# GATTCCharacteristic

The smallest concept in GATT is the Characteristic, which encapsulates a single data point (though it may contain an array of related data, such as X/Y/Z values from a 3-axis accelerometer, longitude and latitude from a GPS, etc.).

The following class allows you to manage characteristics from a Client.

## Methods

#### characteristic.uuid()

Returns the UUID of the service. In the case of 16-bit or 32-bit long UUIDs, the value returned is an integer, but for 128-bit long UUIDs the value returned is a bytes object.

#### characteristic.instance()

Returns the instance ID of the service.

#### characteristic.properties()

Returns an integer indicating the properties of the characteristic. Properties are represented by bit values that can be OR-ed together. See the constants section for more details.

#### characteristic.read()

Read the value of the characteristic, sending a request to the GATT server. Returns a bytes object representing the characteristic value.

#### characteristic.value()

Returns the locally stored value of the characteristic without sending a read request to the GATT server. If the characteristic value hasn't been read from the GATT server yet, the value returned will be 0.

#### characteristic.write(value)

Writes the given value on the characteristic. For now it only accepts bytes object representing the value to be written.

```python
characteristic.write(b'x0f')
```

#### characteristic.callback(trigger=None, handler=None, arg=None)

This method allows to register for notifications on the characteristic.

* `trigger` can must be `Bluetooth.CHAR_NOTIFY_EVENT`.
* `handler` is the function that will be executed when the callback is triggered.
* `arg` is the argument that gets passed to the callback. If nothing is given, the characteristic object that owns the callback will be used.

#### characteristic.read\_descriptor(uuid)

Returns the value of the descriptor specified by the `uuid` parameter. If no descriptor found for the characteristic returns None.

```python
descriptor = char.read_descriptor(0x2900)
if(descriptor != None):
    print("Characteristic Extended Properties: " + str(binascii.hexlify((descriptor))))

descriptor = char.read_descriptor(0x2901)
if(descriptor != None):
    print("Characteristic User Description: " + str(binascii.hexlify((descriptor))))

descriptor = char.read_descriptor(0x2902)
if(descriptor != None):
    print("Client Characteristic Configuration: " + str(binascii.hexlify((descriptor))))

descriptor = char.read_descriptor(0x2904)
if(descriptor != None):
    print("Characteristic Presentation Format: " + str(binascii.hexlify((descriptor))))
```


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