MOBILE APPLICATION

PROGRAMMING AND DESIGN

Chapter 5: Bluetooth Control Programming
MS. DAO TO HIEU
Office: A4 704 Mobile: 0389959524
Email: hieu.daoto@phenikaa-uni.edu.vn
11/09/2023 1
 CONTENTS

Bluetooth and Environment

Bluetooth on Android

Program BLE

Exercise

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 What’s Bluetooth?

✓ Wireless protocol for exchanging data over short

distances from fixed and mobile devices

✓ Initially proposed as a wireless equivalent to RS-

232 (COM)

✓ Developed and maintained by Bluetooth Special

Interest Group (Bluetooth SIG)

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 What doest Bluetooth mean?

❑ Named after Harald I Bluetooth (Danish

Harald Blåtand) who united Scandinavian
tribes – just like bluetooth unites different
devices.

❑ The Bluetooth logo unites the Runic

alphabetic characters "H", which looks similar
to an asterisk, and a "B", which are the initials
for Harald Bluetooth. If you look close enough
you can see both embodied in the logo.

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 TIME LINE

The Bluetooth
Bluetooth
Bluetooth Bluetooth 3.0 + HS
5.3
appeared at 1.0 Bluetooth
(High Speed)
Bluetooth Release.
Swedish Releases Releases
2.0 + EDR 5.0
electronics (Enhanced
Data Rate)
Releases
company
Ericsson Releases
5.2021
1994 1999 2004 2010 2016

1998 2002 2007 2013 10.2020

Bluetooth SIG Bluetooth Bluetooth

formed of five 2.1 + EDR 5.2
Bluetooth
companies Releases Releases
4.0
Bluetooth (Bluetooth
1.2 Low Energy)
Release Releases
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 Radio Layer

✓ Equivalent to Physical Layer of the Internet Model

✓ Operates in the 2.4 GHz ISM band (May interfere with
802.11b and 802g and DECT telephones)
✓ Bandwidth is divided into 79 RF channels which are ordered
from channel number 0-78 and are spaced 1 MHz beginning
at 2402 GHz
✓ Lower Guard Band – 2MHz, Upper Guard Band - 3.5 MHz

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 Baseband Layer
✓ Basic Bluetooth communication is performed in a
Master-Slave manner
✓ Each Master and its connected slave(s) form a Piconet
clock
✓ A Master can have up to 7 active slaves
✓ Slave may send data only if was poled by a Master

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 Piconet Clock
✓ All timing and scheduling activities in the Piconet shall
be done according to single clock - the Master clock.

✓ The clock is derived from the native device’s clock by

adding an offset

✓ All clocks in the devices run at the same nominal rate,

but mutual drift causes inaccuracies .

✓ The offsets in the slaves must be regularly updated

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Setting up a Piconet – Paging Mode
➢ The device formerly performing inquiry enters page
mode
➢ In the page mode the paging device continuously
transmits an ID packet containing slave’s access code
➢ The device that responded to an inquiry may enter the
page scan mode
➢ On receiving a page message with its access code the
scanning device responses with an FHS (Frequency
Hopping Synchronization)
➢ Master then responses with another FHS
FHS
s
FHS

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 Connection Established
 Paging device becomes master
 Scanning device becomes slave (roles may be
exchanged)
 Clocks and hoping sequences are synchronized

Master Slave

Clean my
buttons!

Okay…

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 Bluetooth Packet Format
Basic Rate Packet (Bluetooth 1.0-3.0)

Enhanced Data Rate Packet

Acess code

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 Packet Exchange Examples
Page Scan Physical Channel

Same Frequencies used in the first and second 635ns periods

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 Addressing and Access codes

Bluetooth (BD_ADDR) including 48 bits address:

➢ 3 Type of access codes derived from the address

➢ Device access code (DAC) (Device’s LAP)

➢ Channel access code (CAC) (Piconet Master’s LAP)

➢ Inquiry access code (IAC) (Paged Device’s LAP)

UAP
LAP( 24 bit) NAP (16 bit)
(8 bit)

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 Physical Channels
 Pseudo-random RF channel hopping sequence

 Sequence is algorithmically derived from the Piconet

Master’s address

 The frequency hopping in the Piconet physical channel is

determined by the Piconet clock

 The maximum hop rate is 1600 hops/s in the connection

state and 3200 hops/s in the inquiry and page substates

 4 Physical channel types are defined

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 Physical Channel Types
Basic Channel
Adapted Physical Channel •The basic Piconet physical channel is
defined by the master of the Piconet.
•May be based on less than • The master controls the traffic on the
the full 79 frequencies of the Piconet physical channel by a polling
basic Piconet physical scheme
channel. •Characterized by a pseudo-random
hopping through all 79 RF channels.
Inquiry Scan Physical Page Scan Physical Channel
Channel
•Used in Page and Page Scan Modes
•Used in Inquiry and Inquiry
Scan Modes •Follows a slower hopping pattern than the
basic Piconet physical channel
•Same characteristics as
Page Scan Physical Channel •Short pseudo-random hopping sequence
through the RF channels.

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 Active Mode
❑ Both master and slave actively participate on the channel.
❑ Up to seven slaves may be in the active mode at any given time.
❑ The master schedules the transmission based on traffic demands
to and from the different slaves. In addition, it supports regular
transmissions to keep slaves synchronized to the channel.
❑ Slaves in the active mode listen in the master-to-slave slots for
packets. These devices are known as active slaves. If an active
slave is not addressed, it may sleep until the next new master
transmission.
❑ Slaves can derive the number of slots the master has reserved for
transmission from the packet header
❑ Only the slave that is may return a packet in the next slave-to-
master slot. If no valid packet header is received, the slave may
only respond in its reserved SCO or eSCO slave-to-master slot
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 Park Mode

❑ When a slave does not need to participate on the Piconet

channel, but still needs to remain synchronized to the
channel, it can enter PARK state

❑ The parked slave wakes up at regular intervals to listen to

the channel in order to re-synchronize and to check for
broadcast messages.

❑ Synchronization and channel access of the parked slaves

is done by means of a Beacon Train

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 Beacon Train

Transmission of master-to-slave packets which the parked slaves

can use for re-synchronization
Carrying messages to the parked slaves to change the beacon
parameters
Carrying general broadcast messages to the parked slaves
Unparking of one or more parked slaves

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 L2CAP Layer
✓ Abbreviation for Logical Link Control and Adaptation Protocol.

✓ A link-layer protocol between Bluetooth devices with multiple

services

✓ Makes use of ACL logical transport (does not support SCO).

✓ Passes data to the HCI, or to the directly to the Link Manager

in a hostless system

✓ Note that L2CAP transports data, not audio (though protocols

like VoIP are regarded as data and would use L2CAP if
transferred over BT systems)
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 L2CAP Configuration Options
✓ The L2CAP_ConfigReq commands packet can negotiate terms with
other L2CAP layers, those options will affect the MTU, Flush
timeout and QoS.
✓ Maximum Transmission Unit: The maximum transmission size in
bytes the device is willing to accept, it will reject any payload larger
with a reject message containing the MTU it can handle
✓ Flush Timeout :The ammount of time in ms the device will try to
transmit an L2CAP packet segment before it gives up. If the
segment can't get through during that period – the entire packet is
flushed.
✓ Quality of Service): The quality of service option can select best
effort, or guaranteed QoS. Values such as token rate, token bucket
size, peak bandwidth, latency and delay variation can also be
negotiated.
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 L2CAP Diagram

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