Coffeeeeee...

The fact is, I really like coffee... strong coffee...

Last year I bought a new cafeteria a Bialetti Brikka, it has a special valve that creates some pressure when the hot water is going through the coffee. The result is a almost expresso like coffee, without the mess and size of an expresso machine or beeing limited to the cartdrige or pad type pseudo-expresso.
For the best coffee I use fresh milled coffee beans (kept in the fridge), the Brikka and filtered water (this last one really makes a difference here in Holland).
Enjoy your coffee....

My new bike wheels

A couple of months ago we had an accident with the bike. Ana was siting on the back, I was driving through Bezuidenhoutsweg when a (stupid) Girl hit us coming from the side. None of us was really hurt, but the front wheel of my kronan was slightly bent. I ordered a new set of front and back wheels, inner tube, and tires and last Saturday I prepared and fitted them. My bike is black and from the picture you might notice that the rims are painted in blue.... Yes, they were cheaper in blue, now my bike looks like it came out of a Bauhaus design shed. Since my last set of tires I started using "Slime TM" to prevent fixing the inner tube every time I have a puncture (quite common). It's really great, once you have a small puncture, just fill the tire back again until the leak stops, and you're up and running. I also changed the chain (good policy once you change the rear hub).

Minimalist CP/M system

The idea came up last year when I learned that the floppy was considered dead. I decided to go back in time and build the smallest and simplest CP/M computer that still used a floppy (90mm / 3.5 inch) as storage media.
My project objectives were the following:
- build a CP/M v2.2 compatible computer;
- use the smallest number of integrated circuits and the simplest possible configuration;
- no programmable logic devices, only 74' and 40' series;
- use a 3.5 inch floppy disk as storage;
- the console for the CP/M system would be a terminal VT100 (on a Laptop linux/windows);
- be able to build an fully functioning computer in a breadboard;
- if possible do most of the software development in linux;
- build a wire-wrap version of the final hardware;
- design a PCB, build a box to host it and build a computer.
I started searching computers I knew that supported CP/M, and based the design from it. I looked at the Amstrad CPC 664 and PCW series, and also at the Sinclair Zx Spectrum +3. All these came from effectively the same place so their floppy disk interface was very similar. The used a NEC UPD 765 and a data separator (FDC 9216 or SED 9240) for the MFM encoding.
For the processor I settled on a Intel 8085 (8085AH-2) because I had a few in my parts box, it had an on-chip oscillator and seemed simple enough to build the console serial interface with the SID and SOD lines. The extra address decoder 74573 seemed a cheap option compared to the clock generation circuit for the Z80. I also have a NSC800 but not so much hardware information on it. Using the 8085 at 8MHz also allowed me to drive the UPD765 at the same clock or 4MHz with little or no changes. I also had it running it at 10.24MHz, but then the floppy disk needed a separate oscillator.
For the memory I wanted to use my EPROM emulator bought on ebay and a small enough RAM to run CP/M. I chose a 62256 with 100ns access time and my emulator simulating a 27C256, so 32K RAM and 32K ROM.
As a help circuit, to get me started with a serial interface and some digital inputs and outputs I added an Intel 8256AH. This IC is not very easy to find but it packs two 8bit ports, a serial interface and some timers. The perfect peripheral IC, a bit like the 6522 VIA for the Motorola 6800 or Rockwell 6502 processors.
I'll post more on this one.

Portico

Opening a blog is very easy and straight forward, find something to put there is not...
The title reflects some of my interests, but hopefully this blog will not be limited to that.
I'll also try to post ideas of things I would like to do but I don't have either the skills or the materials, and links to projects from someone else I would like to do.
I hope you enjoy reading.