Bluetooth LE Device scan in background from iOS

Question

I am working on to scan BLE in Background mode.

Issue is not working in Background scan. Its working very fine in Foreground mode.

Below is few code lines.

dispatch_queue_t centralQueue = dispatch_queue_create("com.XXXXX.BLEback", DISPATCH_QUEUE_SERIAL);// or however you want to create your dispatch_queue_t
manager = [[CBCentralManager alloc] initWithDelegate:self queue:centralQueue options:nil];

- (void)centralManagerDidUpdateState:(CBCentralManager *)central 
{
    if (central.state == CBCentralManagerStatePoweredOn) {

        [self startScan];
    }

    if (![self supportLEHardware]) 
    {
        @throw ([NSError errorWithDomain:@"Bluetooth LE not supported"
                                    code:999
                                userInfo:nil]);
    }
}

- (void)startScan
{
    NSDictionary * options = [NSDictionary dictionaryWithObject:[NSNumber numberWithBool:false] forKey:CBCentralManagerScanOptionAllowDuplicatesKey];
    [manager scanForPeripheralsWithServices:nil options:options];
}

here i am passing nil as a services.

I receive log in Devices section in Xcode. But not in application.

Notice>: (Error) Discovered unknown type for scan: {
        kCBAdvDataChannel = 37;
        kCBAdvDataIsConnectable = 1;
        kCBAdvDataManufacturerData = <00003962 6708f4c1 00000000 00d02b00 20d03300 20d03300 20>;
        kCBAdvDataWSaturated = 0;
        kCBAdvDataWlanRSSI = 0;
    }, -51, puck type: 57

Please show more code - in particular your `centralManagerDidUpdateState` delegate method and where you perform the `scanForPeripheralsWithServices` in relation to receiving the powered on state in that delegate method — Paulw11, Oct 28 '14 at 10:01
Have you tried the LightBlue app from the app store to see if your peripheral is discoverable? — Paulw11, Oct 28 '14 at 10:22

score 14 · Accepted Answer · answered Oct 28 '14 at 10:33

14

You cannot scan for nil services in the background - you must specify the service(s) that you are interested in. From the documentation

Apps that have specified the bluetooth-central background mode are allowed to scan while in the background. That said, they must explicitly scan for one or more services by specifying them in the serviceUUIDs parameter.

answered Oct 28 '14 at 10:33

Paulw11

108,386
14
159
186

I think so, But which serviceUUIDs required. Is it relates to Hardware services ? https://developer.bluetooth.org/gatt/services/Pages/ServicesHome.aspx – Solid Soft Oct 28 '14 at 10:35
1

You need to identify the service that your peripheral is advertising. LightBlue can help with this or you can use your app in foreground mode to discover the services - for example heart rate is 0x180d – Paulw11 Oct 28 '14 at 10:39
Is LightBlue app scan in background ? – Solid Soft Oct 28 '14 at 10:54
1

No, but it will show you the services that your peripheral is advertising – Paulw11 Oct 28 '14 at 10:57
OK, Let me check.. Do you have any idea how to achieve this Background scan stuff ? – Solid Soft Oct 28 '14 at 11:01
1

Yes, you need to pass the UUIDs of the services that you want to scan for when you start the scan. – Paulw11 Oct 28 '14 at 13:01
In Background scan, Actual issue is, when i pass nil as services, I got above values {Notice>: (Error) Discovered unknown type for scan: } in Device console. Not in Application. So i think there is something need to change will solve my issues. – Solid Soft Oct 30 '14 at 06:59
2

**You cannot pass nil and expect to get call backs in your application**. It doesn't matter what you see in the device console. The documentation I quoted in my answer is quite clear on this – Paulw11 Oct 30 '14 at 07:04
Achieved. Problem with hardware side. Thanks for your time to support. accepted answer.. Peripheral was not advertising services, That is issue. – Solid Soft Oct 31 '14 at 07:00

score 3 · Answer 2 · answered Oct 28 '14 at 10:29

3

For your app to continue to receive Bluetooth updates in the background, you need to add a UIBackgroundModes entry to your Info.plist and include the value bluetooth-central in the list.

answered Oct 28 '14 at 10:29

grahamparks

16,130
5
49
43

Bluetooth LE Device scan in background from iOS

2 Answers2

Linked