EN1002 Engenharia
Unificada I
FERRAMENTAS E EXEMPLOS DE PROJETO COM O LEGO
MINDSTORMS
Centro de Engenharia, Modelagem e Ciências Sociais
Aplicadas
Bluetooth control using Lego Mindstorms for
Educational Engineering
The Agenda:
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Wireless technology overview
Bluetooth protocol
LabVIEW
Lego Mindstorms NXT
Project implementation
Project planning
1
Wireless Technology
Frequency- hopping
Frequency- hopping
Wi-fi Hops about every 0.1 sec
Bluetooth is hopping every 625 microseconds
and as fast as 3200 hops a second when initially connecting.
Hopping Benefits are:
bandwidth can be utilized more efficiently
Security level (difficult to intercept)
In order to avoid collisions with other Bluetooth transmitters in the same
area, Bluetooth uses pseudo-random generation algorithm to identify the
frequency hopping pattern between two devices.
The hopping pattern is based on the Bluetooth Device Address information, a
unique identifier that is assigned to every Bluetooth transmitter.
OSI reference model and
Wireless
The Physical layer of the OSI model is a physical infrastructure of
the network.
the Data Link Layer receives information on its software side from
higher layers, places this information inside of "frames",
and finally gives this frame to the Physical Layer, for transmission.
The data link layer of the 802 protocols is split into:
Medium Access Control sub-layer which determines who gets to
transmit next
LLC (Logical Link Control) sub-layer, hiding the differences between
the different 802 variants and make them indistinguishable for the
network layer.
Bluetooth Protocol
Bluetooth Physical Layer (RF)
• Utilizes the license free 2.4GHz
ISM radio band
• Pseudo-random frequencyhopping scheme with 1600
frequency hops per second
(FHSS)
79 carriers (f=2402+k MHz,
k=0,…,78)
• Performing Gaussian Frequency
Shift Keying modulation
Power classes :
– I : max output power : 100mW (20dBm) => 100m
– II : max output power : 2.5mW (4dBm) => 20m
– III : max output power : 1mW(0dBm) => 10m
Bluetooth Protocol
Baseband Layer
• Enables RF to form a piconet
(physical channel shared among several
devices)
• Up to 7 slaves can be connected to 1
master
• Provides 2 different kind of physical links,
with their corresponding packets
– Synchronous Connection-Oriented (SCO)
– Asynchronous Connection-Oriented (ACL)
• Responsible for assembling the Bluetooth
packet header information, and for
applying error checking and data whitening
Baseband: The Baseband and Link Control Layer enables the RF link Bluetooth
units in a piconet. This layer uses inquiry and paging procedures to synchronize
the transmission between different Bluetooth devices.
Bluetooth Protocol
Link Manager Protocol (LMP)
• Responsible for link set-up between
devices, including security functions :
– Authentication
– Encryption
• Controls and negotiates baseband packet
size
• Controls power modes and connection
states
Link Manager Protocol (LMP): The link manager protocol is responsible for setting
up link channels between Bluetooth devices after performing security methods like
authentication and encryption by generating, exchanging and verifying linking and
encryption keys and negotiating baseband packet size.
Bluetooth Protocol
Logical Link Control and
Adaptation
Protocol (L2CAP)
Its role is to adapt upper protocols over the
Baseband :
– Multiplexing capability
– Segmentation and reassembly operations
Permits to transmit and receive upper layer
data packets up to 64kB in length
Also permits per-channel flow control and
retransmission
In standard Bluetooth hardware, the lower three layers are implemented in firmware
or in hardware, and are generally not accessible to Bluetooth developers.
Instead, Bluetooth developers interact with the host controller layer (HCI)
which resides at a boundary between the host operating system (such as Windows or
Linux) and the Bluetooth hardware.
Above the HCI layer is the Logical link Control and Adaptation Protocol (L2CAP)
is an abstraction layer above the HCI and LMP layers, handling application
functionality for upper-layer protocols.
Bluetooth Protocol
SDP - Service Discovery Protocol:
Using SDP, device information, services
allowed and characteristics of the services
are queried between Bluetooth enabled
devices.
RFCOMM - Cable Replacement Protocol:
RFCOMM is a serial line emulation protocol.
TCS Binary, AT Commands are used to establish speech and data calls between devices
and control mobile phones and modems respectively (Telephony Control Protocol).
Adopted Protocols: Bluetooth also supports PPP, TCP/UDP/IP, OBEX and WAP protocols
to maximize interoperability.
Bluetooth Protocol
In order to accommodate the relatively
low cost of a Bluetooth radio, the
Bluetooth protocol stack is designed in a
layered approach. The layered approach
allows different portions of the protocol
stack to be designed independently and
tightly integrated into hardware, which is
important for lightweight devices such as
headsets that have limited memory
availability.
In this project, three lower layers can be attributed to Bluetooth USB
dongle, while above it are host controller and adaptation protocols,
which realized with Lego Fantom driver. Upper protocols are provided by
operating system.
LabVIEW
Visual Programming:
• Utilizes human visual system
􀂄 Should be more “natural”
•Avoid syntax
•People were already using
graphical notations
􀂄 Flowcharts and Data flow,
State-Transition Diagrams,
Wiring Diagrams
• Use these directly
LabVIEW example
This VI continuously
generates two signals:
a pure sine wave of
variable frequency and
amplitude and a white
noise signal of a variable
amplitude
The noise is then added to
the sine wave
The sine wave with and
without the noise are then
shown in a time domain
graph.
Additionally an FFT is
calculated for both
signals
and the results are then
shown in the frequency
domain graph. Note that
the square shaped
functions are
subroutines in the form
of sub-VI’s
LabVIEW
LabVIEW advantages
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Compiled language
Intuitive interface
Easy to learn
Widely used in industry for R&D and production automation
Build executables
Run VI’s as web site
In-built math functions and examples
Community of users and shareware resources
Lego Mindstorms NXT
The LEGO Mindstorms® is a robotic building
system consisting of:
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The NXT Intelligent Brick: the brain of
the system
Sensors and servo motors
LEGO TECHNIC Elements
Programming software
Lego Mindstorms NXT
iRobot Create, Roomba
http://www.irobot.com/
2 bump sensors
Odometer
IR wall sensor on right side
Virtual wall infrared sensor
Remote control infrared sensor
Vacuum and motor control
Serial interface
RoombaDevTools Bluetooth Interface
($100)…
Lego Mindstorms NXT
Scribbler
www.scribblerrobot.com
Sensors
IR “ranger”;
2 receivers and emitter
Stall sensor
3 light
2 “line” (IR pairs)
2 DC motors
Programmed in PBasic
Serial communication (up to 38400 baud)
SD202 Bluetooth adapter ($100)
Serial emulation
Class 1
Lego Mindstorms NXT
Mindstorms in Engineering Educational Community
MIT Media Lab
http://www.media.mit.edu/
http://www.roboteducation.org/
http://www.ni.com/academic/mindstorm
s/
http://www.mindstorms.rwth-aachen.de/
http://www.engr.utexas.edu/dteach/
Project Implementation
The system:
PC with USB
Bluetooth adapter,
running control
LabVIEW software
and an NXT sensorequipped robotic
vehicle
Project Implementation
LabVIEW
control code
Project Implementation
LabVIEW
Front Panel
Project Implementation
LabVIEW independent
mode sequence,
monitoring the events
of two sensors until
new pairing passkey
from master arrives to
Bluetooth mailbox.
Ultrasonic sensor event
A Touch sensor event
Project Planning
Why project management?
By having good project management, we can
Achieve the project goal on time and within the budget
Keep the focus on the goal and work well
Have a good practice for future work situations
Present the project materials by acceptable engineering standards
Project Planning
The process of project development is full of uncertainties
The more uncertainties you have, the less possible that the project can be
successful
Uncertainties can be reduced by having a good feasibility study before the
project
Background research
Understand the resource required and acquired
Risk analysis
Project Planning
Project Initiation
document
• The purpose is to identify and document the
exact requirements for the project
• Much interaction must take place between
the customer (e.g. advisor) and the
developer (student)
• Should be well documented since very often
it serves as an agreement of the functions
that will be provided by the system
developed
• The document is sometimes called user
specifications or functional specifications.
• May form the basis for project
commissioning
Project Planning
System design and specification
Split into two sub-phases: architectural and
detailed design
• Architectural design
Define the overall organization of the
system in terms of high-level components
and their interaction
• Detailed design
Lower level modules in each component
and their interfaces
The document is sometimes called
technical specifications
Project Planning
Implementation – Work breakdown – MS
Project
• Split project into tasks and
estimate time and
resources required to
complete each task
• Minimize task
dependencies to avoid
delays caused by one task
waiting for another to
complete, considering the
fact that concurrent
organization of the tasks is
limited since all the work is
done by one student