Hardware Reference
In-Depth Information
Scanning for Remote Peripherals
To get started, you'll first need to allocate an instance of the
CBCentralManager
and start
the BLE scanning (see
“Advertising and Scanning” on page 19
) operation for the battery
level service:
// using the predefined BLE UUIDs for the battery level service
#
define
BATTERY_LEVEL_SERVICE_UUID
0x180f
#
define
BATTERY_DEVICE_INFO_SERVICE_UUID
0x180a
// build an array of services UUIDs of interest
NSArray
*
services
=
@
[[
CBUUID
UUIDWithString:
BATTERY_LEVEL_SERVICE_UUID
],
[
CBUUID
UUIDWithString:
BATTERY_DEVICE_INFO_SERVICE_UUID
]];
// instantiate and start Central Manager object
CBCentralManager
*
centralManager
=
[[
CBCentralManager
alloc
]
initWithDelegate:
self
queue:
nil
];
// scan for peripherals with services listed in services UUID array
[
centralManager
scanForPeripheralsWithServices:
services
options:
nil
];
self
.
centralManager
=
centralManager
;
First, you use Core Bluetooth framework to create a list (
NSarray
) of the service UUIDs
of interest, named
services
in this case. You will need to convert the UUID strings into
CBUUID also converts the predefined 16-bit service and characteristic UUIDS into the
their fully formed 128-bit equivalents (for more information, see
“UUIDs” on page
52
). Next, the
CBCentralManager
object is instantiated and the list of UUID objects is
provided as the first parameter for its
scanForPeripheralsWithServices
method. In
this case, the app scans for just two services, the device info service (
UUID
16
=0x180A
) and
the battery level service (
UUID
16
=0x180f
). Only peripherals that include the required
service UUIDs in their advertising data (see
Table 3-3
) will be returned as found.
Note that if the
scanForPeripheralsWithSevices
method were given
nil
for the first
parameter instead of the list of CBUUIDs of interest (
services
), it would return all BLE
peripherals in range. This is generally not a good practice, unless you really want to
explore all the possible peripherals with services, because it works the BLE radio hard‐
ware more, which decreases battery life.
Connecting to Remote Peripherals
When a peripheral of interest is discovered in the scanning process, the
centralManag
er
invokes
didDiscoverPeripheral
, which is where you include the delegate method
connectPeripheral
. This method returns associated instances of peripheral objects
that can be examined later using
CBPeripheral
methods:
