Part 3: Bluetooth communications with 2 Arduino devices, using App Inventor

Please start with “Part 1: Basic Bluetooth communications using App Inventor” to learn how to configure, set up and program an App Inventor app that communicates over Bluetooth between two Android devices. Then, read “How to connect App Inventor apps to Arduino using Bluetooth” before going through this tutorial!

Then continue with this tutorial.

This tutorial shows how an App Inventor app can communicate with 2 (or more) Arduino boards and Bluetooth devices simultaneously. These instructions assume you are familiar with the code and hardware presented in Part 1 and Part 2 and How to connect App Inventor apps to Arduino using Bluetooth“. This tutorial uses the same Arduino source code as in that tutorial.

A follow up tutorial will show how to simplify some of this code for supporting multiple Bluetooth devices.

Brief Reminder

Bluetooth is a short range, low power, limited speed wireless communications technology. The original Bluetooth technology provided a serial communications link between two paired devices (as compared to an individual data packet sent between up to n devices using the much newer Bluetooth LE – see here and here for information on Bluetooth LE).

Arduino is a microcontroller board for building hardware projects. You can write software for Arduino using a programming language similar to the C++ programming language.

The code used in these examples has been tested with some specific Bluetooth modules connected to Arduino. These include the JY-MCU (Amazon (Prime), Amazon (non-Prime) and also some HC-05 and HC-06 based Bluetooth modules.

Getting Started

  • Read the prior tutorials (Part 1 and Part 2 and How to connect App Inventor apps to Arduino using Bluetooth“)
  • Build two Arduino boards each with an appropriate Bluetooth module as described in the prior tutorial.
  • Compile and load the Arduino software in to each of the Arduino boards.
  • Test and confirm that your basic LED lights flash for the original, single Bluetooth connection case.
  • Then, with two working boards, continue to this tutorial.

User Interface View

The original app supported just one device, so there was just a single “Connect” and “Disconnect” button. This version demonstrates how to connect more than one Bluetooth device so we need separate buttons for each device. Similarly, we must add a second status and data sending item to the screen:

 

Before running this app, be sure to use Android | Settings | Bluetooth to “pair” your Bluetooth devices with Android.

Then, run the app and select Connect to Device 1. This displays a list of available Bluetooth devices in the vicinity. Select your specific Bluetooth device for the connection. Do this for both Bluetooth devices.

Once connected, you can send some simple commands to the Arduino board. Commands are very simple – a single number – to tell the Arduino to do something (this confirms that the Bluetooth link is working). If we enter a single digit 1 and then press Send Numeric 1, the Arduino board will send back 2 bytes of data which will then be displayed on the app screen. If we enter a single digit 4 and then press Send Numeric 1, a value of 4 is transmitted over Bluetooth to the Arduino board, which responds by flashing the externally connected LED.

Because the text box for data entry has its property set to NumbersOnly, a pop up numeric keypad displays when entering data, rather than the usual Android text keyboard.

Video Demonstration this App

I created a short video showing this app in operation. There are two versions of the video – one is standard 2D format and the other is in VR 3D format for viewing on Google Cardboard-like viewers used with smart phones to watch VR videos.

2D (normal) version: https://youtu.be/BU2gIAxbY_o

VR 3D SBS version: https://www.youtube.com/watch?v=UJIggzZgld4

That version is in 3D, for viewing with VR 3D viewers or 3D TVs or monitors.

Continue reading Part 3: Bluetooth communications with 2 Arduino devices, using App Inventor

Using the Pedometer in MIT App Inventor

The pedometer uses the phones motion sensors (accelerometers) to identify when the phone (or tablet) is being carried by someone that is walking – and uses this to measure the number of steps you take as you walk. When calibrated to the length of your stride, the pedometer provides a way to estimate the distance you have traveled.

The pedometer is so simple to use, I put this example together while eating lunch today.

User Interface

This is a simple program!

To use this app, enter your stride length in meters. For illustration, I set the stride length to 1/2 meter or 0.5, as seen in this screen shot:

Screenshot_20161206-153814

Press the Start measuring steps button to activate the pedometer and then start walking with your phone. You will soon see the Elapsed distance value increase as you move around.

Designer View

Continue reading Using the Pedometer in MIT App Inventor

Does your device support Bluetooth LE? Here is how to find out.

See Part 0 for a brief introduction to this series and Bluetooth LE plus our past tutorial series on classic Bluetooth for communicating between Android devices, and between an Android device and an Arduino board with external Bluetooth transceiver.

Note – Bluetooth LE was introduced in the Bluetooth 4.0 specification. As of this writing, the latest version of the specification is 4.2. Bluetooth LE introduced capabilities to support very low power, battery operated devices that are designed to operate for weeks to months on a single battery or battery charge

Does Your Device Support Bluetooth LE?

To find out if your smart phone or tablet can work with Bluetooth LE: Go to the Google Play store and install the free app “BLE Checker” on your Android device. The app is simple – it tells you whether your device supports Bluetooth LE or not and that is all it does.

Devices that support Bluetooth LE will support BLE connections between compatible devices. However, this app does not tell you if your device supports a special BLE feature called “advertisements”. You can use Bluetooth LE without the “advertisements” feature but you will not be able to use all BLE features.

Continue reading Does your device support Bluetooth LE? Here is how to find out.

Appinventor.pevest.com web site read in 183 countries around the world!

Wow! I just checked the web server data and the server estimate the http://appinventor.pevest.com web site is now read in 183 countries!

Using the United Nation’s count of 241 countries and territories, that means residents of 58 countries and territories have not visited yet!

But that means people in up to 183 countries are learning how to program Android apps using MIT App Inventor!

Learn to program with App Inventor