# Important Information About Bluetooth LE

## Important Information About Bluetooth LE

* When calling functions startScanningForPeripherals or openDevice, the application should make sure bleReaderStateUpdated has received a device status and that the most recent status was OK , otherwise the device will not be able to connect, and iOS will not throw any error if Bluetooth is not ready.
* Starting in iOS 13, app projects must specify the Privacy Usage Description for Bluetooth by NSBluetoothAlwaysUsageDescription in the info.plist file. file. Accessing Core Bluetooth without the usage descriptions will cause a runtime crash. For backward compatibility with older versions of iOS, define NSBluetoothAlwaysUsageDescription as well.

<figure><img src="/files/P28CnOuNoB5WTjxt0Hcy" alt=""><figcaption></figcaption></figure>

* Make sure device is in pairing mode. If not, press and hold the button for 3 seconds until the blue light blinks, and then release the button.&#x20;
* Set device type and connection type.

```
self.lib.setConnectionType(UInt(BLE_EMV)) 
self.lib.setDeviceType(UInt32(MAGTEKEDYNAMO))
```

* Wait for callback bleReaderStateUpdated(), and then call startScanningForPeripheral().

<pre><code>func bleReaderStateUpdated(_ state: MTSCRABLEState) { 
        print("readerStateUpdated - ", state)

        if (state == 0) {
                // dispatch in main queue is very important
                DispatchQueue.main.asyncAfter(deadline: .now() + 0.1,
execute: {
                        self.lib.startScanningForPeripherals()
                })
<strong>        }
</strong>}

</code></pre>

* Wait for onDeviceList() callback. Here you can call getDiscoveredPeripherals().

```
func onDeviceList(_ instance: Any!, connectionType: UInt, deviceList: 
[Any]!) {
        let devices = deviceList as! [MTDeviceInfo] 
        devList.removeAll()

        let peripherals = self.lib.getDiscoveredPeripherals() 
        print(peripherals as Any)
        ...
}

```

* Select the device in the list.
* Open the device you want to connect.

```
lib.stopScanningForPeripherals()

lib.setAddress(devList[selected].address) 
lib.openDevice()
```

* &#x20;Library will pair the device. After inputting passcode, device is ready to use.


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