Author’s Journey through Embedded Platforms

Klaus Elk - Author of Embedded Software for the IoT

Author's Journey

Author’s Journey – Embedded Platforms

For anyone to write a book, primarily he or she must enjoy writing. And surely, this is turning into a time-consuming hobby.  I taught for 10 years at the Danish Technical University in Copenhagen, while working in the industry. I stopped teaching, and suddenly found myself writing.

Secondarily it helps to have some hard earned prior knowledge.

The figure above shows the most important platforms & targets I have worked with over the years.

Hardware Platforms, Operating Systems and Languages are chosen and color coded.

The thesis and the PDP11 stuff both were pre-studies, the rest made it into real products sold. The Production Control job was an extra-thing, very different from designing COTS (Commercial Of-The-Shelf) boxes, which is the type of products I normally work with.

Even though some years were spent purely in the PC-world, most of the time I have worked with embedded. There are no “lanes” for managing, general networks and SQL-servers. These domains have also taken up a lot of time, maybe they will be subjects of future books.

The last many years I have worked with Internet technologies – TCP/IP/Ethernet and WiFi. The products are probably not what most people would classify as IoT. However, it is exactly the IoT technologies – only mostly used in non-public installations.

Reflections on the Platforms


TMS320. This was the very first DSP from Texas Instruments, the TMS320C10. It was the second DSP the world saw. I later tried the very first one, the NEC7720, but that was only in a small part-time job. As I recall it, assembler was the only way to program the DSP’s back then, but it was a big step forward compared to bit-slice. See below. Today, DSP’s are mainly programmed in C. Many have OS’es.

8051. A classic microcontroller – that is, a microprocessor with a few built-in peripherals. The first I used, was the 8052, which had slightly more resources than the original 8051. Later, in another company, we used two Siemens SAB 80535. This was to get access to two HDLC serial ports. Thus we had moved a small step closer to the modern SoC – System on Chip.

PDP11. From good old Digital. This had a 10 Mbyte hard drive at the size of my modern Roomba vacuum cleaner – and sounded like it. This was my first job after graduating. I clearly remember chasing a problem so long, that I decided that the problem was a faulty RAM-board. I wrote a diagnostics routine to prove it. I halfway convinced my manager, and got the permission to buy a new board at Digital. I plugged it in – and my program worked. Looking back – credits to my boss. Incidentally, the best book written about PDP11 was written by a chemical engineer.

AMD2901 bit-slice. I am happy I got to try this. Bit-slice was a number of discrete components that you added, kind of LEGO-like, to build a CPU. We used five 4-bit Arithmetic-Logic-Units together with Multiplier and Sequencer. With this we could create our own DSP. This design filled 4 double Europe Boards. When coding, it was all about keeping the multiplier occupied – all the time. It only took me a week to code an FFT. We were all impressed of the efficiency of our design and home-grown language. Today that’s a simple library call. Another lesson learned: The FFT was fast because the HW was structured for it. However, following this I needed to reorganize the output, as the nature of an FFT is that outputs are spread-out in the buffer. We had no reverse-addressing HW, and this process took the same time as the complex FFT.

Operating Systems

MTOS. This was my first meeting with a real-time-operating-system. Aka RTOS. It was like many other of the time.

OS-9. I really loved this small OS. It was years before Linux, but it was a realtime, unix-like (posix) kernel. Fantastic. However, there was no big internet community to browse for answers. I learned it in the slow way.

RT-11. This was naturally used on the PDP11. Very rudimentary. Once in a-while an input-sample got hugely delayed. I realized that the OS’es update of its “wall-clock” had top priority, and thus interfered with my A/D-conversion. This was the standard system. I had to disable the wall clock before sampling, and re-enable it afterwards. Looking back I think that there must have been some kind of config I overlooked. This cannot be standard behavior.

Windows CE. Microsoft’s small, realtime OS. It works. Unfortunately nobody writes drivers for it. I have little personal direct feel for it. Nevertheless I know it pretty well, as a manager.

Linux. Great OS with tons of users, drivers and Board-Support-Packages. I like the use of stdin & stdout, and old-style use of parameters to programs, instead of new API’s each day. I programmed Linux in a project where we were building a TOE – TCP Offload Engine.

DOS. I have spent countless hours on testing DR-DOS instead of MS-DOS, and writing strange autoexec.bat and config.sys files for family and friends. I don’t miss it. Writing my first TSR in assembler was, however, fun. Terminate-Stay-Resident was a way to have background programs in a single-task OS. My first experience with databases was on DOS, using Modula-2 programming on – I think – a dBase III thing.

Windows. Still the most used on PC’s. I have used it since Windows 3.1 – the one which gave us “True Types” – making my stupid printer usable. Windows NT was a huge step forward in terms of robustness and programming environment.

kernel-32. Yet a small locally designed RTOS. It had a limited feature set, but the debug-feature that allowed you to dump the contents of all pools and queues was great. We used it for 8051, and were forced to get it extended with “bank-switching”, to make room for all our programs. Very interesting, and extremely time-consuming.

Programming Languages

PLM. This was the PLM51-derivate. It was like a simple version of C.

C. C51 from Keil. C for the 68k-family with OS-9. HP C. Microsoft C. And later C++ and C#. My experience with C# is from PC-programming. Recently I wrote a database program, interfacing to SQL-Server as well as Oracle.

Modula-2. A language ahead of its time. From JPI – an offspring of Borland.
It was a great language, but could not compete with both Borland and Microsoft.

Forth. That was a strange language. Luckily I was assigned to the project one day, and reassigned the following day (very strange company too), so I never learned it. Which is why it is not included in the figure above.

Java. I taught this language, and used it for test-tools later, but never got around to use it in embedded systems.  Many people in the company did not want garbage collection, which made sense to me. However, I never understood why the same people wanted to use embedded C# the next minute.

Python. Great language, with a refreshing view of how to define blocks. ScaPy – a library for Python – was a great tool for making legal as well as illegal Ethernet and IP packets for testing.

ASM. Each assembler is different from the one before. I liked the PDP and the 68k more than intel’s. They were much more “orthogonal”. This means that e.g. all register instructions work the same way on all registers. The most complex assembler was the 80×86, which was used in an embedded project. For some time we used segment-registers that were 16-bit wide, like the normal registers, but were only shifted 4-bits left before they were added. This gave us a 20-bit address space where we could have had 32-bit. Naturally, the world got the 32-bit version later.  I dare not think how many hours, programmers all over the world spent on this steppingstone.

Short Bio

I graduated as Master of Science (Electronics) in 1984, with a thesis on “Time-Delay Spectrometry” – a Digital Signal Project. Two years later I graduated as Bachelor of Echonomics (Marketing).

I have since then worked mainly with Telecommunication, Medical Electronics and Sound & Vibration in the private industry. In parallel with this work, I taught at the Danish Technical University. Main subjects here were Object Oriented Programming and the Internet Protocol Stack.

Today I work at Brüel & Kjær Sound & Vibration as R&D Manager of Instrumentation. You can find me in many ways – please see:  Contact page.

Article in  “Elektronik & Data”

In November 2016 the danish magazine “Elektronik & Data”,  brought an article about the first edition. You need Flash – as well as the ability to read danish: Artikel