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Bachelor of Engineering / Science

Electronic Engineering

Module Laboratory Reports

Bachelor of Engineering / Science

in Electronic Engineering

Data Structures and Algorithms

Lee Siang Wei

Semester 1

Academic Year 2014/15

Department of Engineering Technology

School of Engineering

Waterford Institute of Technology,

Ireland.

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Table of contents

Introduction

What is mbed 3

Scope of project 4

Hardware

Details of main components 5-6

Block diagram 7

Wiring diagram 7-8

Description 8

Software

Overview 9-11

Implementation & Testing

Implementation step by step guides 12-14

Testing & Results 15-17

Problems Encountered 18

Future Recommendations 18

References 18

Appendices 19-21

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Introduction

What is mbed?

mbed is a platform for developing smart devices that are based on 32-bit ARM

Cortex-M microcontrollers. It is designed to provide a highly productive solution for

rapid prototyping and product development, with a focus on connected Internet of

Things devices.

It is a project developed by ARM, its technology partners and a community of core

developers, and it is used by tens of thousands of professional developers to create

intelligent products that take advantage of the power of modern microcontrollers and

connectivity. The mbed microcontroller was the first hardware used to bootstrap the

mbed platform, used for creating smart devices based on ARM Cortex-M

microcontrollers.

The mbed software development kit (SDK) provides the mbed C/C++ software

platform and tools for creating microcontroller firmware that runs on smart devices. It

consists of the core libraries that provide the microcontroller peripheral drivers,

networking, RTOS and runtime environment, build tools and test and debug scripts. A

components database provides driver libraries for components and services that can

be connected to the microcontrollers to build a final product.

The mbed hardware development kit (HDK) provides the recipes to build custom

hardware for devices that support the mbed SDK. This consists of interface firmware

and schematics of the microcontroller subsystems that can be used to easily create

development boards, OEM modules and re-programmable/hackable products suitable

for production and that can take advantage of the mbed software platform and

development tools. There are various hardware platforms based on the HDK available,

with the first platform being the original mbed Microcontroller board used to

bootstrap the project.

The mbed platform now supports different ARM Cortex-M hardware though porting

of the mbed SDK to support new microcontrollers, and use of the mbed HDK to

create custom boards that support the software platform.

http://en.wikipedia.org/wiki/Mbed_microcontroller

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Scope of project

The scope of this project is that to capture a photo for a racing car when the sensor

detects the motion of itself before reaching the final line. The photo will then save

into a SD memory card.

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Hardware

Details of main components

In the construction of this project, it consists of some of the main components: mbed

LPC1768, PIR Motion Sensor, LS-Y201 Camera and Breakout Board for microSD.

The mbed Microcontroller (more precisely mbed NXP LPC17680) is based around an

NXP microcontroller, which has an ARM Cortex M3 core, running at 96 MHz, with

512 KB flash, 64 KB RAM, as well as several interfaces including Ethernet, USB

Device, CAN, SPI, IC and other I/O. It is the most important part of this project as it

control all the activities of the project.

For LinkSprite JPEG color / infrared camera, it is used to capture and output JPEG

images through UART, making it easy to integrate into an existing design. It can

capture high resolution pictures using the serial port.

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PIR motion sensor with Grove compatible interface allows to sense motion, usually

human movement in its range. Simply connect it to Grove - Base shield and program

it, when anyone moves in its detecting range, the sensor will output HIGH on its SIG

pin and then activate the capture function of camera. Otherwise, it will output LOW.

It is used to detect the motion of people.

Breakout board for the microSD socket compatible with the SPI interface found on

any SD card, this tiny form factor was created for any media storage such as music

and pictures.

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Block diagram

In this project, the modular design is employed. The block diagram of this project is

shown below:

The PIR Motion Sensor acts as input as it detect the any tiny movement of things so

that it can send the signal to the main brain mbed LPC1768. Therefore the LPC 1768

will collect and progress the data in order to determine whether to activated the

infrared camera to take picture and then save the picture into microSD or not.

Wiring Diagram

The schematic diagram for this project without SD breakout board is shown above.

There are total 5 pins of LPC 1768 used in this project, pin VOUT, pin GND, pin 13,

PIR

Motion

Sensor

mbed LPC1768

microSD

LinkSprite JPEG

color / infrared

camera

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14 and 21. The VOUT is the positive side of power supply which supply the voltage

to each of the components. On the other side, the GND is ground that all the ground

of components must be connected to it. Pin 13 is TXD which is connected to the RXD

of the LS-Y201 Camera while pin 14 is RXD that connected to the TXD of the LS-

Y201 Camera. Pin 21 is the receiver signal where it connected with the pin OUT of

PIR Motion Sensor. With SD breakout board, the connection pins is shown as below:

SD Breakout Board Mbed

RSV -

CS Pin 8

DI Pin 5

VDD Pin 40 (VOUT)

CLK Pin 7

VSS Pin 0 (GND)

DO Pin 6

RSV, S1 & S2 -

Description

Each of the components gets their power supply from LPC 1768 to perform their

function as well. Therefore each of the positive side and negative side of voltage of

the components has to connect with positive and negative of LPC 1768

simultaneously. For the LS-Y201 Camera, pin TXD work as transmitting data out to

LPC 1768 and pin RXD is work as receiving data from LPC 1768. When the motion

is detected, the PIR Motion Sensor will send a high signal to pin 21, the LPC 1768

will collect the signal and process it. After processing, it will send a signal from TXD

of itself to RXD of LS-201 Camera. At this time, the camera will start to take a photo

and then the data will send back to the RXD of LPC 1768 for memory storage.

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Software

The software is designed in order to support the effectiveness of the hardware device.

The software was written in C language, and was written in sections for easy

debugging and troubleshooting. Each section is tailored to meet the duty that will be

imposed on the corresponding hardware unit.

Overview

i) Inclusion of library

First, I have to include the library of mbed.h so that the program can run smoothly

without any debugging error. This is because I use the platform of mbed to run this

project. Besides, I have to include the library of Camera_LS_Y201.h and

SDHCFileSystem.h in order to make me easier to troubleshoot the program if any

debugging error exist. Of course, you can insert all the codes into the same form too.

For PIR Motion Sensor, pin 21 defined as pin receiving signal from it, mean that

when any motion is detected, pin OUT of PIR will send signal to this pin. In addition,

pin 13 and 14 of LPC 1768 also defined simultanuesly as TXD and RXD in early

program.

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ii) Definition of SD Card

USE_SDCARD is a variable that have to defined for memory storage of captured

images. The codes above explained that 2 condition:

if SD card is detected, the captured images will automatically save into the

SD card with name of /sd/photos/IMG_%04d.jpg

if SD card is not exist, it will save into another local file with name of

/local//IMG_%04d.jpg

iii) Main program

Firstly, the camera has to reset as 0 in order to detect the connection of pin TXD and

RXD whether they both connect to the RXD and TXD of LPC 1768 or not. If the

condition didnt meet, it will display Reset fail. on the screen and the camera wont

take any photo as there are no connection between LPC 1768 and LS-Y201 camera.

Once both the connection are detected, it will display Reset OK. and the program

will continue run to the next code.

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As the camera got to take photo once PIR Motion Sensor detects the motion of human

or stuff, the program have to continue loop without ending. If any motion within the

range is detected, the if statement will run while if there is no motion detected, the

while loop will also run so that the program is said to be endless unless there is no

power supply.

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