Page 518 - From GMS to LTE

504 From GSM to LTE-Advanced Pro and 5G

Figure 7.33 A practical example.

In step 6 a query for the content behind handle 0x0003 is performed, which is then
displayed as hexadecimal numbers by the tool in step 7. By converting the hexadecimal
numbers to ASCII characters by using a conversion table or an online tool, the device’s
name is revealed to be ‘SensorTag 2.0’.
By applying the same methodology, any other attribute, i.e. variable, such as temperature
values, switch positions, light sensor information, etc., can be read or written to.
Typically, handle numbers do not change between connections to the device. Therefore,
requesting the list of services and characteristics of the device to find a particular variable
to read from or write to only needs to be done once. This is not guaranteed, however, so
GATT clients should check a change indicator variable after reconnecting to a remote
GATT server device.

7.7.7 BLE Beacons
While the focus of this chapter so far has been on interactive Bluetooth and BLE com-
munication, we now look at a new device category enabled by BLE that only broadcasts
information. These devices are referred to as Bluetooth Low Energy beacons and are
one way to link physical objects into the Internet of Things (IoT). One company that
uses the BLE broadcasting features for indoor positioning for mobile devices and apps