Embeddded paper

1. Analysis and Design of an Embedded System to aid
the navigation of the Visually Impaired
Carlos Solon S. Guimarães Junior#1
, Renato V. Bayan Henriques#2
, Carlos Eduardo Pereira#3
#
Post Graduate Program in Electrical Engineering – PGPEE, Federal University of Rio Grande do Sul – UFRGS
Avenue Osvaldo Aranha, 103, Bom Fim. Zip Code: 90031-190, Porto Alegre, RS, Brazil
1
carlos.solon@ufrgs.br
2
rventura@ece.ufrgs.br
3
cpereira@ece.ufrgs.br
Abstract — This article aims to present the methodologies of
development, analysis and system design of an Electronic
Bengal, with object-oriented and structured methods, trying to
establish the main features of these. From this scenario, several
methods of system analysis are available for use. Among the
studies conducted to develop the system, using automation
techniques, are SART (Structured Analysis Real-Time) and
UML (Unified Modeling Language) modelings. Each has its
peculiarities, both in the way of diagramming and about the
script. The project proposes an electronic device with an
embedded system that contains a control algorithm to enable
vibration and audio electromechanical transducers. The project
is an electronic device based on open-source flexible platforms to
assist in the orientation and mobility of the visually impaired
during their displacement.
Keywords – Actuators, Assistive Technology, Embedded Systems,
Visually Impaired.
I. INTRODUCTION
Assistive Technology (AT) is any item, equipment or
system, acquired commercially, modified or customized, that
is used to increase, maintain or improve functional capabilities
of individuals with disabilities [1]. The definition, although
quite extensive, is used in this context to refer to tools used to
improve or enhance the functionality of technologies based on
software or hardware. Among the resources used by visually
impaired for locomotion, the white cane is presented as one of
the cheapest and safer, that is, when handled correctly [2].
Secure Mobility is one of the biggest challenges faced by the
visually impaired in their day-to-day. The traditional white
cane is part of the category "Mobility Assistance" in Assistive
Technology and is widely used to probe through the tactile
perception-coenesthetic the space ahead. Moreover, the
traditional white canes are mechanisms only useful in helping
to detect obstacles within the immediate environment
surrounding the visually impaired (micro-navigation) and
cannot predict obstacles in advance above or below the waist
line and do not report the location or global position (macro-
navigation) [3]. Due to technological advancement most of the
tasks performed by humans are aided by computers. In this
assumption, embedded computing systems are present in
various activities, are dedicated systems that have a restrict
functionality to meet a specific task in larger systems in which
they are inserted. These systems are naturally heterogeneous;
because they are composed of hardware and software
components [4].
This article describes the methodologies and tools used for
the analysis and design of the development of an electronic
device called ‘Prototype of an Integrated System for Aid to
Macro and Micro navigation of the Visually Impaired’ [5].
The project is a System of Aid to Navigation (SAN) for
substitution of vision by sound and touch (Fig 1).
Fig. 1 - Description of the electronic device.
The project is being developed at the Post Graduate
Program in Electrical Engineering (PGPEE) and is the second
phase of designing a prototype to assist in orientation and
mobility of the visually impaired for small and long distances.
The stages of the development of real-time systems are
modular and structured, however, as in any automation design,
tools and methodologies are available to assist in the
development of projects, among which we can mention the
specification using structured analysis with SART (Structured
Analysis Real-Time) methodologies and design
methodologies based on the paradigm of object orientation
with UML (Unified modeling Language) modeling.
Regardless of the chosen methodology it should give you the
breakdown of the project into parts in order to make possible
its understanding and to manage its complexity. These parts
can be represented as models that describe and abstract the
essential aspects of the system [6].
This paper is organized into four sections: section 1
presents a brief introduction of the work; section 2 discusses

2. the design of embedded system; section 3 presents the test
results of the project; finally section 4 brings the conclusions
and future work.
II. EMBEDDED SYSTEMS
The use of computer systems is growing in society, thus,
real-time applications become frequent. They vary regarding
complexity and guarantee needs for the care of temporal
requirements. The embedded applications have characteristics
that differ them from the other systems. Features such as
dedicated systems, reactive systems, reliability, real-time
restrictions, code size, performance, low power and energy
consumption, physical (size and weight) should be considered
in the development of an embedded system. To deal with
these restrictions on building an embedded system are used
high abstraction level modeling languages. Thus, the design of
an embedded system parts from an abstract view and
throughout the development refinements are being made until
the finalized product [7]. The design of the embedded system
involves steps with different abstraction levels, as the flow
illustrated in Fig. 2.
Fig. 2 - Levels of abstraction for the design process of embedded systems
According to this flow, the design steps comprise:
 requirements analysis: definition of system
requirements;
 specification: detailing the features of the system;
 system architecture: internal detailing of the system as
well as of the components that make up the system;
 project of components: designing system components;
 system integration: integration of the components
developed for the system and their validation.
There are several models of life cycle. In the project of the
electronic device are used two development strategies. The
top-down approach, where the project starts with a more
abstract perspective and through successive refinements the
system itself is obtained, and the bottom-up approach, in
which the project starts with a description at the level of
components and from these components is build up the
complete system allowing decisions about the cost of the
components and understand what is the best architecture for
the system. It is a mix of the two approaches so that critical
decisions can be taken in time to avoid rework [8].
A. Specification of Hardware
Unlike traditional white cane, that accompanies unevenness
of the floor but cannot predict objects in different positions
and neither inform the global location, the proposed device
has an embedded system. For a better description of the
system it has been developed a block diagram (Fig. 3), whose
goal is the graphical representation of the process and model
of the system. Through geometric figures and connections, we
describe the relationships between each subsystem and the
information flow. The system hardware prototype currently
consists of a module GPS (global positioning system), GSM
(Global System for Mobile Communications), LDR (light
dependent resistor) and two sonars (ultrasonic sensors) that
are inserted into the device, through an trigonometric
analytical model developed to calculate the distance and
height of obstacles, using geometric relationships of
inclination (angle α) of the sonars to determine the best points
of coverage.
Fig. 3 - Block Diagram of Electronic Bengal
The GPS module sends the global positioning information
using the NMEA 0183 protocol. The protocol is based on
ASCII and transmitted serially to the controller who transfers
the data from a GSM connection to a GGSN (Gateway GPRS
Support Node) of the mobile operator that provides the data to
a remote server throug a TCP (Transmission Control Protocol)
connection. After receiving the connection, all information
sent over the cellular network are received, processed and
stored on the application server. This phase of the project is
under development and study [9][10]. So, we intend to obtain
an ideal system for tracking people with visual impairments
and thus helping in their displacement returning information
of the global location and their environment (Fig. 4).
Fig. 4 - Architecture of the tracking system

3. The treatment of the information received and transmitted
by the modules and sensors is processed by a microcontroller,
with a control algorithm to activate the sound and vibration
actuators (Fig. 5). The modules and sensors stimulate the
actuators indicating the global location, light level of the
ambient and the evidence of objects above and below the
waistline. The global location and intensity of light are
informed by audio, since the existence of obstacles is
confirmed by the vibration generated by vibrating actuators
(micro motors) inserted into a tact device, located on the
handle of the prototype. Thus the device user can make
decisions according to the information received from the
actuators and gain more confidence in his displacement.
Fig. 5 - Hardware components of the electronic device
The prototype is a hardware and software work based on
open-source flexible platforms for its development. For the
construction of the proposed project initially we will use the
microcontroller ATmega328P by ATMEL. The choice was
due to a combination of factors: low price, community of
developers, development time, programming and ease to find
the Integrated Circuit (IC) in the market. Part of the hardware
circuit was designed in the Eagle software (software for
design of Printed Circuit Boards) (Fig. 6), so that
subsequently be created a PCB of the project with all
components on a single hardware platform. The circuit
presents some of the connections of the peripherals of the
microcontroller ATmega328P that will be replaced later. The
work is ongoing and the Shield GSM module is being tested
with the circuit until it be incorporated into the project.
Fig. 6 - Partial circuit design software in Eagle
The communication between the control interface and the
device is via a standard serial connection. The ATmega328P
allows serial communication in the UART TTL standard (5 V),
which is available on digital pins 0 (RX) and 1 (TX). A USB-
TTL FTDI converter was used in the prototype and is
responsible for serial communication. An FTDI FT232RL
chip forwards this serial communication through USB and the
FTDI drivers provide a virtual port for the software in the
computer [11].
B. Development System: Analysis Structured
Like all methodologies of software requirements analysis,
structured analysis is used to be an activity of developing
models with data flow and content of information divided into
functional partitions, representing the characteristics of what
must be developed. The first design methodologies focused on
real-time systems have emerged as an extension to the
techniques of structured analysis. The most important of these
extensions were the SA-RT (Structured Analysis Real-Time)
methodologies [12]. From the SA-RT method, we can
describe the problem to be solved by using a functional
decomposition with the use of diagrams, lists, state machine
and data dictionaries.
The design requirements are presented through Data Flow
Diagram (DFD) that shows how the data is processed by the
system in terms of inputs and outputs. The fundamental model
of the system or context model (Level 0) presents the control
system of the design of the embedded system represented by a
main process and around it entities and data flows which have
direct relation with the control system. The Fig. 7, shows the
context diagram of the project.
Fig. 7 - Context diagram of the electronic device
The level 1 DFD, shown in Fig. 8, is partitioned using
Ward and Mellor extensions to represent more details of the
global system. The first level of the DFD shows the main
processes of the system. The processes that make up the
system are sub functions of the global system described in the
context model and are defined as tasks that are performed in
parallel. The process control (dashed bubble) termed as

4. ‘Control Processing’ performs all data flows received from
other processes of the data system and according to the
information flows it starts the vibration and audio actuators.
Fig. 8 - Extension Ward and Mellor representing DFD level 1 system
The State Transition Diagram (STD) (Fig. 9) is the
detailing of the control process ‘Control Processing’ and
represents the behavior of the system showing the states and
the events that cause the system to change state. The STD
indicates which actions are initiated as consequence of events.
A state is any observable behavior mode, through it the
system data flows are initialized and sequenced and initiated
according to the request.
Fig. 9 - State Transition Diagram of the system
The main advantage of the structured analysis is in the
development of a system requirement. Having a complete
requirements model in a diagram structured helps to ensure
that all requirements are assigned to the components of the
system architecture, which leads to present a situation in terms
of data rather than presenting it from the standpoint of any
person or company. Users get a clearer idea of the proposed
system by the data flow diagram, than that obtained through
the narrative and flowchart of physical systems, the
presentation in terms of logic flow can show
misunderstandings and controversial points.
As a disadvantage, we can cite the difficulties caused by
communication problems, difficulty in describing procedures,
lack of appropriate methodologies to assist in the specification
of systems, maintenance problems of specification document,
level of detail required, mainly in the construction of the data
dictionary. Changes of requirements make structured analysis
a critical stage in the development of systems [13].
C. Development System: Orientation Objects
In recent years, design methodologies based on the
paradigm of object orientation has been identified as an
interesting alternative to combat the deficiencies presented by
the techniques of structured analysis. This paradigm has
several features that facilitate the understanding of the model
and allows a higher encapsulation for the data and facilitates
re-use. Consequently, the paradigm of object orientation also
ended up being successfully applied in the development of
real-time systems.
The Unified Modeling Language (UML) is a language and
not a method, it is a project notation standard language. For
notation it is meant to specify, visualize and document the
elements of an object-oriented system [14]. A class diagram in
UML (Fig. 10) is a type of static structure diagram that
describes the structure of the system, showing the project's
classes, its attributes, operations and the relations of messages
between themselves.
Fig. 10 - Partial class diagram of the project
The case use diagram describes the proposed functionality
for the system. A use case represents a discrete unit of
interaction between an user (human or machine) and the
system. The project has eight actors and their respective
interactions with the use cases of the project. Thus the
diagram is demonstrating the functionality of the system.
Fig. 11 - The case use diagram of the project

5. The partial sequence diagram of the project (Fig. 12) is a
kind of interaction diagram that shows how processes interact
with each other and in which order. It is a construction of a
chart of message sequence and interactions of object arranged
in time sequence.
Fig. 12 - Part of the sequence diagram of the project
The advantage of object-oriented analysis is that it can
better represent the real world. It is also used from analysis to
design and implementation, so that the information added in a
stage of development is not necessarily lost or translated to the
next step. There is a reduction in the amount of errors with
consequent reduction of the time in the steps of coding and
testing. The creation of new objects that communicate with
existing ones does not require the developer to know the
interior of the latter. The analyses of an object-oriented design
aim to identify the best set of objects to describe a software
system. The operation of this system happens through the
relationship and exchange of messages between these objects.
Disadvantages include the appropriation, because the
object-oriented analysis does not always solve the problems
elegantly. The criteria for classifying objects may change
significantly. Moreover, sometimes it is not possible to
decompose real-world problems in a class hierarchy. The
paradigm of objects does not treat well the problems that
require fuzzy boundaries and dynamic rules for classifying
objects. This leads to the next problem: fragility. Since an
object-oriented hierarchy requires precise definitions, if the
fundamental relationships between the key classes change, the
original object-oriented design is lost. It becomes necessary to
re-examine the relationships between the main objects and
redesign a new class hierarchy [15].
D. Software Development
The object-oriented programming is different from the
structured programming. In object-oriented programming,
functions and data are together, forming the object. This
approach creates a new way to analyse, design and develop
programs, it is a more abstract and generic way, which allows
greater reuse of codes and facilitates their maintenance, for
these reasons the chosen programming language uses the
concepts of Object Oriented Programming (OOP). What
defined the choice of the method was the reusability,
developer experiences and development time of the product to
be produced. To carry out the development of the embedded
system design in OOP was used the programming language
C/C++. It’s important to say that not all design classes were
implemented. Coded system classes are shown in Table 1, the
other system classes are in development and heuristics process.
TABLE I
IMPLEMENTED PROJECT CLASSES
Class Description
Main
Class responsible for running our program, where
are instantiated the objects of other classes of the
project, Fig. 13 shows the output on the „Serial
Monitor‟. The builders of the objects as a parameter
receive the pins of electronic components:
#include "ControlCane.h"
#include "Sonar.h"
#include " Light.h"
#include "SkyGPS.h"
#include “MotorVibration”
#include <NewSoftSerial.h>
:
void setup () {
Motor umotor = Motor (pinMOTOR);
SkyGPS gps = SkyGPS(RX, TX);
Sonar obstacle = Sonar(ECHO, TRIGGER);
Light intensity = Light (ldrPin);
ControlCane control = ControlCane(name);
}
Sonar
Obstacles sensor class with method that returns the
distance of obstacles in inches:
 distance = obstacle.getDistance();
SkyGPS
Class for GPS receiver with method that returns the
Global Location (latitude and longitude):
 delta = gps.getGPS();
Light
Class for the light sensor with method that returns
the ambient light level:
 level = intensity.getLight ()
Motor
Class for vibration actuators with methods that turn
on and off the micromotors:
 umotor.onMotor();
CaneControl
Class that controls and checks the return values of
the sensors and modules:
 control.checksGps(delta);
 control.checksSonar(distance)
 control.checksLight(level);
The developed classes consist of libraries in C/C++ and
should be inserted inside the folder ‘libraries’ of the Arduino
software to run the tests in the main program. The
implemented classes use the API of the language ‘Wiring
C/C++’ for its development. The libraries are being tested also
in programming environments Atmel Studio 6 and
Codeblocks IDE.
III. RESULTS SYSTEM
For testing we used initially the Arduino integrated
development environment [16]. The serial communication
between the hardware prototype and the computer starts the
samples of the results in real time via the ‘Serial Monitor’ of
the software which allows simple textual data to be sent and
received (Fig. 13).

6. Fig. 13 - Results of acquisition module and sensors in real time
The results of the values of acquisitions of sensors and
actuators activation consist of instantiated objects and can be
viewed on a screen in text that provides the real time
information of the test. The GPS receptor tells you the latitude
and longitude, global position data are passed to a map using
‘GPS Visualizer’ for initial testing [17]. The sonar reports the
distance of obstacles in inches, if the obstacle is at a distance
shorter than the chosen threshold (40 inches), it is fired the
DC micro motor and, lastly, the LDR informs the level of
ambient light. The embedded system was tested in PGPEE -
UFRGS.
IV.CONCLUSION AND FUTURE WORK
Throughout the article were presented the elements that
are part of the proposal of the system, ie, methods based on
the structured and object-oriented paradigm that address
development concepts of the embedded system. The work
presented covers the study area widely, as it includes the steps
of modeling, design, implementation of a real time application.
The biggest benefit of the method chosen for implementation
(OOP) is that the project is divided into components and not
processes. Structured languages have routines and functions
scattered throughout the system. As the project is constantly
evolving, if in the future there’s need to change some data,
function or property, would be necessary to return to the stage
of testing and analysis of the entire system to make sure that
the change did not trigger changes in the rest of the schedule.
OOP contain properties, functions and routines of the objects,
all in a single object, encapsulated, facilitating the future need
for changes, updates and code reuse, besides the ease that it is
possible to inherit attributes and behaviours from other objects.
Future works include the development of Threads,
replacing microprocessor ATmega328P by the ARM Cortex-
M3 (32-bit) and sonar for another with greater coverage and
precision to achieve the desired performance for the
application. Accelerometers, audio processing, images and
radio frequency identification are also being investigated.
With the global positioning system, the goal is to write in a
data file the latitudes and longitudes of the GPS. Considering
that the micro controller data storage memory is quite limited,
are being used memory cards as an alternative to store data in
general. With the data file generated we will send data
through the GSM/GPRS module to a central server that will
convert location data into positions on a map initially using
the ‘GPS Visualizer’, a free site that creates maps, driving
routes , addresses or simple coordinates from GPS data in
order to see where you've been, plan where you're going or
visualize geographic data only. This goal was achieved and
are being developed and investigated other ways to implement
a dedicated maps server using the ‘Google Maps’ API. It was
not possible to perform usability testing with visually
impaired because the prototype has not yet reached sufficient
level of usability. The final tests showed that there is still
room for improvement in the overall project.
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