I am feeling a bit nostalgic today, so I will bother you with memories of the past – how it all got started when I was 12 years old. For more than 20 years my soldering iron (Weller, of course!), my oscilloscope, my pile of spare components, home-made PCB’s and other stuff has been stashed away in a few boxes in a dark place. Recently in a burst of nostalgia, I grabbed these boxes from the attic and started snooping around. It brought back memories of etching PCB’s in my mom’s backing dish (she hated that!), countless hours of finding the flaw in a circuit I built on a breadboard and assembler programming on home built microprocessor systems just to flash some LED’s or 7-segment displays.
Once upon a time
It all started around the time I almost turned 12. The uncle of a friend of mine was radio amateur and member of VERON, the Dutch amateur radio club. He invited us to a radio camp in the woods in the Eastern part of the country, where we walked around at night on a so called ‘fox hunt’, like this. You were supposed to find the fox - a small transmitter hidden in the woods - by using a simple receiver (2m band if I remember correctly) with directional antenna’s. Wanting to build a receiver like that kick-started my fascination for electronics. I started with the well-known, very simple, crystal radio receiver consisting of nothing more than a germanium diode, a ferrite coil, a variable capacitor and a small crystal earphone.
I remember how fascinated I was by the fact that such a simple circuit could actually receive AM radio signals. Of course, all this soon escalated and before I knew it I was building small radio transmitters and receivers and by the time I was 15 or so, I got my license for the 2 meter band (144 MHz).
Of course, this was all in the pre-internet era (the 70’s to be more precise), so books and magazines were my primary source of information. The Elektor magazine, which originally started as Elektuur in The Netherlands, was my bible and I learned a lot by reading over and over again these articles and building and testing various circuits. I remember building audio amplifiers, radio transceivers and various small, essentially useless, things. Soon I was building stuff for friends at school, which helped me getting some funds for buying new equipment and components.
The dawn of the microprocessor
Everything changed when the May 1977 issue (if I remember correctly) of Elektuur dropped on the doormat. Obviously, I immediately started reading it as I always did, totally ignoring my homework. One article in particular caught my attention: about a microprocessor from National Semiconductor called SC/MP. The circuit had dip-switches and LED’s to program the microprocessor and show some output and you could change its function by changing the program. It sounded very interesting, so I wanted to build one and learn to program it. I regret not having that little microcomputer anymore. I have thrown it away at some point in time when cleaning up my room before moving out of my parent’s house. I should mention that I already started programming around the same time I got interested in electronics. At high school we had an elective computer class where you could learn programming in a simple BASIC-like language called ECOL. By marking small squares on punch cards with a pencil like this one:
You could send a program to a central computer somewhere at a university, I don’t recall which one, and receive the compiler output, and if all was well the program’s result, on paper the next week.
After the Elektuur SC/MP, other computer systems followed quickly and they grew in features and complexity. After the SC/MP I started to use and built systems with the Motorola 6800 and 6809 processors, they had a number of 7-segment LED displays to show data and a small hexadecimal keyboard. A quick summary of the various computer systems I have owned in the late 70’s and early 80’s:
• Elektor (Elektuur) SC/MP microprocessor (home built), with 128 bytes of RAM • Motorola MEK6800 Kit Mk II, with 512 bytes of RAM and 6 7-segment displays. • Home designed/built 6809 based microprocessor with RS232 serial I/O and parallel I/O, with 4KB RAM if I remember correctly. • Comodore VIC-20 (6502-based) • Comodore PET (6502 based, all-in-one) • Comodore 64 with floppy drive (6502 based) • North Star Horizon (a Zilog Z80-based S100 bus system) running CP/M and TurboDOS 2000 (a quite advanced multi-processor, multi-user DOS clone) • North Star Advantage (all-in-one model with 2 floppy drives based on a 4MHz Z80) running CP/M • IBM PC clone (one of the first, but cannot remember the brand) with EGA screen and 10MB Seagate hard disk running MS-DOS. It had 512 KB of RAM.
After that I started building, more like assembling actually, my Personal Computers as they were called since the introduction of the original IBM PC. I don’t remember all the CPU and memory configurations I have owned over time, but it started with a 80386 and next a 80486 with as much as 16MB or RAM – quite expensive those days!
I created my first compiler on the Commodore PET. This computer had a built-in BASIC interpreter I created a compiler that translated Pascal into BASIC. It took ages to get something complied but it was thrilling to see a ‘compiled’ Pascal program running on the PET. But the very first program on one of my own computers was a ‘walking light’ on the SC/MP, since it only had 8 LEDS as output device, I programmed it in assembler (the binary code that is) and had to upload it in memory byte by byte. There was a time when I knew all instructions of the SC/MP, 6502, 6800, 6809 from memory and even most binary codes of those instructions. With the Z80 it became a little harder. First, because it had more instructions. And second, because the instruction set was not very structured and logical. But around that time I was able to start using C compilers, so that wasn’t a problem anymore.
The age of IoT
Now that we have entered the age of IoT amd Home Automation in particular, it has sparked my interest in electronics en microcontrollers. The nice thing about being used to progrsm devices with little memory and CPU power (the smallest one, the SC/MP, had just 128 bytes in total), comes in handy when building small and cheap devices with Atmel (Microchip nowadays) microcontrollers...
That's why this blog is primarily about Home AUtomation related stuff.