Arduino Tutorial: Integrating Bluetooth LE and iOS

Creating machines that interact with the physical world is an incredibly satisfying thing. Controlling them via Bluetooth with your iOS device is just plain awesome!

In the past, the only way to create an Apple-approved Bluetooth device was by being part of the MFi program. With Bluetooth Low Energy 4.0, individuals and small companies can develop their own products and market them without the overhead of Apple’s MFi regulations. That means you can talk to devices over Bluetooth LE with very little configuration and code, which opens up an entire world of opportunity for iOS developers.

This tutorial will teach you how to create your own Bluetooth LE device using standard off-the-shelf components that you can control wirelessly with a simple iOS app. Since the focus of this project is building a BLE device, you’ll be using the iOS Core Bluetooth framework. If you’re unfamiliar with Core Bluetooth, check out our Introduction to Core Bluetooth: Building a Heart Rate Monitor tutorial.

Let the building begin!

Getting Started

Using off-the-shelf components for this build makes creating a Bluetooth device a snap. Here’s an image showing the basic elements you’ll use in this project:

A look at the parts you’ll need to complete this project.

A look at the parts you’ll need to complete this project.

Here’s the list of parts you’ll need to complete the project, and where to obtain them:

• iPhone 4s or newer with Bluetooth LE
• Arduino Red Board, $19.95 at SparkFun.com



• USB Mini-B Cable, $3.95 at SparkFun.com
  
• Servo Motor, $8.95 at SparkFun.com



• Jumper Wires, $4.95 at SparkFun.com)



• BLE-Shield v2.0.0 based on Bluegiga’s BLE112 Module, $69.00 at www.seeedstudio.com.

The Arduino, servo and jumper wires can be purchased together from SparkFun.com in the SparkFun Inventor’s Kit for Arduino. This kit comes with many useful components and tutorials to get you started in the hardware world.

You can find less-expensive BLE Shields other than the one listed in this tutorial, but be aware that many of them sacrifice flexibility to save on cost. The BLE-Shield v2.0.0 allows you to program your own custom BLE Services and Characteristics onto the module. This means you can take full advantage of the Bluetooth 4.0 data structure.

That takes care of the hardware side of things – there’s a few extra software pieces to take care of as well.

Download the Xcode starter project here. The starter project includes the view controller and base Core Bluetooth implementation to save you time. You’ll add more code to interface with the BLE Shield later on in the tutorial.

Next, download and install the Arduino IDE from the Arduino Download page; it’s available for Windows, Mac OS X and Linux platforms. You’ll use the Arduino IDE to write and compile the code for the Arduino. Ensure you grab the latest release version, not the beta or nightly builds.

The Basic Design of your App

Your finished project will consist of an iOS app that will send messages via Bluetooth to the BLE Shield module. The module will then send the message to the Arduino board to tell the servo which position it should rotate to.

Here’s an example use-case of your project:

1. The user of the iOS app moves the slider to the middle position.
2. The app sends the number 90, which represents 90 degrees in this case, to the BLE Shield module using the active Bluetooth connection.
3. The BLE Shield transfers the number 90 to the Arduino board.
4. The Arduino board rotates the servo to the 90 degree position.

Seems pretty straightforward! To begin, you’ll work with the Arduino IDE and program the board logic.

Programming the Arduino

Start the Arduino IDE; you’ll see the editor appear with a blank document, or “sketch”, as shown below:

Before doing anything else, click File\Save in the top menu and save the current file to a convenient location as Arduino_Servo_Controller. This creates a folder in your save location that contains a file with a .ino file extension.

Before you start writing code, you’ll need to set up the IDE to communicate with the Arduino Uno board.

Select Tools\Board\Arduino Uno to let the IDE know what kind of board you’ll be dealing with. Next, connect the Uno to your computer with the USB cable as shown below:

This lets the Arduino IDE recognize the serial port to which the Uno is connected.

Once that’s done, select Tools\Serial Port\… and select the USB port the Arduino is connected to. Generally it’s similar to /dev/tty.usbserial… or /dev/tty.usbmodem….

At this point the Arduino IDE is ready for programming.

Add the code below to your project using the Arduino IDE:

// Arduino Bluetooth LE Servo Controlled by iOS
 
void setup() // Called only once per startup
{ 
} 
 
void loop() // Continuous loop
{
}

Arduino programs are typically split into two main functions: setup() and loop().

The setup() function does exactly what it is says: it’s called only once on startup and is a great place for setting up your hardware and software. The loop() function is called once setup() is done. Once you enter loop() you never exit, but continually execute the code within in linear order until the board is reset or powered down.

Click the Verify button (the checkmark icon) to ensure everything compiles correctly. If so, you’ll see a confirmation message similar to below:

Now that you have the basic framework of the Arduino program in place, it’s time to add some logic to control the board.