Table Of ContentEmbedded Software Development for the
Internet Of Things
Embedded Software Development for the Internet Of Things
Klaus Elk
August 30, 2016
©2016, by Klaus Elk
Information provided in this book is derived from many sources, standards, and analyses - including subjective personal
views. Any errors or omissions shall not imply any liability for direct or indirect consequences arising from the use of
this information. The author make no warranty for the correctness or for the use of this information, and assume no
liability for direct or indirect damages of any kind arising from technical interpretation or technical explanations in this
book, for typographical or printing errors, or for any subsequent changes.
All rights reserved.
See also: facebook.com/klauselkbooks and www.klauselk.dk
Chapter 1
Introduction
1.1 Preface
This book is not a programming textbook. It is not a Software Engineering book either.
Software Engineering typically only deals with the processes surrounding software
development - e.g. Agile or Waterfall.
This book is about embedded software development. That means that you will see
some programming - almost exclusively in “C” - as well as something about processes and
tools. Nevertheless, the main scope is to cover the major domains an Embedded Software
developer will typically meet. Operating Systems and CPU’s are the most basic and an
overview of these is what Part I is all about.
The target is development for IOT - the Internet Of Things. The main difference
between embedded and IOT is that IOT is always using the Internet Protocol stack1 . For
this reason Part II has two textbook chapters on networking - wired and wireless (with
focus on WiFi). Wireshark is heavily used here to visualize the theory. Since IOT is very
often about interpreting data from sensors, basic Digital Signal Processing is relevant.
Many modern CPU’s have built-in DSP’s for this reason and Part II therefore also has a
textbook chapter on digital filters.
Finally Part III is about Best Practices in software architecture as well as tools and
processes. Throughout the book the author draws on good and bad real-life experiences,
which makes the book informal and relevant.
1.2 Who is this book for?
Details can be found on the web - when you know what to look for. The goal of this book
is to provide a qualified overview and help the reader to find more. It may be read by
senior students, but it is more likely to be read by programmers and developers who have
done some programming of PC’s in Windows or Linux and are now faced with developing
devices for the Internet Of Things. Basic programming skills are thus assumed whereas no
prior knowledge on TCP/IP and digital signal processing is needed. Based on 30+ years’
experience as a developer, university-teacher and manager the author’s personal views on
best practices in the embedded world are offered.
Part I introduces the main features of Operating Systems and the current state on
CPU’s and thus mainly builds the foundation for part II.
Part II - on Internet Protocols and Digital Filters - is the main “textbook” and
measured in pages is half the book. It gives a lot of facts, backed up by examples.
Part III is the author’s experience with best practices when working with mainly
embedded networking. This is more than general processes - many examples of tools
and how to use them are given.
The three parts may be read individually with references between them serving as
appetizers. Each chapter ends with a section containing suggestions for further reading.
1.3 About The Author
Klaus Elk graduated as a Master of Science in Electronics, from the Danish Technical
University in Copenhagen in 1984 with a thesis on Digital Signal Processing. Since then
he has worked in the private industry within the domains of telecommunication, medical
electronics, and sound and vibration. He also holds a degree as a Bachelor in Marketing.
In a period of 10 years Klaus Elk was - besides his R & D job - teaching at the Danish
Technical University. The subjects were Object Oriented Programming (C++ and Java),
and the Internet Protocol Stack. Today he is R & D Manager in Instrumentation at Brüel &
Kjær Sound & Vibration.
Part I
The Basic System
Chapter 2
How to select an OS?
In “the old days” you would pick a CPU first and then discuss the Operating System (OS)
- after discussing whether such was really necessary at all. Today it is more common to
choose the OS first and then a CPU - or a CPU-family. In reality it is often an iterative
process. You may e.g. decide to go for Linux, but this requires an MMU (Memory
Management Unit), and this may drive you towards too big and expensive CPU’s. In that
case you may have to redo you original choice. The following table is a “kick-start” to this
chapter - showing an overall trend from simple to advanced:
OS/Kernel/Language Type
Simple Main Strictly Polling
Ruby Co-Routines
Modula-2 Co-Routines
Windows 3 Non-preemptive scheduler
ARM mbed simple Interrupts + Main with FSM
OS-9 Preemptive Real-Time kernel
Enea OSE Preemptive Real-Time kernel
Windows-CE Preemptive Real-Time kernel
QNX Neutrino Preemptive Real-Time kernel
SMX Preemptive Real-Time kernel
Windows-NT Preemptive OS
ARM mbed advanced Preemptive scheduler
Linux Preemptive OS
RT-Linux Preemptive Real-Time OS
VX-Works Preemptive Real-Time OS
We will dive into the various types and degrees of operating systems and their pros
and cons. Along the way important parameters are introduced. The solutions are ordered
in the most reader-friendly way towards a full preemptive RTOS - “Real Time Operating
System”.
2.1 No OS and strictly polling
The simplest embedded system has no operating system, which leaves some low-level
details to the programmer. If you are using “C” there is a “main()” function that your
“official” program starts from at power-up. Since there is no OS, this must be assured by
configuring compiler, linker and locater 1 - and also by calling a small assembly program
first that copies the program to RAM, disables interrupts, clears the data-area and prepares
the stack and stack-pointer.
I once used a compiler-package that did all the above. Unfortunately, the vendor had
