Bluetooth APPLICATION NOTES/WHITEPAPERS - Atmel Corporation

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Bluetooth™ General Information

White Paper

Rev. 1993A–11/00

White Paper

Introduction

The Bluetooth wireless technology is the world’s new short-

range RF transmission standard for small form factor, low-

cost, short-range radio links between portable or desktop

devices. The technology promises to eliminate the confu-

sion of cables, connectors and protocols confounding

communications between today’s high tech products.

Mobile phones, pagers, laptops, PDAs, digital cameras and

more, all now have a common structure for communicating

across their product platforms.

Bluetooth wireless technology provides a solution to a con-

tinuously increasing need for mobile freedom. The increase

in the number of users, and the constant shrinking, of por-

table computers, as well as the trend towards the

replacement of desktop computers from portable ones,

form an ideal market environment for a solution that elimi-

nates the annoying cable and its limitations regarding

flexibility and range.

Bluetooth is a low-cost, low-power, secure and robust stan-

dard for short-range connectivity. The technology has been

designed for ease of use, simultaneous voice and data and

multi-point communications. It supports a range of

10 meters, which can be increased up to 100 meters with

the use of an amplifier.

The initiative for the specification belongs to the Bluetooth

Special Interest Group (SIG) (www.bluetooth.com) which

was founded in February 1998. At the start, it consisted of

Ericsson Mobile Communications, Intel, IBM, Toshiba and

Nokia Mobile Phones. This group represented the diverse

market support that was needed to generate good support

for the new technology. With over 2,000 companies now

part of the Bluetooth Special Interest Group (SIG), tomor-

row’s products will fall into one of two categories: those that

are enabled with Bluetooth and those that are not.

Apart from the definition of the radio and link protocols, the

job of the Bluetooth SIG is to ensure the same interpreta-

tion of the Bluetooth standard by all future vendors.

Therefore, it has defined a number of user models and pro-

tocol profiles, as well as specific procedures for

interoperability verification.

White Paper

How Does It Work?

Any Bluetooth system has four basic parts: a radio (RF)

that receives and transmits data and voice; a baseband or

link control unit that processes the transmitted or received

data; link management software that manages the trans-

mission; and supporting application software.

The Bluetooth radio is a short-distance, low-power radio

that operates in the unlicensed spectrum of 2.4 GHz. This

spectrum is shared by other types of equipment (e.g.

microwave ovens). In order to avoid interference, the Blue-

tooth specification employs Frequency Hopping Spread

Spectrum (FHSS) techniques. Using a nominal antenna

power of 0 dBm, the range is 10 meters (33 feet). Option-

ally, a range of 100 meters (328 feet) may be achieved by

using an antenna power of 20 dBm. Data is transmitted at a

maximum gross rate of up to 1 Mbps. Protocol overhead

limits the practical data rate to a little over 721 kbps. Inter-

ference or being out of range may further decrease the

achievable data rate.

Baseband is the hardware that turns received radio signals

into a digital form, which can be processed by the host

application. It also converts digital or voice data into a form

that can be transmitted using a radio signal. The baseband

processor takes care of converting data from one form to

another (such as voice to digital data), compressing it, put-

ting it into packets, taking it out from packets, assigning

identifiers and error correction information and then revers-

ing the entire process for data that is received. In

Bluetooth, the baseband function is called the link

controller.

The link manager software runs on a microprocessor and

manages the communication between Bluetooth devices.

Each Bluetooth device has its own link manager, which dis-

covers other remote link managers, and communicates

with them to handle link setup, negotiate features, authenti-

cate QoS and to encrypt and adjust data rate on link,

dynamically.

The application software is embedded in the device that

operates an application over the Bluetooth protocol stack

(see Figure 1). This software allows the PDA, mobile

phone, or keyboard to do its job. All Bluetooth devices must

have compatible sections in their Bluetooth stack, so that

all Bluetooth devices will be able to interoperate with each

other.

Figure 1. The Bluetooth Protocol Stack

Host Controller Interface (HCI)

Link Manager Protocol (LMP)

Link Controller (LC)

Bluetooth PHY

(Baseband Processor and RF )

Host Controller Interface

Transport layer (HCI Transport)

Link Control & Adaptation

Protocol (L2CAP )

Host Controller Interface

Transport layer (HCI transport )

Host side

BT device side

Service

Discovery

Protocol

(SDP)

Applications &

OS Drivers

Host Controller Interface Driver

Host - BT device boundary (PCMCIA, USB or UART)

White Paper

The Components of a Bluetooth

System

All Bluetooth designs require an antenna, a transceiver and

a baseband controller that meet the Bluetooth specification

(see Table 1). A microcontroller (MCU) to run the link con-

trol, link manager and Host Controller Interface (HCI)

and/or Logical Link Control and Adaptation Protocol

(L2CAP) firmware, as well as memory to store the firm-

ware, configuration information and short-term operating

information are also needed. Alternatively, developers can

choose to implement protocols up to and including, HCI on

the microcontroller, and to implement the HCI driver and

L2CAP on the machine that hosts the Bluetooth chipset.

Quite a few combinations for the Bluetooth hardware are

possible. These range from single-chip solutions (RF,

Baseband, Microcontroller and memory integrated into one

chip), up to four-chip solutions (RF, Baseband, Microcon-

troller and memory in separate chips).

Atmel Offering

Atmel, a Bluetooth SIG member, is one of the world’s few

companies that offers systems designers a complete, sin-

gle-vendor Bluetooth solution – RF, baseband/

microcontroller, Flash, software and firmware. Atmel has its

main chip fab facilities in Colorado Springs, Colorado, in

Rousset, France and Heilbronn, Germany and has exten-

sive experience refining its process technologies to achieve

the system-level integration of all the components of the

Bluetooth standard.

Currently, Atmel offers a complete three-chip solution:

baseband and microcontroller functions into one chip, RF

transceiver and Flash memory. Our roadmap includes the

eventual integration of these three chips into a single-chip

solution.

Figure 2. Atmel’s AT76C551 Bluetooth Module

Table 1. Bluetooth V1.0 Specification Summary

Radio Frequency 2.45GHz (ISM band)

Spread Spectrum

Te c h n i qu e

Frequency Hopping

Hop Frequencies 79 (spaced 1 MHz apart)

Hop Rate 1,600 hops/sec (625 µs

dwell time)

Transmitting Power 1 - 100 mW

Max. Range 10 m (0 dBm)/100 m (20 dBm)

Max. Gross Bit Rate 1 Mbps

Max. Practical Bit Rate

(ACL-Symmetric)

433.9 Kbps

Max. Practical Bit Rate

(ACL-Asymmetric)

723.2 Kbps/57.6 Kbps

Bit Rate (SCO) 64 Kbps

Max. Piconet Units 8 (1 master - 7 slaves)

Power Save Modes Hold-Sniff-Park

White Paper

Atmel’s Bluetooth ICs

Atmel’s Bluetooth baseband controller, in conjunction with

a 2.45 GHz transceiver, provides a low-chip count solution

for a wide range of digital communication devices and com-

puter peripherals. The baseband is based on an

AR7TDMI™ processor, includes 64K bytes of internal

SRAM and supports three different interfaces: PCMCIA,

USB and UART. Some versions will also include a 16-bit

voice Codec capable of either log PCM or CVSD voice

coding.

For the RF part, Atmel offers T2901, which is a 0 dBm RF

transceiver with integrated synthesizer and VCO. The

transceiver supports Bluetooth’s 10 meter “Pico-Cable”

specification and features a proprietary image rejection

mixer and advanced closed loop modulation. It does not

require mechanical tuning.

Also, Atmel offers T7024, which is a 20 dBm RF front end

supporting Bluetooth’s 100 meter “Mega-Cable” specifica-

tion. The chip features 23 dBm POUT typ, low noise (2.0 dB

typ), high gain and ramp controlled output.

Atmel’s Bluetooth Firmware and

Software

ATMEL provides customers all firmware on the device side.

L2CAP and Service Discovery Protocols on the host side

can be made available to qualified customers. Software is

available up through the HCI transport layer, as well as

drivers for PCMCIA and UART interfaces. Drivers for the

USB interface will soon be available.

Figure 3. ATMEL Bluetooth Firmware Architecture Model

PCMCIA driver

UART driver

Bluetooth

Link Controller

USB driver

Voice Codec driver

Logical Link

Control &

Adaptation

Protocol

Bluetooth Device

Driver

PCMCIA driver

UART driver

USB driver

non-critical modules

executed by ARM in

user mode

time-critical modules

executed by ARM in

interrupt mode

Bluetooth

Device

Host

data Path

control path

Bluetooth

Link Manager

Host

Control Interface

PCMCIA driver

UART driver

Bluetooth

Link Controller

USB driver

Voice Codec driver

Logical Link

Control &

Adaptation

Protocol

Bluetooth Device

Driver

PCMCIA driver

UART driver

USB driver

non-critical modules

executed by ARM in

user mode

time-critical modules

executed by ARM in

interrupt mode

Bluetooth

Device

Host

data Path

control path

Bluetooth

Link Manager

Host

Control Interface

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not authorized for use as critical components in life support devices or systems.

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Printed on recycled paper.

1993A–11/00/xM

Bluetooth is a trademark owned by Telefonaktiebolaget L M Ericsson Sweden and is licensed to Atmel.

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