Hardware Reference
In-Depth Information
• Host Controller Interface (HCI), Controller side
• Link Layer (LL)
• Physical Layer (PHY)
In this chapter, the order of sections will describe the different parts that make up a BLE
device from bottom (antenna) to top (user interface).
Figure 2-1. The BLE protocol stack
Physical Layer
The physical (PHY) layer is the part that actually contains the analog communications
circuitry, capable of modulating and demodulating analog signals and transforming
them into digital symbols.
The radio uses the 2.4 GHz ISM (Industrial, Scientific, and Medical) band to commu‐
nicate and divides this band into 40 channels from 2.4000 GHz to 2.4835 GHz. As shown
in
Figure 2-2
, 37 of these channels are used for connection data and the last three chan‐
nels (37, 38, and 39) are used as advertising channels to set up connections and send
broadcast data.
