# Pairing with QR Codes

Pairing a HomeKit device using its 8-digit *Setup Code* requires you to:

* Select the specific HomeKit device you wish to pair from a list of unpaired HomeKit devices the Home App finds on your local network
* Input the *Setup Code* for that device into the Home App.

The order of the steps above depends on whether you input the *Setup Code* by manually typing it, or scan it from a printed tag (see the User Guide for details on how to create your own scannable *Setup Code* tags)

On the other hand, pairing a HomeKit device with a **QR Code** requires you only scan the QR Code.  You do not need to identify the device you want to pair - the Home App automatically searches for it on your local network and, if found, pairs to it.

This is possible because the QR Code contains within a 4-character *Setup ID* that is unique to the device associated with that QR Code.  The QR Code also contains other informattion about the device, such as its type (e.g. Light, Fan, Door) as well as its 8-digit *Setup Code*.

HomeSpan supports pairing with QR codes and uses "HSPN" as its default *Setup ID*.  If you have more than one device that you intend on pairing with a QR Code, you'll need to change their default *Setup IDs* from "HSPN" to something unique using the method `homeSpan.setQRID(const char *ID)` (see the API Reference for details).  If you do not intend on pairing your devices with QR Codes, it is fine fore them to all have the same *Setup ID*, as this ID is only used to initiate the pairing process via a QR code and serves no other purpose.

### Creating Scannable QR Codes

Just as you can create your own scannable tag based on a device's *Setup Code*, you can also create your own scannable QR Code for that device.

One method is to use the QR Code generator provided by Apple in its [HomeKit Accessory Simulator Add-on for Xcode](https://developer.apple.com/documentation/homekit/testing_your_app_with_the_homekit_accessory_simulator):

As shown above, the Simulator's QR Code Generator requires the input of the following fields:

* **Version**.  Always set this to zero, else the Home App will not recognize the QR code.
* **Reserved**.  Always set this to zero, else the Home App will not recognize the QR code.
* **Category**.  Set this to match the catgory of your HomeSpan device (e.g. Lightbulb, Fan, Door Lock).  Note the Home App only uses this for display purposes when you first scan the QR Code.  The Home App does not actually check to see that the Category listed in the QR Code actually matches the Category of the device you are pairing.
* **Setup Flags**.  These flags provide information on which methods of pairing are supported by the device.  HomeSpan only supports IP Pairing, so check that box.  However, similar to Category, the Home App does not seem to do anything with these flags, and HomeSpan devices seem to be able to pair with the Home App regardless of which check boxes (if any) are checked.
* **Setup Code**.  This is the 8-digit *Setup Code* you set for your device using either HomeSpan's Command-Line Interface or HomeSpan's Setup Access Point.  Note the code shown in the above screenshot is the default HomeSpan uses if you do not set your own.
* **Setup ID**.  This is the 4-character *Setup ID* you set for your device from within your sketch code using the method `homeSpan.setQRID(const char *ID)`.  Note the ID shown in the above screenshot is the default HomeSpan uses if you do not set your own.  Also note case matters!  HSPN is not the same as "hspn".
* **Setup Payload**.  This is the output that results from the above inputs, and is the text that is representing by the QR Code shown.  If you've not changed HomeSpan's default *Setup Code* or *Setup ID*, you can pair your device by scanning this graphic with the Home App.  Even easier is to scan it right from your camera - your iPhone will recognize that this is a HomeKit QR Code and open the Home App for you.

You probably noticed that this QR Code contains Apple's HomeKit logo in the upper left.  This is purely cosmetic and not required by the Home App for pairing.  Similarly, the device's 8-digit *Setup Code* shown in big numerals in the upper right is also cosmetic and not needed for pairing, though it may be handy if you have problems scanning the QR Code and need to manually enter the *Setup Code* into the Home App.

The only portion of the graphic actually scanned by the Home App is the QR Code itself, which means that you can use any generic QR Code generator instead of Apple's version, provided the generator allows you to create a QR Code from arbitrary text (most do).

The text input you'll need to provide to a generic QR Code generator is the Setup Payload.  There is a relatively straightfoward algorithm yuo can follow to determine the Setup Payload for your device based on all the inputs (see below), but its even easier to let HomeSpan do it for you.

HomeSpan outputs its Setup Payload to the Arduino Serial Monitor whenever it generates a *Setup Code* or you set/change the *Setup Code*.  Simply copy the *Setup Payload* from the Serial Monitor into a generic QR Code generator, and viola, you have a scannable QR Code you can use to pair your HomeSpan device.