Category Archives: Electronics

System Backplane for the Whizz80

The system backplane for the Whizz80 has been redesigned and refined.

I’ve been using Eagle to design the schematic for the Whizz-80 computer. I originally started to hand wire parts of the circuits on prototyping PCB board but found that point to point wiring was just too hard, so I’ve now decided to get PCBs manufactured instead.

So I’m starting with the System Backplane – this is a rather easy board to produce as it is almost a ‘stripboard’ but with a custom silk screen.

System Backplane of the Whizz-80 computer
System Backplane of the Whizz-80 computer

I can only produce a board that is 100mm x 80mm in size with the current version of Eagle that I am running (the Express version). This should be big enough for the sytem backpane, but for the IO board I might need something bigger.

I’ve sent the system backplane off to be manufactured. I’m getting 5 prototypes so hopefully I should get them in a week or so.


I may have been a little quiet on my blog about the Whizz-80 computer I’m building, but I have been spending lots of time reading and learning more about the z80, and its inner workings.

I’ve also decided to put the day-to-day progress on the website as it can reach out to a target audience rather than relying on people stumbling onto my little blog here. 🙂

If you want to see the latest things happening with the Whizz-80 then head over to my project page at


No Connection symbol for Eagle

I have created a simple No Connection symbol for Eagle CadSoft.

At the moment I have only 1 symbol/package included in this library and that is the ‘NO CONNECTION’ symbol. The intent is to add more things as I come across it.

no connection symbol for eagle

It is quite simple to use, it simply places an ‘x’ on the schematic. There is no PCB footprint (as there isn’t one) so it is purely for visual aesthetics.

I’m surprised that Eagle doesn’t have this in one of their default libraries.

You can download the latest version of the library from my eagle-lbr github repository. If you don’t know how to use github then you can always download a pre-zipped version here.

Introducing the Whizz-80 computer

The Whizz-80 is my latest electronic project that I am starting. It is a combination of hardware and software so it aligns both my passions.

My Whizz-80 computer will be a retro based computer using the Z80 CPU. The Z80 was used in early microcomputers (such as the Microbee and the TRS-80). It will however run it’s own operating system and it’s own specific hardware configuration. I don’t intend on making a clone, (there are plenty of emulators for that) but a unique computer just for me.  It’s a great way to learn how computers actually work and since studying it I have a greater appreciation and respect of the hardware of modern computers.

So why use a Z80 chip instead of a different one like based on the 6502 (as in Commodore64)? There are many blogs out there compring the 2, but the reason why I chose the Z80 over the 6502 was simplicity and documentation. The Z80 requires minumum components to get started while the 6502 needs a few extra chips to get started. There also seems to be a better supply of Z80 components (They still make them!) than the 6502, so Z80 components are more easier for me to obtain (I’m sure your milage might be different). Also, since this is my first major build, I wanted to keep it as simple as possible and have something up and running as early as possible.

My initial thoughts, goals and ideas for the Whizz-80 computer are as follows:

Whizz-80 Hardware Specs:

  • The CPU will be based on the Z80 CPU running at around 6Mhz max.
  • 32Kb ROM and 32Kb RAM. This is more than enough memory for our needs, however it simplifies the amount of extra logic circuitry required if you use smaller memory chips.

Whizz-80 Software:

  • Operating System I will write and will be Forth based. I’ve always been intrigued with the Forth language, but I will probably tackle this once I have the hardware built

Stay tuned for upcoming blog posts on more of the Whizz-80 computer.

Beyond the Arduino

I’ve been playing around with the Arduino for a while now (offline to the blog) and while it is a great platform to get into the embedded arena (and electronics in general), I am yearning for something a little bit more, something beyond the Arduino.

I haven’t done a blog post in a while (I had great plans on posting my experiments and circuits as I learned) but the time it takes to create a post on a simple circuit that I built during the learning iteration process just didn’t work.

I was keen to move onto the next ‘idea’ so by the time it came to sit down and write something it was 3 mini-projects later. All I can say is that the best way to learn is to just physically build it.

Recently I’ve been studying digital circuits (nand2tetris is a good course) instead of analogue circuits and have been fascinated on how an actual the computer works (right down to the inner workings of the logic chips).

I think it is now time to move beyond the Arduino and get myself into some other projects. Maybe something that isn’t Arduino but is a little bit old and feeds my nostalgic urge (hint: z80).