Circular motions
Apr 19, 2017

Just back from a few days in Paris, visiting friends (a bit south of Paris, actually), but we did manage to squeeze in a stroll in the Jardin du Luxembourg - with memories of a (brief) childhood there, bringing my sailboat to the pond, always hoping that it wouldn’t get trapped under the fountain…

Once back, I fell into all the procrastination traps there are - yak shaving, bikeshedding, and other rabbit holes. Dealing with some updates, failing laptops, and “researching” (ahem) all sorts of “interesting” (cough) topics, from Qubes OS to Awesome WM.

So nothing useful to write about this week.

Oh well, c’est la vie…

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EZ-Retro Z80 - part 2
Apr 12, 2017

Getting CP/M working on this two-chips-plus-a-blue-pill setup took more time than I thought, especially on the software side.

This week, I’ll turn Forth into a peek-and-poke monitor for the eZ80, describe how to bootstrap the initial code, build a minimal BIOS for CP/M, add a µSD card socket with SPI request bus, and finish off with a FAT-file mapped jukebox style floppy disk setup.

Let’s get started, this will be a long episode!

As always, these articles appear spread out over separate days of the week, to give me some time to prepare and test it all, but also to show that it’s all part of a “fun” journey!

Will it end here? Probably not. I’m thinking of making a PCB board for this. It’s been a delightful mix of a variety of technologies, new and old, and the retro aspect made it really satisfying once it all came together.

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EZ-Retro is a Z80 running CP/M
Apr 5, 2017

And now something completely different!

I’ve always been fascinated by those 8-bit computers that started it all. As a teenager, I spent many hours reading about them, but never could afford a Z80 system capable enough to run CP/M, for example. While BASIC and games were never my thing…

Floppies were totally out of reach for me. Later came MS-DOS and the PC clones, and things changed. But so did the fun: these were no longer systems to tinker with, all I did was get expansion cards and insert ‘em.

Long-time readers might remember the FPGA-based Z80 I built, end 2015. Great fun, but also not so much about tinkering as about installing an FPGA toochain and generating a pre-defined “bitstream”.

So a few weeks ago, I decided to have yet another go at it, using this huge chip:

This time, it’s really about creating a flexible setup that can run existing Z80 and CP/M software, while using modern techniques to deal with all the practical details:

This is not about re-creating old hardware, but about re-creating a compatible system that lets me try (much of) the old software.

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