Let's face it: a lot of us buy dev boards but never get around to doing anything with them. We have the attention span of gnats. But not Roger Milne! He's been on a three-year mission to build a Z80 computer in his spare time. And he did it! Take a look at the block diagram for his home build:
There's a load of stuff in there:
Most of these components are mounted on a couple of 6" × 6" PCBs (a size he selected to allow etching in a typical Pyrex baking dish):
In addition to constructing the hardware, there's the equally daunting task of developing the firmware for the microcontrollers, HDL for the FPGAs and CPLDs, and software for the Z80. To assist with this, he built a bunch of support tools:
Finally, knowing that modifications to the CPLD and FPGA HDL would cause changes to register addresses that would have to be propagated into the firmware of the processors, he created a tool to take a hardware definition in a text database and spit it out as headers for various compilers. That made it much easier to keep all the pieces of his design in sync. His tool even outputs a nice table of register addresses that can be used for documentation.
Now, some will look askance at building a Z80-based computer in an age where a four-core Raspberry Pi running at 900 MHz goes for $35. But there's no denying that Roger mastered a tremendous range of technical subjects during his three-year odyssey that will have a large payback as he continues building stuff. This really is a case where it's the journey and not the destination.Share on Twitter Share on Facebook Share on Reddit