Hardware Reference
In-Depth Information
More and more BR/EDR devices entering the market include BLE as well, and the trend
is expected to continue as single-mode BLE sensors become more ubiquitous. Those
dual-mode devices can forward the data obtained from a single-mode BLE device to
the internet using their GSM or WiFi radios, a feature that is becoming more and more
common as more BLE sensors enter the market.
Based on Chip Count
Chapter 2
introduces and discusses the several protocol layers that constitute the Blue‐
tooth protocol stack, but for now it suffices to outline the three main building blocks
of every Bluetooth device:
Application
The user application interfacing with the Bluetooth protocol stack to cover a par‐
ticular use case.
Host
The upper layers of the Bluetooth protocol stack.
Controller
The lower layers of the Bluetooth protocol stack, including the radio.
Additionally, the specification provides a standard communications protocol between
the host and the controller—the Host Controller Interface (HCI)—to allow interoper‐
ability between hosts and controllers produced by different companies.
These layers can be implemented in a single integrated circuit (IC) or chip, or they can
be split in several ICs connected through a communication layer (UART, USB, SPI, or
other).
These are the three most common configurations found in commercially available
products today:
SoC (system on chip)
A single IC runs the application, the host, and the controller.
Dual IC over HCI
One IC runs the application and the host and communicates using HCI with a
second IC running the controller. The advantage of this approach is that, since HCI
is defined by the Bluetooth specification, any host can be combined with any con‐
troller, regardless of the manufacturer.
Dual IC with connectivity device
One IC runs the application and communicates using a propietary protocol with a
second IC running both the host and the controller. Since the specification does
not include such a protocol, the application must be adapted to the specific protocol
of the chosen vendor.
