DESIGN, FABRICATION AND CONSTRUCTION OF A CAN SATELLITE

A RESEARCH PROJECT

BY

SENDY, INIEKE UMOETTE08/EG/CO/347

SUBMITTED TO

THE DEPARTMENT OF COMPUTER ENGINNERING FACULTY OF ENGINEERING

UNIVERSITY OF UYO

IN FULFILLMENT OF REQUIREMENT FOR THE AWARD OF BACHELOR OF ENGINEERING (BNG)

IN COMPUTER ENGINEERING

MARCH, 2014

ABSTRACT

For over a decade, student ballooning projects have provided a wonderful

opportunity of launching small scientific payloads to near space environment in a

small budget. Apart from the obvious merits of such projects, one significant

outcome is the cross disciplinary training for undergraduate science and

engineering students that prepares them for a future career in industry. Students

are also exposed to research technique that is a strong motivational factor to

work towards a graduate degree.

0.1kg satellites, called CanSats, are small and cheap enough that most universities

are able to design and build them as fully functional satellites. Designing satellite

systems in this new, small, and light-weight design presents a new challenge to

satellite developers. This report describes the design of a flexible CanSat capable

of acquiring information at Near space regions

The CanSat in this work was designed and built in 10 weeks and was used to

generate location information of its flight path and also used to measure

parameters like temperature, relative humidity, atmospheric pressure variation of

a location in real time with the aid of the onboard sensors.

The design and implementation of this project is geared towards achieving results

which will answer the objectives set for this project. This research is carried out in

University of Uyo Permanent site. The data received is clearly analysed and

explained. Experimental results show the variation of pressure, temperature, and

relative humidity with altitude.

TABLE OF CONTENTS

ABSTRACT..............................................................................................................2Table of Contents......................................................................................................5

Abbreviations..........................................................................................................10

INTRODUCTION...................................................................................................13

1.1 Background of Study..................................................................................13

1.1 Objectives of Study.....................................................................................14

1.2 Significances of CanSat Projects................................................................15

1.3 Statement of Problem..................................................................................16

1.4 Scope and Limitations of the Project Work................................................17

1.4.1 Area of Coverage:..............................................................................17

1.4.2 Hardware limitations:........................................................................18

1.5 Project Structure..........................................................................................18

LITERATURE REVIEW........................................................................................20

2.1 Introduction.................................................................................................20

2.2 OVERVIEW OF SATELLITES.................................................................20

2.3 CLASSIFICATION OF SATELLITES......................................................22

2.4 MINIATURIZED SATELLITES...............................................................24

2.5 PICO-SATELLITES...................................................................................26

2.6 CANSAT.....................................................................................................26

2.6.1 TYPES OF CanSat............................................................................27

2.7 ARCHITECTURE OF CANSAT...............................................................28

2.7.1 Structure............................................................................................28

2.7.2 Power Supply Unit............................................................................29

2.7.3 Communication system.....................................................................29

2.7.4 Onboard Computer............................................................................35

2.7.5 Mission Subsystem............................................................................38

2.7.6 Lunching Systems.............................................................................45

2.7.7 Definition of interfaces......................................................................45

2.8 An Overview of Existing Pico Satellites....................................................46

2.8.1 CubeSat XI-IV [sai-four] University of Tokyo.................................46

2.8.2 YANKEY and ROSAM Ghana.........................................................47

2.9 Conclusion..................................................................................................48

METHODOLOGY AND IMPLEMENTATION....................................................49

3.1 Introduction.................................................................................................49

3.2 Components used for the Payload...............................................................49

3.3 Components used for the Ground Station...................................................54

3.4 Design.........................................................................................................55

3.4.1 Setup design.......................................................................................55

3.4.2 Information flow................................................................................55

3.4.3 Design Specification..........................................................................56

3.5 Device Configuration..................................................................................58

3.5.1 XBee Module.....................................................................................58

3.5.2 OPENLOG........................................................................................60

3.6 Microcontroller Programming....................................................................61

3.6.1 Microcontroller..................................................................................61

3.6.2 Programming Tools Used..................................................................62

3.6.3 Interface to Radio Module and Sensors.............................................64

3.6.4 General Description of the Microcontroller Program.......................66

3.7 Construction................................................................................................69

3.7.1 Power Consumption..........................................................................69

3.7.2 Structural Design...............................................................................73

CHAPTER FOUR...................................................................................................77

TESTING AND DATA ANALYSIS......................................................................77

4.1 Testing.........................................................................................................77

4.1.1 Unit Testing.......................................................................................77

4.1.2 Integration Testing.............................................................................77

4.1.3 Impact Testing...................................................................................78

4.2 Launching...................................................................................................78

4.3 Conclusion..................................................................................................84

CHAPTER FIVE.....................................................................................................85

CONCLUSION.......................................................................................................85

5.1 Introduction...................................................................................................85

5.1 Limitations..................................................................................................85

5.1.1 Area of Coverage:..............................................................................85

5.1.2 Hardware Limitations:.......................................................................86

5.1.3 Launching..........................................................................................86

5.2 Recommendations.......................................................................................86

Future Work.....................................................................................................87

Additional Sensors...........................................................................................87

5.2.1 The CanSat Improvement..................................................................88

5.2.2 Weak Points and Improvements in the Structural Design.................88

5.2.3 Additional Tests.................................................................................89

5. REFERENCES................................................................................................90

Appendix A. XCT-U CONFIGURATION..........................................................97

Appendix B. PICKIT 3 PIC BURNER..............................................................101

Appendix C. CANSAT C CODE......................................................................104

ABBREVIATIONS

1. GPS Global Positioning System

2. NASA National Aeronautics and Space Administration

3. NMEA National Marine Electronics Association

4. ROM Read Only Memory

5. ISP In-System Programming

6. USART Universal Synchronous/Asynchronous Receiver/Transmitter

7. SPI Serial Peripheral Interface

8. EPROM Erasable Programmable Read Only Memory

9. EEPROM Electrically Erasable Programmable Read Only Memory

10.RF Radio Frequency

11.ISM Industrial, scientific and medical (ISM) radio

12.PIC Programmable Intelligent Computer

13.DOP Dilution of Precision

14.GGA Global Positioning System Fixed Data

15.GLL Geographic Position-Latitude/Longitude

16.GSA GNSS DOP and Active Satellites

17.GSV GNSS Satellites in View

18.RMC Recommended Minimum Specific GNSS Data

19.VTG Course Over Ground and Ground Speed

20.PAN Personal Area Network

21.GUI Graphic User Interface

22.MIPS Million Instructions Per Second

INTRODUCTION

1.1 BACKGROUND OF STUDY

The need for telecommunications, micro-gravity experiments, multidisciplinary

academic participation and the miniaturization of technology has made the dream

closer to reality space for academic institutions (public and private) and business

through technology integration designed reduction of size, resources, and costs of

artificial satellites. This process has lead to development of CubeSat specifications

with overall weights of less than 1kg in 1999 by California Polytechnic University

(CalPoly) by Prof. Jordi Puig-Suari and Stanford University by Professor Bob

I2Cggs to help universities worldwide to conduct space science and exploration

(Franco, 2008).

Picosatellite developments have gained popularity over the years which have

led to the development of a large number of CubeSats by CubeSat-class platforms

such as University of Surrey, Stanford University , Hawaii Space Flight Lab,

Aerospace Corporation, Angstrom Aerospace in Sweden, etc (Bordetsky et al,

2010).

There are now more than 20 organizations worldwide that are developing

and launching of CubeSat picosatellite annually (Puig-Suari, 2011). Not only is the

CubeSat project beneficial to the academia, but also in Picosatellite integration

experiments, enabling finding enhanced tagging, tracking, and global data sharing

solutions for emerging network ‐ controlled Operations scenarios (Rodrigo, 2011).

At first, development of a satellite was huge government project - involving

huge amount of money and human resources; since the advent of picosatellite,

satellite development has been reduced in cost, achieved the aim and goal of a full-

sized satellite, and also has changed aerospace engineering education in

universities from desk theory study to practical study (I2C, 2007).

The idea behind the CanSat concept was to let students be able to deal with

some of the same challenges in building a satellite, but at the same time it had to be

done over a much shorter period of time and with small expenses. The students

have to design and build instruments, place them inside a soda can and launch it

with a rocket or balloon. The soda can then falls down to the ground in a parachute

while doing different kind of experiments (Nylund, 2008).

This experimental research is based on the CanSat concept. The onboard

computer as well as all the sensors and GPS will be placed inside the Soft Drink

Can and launch with a helium- filled weather balloon.

1.2 OBJECTIVES OF STUDY

Below are objectives of this project work:

1. To learn the basis of microcontroller programming.

2. To learn and understand the working principles of PIC16F8774

microcontroller from microchips Inc.

3. To learn the basic of satellite design, fabrication and operation.

4. To acquire atmospheric data such as temperature, atmospheric pressure and

relative humidity.

5. Demonstrate the ability of the University of Uyo to design, fabricate,

integrate, test, and operate a Can-satellite of approximately 1kg in mass.

6. To have a practical knowledge of space engineering.

7. Promote and sustain research and education focused on small satellites and

related technologies.

1.3 SIGNIFICANCES OF CANSAT PROJECTS

1. Building a CanSat is a practical supplement to school subjects, such as

mathematics, design & technology, and physics.

2. Working towards a launch campaign is inspiring and raises enthusiasm

amongst the next generation of scientists, engineers and astronauts. It

communicates the excitement of space exploration and can encourage the

students to pursue a scientific degree and career.

3. Students gain the satisfaction of being involved with the end-to-end life

cycle of a complex engineering project.

4. The activity exposes students to the satellite development process, starting

with design, through integration, testing and launching, and finally data

analysis and presentation of results.

5. CanSats serve as a model to explain the composition of a satellite and

functions of the various subsystems.

6. Participants learn the importance of teamwork and project planning. They

must be organized, respect the role of each team member, set objectives and

accomplish them, have meetings and adhere to a schedule.

7. Students can develop their technical skills by designing a concept, building

it, solving problems and redesigning it if necessary.

8. The activity challenges the student’s knowledge, encouraging creativity and

innovation.

9. Students learn how to make presentations and defend their project in front of

a jury.

1.4 STATEMENT OF PROBLEM

The following factors led to the Design, Fabrication and Construction of a

Can Satellite (UyoSat1);

a) A result of the high cost involved in designing, constructing, and

launching of satellites into orbit.

b) The time it take for an amateur (and non amateur) to construct a satellite;

always in years.

c) Cost of telemetry (sending and receiving signals from satellite in orbit).

d) How to enable students have experienced in all process of designing,

fabrication, and operation of a satellite.

e) How to changed aerospace engineering education in universities from

desk theory study to practical study.

1.5 SCOPE AND LIMITATIONS OF THE PROJECT WORK

This project was limited in two key aspects - area of coverage and the hardware

used.

1.1.1 Area of Coverage:

The balloon and its payload may or may not fly beyond the vicinity of

University of Uyo Permanent Site due to environmental factor like the windy

nature of the launching site, lack of tracking devices, and topography of the area.

As a result of this, the environmental data (Temperature, relative humidity,

atmospheric pressure) taken by the onboard sensors is peculiar to the location of

the balloon.

1.1.2 Hardware limitations:

Due to the high cost of sensors and the uneasiness of interfacing them with the

microcontroller (onboard computer), several sensor have not been incorporated in

the payload like accelerometer, gamma ray burst detector, magnetometers etc.

1. The project lack mobile tracking station which would make the payload

recovery much easier.

2. High cost and complexity deter us from going for high earned

microcontrollers like the PIC18 and PIC32 families.

3. The project lack imaging system which would capture the aerial view of the

environment as the payload rises.

1.6 PROJECT STRUCTURE

Literature Review: This chapter gives an insight into satellite systems. This

leads to an overview of satellite and their classification. This review identifies the

underlying subsystem of the Can Satellite, the communication protocol use by the

components, the Cansat interfaces, and review of the existing Cansat.

Methodology and Implementation: The research methodology is outlined in this

chapter which focuses on the design requirements and experimental setup. An in

depth explanation of the different components interfaces, design setup, and

integration is illustrated in this chapter.

Result Analysis: This chapter explains the result obtained in the Cansat flight. The

telemetry receive from the Cansat is also analysed.

Conclusion: The entire work done is summarised in this chapter. A set of

recommendations is drawn from the experiments carried out in this research as

well as suggestions for future work to be done in this research.

Critical Evaluation: This chapter critically evaluates the research carried out. A

discussion of how the objectives were met will be carried out in this chapter and

the extent to which the aim of this research work has been achieved.

LITERATURE REVIEW

1.7 INTRODUCTION

This chapter gives an insight into satellite systems and forms the basis for

this project initiative. Detailed information on satellite systems based on size and

mission type will be discussed. This chapter will give an overview of the CanSat’s

subsystem – the structure, Electronics, Power, communication subsystems,

Microcontroller and as well as existing Can satellite systems.

1.8 OVERVIEW OF SATELLITES

Satellites are semi-independent computer-controlled systems. Satellite subsystems

attend many tasks, such as power generation, thermal control, telemetry, attitude

control and orbit control (NASA, 2011).

Fig 2.1 GPS satellite

Etymologically, it is derived from the Latin word “satellitem” or “satelles” -

meaning an attendant, one who is constantly hovering around and attending to a

“master” or big man (Etymology Dictionary).

In the context of spaceflight, a satellite is an artificial object which has been

intentionally placed into orbit. Such objects are sometimes called artificial

satellites to distinguish them from natural satellites such as the Moon.

The world's first artificial satellite, the Sputnik 1, was launched by the Soviet

Union in 1957. Since then, thousands of satellites have been launched into orbit

around the Earth.

Satellites are used for a large number of purposes. Common types include military

and civilian Earth observation satellites, communications satellites, navigation

satellites, weather satellites, and research satellites. Space stations and human

spacecraft in orbit are also satellites. Satellite orbits vary greatly, depending on the

purpose of the satellite, and are classified in a number of ways. Well-known

(overlapping) classes include low Earth orbit, polar orbit, and geostationary orbit.

They are usually semi-independent computer-controlled systems. It subsystems

attend many tasks, such as power generation, thermal control, telemetry, attitude

control and orbit control.

1.9 CLASSIFICATION OF SATELLITES

Satellites are launched into space to do a specific job, thus they perform specific

Function(s). The type of satellite that is launched to monitor cloud patterns for a

weather station will be different than a satellite launched to send television signals

across Canada. The satellite must be designed specifically to fulfill its function.

1. Anti-Satellite weapons/"Killer Satellites" are satellites that are designed to

destroy enemy warheads, satellites, and other space assets

2. Astronomical satellites are satellites used for observation of distant

planets, galaxies, and other outer space objects.

3. Biosatellites are satellites designed to carry living organisms, generally for

scientific experimentation.

4. Communications satellites are satellites stationed in space for the purpose

of telecommunications. Modern communications satellites typically use

geosynchronous orbits, Molniya orbits or Low Earth orbits.

5. Miniaturized satellites are satellites of unusually low masses and small

sizes.[17] New classifications are used to categorize these satellites:

minisatellite (500–100 kg), microsatellite (below 100 kg), nanosatellite

(below 10 kg).

6. Navigational satellites are satellites which use radio time signals

transmitted to enable mobile receivers on the ground to determine their

exact location. The relatively clear line of sight between the satellites and

receivers on the ground, combined with ever-improving electronics, allows

satellite navigation systems to measure location to accuracies on the order

of a few meters in real time.

7. Reconnaissance satellites are Earth observation satellite or

communications satellite deployed for military or intelligence applications.

Very little is known about the full power of these satellites, as governments

who operate them usually keep information pertaining to their

reconnaissance satellites classified.

8. Earth observation satellites are satellites intended for non-military uses

such as environmental monitoring, meteorology, map making etc.

9. Tether satellites are satellites which are connected to another satellite by a

thin cable called a tether.

10.Weather satellites are primarily used to monitor Earth's weather and

climate.[18]

11.Recovery satellites are satellites that provide a recovery of reconnaissance,

biological, space-production and other payloads from orbit to Earth.

12.Manned spacecraft (spaceships) are large satellites able to put humans

into (and beyond) an orbit, and return them to Earth.

1.10 MINIATURIZED SATELLITES

Miniaturized satellites or small satellites are artificial satellites of low mass and

size, usually under 500 kg. Small satellites with a mass between 10 to

500 kg have become a competitor to large satellites with a mass

of over 1000 kg. This development has come about through the

technological advances in microelectronics. Small satellites are

obviously less costly for launch. However, limitations for uses of

small satellites exist through special requirements imposed in

particular for remote sensing missions such as orbital and attitude

control, sensor design and data readout. While all such satellites can be

referred to as small satellites, different classifications are used to categorize them

based on mass;

1. Mini-satellites: These refer to an artificial satellite with a wet mass between

100kg and 500kg. Examples: Demeter, Essaim, Parasol, Picard etc

2. Micro-satellite: These satellites are artificial satellites with a weight mass of

between 10kg and 100kg. Examples: Astrid-1 and Astrid-2

3. Nano-satellites: The term is applied to an artificial satellite with a wet mass of

1 and 10kg. It could be lunched individually of as multiple satellites all

working together. For example, a 6U CubeSat, CanSat etc.

4. Pico-satellites: is usually applied as the name of an artificial satellite with a wet

mass between 0.1 and 1 kg (0.22 and 2.2 lb). Again designs and proposed

designs of these types usually have multiple Pico-satellites working together.

5. Femto-satellite or "femtosat" is usually applied as the name of an artificial

satellite with a wet mass between 10 and 100g. (Tristancho 2010)[1][2] Like

Pico-satellites, some designs require a larger "mother" satellite for

communication with ground controllers. Kick-Sat Sprites "chipsats" would be

in this weight class.

One reason for miniaturizing satellites is to reduce the cost: heavier satellites

require larger rockets with greater thrust which also has greater cost to finance. In

contrast, smaller and lighter satellites require smaller and cheaper launch vehicles

and can sometimes be launched in multiples. They can also be launched

'piggyback', using excess capacity on larger launch vehicles. Miniaturized satellites

allow for cheaper designs as well as ease of mass production, although few

satellites of any size other than 'communications constellations' where dozens of

satellites are used to cover the globe, have been mass produced in practice.

Besides the cost issue, the main rationale for the use of miniaturized satellites is the

opportunity to enable missions that a larger satellite could not accomplish, such as:

Constellations for low data rate communications

Using formations to gather data from multiple points

In-orbit inspection of larger satellites

University-related research

1.11 PICO-SATELLITES

Dr Antunes an astrophysicist and programmer with decades of NASA experience

is a proponent of picosatellites. These tiny birds weigh around a kilogram and are

shot up in lieu of ballast or in empty nooks and crannies on full blown satellite

lunch missions. An example of a picosatellite is the CubeSat and CanSat. The most

popular CubeSat was devised by California Polytechnic State of University and

Stanford University. It is a cube 10cm on a side, with standard electrical, physical

and lunch parameters (“The Economist”, 2012).

1.12 CANSAT

In November 1998 at the University Space Systems Symposium (USSS) held in

Hawaii, Prof. Bob Twiggs (Stanford University Space Development Laboratory)

proposed "CanSat" concept. (Emiko 2009)

CanSat is a small satellite analog, which has been used for introduction of practical

space engineering for more than ten years. All of the components, such as sensors,

actuators, and GPS, are housed inside a 350-ml cylindrical can. CanSat provides an

affordable opportunity for educators and students to acquire basic knowledge of

space engineering and to experience engineering challenges in building a satellite.

In addition, they can learn basics of system engineering, project management,

teamwork through CanSat activities. (Yamaura 2011)

1.1.3 TYPES OF CanSat

a. Telemetry: This is the one whose primary purpose is to collect and transmit

data from the flight and weather conditions in real time to be processed by

a ground station. CanSats in this category do not use a steering system since

its objective is not to fall at a particular point but to collect data while the

descent (which is not usually controlled). Of the systems mentioned in the

previous sections the most used are: barometer, thermometer, GPS and

camera.

b. Comeback: The main task of these is to land in a controlled manner as close

as possible to a target marked by GPS coordinates. These devices can be

guided by GPS or by and Inertial Navigation System INS. This position is sent

to the microprocessor which compares the position of the target from the

analysis of these data to calculate the angle at which it should turn to

address the target and gives appropriate instructions to the steering system.

1.13 Architecture of CanSat

The General Architecture of a typical CanSat is made of the power supply unit,

communication system, onboard computer, mission subsystem, data handling and the

lunch/recovery system. The onboard computer which is the microcontroller is the heart of

the CanSat and interfaces with the transducers and actuators as well as sending the data and

receive commands from the ground station PC. During the data acquisition mission CanSat

only read data from sensors, store and send it to the ground station PC. However, in come-

back and fly-back mission the data is processed on-board the CanSat and decision taken to

deploy actuators for controls.

1.1.4 Structure

In order to protect the electronics from the environment and to increase the overall

durability of the components, the appropriate packages for the Cansat and the

communication module of the ground station should be developed.

• Protect the electronics from the harsh influence of the environment.

• Minimize the heat dissipation outside the Cansat.

• Increase the overall durability of the Pico Satellite and the communication

module of the ground station.

1.1.5 Power Supply Unit

The Power subsystem provides electrical power to the satellite; Energy can come from

Solar panels, batteries, or some type of fuel cell. The solar panels are comprised of solar

cells, i.e., semiconductor devices called photovoltaics. As the word implies, photovoltaics

(Photo = Light, Voltaic = Electricity), convert sunlight directly into electricity. Wide

Variety of Types of Solar Cells include (e.g., Silicon (Si), Gallium Arsenide (GaAs),

Gallium Arsenide/Germanium (GaAs/Ge), and Amorphous Si Cells; Each Has Different

designers select the types of solar cells to meet their power requirements, budget, mass, and

size (Ivan Galysh, 2004).

There are only a few types of batteries commonly used in small satellite systems which

include: Nickel Cadmium (NiCd) Batteries which is the most commonly used today, Nickel

Hydrogen (NiH 2) Batteries and Lithium Ion (Li-Ion) Batteries (Ivan Galysh, 2004).

1.1.5.1 Challenges in Power supply

The small mass limits the amount of energy provided by solar arrays as well; therefore,

power availability is a constraint on both the spacecraft processor and the communications

systems. RF power available on low-cost, small satellites ranges from 0.5 watts on

nanosatellites to a few dozen of watts on microsatellites.

1.1.6 Communication system

A satellite is a complex system which encompasses nearly all the different

technologies and has eased many a problem, but to manufacture and to maintain a

satellite especially during operation in the outer space when it is on its own is a big

task. For this purpose a series of parameters and satellite conditions are

continuously transmitted to a ground station from the satellite where it is

monitored and actions are taken accordingly by sending a command back to the

satellite. The satellite can be stationed thousands of miles away and the data sent

has to pass through different atmospheric conditions and degradation. So a series

of measures are taken to send this data securely to ground as a small error can lead

to billions going to waste. It is specifically for this purpose, a satellite contains a

telemetry subsystem. This subsystem obtains health data i.e. data from sensors and

the mission data from payload and then formats the data and transmits it so that it

reaches its destination error free (Waqas and Adnan, 2008).

1.1.6.1 Telemetry

According to the American Heritage Dictionary of English Language, telemetry is

the science and technology of automatic measurement and transmission of data by

wire, radio, or other means from remote sources as from space vehicles, to

receiving stations for recording and analysis.

The purpose of a telemetry system is to, “reliably and transparently convey

measurement information from a remotely located data generating source to users

located in space or on Earth.

1.1.6.2 Radio amateur band and limitations

To remote control the satellite and obtain data from the electronic payload, a

reliable communication link between the ground station and the satellite is needed.

Most of the developers use narrowband ham radio frequencies for communication.

Concerning data rate, the downlink is the outstanding challenge to get the

payload’s data from the onboard experiments back to earth. In the former CubeSat

designs, fixed symbol rate communications setups were used with a maximum of

9600 symbols per second (Ralf, 2011).

For small satellites communication the most often used bands are: VHF (145.800-

146.000MHz), UHF (435.000-438.000MHz) and S-band (2.400-2.450GHz). The

communication channel can be encrypted but it cannot be used commercial

purposes. There is a strong recommendation to use modulations which are popular

among radio amateurs and to add services for radio amateur usage on satellites.

The most common digital mode is AFSK 1200bps with use of Packet Radio

protocol (AX.25). The disadvantages of this modulation are the minimum Eb/No

level at 21 dB for bit error rate (BER) less than 1E-4. Another common modulation

is FSK G3RUH 9600bps,

It requires Eb/No≥17dB to achieve BER≤1E-4. The next popular modulation is

CW (carrier keying with Morse code). The disadvantages include low throughput

(typically about 8bps) and big problems with automatic reception (CW is tailored

to decode from hearing by the operator - computers are doing this task poorly)

(Marcin and Grzegorz, 2012).

Most small satellites use different Transmitters and receivers for both uplink and

downlink depending on the bandwidth required for the system. Such

communication systems include the Terminal Node Control for the Nano Com

U480 transceiver, Xbee transmitter/receiver module, S-band ground station

receiver, VHF/UHF ground station Transceiver etc.

1.1.6.3 Xbee module

The XBee is an arrangement of modular products that make deploying wireless

technology easy and cost-effective. The module can communicate up to 100 feet

indoors or 300 feet outdoors. It can be used as a serial replacement or you can put

it into a command mode and configure it for a variety of broadcast and mesh

networking options. XBee modules are intended for high-throughput applications

requiring low latency and predictable communication timing. And they ideal for

low power and low cost applications. The very popular XBee module is 2.4GHz

from Digi and uses the IEEE 802.15.4 networking protocol for fast point to

multipoint or peer-to-peer networking (Harshad, 2013).

Features

Complete RF transceiver

Onboard data encryption

Automatic collision avoidance

Low current consumption

Wide operating voltage 1.8-3.6 Volts

Operating frequency: 2.4-2.483 GHz

Data rate 1.2-500 kbps

1.1.6.4 RF module operation

The XBee RF Modules interface to a host device through a logic-level

asynchronous serial port. Through its serial port, the module can communicate

with any logic and voltage compatible UART; or through a level translator to any

serial device (for example: through a RS-232 or USB interface board).

1.1.6.5 UART Data Flow

Devices that have a UART interface can connect directly to the pins of the RF

module as shown in the figure below.

Fig2.2 Serial Data

Data enters the module UART through the DIN (pin 3) as an asynchronous serial

signal. The signal should idle high when no data is being transmitted. Each data

byte consists of a start bit (low), 8 data bits (least significant bit first) and a stop bit

(high). The following figure illustrates the serial bit pattern of data passing through

the module.

Fig2.3 UART Digital Signal

Serial communications depend on the two UARTs (the microcontroller's and the

RF module's) to be configured with compatible settings (baud rate, parity, start

bits, stop bits, data bits). The UART baud rate, parity, and stop bits settings on the

XBee module can be configured with the BD, NB, and SB commands respectively.

1.1.6.6 Challenges in Small Satellite communications

The constraints placed upon small satellite design for remote sensing missions

have traditionally been power availability, heat dissipation and aperture

requirements however as small satellite sensor technology approaches the 1 meter

resolution threshold, data throughput is becoming a new and particularly

challenging constraint on mission design. Ever-improving sensor resolution

increases the demand on data transfer in a non-linear fashion even when

corresponding improvements in data compression techniques are included. Hence,

very small satellites are rapidly becoming data-bound (Jan, John, Grant and

Michael, 2011).

Approach to solve this problem has lead to increasing the memory size of the

payload in other to store the large amount of data collected by the onboard sensors.

The limited communications opportunities and limited bandwidth also impose

constraints on data handling, fault detection and correction and instrument

commanding in general. Because of this, the spacecraft need to operate

autonomously and handle any anomalies that occur. This autonomy must be

accomplished within a processing capability that is less powerful than on a

conventional satellite (Maria-Mihaela Burlacu and Pascal Lorenz, 2010).

1.1.7 Onboard Computer

The term “On Board Computer” can be described as any unit flying on board a

satellite which provides processing capability. However, the On Board Computer,

or OBC, more commonly refers to as the computer of the satellite’s avionic sub-

system, i.e. the unit where the On Board Software runs. The “On Board Software”

is known as the software implementing the satellite’s vital functions such as:

attitude and orbit control in both nominal and non-nominal cases, tele-commands

execution or dispatching, housekeeping telemetry gathering and formatting, on

board time synchronization and distribution, failure detection, isolation and

recovery, etc (esa, 2012)

Based on the description above, the very essence of an OBC is the microprocessor

board, consisting of microprocessor or microcontroller, non-volatile memories,

volatile memories and the companion chip that connects the microprocessor or

microcontroller to different peripherals. Some functions of the on-board include:

Data handling, Computation for other subsystems, System health log, Command

execution, Payload Operation, Error handling and diagnosis, Communication with

Ground station etc.

Small satellites use different microprocessors for their onboard computer due to the

architecture of the chip and based on how sophisticated the satellite system is.

These processors could be 8 or 16bit processors such as the ARM microcontrollers,

AVR and the PIC series.

1.1.7.1 PIC microcontroller

The PICmicro was originally designed around 1980 by General Instrument as a

small, fast, inexpensive embedded microcontroller with strong I/O capabilities.PIC

stands for "Peripheral Interface Controller". The following are the advantages of

PIC microcontrollers:

1. It is a RISC (Reduced Instruction Set Computer) design

2. Only thirty seven instructions to remember

3. Its code is extremely efficient, allowing the PIC to run with typically less

program memory than its larger competitors.

4. It is low cost, high clock speed

The PIC is a Harvard machine, hence making it simpler and faster. The Harvard

architecture rose due to the need to speed up the work of the microcontroller. Here,

data access and Address access are separate hence a greater flow of data in the

processing unit. PIC16F877 uses 14 bits for instructions which allows for all

instructions to be one word instructions (Abd and Yaacob, 2010).

RISC Architecture

1. Complex/Reduced Instruction Set Computers

2. A minimal set of instructions, combined, can do every operation

3. Usually execute in a single cycle

4. CPU is smaller and few address mode.

5. Other hardware can be added to the space: (overlapping register windows)

1.1.7.2 PIC16F877A

This powerful yet easy to program with only 35 single word instructions and

CMOS flash-based 8 bit microcontroller packs with 40 pin package. It has 256

bytes of EEPROM data memory, self-programming, an ICD, 8 channels of 10-bit

A/D converter, two additional timers, 2 capture/compare/PMW functions, the

synchronous serial port can be configured as either #-wire serial peripheral

interface or the 2-wire inter-integrated circuit (I2C) bus and USART, speed of

5MHz and operating voltage range of 2 to 5.5.

Fig 2.4 PIC16F877A Microcontroller

1.1.8 Mission Subsystem

The mission subsystem is a vital part of a picosatellite which is made up of the

GPS receiver, sensors such as the humidity sensor, temperature sensors to sense

the internal and external temperature of the satellite, pressure sensor, altitude/speed

sensors and other devices added to the payload to capture data from the

environment.

1.1.8.1 GPS Receiver

The Global Positioning System (GPS) is a satellite-based navigation system that

was developed by the U.S. Department of Defense (DoD) in the early 1970s as the

next generation replacement to the Transit system. GPS provides continuous

positioning and timing information anywhere in the world under any weather

conditions. Since GPS is a one-way-ranging (passive) system, it serves an

unlimited number of users. That is, users can only receive the satellite signals. GPS

consists, nominally, of a constellation of about 24 operational satellites (“Can

Satellite (CanSat) Design Manual”, 2011).

GPS consists of three segments: space, control, and user. The space segment

consists of about 24 satellites constellation. The control segment of the GPS

system consists of a worldwide network of tracking stations. The user segment

includes all military and civilian users. With a GPS receiver connected to a GPS

antenna, a user can receive the GPS signals, which can be used to determine his or

her position anywhere in the world. GPS is currently available to all users

worldwide at no direct charge (“Can Satellite (CanSat) Design Manual”,

2011).Small satellite systems can use different GPS devices such as EM 406, EM

408, and Jupiter TU30-D140 OEM etc

GPS standard data format

Since each individual manufacturer have their own format for storing GPS

measurement, it is difficult to combine data from different receivers hence a

number of research groups have develop standard formats for various users needs

such as the NMEA format.

NMEA SENTENCE DESCRIPTIONAIM GPS almanac dataGBS GNSS satellite fault detectionGGA GPS fix dataGMP GNSS map projection fix dataGNS GNSS fix dataGRS GNSS range residualsGSA GNSS DOP and active satellites

GST GNSS pseudorange error statisticsGSV GNSS satellites in view

Table 2.1 NMEA Sentence and Description

NMEA Format

NMEA was founded in 1957 by a group of electronics dealers to strengthen their

relationships with electronic manufacturers. The NMEA 0183 standards are data

streams in the ASCII format, transmitted at a rate of 4,800 bps, from a talker to a

listener (one-way), where a talker is a device that sends data to other devices (e.g.,

a GPS receiver) and a listener is a device that receives data from another device

(e.g., a laptop computer interfaced with the GPS 78 receiver). It also includes data

streams which may have information on position, datum, water depth, and other

variables. The data is sent in the form of sentences, each starting with a dollar sign

"$" and terminating with a carriage return-line feed "<CR><LF>"; the dollar sign

"$" is followed by a five-character address field, which identifies the talker (the

first two characters) and the format and data type (the last three characters) (“Can

Satellite (CanSat) Design Manual”, 2011).

Sources of GPS Error

There many sources of possible errors that will degrade the accuracy of positions

computed by GPS Receiver. The travel time of GPS satellite signals can be altered

by atmospheric effects as it passes through the ionosphere and troposphere hence

affecting the speed. Sunspot activity also causes interference with GPS signals.

Another source of error is measurement noise, or distortion of the signal by

electrical interference. Errors in the ephemeris will also cause errors in computed

positions, because the satellites weren’t really where the GPS receiver “thought”

they were when it computed the positions (Diana, 2013).

Geometric Dilution of Precision

Satellite geometry can also affect the accuracy of GPS positioning. This effect is

called Geometric Dilution of Precision (GDOP). GDOP refers to where the

satellites are in relation to one another and is a measure of the quality of the

satellites configured. In general, the wider the angle between the satellites, the

better the measurement (Diana, 2013).

GPS receivers usually report the quality of satellite geometry in terms of Position

of Dilution of Precision, or PDOP.PDOP refers to horizontal (HDOP) and vertical

(VDOP) measurements (Latitude, longitude and altitude). A low DOP indicates a

higher probability of accuracy and a high DOP indicates a lower probability of

accuracy (Diana, 2013).

1.1.8.2 Sensors

Attitude determination and control, performing attitude determination and control,

is consist of mainly two parts; Attitude determination and attitude control. Attitude

determination and control performs attitude determination of satellite at first. The

data, as direction of the sun and vector of geomagnetic, angular velocity, position

of star, that necessary in order to determine the attitude of satellite is gotten by

sensor.

Function of sensor aim at detection of every possible information and energy so

subject of detection covers a wide range. However, in case of sensors that is

usually used around us, that variety is limited naturally. Sensors that are usually

used are following.

1) Optical sensor

2) Magnetic sensor

3) Pressure sensor

4) Thermo sensor (infrared light)

5) Vibration sensor (very low frequency, frequency of audible range, ultrasonic

wave)

6) Gas sensor (distinction of gas, detection of stink, detection of humidity)

In these sensors, sensors used to attitude determination and control is shared

roughly (1)Angle sensor, (2)angular velocity sensor, (3)the others such as

acceleration, positioning sensor(Eisei-kobo Miyazaki laboratory, 2011)

1.1.8.3 Microcontroller

The microcontroller in the satellite is controlling the operations onboard of

the satellite. All the sensors need to be interfaced and it should also handle the

communication with the ground station (Tamashiro, 2010).

Subsystem goals:

1. Collecting data from sensors.

2. Data processing/handling

3. Communication with the ground station.

4. Controlling of the satellite.

1.1.9 Lunching Systems

Usually Can-Sat can be launched using one of the following methods:

1. Model rocket

2. RC model airplane

3. Balloon

4. High raise building

1.1.10Definition of interfaces

The whole system is more than the sum of the subsystems. There are

different links between the subsystems, where one subsystem needs to interact with

a different subsystem. Those links are listed below.

Interface between the ground station and the Cansat Satellite (radio link)

using the communication protocol.

Interface between the microcontroller and the electronics on the Satellite.

1.1.11An Overview of Existing Pico Satellites

Over the years, several Cansat Picosatellites have been launched both as

student academic project and as well as for research purposes. Some of the Cansat

projects are reviewed below.

1.1.11.1 CubeSat XI-IV [sai-four] University of Tokyo

Nakasuka laboratory built its first pico-satellite CubeSat XI-IV [sai-four] by

2002, which was launched by the Russian rocket “Rockot” together with other

seven micro- and pico-satellites on June 30, 2003. XI-IV, which is shown in Figure

2-5,

Fig 2.5 Images taken by CubeSat XI-IV

has verified pico-satellite bus technologies and commercial-off-the-shelf

components including SELF-protection circuit, low power consumption micro-

controller, compact HAM transceiver unit, Li-ion secondary battery, passive

attitude control using permanent magnet, and a CMOS camera. Figure 2-6 shows

images taken by the camera on XI-IV (Enokuchi, 2006).

1.1.11.2 YANKEY and ROSAM Ghana

The All Nations University College space and satellite programme launched

two satellites on the 15 of May 2013 which made history worldwide since it is the

first ever satellite (CanSat) to be launched in Sub Saharan Africa by a Ghanaian

university.

The event being one of its kind in sub Saharan Africa really created the

awareness of the public and attracted personnel from diverse background such as

student, industrial personnel’s and international and local press to the launching

grounds prior to the 2nd space science and satellite technology workshop (20th to

21th of March 2013) which pointed out the need for Ghana to go to space and a

CanSat which was going to be launched.

The two CanSats, the YANKEY and the ROSAM were all launched together

in two compartment deployment (which was used as the launching vehicle) unit

fixed to the weather balloon which took it to a height of 172 meters void of their

expected height of 220 m which was due to a heavy rainfall on that very hour.

The launching of the two deployable CanSat was successful despite the

heavy downpour which prevented it from reaching an expected height of 220

meters. The atmospheric pressure and the temperature readings were transmitted to

the ground station as the telemetry and a video of the environment was captured

which together defined the mission for the CanSats (Quarshie, 2013).

1.1.12 Conclusion

This chapter has discussed satellites – artificial and natural, its types and

classifications based on their weight as well as reviewing the basic components

(subsystems) of a typical Cansat system. Small satellites systems (Nano, Pico

satellites) have been discussed as the most effective solution and better platform

than a micro or large satellite to carry out subsystem experiments due to its low

complexity, and lower cost implications and also achieved nearly the same goal

and task of a large satellite. This project will look at designing and launching a

Cansat that collects geographical data throughout its flight. The next chapter will

discuss the methodology and how the Cansat is developed.

METHODOLOGY AND IMPLEMENTATION

1.14 INTRODUCTION

In this chapter, the definition of requirements which include the software

and the components of the payload as well as the experimental design is discussed.

The devices used for the experiment to collect and record data as well as the

software will be discussed as well. This will be followed by the experimental

setup, design and launching of the CanSat.

1.15 COMPONENTS USED FOR THE PAYLOAD

The components used in this experiment for the CanSat payload are explained

below:

GPS MODULE (EM406A0027694)

This is a battery powered SiRF star III high performance GPS Chip Set. The

EM406A0027694 GPS receiver module is used to "lock" on to as many

satellites as it can find and from the complex algorithm processes it is able to

calculate the relative position of the payload (Sparkfun, 2014). The module

outputs the following NMEA 0183 sentences GGA, GSA, GSV, RMC,

VTG, and GLL. The EM406 was chosen because of its Very high sensitivity

(Tracking Sensitivity: -159 dBm), Support NMEA 0183 data protocol,

Power input 4.5V ~ 6.5V DC input, Power consumption - 70mA, and LED

indicator for GPS fix or not fix which makes it much ideal for this project.

Fig 3.1 EM406 GPS reciever

TMP102 Temperature Sensor

The TMP102 is a two-wire, serial output digital temperature sensor available

in a tiny SOT563 package mount on a breakout board manufactured by

Texas Instruments and Packaged by Sparkfun Electronics. Requiring no

external components, the TMP102 is capable of reading temperatures to a

resolution of 0.0625°C. The device is specified for operation over a

temperature range of –40°C to +125°C and it is used to capture the internal

temperature of the Cansat’s payload.

Fig 3.2 TMP102 Temperature Sensor

This particular components was chosen due to its high accuracy and long

temperature range: 0.5°c (–40°C to +125°C), low current: 10µA Active

(max), supply range: 1.4v to 3.6v, resolution: 12 bits, and the easy of

interfacing it with the microcontroller using the two-wire serial interface.

OpenLog

OpenLog is a simple serial logger based on the ATmega328 microcontroller

running at 16MHz. OpenLog is able to talk to very large capacity (tested up

to 16GB) SD cards. The whole purpose of this logger was to create a logger

that just powered up and start logging any serial data received from the on-

board computer.

Fig 3.3 OpenLog serial Data Logger

HIH-6130 Sensor

HIH-6130 Series is a two-wired digital output-type relative humidity (RH)

and temperature sensor combined in the same package manufactured by

Honeywell Electronics and package by Sparkfun Electronics.

Honeywell specifies Total Error Band—the most comprehensive, clear, and

meaningful measurement –that provides the sensor’s true accuracy of ±5

%RH over a compensated range of 5 °C to 50 °C and 10 %RH to 90 %RH.

The sensor was considered based on its Energy efficiency - Low supply

voltage: 2.3 – 5Vdc, Low power consumption: 650 µA, Ultra-small package:

SOIC-8 SMD (Surface Mount Device) package is ultra small, standalone

temperature sensor output, High resolution: 14-bit humidity/temperature

resolution (Honeywell, 2014).

Fig 3.4 HIH-6130 Temperature/Relative Humidity Sensor (x2)

XBEE RF Series 1 Module (Transmitter)

The XBEE Series 1 or XBEE 802.15.4 is a RF Modules that was engineered

to meet IEEE 802.15.4 standards and support the unique needs of low-cost,

low-power wireless sensor networks.

The modules require minimal power and provide reliable delivery of data

between devices. The modules operate within the ISM 2.4 GHz frequency

band and are pin-for-pin compatible with each other.

Fig 3-5 XBee S1 RF Module Fig 3-6 XBee Explorer Regulated

The XBee Explorer Regulated (fig 3.6) takes care of the 3.3V regulation,

signal conditioning, and basic activity indicators (Power, RSSI and

DIN/DOUT activity LEDs). It translates the 5V serial signals to 3.3V so that

you can connect a 5V (down to 3.3V) system to any XBee module. Plug an

XBee into this breakout and you will have direct access to the serial and

programming pins on the XBee unit and will be able to power the XBee with

5V.

PIC16F877A Microcontroller

This is the onboard computer that provides the interface between the

components, controls the flight, and get the signal from other components;

processed it and stored it in the OpenLog data logger as well as sending it to

the ground station.

Program Memory DataSRAM(Bytes)

EEPROM (Bytes)

i/o Master I2C

USART Timers 8/16-bit

Bytes # Single Word Instructions

14.3k 8192 368 256 33 Yes Yes 2/1Table 3.1 PIC16F877A Basic features

This PIC was chosen due to its simplicity in terms of configurations,

interfacing with other devices, diverse used in embedded systems and

numerous help/support forums thus, making it ideal for beginner projects.

1.16 COMPONENTS USED FOR THE GROUND STATION

XBEE RF Series 1 Module (Receiver)

The XBee module is mounted on an XB24-DKS Evaluation Board. This

board contain the level shifter and other circuitry necessary to transform the

receive signal into bits of stream that is sent through the USB cable to the

computer that runs the terminal software (X-CTU).

1.17 DESIGN

1.1.13Setup design

Fig 3-7 Schematic of the architecture of the Cansat system.

1.1.14Information flow

The available sensors are given in section (3.3). The following is measured

directly:

Temperature of the interior, using TMP102.

Temperature of the exterior, using sensor HIH6130.

Relative Humidity, also using HIH6130.

The GPS gives information on: latitude, UTC Time, Longitude, Satellites

Used, Altitude, etc

From this, we will measure the (latitude, longitude and altitude, etc), and also

calculate the atmospheric pressure.

1.1.15Design Specification

Data Handling

The data captured by the various sensors includes GPS, atmospheric

pressure, humidity, external and internal temperature will be send to the

ground station via the XBee and a backup is stored in the Standard Memory

Card(sd Card) mounted on the OPENLOG datalogger.

Communication

The communication system is made up of Xbee S1module and the 20

channel EM406 GPS. The XBee wireless device is directly connected to the

serial port (at 3.3V level) of the microcontroller. By using a logic level

translator it can also be interfaced to 5V logic (TTL) devices having serial

interface. This module supports data rates of up to 250kbps.

The EM406 output the following NMEA sentences:

Fig 3-8 EM406 Typical NMEA sentences

$GPGGA,161229.487,3723.2475,N,12158.3416,W,1,07,1.0,9.0,M,,,,0000*18$GPGLL,3723.2475,N,12158.3416,W,161229.487,A*2C$GPGSA,A,3,07,02,26,27,09,04,15,,,,,,1.8,1.0,1.5*33$GPGSV,2,1,07,07,79,048,42,02,51,062,43,26,36,256,42,27,27,138,42*71$GPRMC,161229.487,A,3723.2475,N,12158.3416,W,0.13,309.62,120598,,*10$GPVTG,309.62,T,,M,0.13,N,0.2,K*6E

For this project, only $GPGGA is captured for analysis. The $GPGGA data

format is shown below in Table 3.1.

Name Example Units DescriptionMessage ID $GPGGA GGA protocol headerUTC Time 161229.487 hhmmss.sssLatitude 3723.2475 ddmm.mmmmN/S Indicator N N= north or S = southLongitude 12158.3416 dddmm.mmmmE/W Indicator W E= east or W=westPosition Fix Indicator

1 0 - Fix not available or invalid1 - GPS SPS Mode, fix valid2 -Differential GPS,SPS Mode ,fix valid3 - GPS PPS Mode, fix valid

Satellites Used 07 Range 0 to 12HDOP 1.0 Horizontal Dilution of PrecisionAltitude 0.9 metersUnits M metersChecksum 0000<CR><LF> *18

End of message terminationTable 3-2. GGA Data Format

Power

The power system is made up of the 9v battery, LM7805 voltage regulator,

filtering and smoothing capacitors. The regulator regulates the 9v supply to

5v needed by the microcontroller and other components. The voltage

regulator onboard the XBee Breakout board regulates the 5v to 3.3v for the

two temperature sensors – HIH6130 and TMP102.

Pressure Determination

The pressure information is calculated using the Altitude information given

by the GPS:

p=p0e Mgh/RT

Where P is the pressure at altitude h, P0 = 101325Pa is the standard pressure

at ground level, M = 28.96gmol-1 is the effective molar mass of air, g =

9.807ms-2 is the gravitational acceleration on the ground, h is the altitude, R

= R8.314J/K·mol is the universal gas constant, T is the temperature.

1.18 DEVICE CONFIGURATION

1.1.16XBee Module

The communication between the payload and the ground station is handled by the

XBee-S1 module. Each of the XBee module function as the transmitter and

receiver. For it to communicate, the two modules must have the same PAN ID -

123, same baud rate – in this case 4800 configured into it. The configuration is

done using the X-CTU software as shown below.

Fig 3-9 X-CTU GUI

The X-CTU software provides both the GUI and the Command interface for

configuring the XBee Module and also functions as a terminal software. Once it is

mapped to a Communication Port (COM Port), the software listened and capture

whatever information is received on that port and display in its terminal GUI.

Thus, the X-CTU is used in these project to configured the XBee Module for point-

to-point communication and also as part of the ground station to display the receive

information from the payload.

Fig 3.10 X-CTU Modem Configuration Terminal

1.1.17OPENLOG

The OpenLog is used as the backup device in case of communication failure

between the payload and the ground station. OpenLog runs at 3.3-5V at 9600bps

by default. The baud rate is configurable from 300bps to 1000000bps. We modify

the config file to work at a different serial speed of 4800, but it can also be

reconfigured via software commands.

The microSD card can be any size from 64MB to 16GB. Before using OpenLog

we format the card to FAT32 file format using windows. Once the OPENLOG is

power on, its create a configuration file called CONFIG.TXT as sown below.

Fig 3-11 OPENLOG Configuration File

From the fig above, the default baud rate is 9600, mode of communication is 1

meaning data logging mode. To change the baud rate, we simply change it in the

configuration file to 4800 and save the changes with notepad and when the device

is power on, its read the new baud rate and start communicating with it.

1.19 MICROCONTROLLER PROGRAMMING

1.1.18Microcontroller

The microcontroller used to control the CanSat module is a PIC16F877A, 16-bit

microcontroller. It is a low power, high performance advanced RISC architecture

controller. By executing powerful instructions in a single clock cycle, the

PIC16F877A achieves throughputs approaching 4 MIPS per MHz allowing the

system designer to optimize power consumption versus processing speed

(Microchip, 2003). The On-chip ISP Flash allows the program memory to be

reprogrammed in-system through an SPI serial interface, by a conventional

nonvolatile memory programmer. The PIC16F877A is supported with a full suite

of program and system development tools including: C compilers, macro

assemblers, program debugger/simulators, in-circuit emulators, and evaluation kits.

1.1.19Programming Tools Used

CSC Compiler IDE

PICKIT 3 GUI software to download programs to chip

Real PIC Simulator for simulating the of the microcontroller I/O ports.

The microcontroller program necessary for CanSat are developed and compiled in

CSC Compiler to generate the hex file. Programs are written in the C programming

language. The hex code is downloaded to the flash program memory of the

microcontroller using the PICKit 3- GUI.

Fig 3-12 Section of Source code in CSC Compiler IDE

Fig 3-13 PICKit 3 Burner

Fig 3-14 PICKit 3 GUI

1.1.20Interface to Radio Module and Sensors

1.1.20.1 Radio module

The radio module (transmitter) of the CanSat is connected to the pin RB2 of the

microcontroller programmed to function as a USART port and in Asynchronous

mode. The radio module and microcontroller communicate in single mode -

normal operation mode. In normal operation mode, the data is received and sent in

combination with the RB2. Baud rate used is 4800baud.

1.1.20.2 GPS

The EM406 GPS is connected to the USART port (TX Pin) of the microcontroller.

By default GPS sends data in 8 bit, 1 start bit 1 stop bit format in 4800 baud rate

every second Sparkfun (2014). Data is read from the USART port and processed it

before sending it to ground station.

1.1.20.3 Temperature sensors

There are two temperature sensors connected to the CanSat – the internal and

external temperature sensor. The interface between temperature sensors and

microcontroller is done using Two-wire Serial Interface I2C. The I2C protocol

allows us to interconnect up to 128 different devices using only two bi-directional

bus lines, one for clock (SCL) and one for data (SDA). This is a master slave kind

of operation in which microcontroller acts as master and the temperature sensors

are slaves.

All address packets transmitted on the I2C bus are 9 bits long, consisting of

7 address bits, one READ/WRITE control bit and an acknowledge bit. If the

READ/WRITE bit is set, a read operation is to be performed; otherwise a write

operation should be performed. The MSB of the address byte is transmitted first.

All data packets transmitted on the I2C bus are 9 bits long, consisting of one data

byte and an acknowledge bit. During a data transfer, the master generates the clock

and the START and STOP conditions, while the receiver is responsible for

acknowledging the reception. The MSB of the data byte is transmitted first.

1.1.20.4 Relative Humidity Sensor

The relative humidity is measured also by the HIH6130 sensor. Separate

commands are issued to the device to take temperature reading and relative

humidity readings.

1.1.21General Description of the Microcontroller Program

The microcontroller is the brain of the CanSat. It samples signals from

various sensors (see section (3.4.1)). It communicates with the ground station using

a radio module. The structure is shown in figures (3-7) and (3-8).

Fig 3-15 CanSat SDL diagram

Fig 3-16 CanSat Flow Chat diagram

1.20 CONSTRUCTION

1.1.22Power Consumption

1.1.22.1 Satellite

The satellite is represented as a remote module, which undergoes the

influence of the low temperatures, low pressures and other sources of impact from

the harsh environment. Thus it is very vital to consider all power consumers

(sensors, radio-module and microcontroller) and the power source (the battery).

Thorough investigation in this field allows to predict lifetime of the remote device,

which is usually much depended on the power resources.

The main power consumers are represented in table 3-2 (all technical

information has been taken from the corresponding data sheets).

ComponentName

Quantity

VoltageRequirements,V

Max. operatingcurrent,mA

Max. power consumption,mW

Percentageof time inuse, %

Average power consumption,mW

GPS MODULEEM406A0027694

1 5 70 350 100 100

Internal Temperature ModuleTMP102

1 3 0.085 0.255 10 0.0255

Data Storage ModuleOpen Log

1 5 5 25 20 5

RADIO MODULEXBEE S1

1 5 45 225 20 45

External Temperature ModuleHIH-6130

1 3 1 3 10 0.3

PIC16F877A 1 5 200 1000 80 800

Table 3-3: Estimation of power consumption for the CanSat

For the power consumption calculations it is required to take into

consideration that some components such as the radio module do not operate all

the time with maximum load. The transmission and the receiving of data takes

approximately 20% of the whole operating time, this is represented in the column

“Percentage of time in use”.

According to the calculations, the estimated overall power consumption of

the CanSat is approximately 950.3255mW. With the knowledge of this data it

becomes possible to predict the lifetime of the CanSat. Unfortunately, it is very

hard to calculate the lifetime of the device in real conditions (in extremely low

temperatures), because the available battery capacity decreases significantly with

lower temperature. And it is difficult to simulate such conditions, special

equipment, such as an extremely low temperature cooling system is required.

Anyway, the obtained results will not be precise.

At least, it is possible to calculate the lifetime of the CanSat under normal

conditions (the temperature here plays the most important role, T = 20oC.)

The battery type is MN1604, alkaline. The battery capacity under these conditions

is 625 mAh, nominal voltage is 9V.

Thus, the lifetime of the CanSat is:

t = (625mAh ∗ 9V) / 950.3255mW

= 5.91hours

Under normal operating conditions the type MN1604 alkaline battery should

provide the operation of the CanSat during more than 6 hours.

1.1.22.2 Ground station

As the ground station should be basically represented by the PC with the running

application and the radio-module, which is connected to the PC via the USB

interfaces, the power consumption of the ground station is not as critical as that of

the remote module. The power consumption characteristics of the ground station

components (without taking into consideration the PC) are represented in table 3-3.

ComponentName

Quantity Voltage Req uirements, V

Max. operatingcurrent, mA

Max. power consumption, mW

XB24-DKS Evaluation Board

1 5 70 350

Table 3-4: Estimation of power consumption for ground station

The estimated maximum power consumption of the ground station is

350mW. It should be taken into consideration that the USB serial bus specification

gives us the following data: U = 5V, maximum I = 500mA, which gives as a total

P = 2500mW. Thus, there is a possibility to supply the ground station directly from

the USB port of the PC.

Fig 3-17 Electronics circuit schematic of the CanSat

1.1.23Structural Design

The body frame of the satellite is made of a malt can. The can is open on the top

and at the side as shown in the image below.

Fig 3-18 CanSat body frame with openings for sensors

Fig 3-19 Rubber stopper for support

The top opening is replaced with a rubber stopper which stops air from flowing

into the can. The rectangle opening on the side which is 8.5cm by 3.0cm will give

us access to place all the switches and sensors in position. The hooks required to

tire the balloon to the can is placed at the upper side of the can 1.5cm from the top

opening as shown in the image below.

Fig 3-20 CanSat top showing the hook

The circuit is attached with bolts to the rubber stopper to form a strong framework

as shown below.

Fig 3-21 CanSat Circuit Board with rubber stopper

The circuit frame with the rubber stopper is dropped into the can from the top

opening, and then the top rubber is fitted into the opening to close it.

The rectangular opening on the side of the can is covered with a thin plastic film

and holes are bored on the film for attaching the switches and the transmitter

antenna. The image below shows the whole system fitted together.

Fig 3-22 Integrated CanSat System

This project brought together the need for both hardware and software design.

Building, coding, and debugging on a large project is incredibly time consuming

and at times painful. However, the whole progress was successful as ground data

were obtained

CHAPTER FOUR

TESTING AND DATA ANALYSIS

This chapter, the will cover the series of test carried out on the satellite and the

results obtain will be analyzed.

4.1 TESTING

Testing is the practice of making objective judgments regarding the extent to

which the system (device) meets, exceeds or fails to meet stated objectives. System

testing is concerned with testing an entire system based on its specifications.

System testing is concerned with testing an entire system based on its

specifications (Lionel, Briand & Labiche, 2002).

4.1.1 Unit Testing

In the unit testing, each of the components that make up the satellite is accessed to

ensure that the y work properly and they give the required data expected from

them. Each of the sensors is connected to the microcontroller in turn and a sample

testing program is programmed into the PIC to test the components behavior. This

was accomplished using breadboard circuit board.

4.1.2 Integration Testing

In the integration testing all the components are connected together and they are

tested as a whole; the PIC is programmed with the CanSat program, the entire

setup is powered on and test. The integration testing takes up the bottom-up

integration testing approach – where the lower level components are integrated

before integrating the upper level components in the design hierarchy. The whole

setup – on a breadboard was tested and confirms working before the components

were soldered to form final circuit board.

4.1.3 Impact Testing

The impact testing is necessary to test the CanSat’s structural strength and to what

extent the impact can cause damage the CanSat. This was done by dropping the

CanSat from a 3storey building.

The damage done was not really a great deal, as the robber stopper used to place

the circuit within the body of the malt can acts as a shock absorber on impact.

4.2LAUNCHING

The preliminary lunch was targeted at a height of 100m above sea level

and we achieved it, a height of 85m above sea level.

The data collected from the onboard sensors and GPS receiver is tabular

below in table 5.1.

TOF(S)

UTCTime

Latitude(N)

Longitude(E)

FixQuality

NumOfSat

HDOP

WGS84 Altitude(M)

Pressure(KPa)

RH(%)

IntTemp(*C)

ExtTemp(*C)

7 173431 502.2929

758.6055 1 5 2.1 17.8 61.1 100.5931 77.18 28.62 28.79

14 173439 502.2917

758.6052 1 7 1.2 17.8 62 100.5824 77.18 28.62 28.79

21 173447 502.2915

758.6052 1 7 1.2 17.8 62 100.5824 77.18 28.62 28.79

28 173539.22 502.2948

758.6065 1 5 1.9 17.8 37 100.8813 75.92 28.75 28.97

35 173551 502.2913

758.6045 1 6 1.4 17.8 61 100.5944 75.92 28.75 28.97

42 173559 502.2912

758.6044 1 7 1.2 17.8 60.5 100.6003 75.92 28.75 28.97

49 173606 502.2909

758.6046 1 7 1.2 17.8 60.9 100.5955 75.92 28.81 28.97

56 173614 502.2904

758.6047 1 7 1.2 17.8 62.3 100.5788 75.92 28.81 28.97

63 173622 502.2896

758.6049 1 7 1.2 17.8 62.8 100.5728 75.92 28.81 28.97

70 173630 502.2888

758.6053 1 7 1.2 17.8 62.7 100.574 75.92 28.81 28.97

77 173637 502.2891

758.6056 1 8 1.1 17.8 64.7 100.5501 75.92 28.87 28.97

84 173645 502.288 758.6057 1 8 1.1 17.8 68.9 100.5 75.92 28.87 28.9791 173653 502.286

5758.6059 1 8 1.1 17.8 73.5 100.4451 75.92 28.87 28.97

98 173701 502.2846

758.6062 2 5 2.8 17.8 73.5 100.4451 75.92 28.87 28.97

105 173708 502.2812

758.6065 2 5 2.8 17.8 70.5 100.4809 75.92 28.87 28.97

112 173716 502.2792

758.6062 2 5 2.8 17.8 67.6 100.5155 75.92 28.87 28.97

119 173724 502.28 758.6059 2 5 2.7 17.8 67.4 100.518 75.92 28.87 28.97126 173731 502.282

9758.6062 1 8 1.1 17.8 67.3 100.5191 75.92 28.87 28.97

133 173739 502.2849

758.6065 2 5 2.7 17.8 70.5 100.4809 75.92 28.93 28.97

147 173755 502.287 758.6059 2 5 2.7 17.8 70 100.4869 75.92 28.93 28.97154 173810 502.288

8758.6065 2 5 2.7 17.8 71.6 100.4678 75.92 28.93 28.97

161 173818 502.2884

758.6065 1 8 1.1 17.8 70.6 100.4797 75.92 28.93 28.97

168 173826 502.288 758.6062 1 8 1.1 17.8 69.8 100.4892 75.92 28.93 28.97

2189 173853 502.287

4758.6064 2 5 2.7 17.8 67 100.5227 75.92 29.06 28.97

196 173900 502.2875

758.6062 2 5 2.7 17.8 68 100.5108 75.92 29.06 28.97

203 173908 502.2876

758.6062 2 5 2.7 17.8 69 100.4988 75.92 29.06 28.97

210 173916 502.2881

758.6061 2 5 2.7 17.8 69.9 100.488 75.92 29.06 28.97

217 174023.56 502.2903

758.613 1 5 1.5 17.8 84.6 100.3128 75.92 30.56 28.97

224 174036 502.2907

758.6057 1 10 0.8 17.8 75.4 100.4225 74.79 29.93 29.08

231 174043 502.2907

758.6055 1 10 0.8 17.8 73.9 100.4404 74.79 29.81 29.08

238 174051 502.2912

758.6059 1 10 0.8 17.8 73.1 100.4499 74.79 29.75 29.08

245 174059 502.291 758.6057 1 10 0.8 17.8 74.8 100.4296 74.79 29.68 29.08252 174107 502.290

4758.6057 1 10 0.8 17.8 76 100.4153 74.79 29.62 29.08

266 174122 502.2906

758.6057 2 5 2.4 17.8 75.7 100.4189 74.79 29.56 29.08

273 174130 502.2898

758.6057 2 6 1.7 17.8 75.2 100.4249 74.79 29.5 29.08

280 174138 502.2892

758.6059 2 6 1.7 17.8 75.2 100.4249 74.79 29.62 29.08

287 175141.48 0 0 0 0 0 0 0.00. 101.325 74.79 29.43 29.08294 180240.22 502.295

4758.6097 1 7 1.2 17.8 87.9 100.2735 75.54 30.87 29.87

301 180252 502.2893

758.6069 1 10 0.8 17.8 77.2 100.401 81.02 30.56 29.24

308 180300 502.2894

758.6074 1 9 0.9 17.8 79.3 100.376 81.02 30.56 29.24

315 180315.58 502.2888

758.6006 1 6 1.2 17.8 65.8 100.537 81.02 30.5 29.24

322 180334.32 502.2844

758.6115 1 6 1.4 17.8 90.2 100.2461 75.89 30.5 29.02

329 180346 502.2899

758.6053 1 10 0.8 17.8 74 100.4392 75.91 30.5 28.86

336 180354 502.2903

758.6057 1 10 0.8 17.8 73.9 100.4404 75.91 30.5 28.86

343 180402 502.2903

758.6065 1 10 0.8 17.8 76.1 100.4141 75.91 30.5 28.86

350 180410 502.29 758.6065 1 10 0.8 17.8 75.9 100.4165 75.91 30.5 28.86357 180417 502.289

8758.6065 1 10 0.8 17.8 76.2 100.4129 75.91 30.5 28.86

364 180425 502.2897

758.6062 1 10 0.8 17.8 75.9 100.4165 75.91 30.5 28.86

371 180433 502.2895

758.6062 1 10 0.8 17.8 75.8 100.4177 75.91 30.5 28.86

378 180441 502.289 758.6064 1 9 0.9 17.8 75.7 100.4189 75.91 30.5 28.86

2385 180448 502.288

9758.6064 1 9 0.9 17.8 75.6 100.4201 75.91 30.5 28.86

392 180456 502.2881

758.6065 1 10 0.8 17.8 76.7 100.407 75.91 30.5 28.86

399 180504 502.2877

758.6066 1 10 0.8 17.8 77 100.4034 75.91 30.56 28.86

406 180512 502.2873

758.6066 1 10 0.8 17.8 77.2 100.401 75.91 30.5 28.86

413 180519 502.287 758.6067 1 10 0.8 17.8 77.8 100.3939 75.91 30.56 28.86420 180527 502.286

7758.6066 1 10 0.8 17.8 78.2 100.3891 75.91 30.5 28.86

427 180535 502.2862

758.6064 1 10 0.8 17.8 78.7 100.3831 75.91 30.5 28.86

434 180543 502.2862

758.6061 1 9 0.9 17.8 78.6 100.3843 75.91 30.5 28.86

441 180550 502.2864

758.6059 1 9 0.9 17.8 78.5 100.3855 75.91 30.5 28.86

448 180558 502.286 758.6059 1 9 0.9 17.8 79 100.3796 75.91 30.5 28.86455 180621.56 502.294

8758.6124 1 6 1.5 17.8 89 100.2604 75.91 30.5 28.86

462 180634 502.286 758.6045 1 8 1 17.8 68 100.5108 76.53 30.5 28.77Table 4-1 Sample CanSat Data

From the above table, the ground station received the first transmitted data at

173431UTC (5:34:31pm local time) and the last telemetry at 180634UTC

(6:06:34pm local time) and also the flight lasted for 32minutes (for both ascent and

descent).

The graphs plotted from the above table are shown below.

a) The graph below shows the variation of pressure with time during the time

of flight.

Fig. 4-1 Pressure Vs Time Graph

b) The figure below shows the variation of relative humidity with time during

flight.

Fig. 4-2 Relative Humidity Vs Time Graph

c) The figure below shows the variation of the temperature with the time

during the CanSat flight. This helps us to the know the temperature of the

environment throughout the flight time

Fig. 4-3 Temperature Vs Time Graph

4.3CONCLUSION

In this chapter, the sets of test carried out in testing the workability of the CanSat

are mentioned. The telemetry data obtained from the CanSat are as shown in the

graphs. The graph gives the atmospheric condition of the environment at the time

of flight.

CHAPTER FIVE

CONCLUSION

5.1 INTRODUCTION

This project focuses on the design and construction of CanSat tagged UniUyoSat1.

Going through the whole process of a satellite development and design, it is the

most practical experience in which we the student have been exposed to. Though

there have been challenges and limitations in the development of this project in

which this chapter will emphasize.

5.1LIMITATIONS

This project was limited in three key aspects - area of coverage, hardware used,

and launching.

5.1.1 Area of Coverage:

The balloon and its payload did not fly beyond 300 meters above sea level due

to lack of tracking device, weak deploying mechanism, disputing efficacy of the

parachute used at high altitudes, and topography of the area. As a result of this, the

environmental data (Temperature, relative humidity, atmospheric pressure) taken

by the onboard sensors is peculiar to the location of the balloon.

5.1.2 Hardware Limitations:

Due to the high cost of sensors and the uneasiness of interfacing them with the

microcontroller (onboard computer), several sensor have not been incorporated in

the payload like accelerometer, gamma ray burst detector, magnetometers etc.

4. The project lack mobile tracking station which would make the payload

recovery much easier.

5. High cost and complexity deter us from going for high earned

microcontrollers like the PIC18 and PIC32 families.

6. The project lack imaging system which would have captured the aerial view

of the environment as the payload rises.

5.1.3 Launching

We faced several challenges in launching the CanSat. Due to high cost of helium,

we couldn’t get enough of it to carry several launch tests. The weather balloons

were fragile and some busted by mere realizing of air out of it and also it lacks

hooks to tie the payload to it.

5.2 RECOMMENDATIONS

Microcontroller used for projects of this magnitude – using multiple UART

devices should be of PIC18 or PIC32 families which have multiple UART I/O

ports to reduce the need of creating virtual UART ports which have

performance impact on the system.

The power supply needs to be properly filtered and decoupling capacitors

should be soldered as closely as possible to the PIC’s Vdd/Vss pins for

transient response.

A 10k resistor should be connected across MCLR pin of the PIC to ground to

ensure the PIC is not operating in reset mode.

It is a necessity to properly equip our laboratories as project of this caliber

cannot be carried out effectively without a standard laboratory as compare

to how it is being done in the developed countries.

Future Work

Additional Sensors

The CanSat may fly to altitude where the ozone concentration is

significantly higher than on ground level (ozone layer). A measurement of

ozone concentration as a function of position would be of scientific

interest.

Accelerometer can be incorporated into the payload to measure the

acceleration of the CanSat.

Magnetometer can be added to the payload to measure the strength and

the direction of the magnetic field at a point in space.

5.2.1 The CanSat Improvement

The CanSat can be improved in a number of ways.

The voltage over the battery can be measured. This would allow for

monitoring and fault detection.

Mobile tracking devices can be added to the payload and the ground

station and this could be integrated with Google Earth.

Camera module can also be added to take aerial photographs as the

payload rises.

5.2.2 Weak Points and Improvements in the Structural Design.

The CanSat body is quite a durable structure, and though there have been carried

out a number of tests with the components and materials separately, some weak

points have been still revealed during the experiments. As a consequence of one of

the free falls of the CanSat body on a concrete floor, the GPS receiver has peeled

off; the glue has not endured the shock. After the experiment the GPS receiver has

been glued back to its place.

Since there has been such a case that the glued surfaces have been separated in

normal temperature, there is a possibility that the same problem may occur during

the landing phase in the real flight. So this has not been considered as the crucial

part, which requires revising and rebuilding, but as one of the points to focus on in

later similar missions.

As an improvement, to minimize the possibility of such cases in the future, it is

possible to change glued connections to welding, or to think about another types of

fixing, that will result in the increase of overall strength and tolerance to applied

mechanical loads and sudden shocks.

Another improvement deals with thermal insulation, as protection from the most

significant environmental factor low temperature. This is of utmost importance to

the performance of the system at high altitudes. Though it has not been taking into

consideration in this design, it needs consideration in future designs.

5.2.3 Additional Tests

Some designed tests have not been carried out. The CanSat has not been put in a

freezer to ascertain the performance of the component at such a low temperature.

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Appendix A. XCT-U CONFIGURATION

X-CTU software for configuring and testing MaxStream radio modems. The

software is easy to use and allows MaxStream customers to test the radio modems

in the actual environment with just a computer and the items included with the

radio modems.

Fig 1 XCT-U Modem Configuration

The software is used to communicate with the ground station consisting of the

XBee module mounted on the XB24-DKS Evaluation Board and connected to the

system through USB cable.

The two XBee modules can be configured under the ‘Modem Configuration’

tab as shown above. The settings in blue are to be modified. The PAN ID is any

integer number (for the transmitter and receiver to communicate, the most have the

same PAN ID), Destination Address High and Destination Address Low of one

XBee module is the Serial Number High and Serial Number Low of the other

XBee. After setting the PAN ID, Destination Address High and Destination

Address Low, the ‘Write’ button is clicked to write the settings to the XBee

module EEPROM. The same setting is done with the other XBee module.

Fig 2 XCT-U GUI - Range Test

The ‘Range Test’ tab is used to test the communication range of the two

XBee modules.

The ‘PC- Setting’ tab allows the configuration of the XCT-U as terminal

software. The communication port (COM Port) in which the XB24-DKS is

connected is selected; the baud rate is selected to match that of the XBee mounted

on the XB24-DKS board.

Fig 3 XCT-U GUI – PC setting

The ‘Test/Query’ button is click and the XCT-U will try to communicate with the

connected XB24-DKS. An appropriate message will be displayed if it was

successful or an action is required as shown below.

Fig 4 XCT-U Showing Communication Failure

After a successful communication to the XB24-DKS is achieved, any other

terminal software can be used to collect the incoming data for further analysis.

Appendix B. PICKIT 3 PIC BURNER

The PICkit 3 allows debugging and programming of PIC microcontrollers

using the powerful graphical user interface of the PICKit 3 Programmer IDE. The

PICkit 3 burner is connected to a PC using a full speed USB interface and can be

connected to the target via a Microchip debug (RJ-11). The connector uses two

device I/O pins and the reset line to implement in-circuit debugging and In-Circuit

Serial Programming.

Fig 1 PICkit 3 Burner

The PICKit 3 burner is connected to the microcontroller as shown in Fig 2 below.

Fig 2 PICKit 3 Burner Connected to the PIC

Fig 3 Schematic diagram showing the connection in Fig 2

After the connection has been done, the PICKit 3 Programmer is

loaded as shown below in fig 4.

Fig 4 PICKit 3 Programmer GUI

In this interface, the hex file containing the CanSat code is loaded (CSC

Compiler was used to generate the hex file) and the targeted device is selected

(PIC16F877A in our case), then the ‘Write’ button is click to program the selected

device.

Appendix C. CANSAT C CODE

#include <16F877A.h>

#include <string.h>

#include <stdlib.h>

#include <math.h>

#fuses HS,NOWDT,NOPROTECT,NOLVP,NOBROWNOUT,PUT

#use delay(clock=20000000)

/* ******************** i2c preprocessor directives ***********************************/

#use i2c(Master, sda=PIN_C4,scl=PIN_C3, FORCE_HW, SMBUS ) //SMBUS FORCE_HW Configure Device as Master

#use rs232(baud=4800,parity=N,xmit=PIN_C6,rcv=PIN_C7,bits=8,stream=UART,ERRORS, BRGH1OK)

#use rs232(baud=4800,parity=N,xmit=PIN_B2,bits=8,stream=Xbee,ERRORS, FORCE_SW)

/* ***************************** Global constants ********************************/

#define BUFFER_SIZE 80

#define TMP_RD 0x91 // Reading Address of the TMP102 sensor

#define TMP_WR 0x90 // Writing Address of the TMP102 sensor. Assume ADR0 is tied to GND

#define TEMP_REG 0x00 // Temperature Address of the TMP102 sensor. Read only

#define HIH6130_ADDR (0x27) // slave address of the HIH6130 sensor

#define HIH6130_STATUS_MASK (0xc0)

#define I2C_RD (1)

#define I2C_WR (0)

#define I2C_ACK (1)

#define I2C_NAK (0)

#define Interval 2000 // set delay interval in seconds

/* ***************** global GPS variables ************************************/

int8 k = 0;

int8 n = 5;

int1 GPS_OK = 0;

char NMEA_RMC[BUFFER_SIZE];

/* ***************** Global GPS variables *******************/

float pre;

float UTCTime; //Complete UTC time

float Lat; //Complete Lat. float

char N_S; //North =1, S =0

float Lon; //Complete Lon. float

char E_W; //East =1, W =1

int8 FixQuality; // GPS fix

int8 NumOfSat; // Number of Satellites

float HDOP; // Horizontal Dilution of Precision

float Alt; // Altitude above sea level

float WGS84; // Height of geoid above WGS84 ellipsoid

char Alt_Unit;

char Term[16];

char *Field;

/* *************** global declarations of preocedures ********************/

float hih6130_raw_rh = 0;

float hih6130_raw_t = 0;

float tmp102Read(void);

void SplitGPS(void);

void hih6130_request(void);

BOOLEAN hih6130_get_data(void);

void TakeShot(void);

/* *************** interrupt routine **************************/

#int_rda

void serial_isr()

{ // serial interrupt

char c;

if (kbhit(UART)) // call to check if there's incoming data on the UART stream (RX register)

{

c= getc(UART); // get a character from the RX register

if (GPS_OK ==0)

{

if (k == 0)

{

if (c== '$')

{

NMEA_RMC[0] = c;

k++; // -------------------------------> k = 1

} else { k = 0; }

}

else if (k==1)

{

if (c == 'G')

{

NMEA_RMC[1] = c;

k++; // -------------------------------> k = 2

} else { k = 0; }

}

else if (k==2)

{

if (c=='P')

{

NMEA_RMC[2] = c;

k++; // ------------------------------> k = 3

} else { k = 0;}

}

else if (k==3)

{

if (c=='G')

{

NMEA_RMC[3] = c;

k++; // ------------------------------> k = 4

} else { k = 0;}

}

else if (k==4)

{

if (c=='G')

{

NMEA_RMC[4] = c;

k++; // ------------------------------> k = 5

} else { k = 0;}

}

else // if k = 5

{

if (c != 13) // 13 is carriage return

{

NMEA_RMC[n] = c;

n++;

} else { GPS_OK = 1;}

}

}

}

}

/* ****************** spit GPS Sentence ***********************/

void SplitGPS()

{

char Working_GPS_Str[80];

strcpy(Working_GPS_Str,NMEA_RMC);

strcpy(Term,","); //load delimiter ","

Field = strtok(Working_GPS_Str, Term); //parse to next delimiter

UTCTime = atof(strtok(0, Term)); //get UTC time float

Lat = atof(strtok(0, Term)); //get latitude float

N_S = *strtok(0, Term); //get N_S char (N or S)

Lon = atof(strtok(0, Term)); //get longitude float

E_W = *strtok(0, Term); //get E_W char (E or W)

FixQuality = atof(strtok(0, Term));

NumOfSat = atof(strtok(0, Term));

HDOP = atof(strtok(0, Term));

Alt = atof(strtok(0, Term));

Alt_Unit = *strtok(0, Term);

WGS84 = atof(strtok(0, Term));

delay_us(10);

}

//Read a tmp102 sensor on a given temp_number or channel

float tmp102Read(void)

{

unsigned int8 msb, lsb;

float nTemp;

int16 temp ;

i2c_start();

i2c_write(TMP_WR); // We want to write a value to the TMP

i2c_write(TEMP_REG); // Set pointer regster to temperature register (it's already there by default, but you never know)

delay_ms(50);

i2c_start();

i2c_write(TMP_RD); // Read from this I2C address, R/*W Set

msb= i2c_read(); //Read the MSB data

lsb = i2c_read(0); //Read the LSB data

i2c_Stop();

temp = ((unsigned int16)msb<<8) | (unsigned int16)lsb;

temp >>= 4; // The TMP102 temperature registers are left justified, correctly right justify them

// The tmp102 does twos compliment but has the negative bit in the wrong spot, so test for it and correct if needed

if(temp & (1<<11))

temp |= 0xF800; // Set bits 11 to 15 to 1s to get this reading into real twos compliment

ntemp = (temp/16.0);

return(nTemp);

}

/* send a measurement request. */

void hih6130_request(void)

{

i2c_start();

i2c_write(HIH6130_ADDR << 1 | I2C_WR);

i2c_stop();

}

/* send a data request; returns 1 if the status shows a valid measurement was received */

BOOLEAN hih6130_get_data(void)

{

unsigned char b1, b2, b3, b4;

long raw1, raw2;

i2c_start();

if (i2c_write(HIH6130_ADDR << 1 | I2C_RD)) { /* no ACK? */

fprintf(UART,"No Ack\r\n");

return FALSE;

}

b1 = i2c_read(I2C_ACK);

b2 = i2c_read(I2C_ACK);

b3 = i2c_read(I2C_ACK);

b4 = i2c_read(I2C_NAK);

i2c_stop();

if (b1 & HIH6130_STATUS_MASK) { /* if any status bits are set, data not ready */

return FALSE;

}

/* now take the raw I2C data and stuff it into the 16-bit holding registers */

raw1 = (b1 & ~HIH6130_STATUS_MASK) << 8;

raw1 |= b2;

raw2 = b3 << 8;

raw2 |= b4;

raw2 >>= 2; // to remove the 'dont care' bits

hih6130_raw_rh = raw1;

hih6130_raw_t = raw2;

hih6130_raw_rh = ((float) hih6130_raw_rh * 6.10e-3); // convert to real relative humidity

hih6130_raw_t = ((float) hih6130_raw_t * 1.007e-2) - 40.0; // convert to real temperature in degree celsius

return TRUE;

}

void TakeShot()

{

output_high(PIN_B4);

output_low(PIN_B4);

}

//// main Sub

void main() {

float Temp = 0.0;

enable_interrupts(int_rda);

enable_interrupts(global);

delay_ms(2000);

output_high(PIN_B5);

delay_ms(2000);

output_low(PIN_B5);

output_low(PIN_B4); // set camera to 0

delay_ms(3000);

fprintf(UART, "%s\r\n", "This readings are taken at 7 seconds interval... ");

hih6130_request();

WHILE (1)

{

if(GPS_OK == 1)

{

output_high(PIN_B5);

temp = tmp102Read();

hih6130_get_data();

SplitGPS();

pre = (float)((101325.0*(pow((1-((2.25577e-5)* Alt)), 5.25588)))/1000.0) ;

// store in openLog

fprintf(UART, "UTC:%f Lat:%.4f%c Lon:%.4f%c FixQuality:%d",UTCTime,Lat,N_S,Lon,E_W,FixQuality);

fprintf(UART, " NumOfSat:%d HDOP:%f Alt:%f%c WGS84:%f Pressure:%.4fKPa \r\n",NumOfSat,HDOP,Alt,Alt_Unit,WGS84,pre);

fprintf(UART, " RH:%f IntTemp:%f*C ExtTemp:%f*C\r\n",hih6130_raw_rh,temp,hih6130_raw_t);

fprintf(UART, "\r\n");

TakeShot(); // take picture with the camera

// send through Xbee

fprintf(Xbee, "UTC:%f Lat:%.4f%c Lon:%.4f%c FixQuality:%d",UTCTime,Lat,N_S,Lon,E_W,FixQuality);

fprintf(Xbee, " NumOfSat:%d HDOP:%f Alt:%f%c WGS84:%f Pressure:%.4fKPa \r\n",NumOfSat,HDOP,Alt,Alt_Unit,WGS84,pre);

fprintf(Xbee, " RH:%f IntTemp:%f*C ExtTemp:%f*C\r\n",hih6130_raw_rh,temp,hih6130_raw_t);

fprintf(Xbee, "\r\n");

k =0;

n =5;

}

output_low(PIN_B5);

delay_ms(Interval);

GPS_OK = 0;

delay_ms(2000); // wait for GPS to send signal (GPS interval ~1s)

}

}