We have already covered services and characteristics in extensive detail in the first chapter; however, we will still do a quick refresher here, just in case. We will go bottom up this time starting with characteristics first.
Characteristics are the lowest and the most important echelon of the Bluetooth Low Energy technology. Encapsulated by a related service, these are the actual state variables, each of which stores a single piece of relevant measurement and information data. It is worthwhile reading about the Heart Rate Measurement characteristic, which we will be covering extensively in this chapter.
To read about the Heart Rate Measurement characteristic, visit https://www.bluetooth.com/specifications/gatt/viewer?attributeXmlFile=org.bluetooth.characteristic.heart_rate_measurement.xml.
Characteristics have a UUID, which can be 16-bit or 128-bit...
