easily actuate this Servo from any web client.


Many thanks to James Coggan and his AndroidThings Workshop (
He's a great inspiration and this project borrows from his work!

Also, thanks to Unsplash for their Philly 'Love' photo.

Let's get started!

Step 1: Hardware Setup

The idea behind AndroidThings is you start with a core Android system hardware module which provides the Android runtime.
That plugs into a prototype board which supports many IO standards (e.g. SPI, GPIO, etc.) and has many headers for making quick connections.
You build your prototype on this board and then eventually you get a more precise board fabricated. This new, smaller board can use the same core Android module. There are a number of purchase options for this 'prototype board'.

I purchased the 'Pico Pi' AndroidThings starter kit from TechNexion. This is based on the NXP i.MX7 processor, but that doesn't really matter as you're going to be pushing stock Android code anyway. This board comes with a nice 5" color touchscreen, build-in WiFi w/ antenna, and a camera.

This board comes in a really nice shipping carton, which, with a little duct tape, can be converted to a holder for your new board, display, and camera:


This project uses this board to actuate a Servo. A Servo is a DC motor with a gear on the end that's been geared-down so it has some torque to move things.
The Servo can be instructed to 'rotate to the X degree position' over an analog interface called PWM (Pulse Width Modulation) on the AndroidThings platform

As shown in the picture above, typically, you attach an arm to the servo as a means of moving something.

I bought the TowerPro SG92R Servo. I recommend using the same Servo as the code in this project is tuned for the control signals expected by this Servo.

The manual that comes with AndroidThings will help you assemble the board and attach all the parts.
Follow these steps to configure your board:

  1. Load the board with the latest firmware

  2. Configure the board to connect to WiFi

After you've assembled and configure the Pico PI AndroidThings board, you can wire up the Servo to the 40-pin expansion header near the top of the board. Here are the pinouts for this expansion header.

Wiring up a Servo requires three connections:

Brown Wire (Servo) - connects to PIN 6 (Ground) on the Pico Pi

Red Wire (Servo) - connects to PIN 1 (3.3V) on the Pico Pi

Yellow Wire (Servo) - connects to PIN 33 (PWM2) on the Pico Pi

The 'PWM2' PIN on the Pico Pi is a 'Pulse Width Modulation' analog output pin. It's the control signal that is sent to the servo and is controlled by the code in this project.

Step 2: Firebase Setup

In addition to controlling the locally connected Servo, this AndroidThings project also synchronizes the 'on/off' state of the Servo with an instance of Firebase Realtime Database.
This database stores the current 'on/off' state of the Servo.

Inside the 'firebaseFunction' directory of this project is a Firebase Function which, when deployed to the web, can change the values stored in the Firebase Realtime Database from any web browser. By calling this Firebase Function 'web hook', you can remotely affect a change in the Servo state.

Step 2.1 Create Firebase Project

You will be creating a Firebase Project strictly for experimentation here which is free of charge.
To start you will need a Google Account. Navigate to the Firebase Console and click on 'Add Project'. Once you create this project, you need the 'Project Id'. This can be found by going into 'settings' on the Firebase Console.

Step 2.2 Configure Firebase Project for Anonymous 'sign-in'

Navigate to the Firebase Console again and click on 'Authentication' tab, then click on 'Sign-in'method. Enabled the 'Anonymous' method.

Next you need to setup this project to use a Firebase Database.

Step 2.3 Create Firebase Realtime Database

Enter your project in the Firebase Console and click on 'Develop' then 'Database'. Scroll down to 'Realtime Database' and click 'create database' and select 'start in test mode' and click 'enable'.
Please be aware that this is creating a completely 'open' database, which is acceptable for this simple experiment. Anyone with your web-hook can change the state of your Servo.

The 'schema' of this database is configured by this project itself so your database is all ready to be used! The next step is to setup the Firebase Function.

Step 2.4 Configure AndroidThings project to talk to your new Firebase Project in the cloud.

There's a lot of 'magic' that happens when deploying Firebase Functions and the Android Studio helps to configure this magic. Launch AndroidStudio and login to your Google Account using the 'User' icon in the upper right corner of the IDE. Once you are logged into your Google Account, Android Studio will be able to find your new Firebae Project. To complete this step, navigate to 'Tools-->Firebase', then scroll down to 'Realtime Database' and select 'save and retrieve data'. This will launch a dialog and from here you can select your new Firebase Project. You will notice that this adds the 'app/google-services.json' file to this project. Now you are ready to configure your project for Firebase Functions.

Step 2.5 Configure and Deploy Firebase Function

In general, you write, compile and test a Firebase Function using a local Node.js instance. Once the function is completed, you can deploy it to your Firebase Project created above. This project already includes the Firebase Function necessary to control our Servo in the 'firebaseFunction/functions/index.js' project file. We need to configure this project to talk to your Firebase Project in order to execute Firebase Functions.

Do all of the following from the main project directory:

First install HomeBrew and Node.js.

>brew upgrade
>brew install node
>brew install npm

Then you need to configure your local 'firebaseFunction/ directory to be able to deploy Firebase Functions:

> cd firebaseFunction
> npm install -g firebase-tools
> firebase login (this will launch a browser and allow you to login to your Google account)
> firebase init (this may redirect you to a web login for your Google Account, which you should do)

Use arrow keys to scroll down to 'Functions'. Press 'space' to select and 'enter' to finish.
Choose the Firebase Project you created earlier to associate with this function. Choose 'Javascript'.
Chose to NOT overwrite the 'index.js' file. This is our existing Firebase Function that will talk to our Android Things! Choose YES to install NPM dependencies.

Before we can deploy our function, we need to modify it slightly. Open the 'index.js' file and change the databaseURL so that it includes YOUR Firebase ProjectId. You can get this by navigating to your project in the Firebase Console (, then navigate to the 'Database' tab:

    databaseURL: 'https://<yourProjectIdHere>'

Now you are ready to deploy this Firebase Function to your Firebase Cloud project:

>firebase deploy --only functions

This will compile and upload your Firebase Function and will give you a Function URL which is how you can call this function from any browser to actuate your AndroidThings Servo!

Step 3: Deploy to AndroidThings

Primarily, this is an AndroidThings project. You load this project into AndroidStudio, connect your AndroidThings device to the computer, and push the build as you would push a build to an Android phone.
Once deployed, this project will present a toggle switch on the LCD display which can be used to set the Servo to one of two positions (currently ZERO and ONE_SEVENTY degrees).

Step 4: Use webhook to control Servo

Below we combine the Firebase URL with the required parameter. A testHardware value of 'true' will set the Servo to ONE_SEVENTY degrees and a value of 'false' will set the Servo to ZERO degrees.

Example Function URL with required Servo parameter:


You should go ahead, and test the above URL now to make sure it responds with OK.

NOTE: It's possible the particular servo you have won't work with this code. If this happens, this is probably due to the 'DutyCyclePercentage' value used in ServoOutputPin.kt. You can recognize this failure if the servo is just making a buzzing sound instead rotating. You can change the 'DutyCyclePercentage' using a breakpoint and experiment with values for ZERO and ONE_SEVENTY.


Refer to


Refer to LICENSE


A simple but solid platform to start experimenting with AndroidThings, Firebase Database and Cloud Functions.




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