Getting Started With EZ-
BLE™ PRoC™ Module
www.cypress.com
Document No.: 001-96841 Rev. **
8
Bluetooth Low Energy Overview
The Bluetooth SIG defines Bluetooth 4.1, also known as Bluetooth Smart or Bluetooth Low Energy as the lowest-power
wireless standard operating in the 2.4-GHz ISM band.
Figure 6
summarizes the BLE protocol stack architecture.
The following sections briefly describe the BLE stack layers. For a detailed architecture description, see the Bluetooth 4.1
specification or the training videos on the
Bluetooth Developer
website. If you are familiar with the Bluetooth BLE stack, you
can skip these sections.
Figure 10
shows the system design for a heart rate monitoring application.
Figure 6. BLE Architecture
Physical Layer (PHY)
Link Layer (LL)
Host Control Interface (HCI)
Logical Link Control and Adaption Protocol (L2CAP)
Attribute Protocol (ATT)
Security Manager (SM)
Generic Attribute Profile (GATT)
Generic Access Profile (GAP)
H
e
a
rt
R
a
te
P
ro
fi
le
B
lo
o
d
P
re
s
s
u
re
P
ro
fi
le
F
in
d
M
e
P
ro
fi
le
G
lu
c
o
s
e
P
ro
fi
le
Controller
Host
Applications
P h y s i c a l L a y e r ( P H Y )
The physical layer transmits or receives the digital data at
1 Mbps using GFSK modulation in the 2.4-GHz ISM band.
The BLE physical layer divides the ISM band into 40 RF
channels with a channel spacing of 2 MHz, 37 of which
are data channels and 3 are advertisement channels.
L i n k L a y e r ( L L )
The link layer implements various key functionalities that
make the BLE protocol robust and low-power. Some of
these are the following:
Adaptive Frequency Hopping (AFH) to provide RF
interference immunity
24-bit CRC and AES-128-bit encryption for robust and
secure data exchange
Advertising, scanning, creating and maintaining
connections to establish a physical link
Establishing fast connections and low duty cycle
advertising for low-power operation
H o s t C o n t r o l I n t e r f a c e ( H C I )
HCI is the interface between the host and the controller.
This layer allows the host and the controller to exchange
information such as command, data, and events over
different transports.
L o g i c a l L i n k C o n t r o l a n d Ad a p t a t i o n
P r o t o c o l ( L 2 C AP )
L2CAP provides protocol multiplexing, segmentation, and
reassembly
services
to
upper-layer
protocols.
Segmentation and reassembly breaks the packet received
from the upper layer into smaller packets that the link layer
can transmit, and vice versa. The Bluetooth Low Energy
L2CAP layer supports three protocol channel IDs for ATT,
SM and L2CAP control. Bluetooth 4.1 allows direct data
channels through L2CAP (connection-oriented channels)
on top of these protocol channels.
