Software design and embedded system tools.

Why Is Load Testing Useful

admin — Sun, 25 Jul 2010 15:50:29 +0000

Load testing is the process of putting increasing demand on a system or software until the system or software breaks or fails to function. The purpose of load testing is to test the system against unusually high usage patterns to determine how the system or software will react.

One example of the need for this type of testing is a web server hosting a web site that is seasonal or receives peak levels of web traffic during highly publicized special events. Another example would be a link to a small web site from a very popular site, that then doubles or triples the number of concurrent visitors to the smaller web site. Load testing in each example could determine ahead of time whether each site could handle the increased traffic without the hosting server failing to serve web pages to visitors during the peak load.

Software load testing

Software programs can be load tested and can be particularly useful if they are network capable as most modern software packages are today. Testing is usually performed by the software company itself, rather than individual users or business users unless determining maximum capacity is critical to the enterprise. Ordinarily however, software will come with a set of benchmarks, stated maximum concurrent users and other statistics that are useful in determining suitability to purpose, often removing the need for individual testing.

With common software packages, like a word processor application or graphics editor application, these can be tested by repeated attempts to load a very large document. Will the document load successfully? Or will a suitable error message be displayed to confirm that the document is beyond the capacity of the application to handle it? Will the application simply crash with or without warning? In the case of other applications like a database that is setup to only handle 100 concurrent users, like some versions of Microsoft Access database application, what happens when the 101st user is attempting to connect to the database? Different software makers will handle the software limits in various ways and it can be helpful to be aware of these. In addition, web applications need to be written to display appropriate messages to the web user if maximum capacity has been reached.

Web server and web application load testing

The World Wide Web (the Internet) is run by networks, and web servers are utilized to offer web site functionality to web users. A lot of the software used on these networks and servers today was designed for the Internet, but quite a few have been inherited and was not specifically designed for it.

Early versions of Microsoft Access are a case in point. The 100 concurrent user limit was fine for most enterprises using a network version of the package. As long as each user quickly accessed the database, ran their database query, saved the results and then disconnected from the relational database management system (RDBMS), hitting the concurrent user limit could be avoided in many cases. Depending on the uses for the database, 1,000 users across an enterprise could have access to the RDBMS as long as no more than 100 employees did so during the same few seconds a database query was being ran.

Some web hosting companies still offer earlier versions of Access for free with their hosting packages and this can create problems for web developers that create a web application, utilizing Access as the primary RDBMS, never anticipating the web site becoming anything but modest success. The concurrent user limit could be quickly reached if traffic grew beyond expected levels and the web site would become inaccessible for many users.

Load testing in the real world

Load testing is useful to determine the maximum usable load for an application, be it standalone, networked or web-based. This can help when attempting to predict outcomes should demand exceed estimates by the wide margin. Software packages will usually come with some internally tested load suggestions but it is useful to conduct your own tests when the application is critical to business operations.

Thank you,
Jitkasem Pintaya

Linux bootloader.

admin — Wed, 21 Jul 2010 15:19:58 +0000

What is a bootloader?

In computing, booting or booting-up, is the process that starts an operating system when a computer system is turned on. A boot sequence is then followed, step by step, running some initial tests of the hardware and then initializing the bootloader.

A bootloader loads the operating system, often from a list of options, selecting the default option if another is not selected by the user within a set period of time. The user interface one sees can be a simply text display or a graphical user interface.

When a computer starts-up, the BIOS is loaded. The master boot record (MBR) is accessed from the first sector on the boot-able media. The MBR is limited to a single operating system, i.e. one distribution on Linux (Ubuntu, OpenSuse, etc.). The MBR is split up into two parts, part or all of the boot loader and information on the drive partitions. The BIOS locates and loads the first part of the bootloader, known as the initial program loader or IPL. The IPL checks the partition table to locate the second stage of the bootloader and load it.

The second part of the bootloader is much larger than the first, which is limited by the size of files the BIOS can access. The second part is also the part that is visible, so often people think it is the only part of the bootloader. This part contains the user interface to display the bootloader to the user and kernels to help the computer function correctly in the initial stages.

With newer Linux bootloaders, you have new options like the ability to load from a list of operating systems, use encrypted passwords and so on. This allows the flexibility to have a number of different operating systems installed on separate drives or separate partitions on the same drive. Different popular distributions of Linux, like Ubuntu Linux and OpenSuse Linux, as well as Microsoft Windows operating systems, can coexist happily together. This gives the user ultimate flexibility at boot time.

Two of the more popular bootloaders on Linux operating systems are LILO and GRUB.

Linux Loader

Linux Loader, or LILO, is the most common bootloader for Linux. It has been around many years, enjoys rich support from the Linux community and continues to evolve with new features added over time. There are many features to help troubleshoot a system having problems booting-up successfully. It also permits dual boot of a Linux distribution with any other operating system.

LILO is file system agnostic that allow to boot the OS from a floppy disc, CD-Rom, DVD, USB pen drive or hard drive. LILO is also flexible enough to be loaded from master boot record or boot sector of harddisk partiton. If you want to load LILO from boot sector then you must set up something in the master boot record in order to call the LILO that place on the harddisk partition.

GRUB

GNU GRUB, or GRUB, is fast becoming the boot loader of choice for many Linux users. The growing popularity of the Ubuntu Linux distribution that uses GRUB as standard is one reason for this, with approximately one third of Linux users using Ubuntu.

GRUB can also install on a range of media – floppy disc, CD-Rom, DVD, USB pen drive and hard drive – but it beats out LILO because the number of boot selections are unlimited. Given enough media options, this allows an enthusiast or Linux technician to load the latest stable release for one distribution of Linux, as well as a number of beta versions and special configurations for testing purposes, without the concern of running out of boot selections.

GRUB is also network ready and comes with an attractive graphical user interface.

Thank you,
Jitkasem Pintaya

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Embedded board

admin — Sat, 10 Jul 2010 08:57:22 +0000

Recommend embedded system development board
1. idea6410 board
This board use Samsung S3C6410 ARM11 as the main processor.It come with
various type of peripheral interfaces as much as necessary. It suitable for automotive , industrial control applications or medical system.This board can run many OS such as Windows Embedded CE 6.0,
Embedded Linux 2.6, Android and Ubuntu.View more information about this board here.

2. HAWK board
This board was developed by Texus Instrument.It suitable for using in DSP
application. The main processor in this board is OMAP-L138 (ARM926EJ-S) run at
300 MHz.The OS and RTOS that can run on HAWK board are WinCE , Android , QNX,
eCos , Linux Angstrom or even if UBUNTU can be ported to this development board too.
The sale price is only 89 USD (cheaper that BeagleBoard-xM) make it one of the interesting
board to buy.

3.ODROID-T
This board is specific for Android developer.It is high performance development board.
Main processor is Samsung S5PC110 Cortex-A8 run at 1 GHz with 3D Accelerator : SGX540.
This board has mini HDMI connector (video out) support up to 1920 x 1080 resolution, so you
can view the Full HD 1080p video on HDTV by using this board as video player. Other features
included in this board are also the same as the features of Netbook.
(It has WiFi , Bluetooth , USB , Audio-out , MicroSD Card Slot , etc).
View more information about ODROID-T at here. Selling price of ODROID-T is around 549 USD.

4.BeagleBoard-xM
This board use Super-scalar ARM Cortex-A8 as its core processor (speed at 1 GHz) .
It contain 512 MB DDR RAM and with this amount of ram enable user to run many applications
from the simple one to the complicate.It also support many OS such as Ubuntu , Android , MeeGo,
WinCE, QNX, Angstrom, Symbian, Debian, Gentoo, and others (View the project that use with this
board on this page). CPU of BeagleBoard-xM has DSP capability so it can perform DSP tasks such
as video streaming. It support Open GL ES 2.0 (make it able to render the 3D graphics user interface), otherwise this board come with S-video port (TV out) , DVI-D port (allow addition of digital computer monitors and HDTVs) , Audio IN/OUT port and Camera port. With this board user can debug the program running on this board via JTAG interface too. Price of this board is only 179 USD and you can buy it from Digi-Key.

Thank you,

Jitkasem

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Embedded scientific calculator.

admin — Sun, 20 Jun 2010 16:59:13 +0000

Casio fx-9860gsd is one of scientific calculator that can use for
calculate scientific formular otherwise it also can be used in controlling
as the embedded calculator.

Casio fx-9860gsd has the graphic LCD display (only two colors , black & white).
It use high performance processor , has the serial port and also has the SD card slot.
This calculator can be programmed without using the external program-burning equipment
(user can write program and download compiled-program to the calculator).
The software development kit for develop the software is free for download (include the compiler,
library and IDE). This SDK can make Casio fx-9860gsd to become good embedded controller board.
The drawback is it doesn’t have input/output port sufficiently to use ,however we can solve this drawback
by use the external equipment to expand I/O port.

Important technical specification of Casio fx-9860gsd are as follow…
- Use CPU from Renesas (SuperH-3 32-bit RISC processor) run at 100/133 MHz (depent on the working
mode)
- RAM 512 kB
- 4 MB Flash memory (can actually use about 1.5 MB)
- Download program to the calculator via mini USB by using FA-124 software.
- One channel serial port.
- Addition application can be appended to the calculator by ourselve.
- Develop program using C language and the SDK is free for download.
- Have SD card slot (SD card used for install new application or store the data).
- Noise tolerant and high stability.
- Can exchange the program between two calculators using the special signal-wire.

Casio fx-9860g sd

Essential software you need to download before start develop the program for Casio fx-9860gsd

First download SDK for fx-9860g (this SDK contain IDE and C
compiler). The registration is required and you must own the real Casio fx-9860gsd
(because it request for the identification number that stick at the back of this scientific calculator).
If you don’t have real Casio fx-9860g series then you can’t download this SDK.
Visit https://edu.casio.com/download_service/register/regist_form.php for register and download SDK.

Second download library Revolutionfx from http://revolution-fx.sourceforge.net.
This library help in reading and writing via serial port of the calculator (You cannot
access the serial port by using only the SDK from casio).
It also has the routine for draw a line or graph and include special function that is
valuable for working with this calculator.

Last software that need to download is Casio FA-124. This software use for download or
burn the program into calculator. You can download Casio FA-124 at http://world.casio.com/edu/resources/fa124/index.html.

When you have all three software above , you must install the fx-9860g SDK first
after that install the Revolutionfx library and Casio FA-124 respectively.

This article doesn’t talk about how to set up the environment for develop the program
and how to write the C code instruction for this calculator because I intend to write the
review for Casio fx-9860gsd only.

Reference :
1. Prototype Electronics Magazine (issue 11 , June 2010)
2. http://www.tpemagazine.com

Thank you,
Admin

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Interest embedded development board

Interest embedded development board

admin — Thu, 10 Jun 2010 08:53:13 +0000

Fez Domino

This development board was developed by GHI Electronics. It use 32 bit ARM7 (LPC2388FBD144 run at 72 Mhz) as the main microcontroller. It also the same as other general embedded development board except
that it use Visual C# 2008 Express Edition as compiler (so you must able to write the C# language) and use Microsoft .Net Micro Framework as the template for development the program on this microcontroller.
This IDE provide the full function of debugging capability. It also provide
an emulator mode , so you can run your developed program
without burning it into the real development board.

The extra capability of FEZ Domino is that its IOs port are correspond with
the hardware standard of Arduino (Pin compatible with Arduino) ,
so it can be used together with Arduino shield board.
For more information about Fez Domino , please visit TinyCLR.com

Picture of Fez Domino board

Below are videos introduce about how to develop program on Fez domino

Thanks,

If you have some questions or want to suggest something to me , please send an email to admin@embedsoftdev.com

Admin
jitkasem pintaya

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Scrum and Extreme Programming

admin — Thu, 03 Jun 2010 13:39:15 +0000

Agile Process (Scrum and Extreme Programming)
The Agile Process or software development refers to a set of software development methods which are based on iterative development. In this process, the solutions and requirements both evolve mutual collaboration between cross functional teams. These teams are self-organizing in nature.
The Agile software development approach usually promotes a regimented kind of project management process which encourages:
* Frequent adaptation and inspection
* Self-organization and accountability
* A leadership philosophy which promotes teamwork
* A business approach which bring into line the development with customer needs and company goals
* And a group of best engineering practices having an intention to allow for rapid delivery of good-quality software.
Extreme Programming (EP)
It is a software development methodology with an intention to enhance software responsiveness and quality to the volatile requirements of customers. Being a type of Agile process, it promotes frequent releases in small development cycles. This introduces checkpoints and improves the productivity in a way that the new requirements from customers can be adopted.
The advantages of Extreme Programming are:
* Unit testing of all code
* Avoiding programming of features until needed
* Programming in pairs or carrying out extensive code review
* Clarity and simplicity in code
* Volatile customer requirements better understood
* A flag management structure
* Frequent communication between the programmers and even with the customer
It has been noted however that there are certain drawbacks with Extreme programming. They are:
* No documented compromises of user conflicts
* Unstable requirements
* Lack of overall design document or specification
* Incorporates inadequate software design
* Necessitates meetings at recurrent intervals at huge expense to customers
* Can enlarge the risk of scope creep due to the lack of thorough requirements documentation
* Requires excess of cultural change to adopt

Scrum
Scrum is an incremental, iterative framework for agile software development and project management. The word “Scrum” is not really an acronym. However, many companies using this methodology spell it with capital letters. Initially Scrum methodology was focused for management of software development projects, but in recent times it can be used to run general program/project management approach or software maintenance teams.
Scrum, which contains sets of predefined roles and practices, is a process skeleton. Main roles in this method are:
1. Product Owner – Represents Stakeholders
2. Scrum Master – The one responsible for maintaining the processes
3. Team – A cross functional group of about 6-8 people who do actual design, testing, implementation, etc.
Each of the iteration is called a “sprint”, typical time frame for which is normally about two to four weeks. The length of each sprint is decided by the team. The product “backlog” pushes the set of features into a spring. These features are prioritized set of higher level requirements for the task to be carried out. Based on this product “backlog”, the team determines how many of the items can be completed in the next sprint. Once the sprint begins, nobody is allowed to alter the sprint backlog, which means that the set of requirements are frozen. On successful completion of a sprint, the team demonstrates the usage of that particular software.
This methodology should be encouraged in organizations since the major advantage of using the Scrum is that it enables the creation of teams which are highly self-organizing in nature. This is achieved by encouraging verbal communication amongst the team members, co-location of all the team members and disciplines which are involved for the project.

Differences between Scrum and Extreme Programming(EP) :
1. The time span for iterative sprints is different in both approaches.
2. Changes are not allowed by the Scrum teams during their sprints. Whereas Extreme Programming teams have to be much more agreeable to changes.
3. Work is done by EP teams in strict priority order. Whereas in case of Scrum, the product owner prioritizes the set of activities.
4. EP does prescribe some engineering practices; Scrum does not.

Thank you

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Performance Testing and Regression Testing

admin — Wed, 02 Jun 2010 13:29:51 +0000

Performance Testing and Regression Testing

Software testing or Testing is an examination conducted to present the stakeholders with data regarding the quality of the service or product under test. This type of software testing as well provides in insight on the independent views and objectives of the software to permit the business to understand all the risks involved during the implementation of the software.
Based on the testing method employed, Software testing can be put into practice at any point of time in the development process. Although, most of the efforts for testing occur after the requirements are defined and the process for coding has been completed.

This article describes two types of testing methodologies.

1. Performance Testing
Performance testing is performed to determine how quick a system or sub-system executes under a particular amount of workload. It can also provide to verify and validate other quality traits of the system, such as reliability, scalability and resource usage.

In the field of Software Engineering, performance testing comes under the testing category which is carried out to how fast a particular aspect of the system under observation performs, given a fixed amount of workload. This sort of testing is a subset of Performance Engineering (up-and-coming computer science practices build to get performance into the architecture and design of a system, prior to the actual effort of coding). There are various purposes which performance testing can serve:
It can compare given two systems and finds out which one is performing better
It can demonstrate whether or not the system meets the required performance criteria.
It can calculate which parts of the system under observation cause the system to perform badly.

2. Regression Testing
This type of testing is any software testing which seeks to find out software errors by partly re-testing a modified program. The intention of this type of testing is to provide a kind of assurance that no additional errors were added during the process of fixing the existing problems. Regression testing is generally used to proficiently examine the system by systematically choosing the appropriate suite of tests which are required to sufficiently cove all of the affected changes.
Widespread methods of regression testing comprise of rerunning earlier run tests and scrutinizing whether previously fixed faults have re-emerged. One of the chief reasons for performing regression testing is that it’s often tremendously difficult for a programmer to outline out how a change in one part of the software will reverberate in other parts of the software.

Ad hoc testing
This term is commonly used to represent software testing without any documentation or planning. The tests are made to run only once, unless a defect is discovered. This type of testing is more of a part of exploratory testing. Here, the tester seeks to find errors by any means that seems appropriate to him/her.

Unit Testing
This type of testing is a software verification and validation method where a programmer tests if individual units of system are fit for utilization. A unit is the least testable part of an application. In procedural programming, a unit might be an individual procedure or function.

Advantages

The advantage of performing Performance and Regression testing are:
Reusable: Can reuse tests on diverse versions of an application, even if the user interface alters
Repeatable: Can check how the software responds under repeated execution of the identical operations.
Programmable: Can program complicated tests that bring out concealed information from the application.
Cost Reduction: Cost is reduced since the amounts of resources for regression test are reduced.
Reliable: Tests carry out precisely the equivalent operations each time they are run, thereby eradicating human error.
Comprehensive: Can build a suite of tests that wraps every feature in the application.
Better Quality Software: Can run additional tests in fewer time with less resources
Fast: Automated Tools run tests considerably faster as compared to the human users.

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GIT vs Perforce vs Clearcase vs CVS

admin — Tue, 01 Jun 2010 14:38:33 +0000

GIT

This distributed revision control system has an emphasis on speed. It was originally designed and developed by Linus Torvalds for the development of Linux kernel. Every working directory of Git is a full-fledged repository with full revision tracking capabilities and complete history, not dependent on a central server or network access. GIT is a free software which is distributed under the terms of version 2 of the GNU General Public License.

Perforce

This is a proprietary and commercial revision control system developed by Perforce Software Inc. Perforce follows a client/server system. Here the server has the responsibility of managing a central database and a main repository of file versions. Developers can work on files in their local client workspace. After altering the changes, they can submit the changes to the main server. Client and server communicate via TCP/IP.

Clearcase

Rational ClearCase is a tool for configuration management of source code and other software assets. This tool is developed by IBM (Rational Software Division). ClearCase is the basis of version control for many mid size businesses, and has the potential to handle projects with thousands of developers.

CVS

This is a free revision control system. This system was developed by Dick Grune as a series of shell scripts during July 1986. CVS turned out to be popular in the open source software space and is released under General Public License of GNU. CVS also uses Client/Server architecture. Here, the clients connect to the server and can “check out” a version of file onto their local disk. Later after modifying the contents, they can “check in” the changes.

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Types of Revision Control Software

admin — Mon, 31 May 2010 13:00:11 +0000

Revision Control Software
Revision Control software are used implement Revision Control on single or multiple sites by organizations. Revision Control, also known as Software Configuration Management (SCM) or Source Control or Version Control, is the management or control of changes to programs, documents and other sorts of information data. This type of setup or mechanism is more often used in software development where a set of people may alter the contents of the same file. The changes made are generally identified by a letter code or number which is called as a revision number or simply revision. For instance, an initial revision for a file is “revision 1”. If this file is altered by any developer, its revision becomes “revision 2”, and so on. A developer can perform many operations on these revisions. These revisions of files or directories can be merged, restored or compared. Software tools for revision management are crucial for the organization where development is simultaneously in progress on multi-developer sites.

Types of Revision Control Software
The various possible approaches for revision control software are:
Local Only: In this approach, it is necessary for all the developers to use the same computer system. Examples:
a. Revision Control System (RCS)
b. Source Code Control System (SCCS)

Distributed Model: In this approach, each of the developer has his/her own setup or local repository. And at some predefined time, all of the changes from various developers are shared or synced between repositories as a different step. Examples:
c. Open Source:
i. Aegis
ii. Codeville
iii. DCVS
iv. GIT
d. Proprietary:
i. Sun WorkShop Team Ware
ii. BitKeeper

Client-Server Model: In this approach, all the developers have to share a single repository. Examples:
e. Open Source:
i. Concurrent Versions System (CVS)
ii. CVSNT
iii. OpenCVS
f. Proprietary:
i. Perforce
ii. Clearcase
iii. Visual SourceSafe

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Beginning guide to RS-485 bus.

admin — Thu, 06 May 2010 16:59:21 +0000

RS-485 is name of standard for data transmission that use only 2 wires.
One wire for sending the data (TxD) and another wire for receiving data (RxD).
RS-485 can be configured to work in Half-duplex or Full-duplex mode.
The example of equipments that use Half-duplex communication are
Fax, Printer, Intercom , walkie-talkie , etc.
Full-duplex equipments such as Telephone or Mobile phone.
RS-485 standard was specified by EIA (Electronics Industries Association)
since 1983.

The advantage of RS-485.
Nowadays, the data transmission used in industrial sector are almost RS-485 bus.
The reasons that people use RS-485 bus in industry instead of RS232 bus are as
follow…
1. Price of equipment to create RS-485 bus system is cheap and it require
only +5V (VDD) power supply.
2. The ability of inter-connection, RS-485 can connect with a large number of
internal equipments and it also support the work like networking system.
It can support up to 32 drivers (transmitter) and 32 receivers while RS-232 can
connect to only 1 transmitter and 1 receiver.
3. The distance that RS-485 bus can connect to the equipment is as far as 4,000 feet
or 1.2 kilometre while RS-232 is limit to only 50 to 100 feet.
4. Baud rate of RS-485 is up to 10 Mbps (in theory only) compare to the baud rate
of RS-232 that is only 20 Kbps. At the longest signal-carrier line, the data will be
transmitted at the slowest baud rate.

Characteristic of RS-485 bus.

- The longest range of signal line is 4,000 feet with baud rate of 90 Kbps and
and with the length of 50 feet , the baud rate can be up to10 Mbps.

RS-485 wire
The signal carrier wire that can be used on RS-485 bus system are
twisted pair and triaxial.Twisted pair line is work fine on RS-485 bus and it also cheap. It comprise
of 2 signal wires that covered by an insulator.Below is picture of twisted pair cable.

Twisted pair cable

Twisted pair can decrease low-frequency noise that arise from magnetic induction
of the carrier wire because twisting two wires cause the confutation of magnatic field
produced from each wire.Otherwise twisted pair also help to decrease the effect that come from external noise too.

Another wire that admired to use on RS-485 bus is Triaxial.
It can protect the noise from the external system but its price is more expensive
than Twisted pair.Triaxial cable is similar to coaxial cable except that it consist of two shield-layers
(inner shield and outer shield) while coaxial is consist of one shield layer.
(shield layer is used for prevent the external noise that may disturb signal transmission)
Both triaxial and coaxial have the “center conductor” that is a wire used for transmit
the signal. Below are the pictures of Triaxial cable and Coaxial cable.

Inner structure of coaxial cable

Inner structure of Triaxial cable

Pictures of this article are come from

1.http://www.gore.com/en_xx/products/cables/copper/networking/shieldedtwisted/index.html
2.http://www.camplex.com/PX1CableFAQrB.shtml