Baffa-2 Homebrew Microcomputer

During pandemics, I've been studing hardware architectures from old computers (like altair 8800, apple I/II and Sinclair's ZX80/81). First, I was interested in build a ZX81 because it was my first computer (It was my first contact with computer programming).

There are many "Retrocomputing" enthusiasts and most are inspired by the designs on the Grant Searle website. He studied Sinclair's original schematics and explained in detail how the machine works. That allowed me to reproduce his project by designing a printed circuit board, acrylic case and keyboard made from pvc stickers. The result is shown in the figure on the side.

Another project I worked on last year was the "Baffa-1 Homebrew CPU Minicomputer" - a fully assembled CPU using TTL logic. Its has 15 registers, microcode manager, ALU, 8 interrupts, etc. The architecture design was proposed by Paulo Constantino for the "Sol-1 Homebrew CPU wirewrap Minicomputer" and I did some improvements by designing pcbs, panel and some other changes. It was really cool, but having more software available helps a lot in testing the hardware and peripherals... at that time I had three options: create/adapt my own software, change the microcode to have a compatible CPU or move on...so... why not try something simpler to help design and test more peripherals and then come back?

Presenting Baffa-2 Homebrew Microcomputer

Well... the development of a machine with a Z80 CPU was already in the goals since the beginning of my projects. When I was designing PCBs for Baffa-1, developed a peripheral bus that could be used as a basis for other projects.

Baffa-2 Homebrew Microcomputer is an expandable Z80 CPU Multi-Board Computers, compatible with most of RC2014 programs (Grant Searle CP/M-80 ROM, Z80 asm progs and ROMWBW CP/M-80/Z-System softwares). The initial version has Dual Clock, 64KB Ram, Pageable ROM (that allows many different Roms/BIOS Versions) , Two Serial Ports, CF Disk support and Video Terminal (60x25 text-mode VGA and PS/2 interfaces).

This is a study project based on old computer architectures and all boards are designed by me, but after studying and evaluating other open source projects. As other projects, it has started with an Emulator Program (CP/M Emulator taking advantage of the Z80 CPU that I programmed for the ZX80 Emulator) and the CP/M Disk Manager based on Baffa-1 Disk Manager.

As every pilot or prototype project, not everything works as planned... I guarantee that the frontend view is much prettier than what we can find in the backend :D ... the important thing is to learn from mistakes and correct the design for applications future. ;) ...but nothing beats the bizarreness that is the back of the Baffa-1 boards!

There are other designed boards that I'm awaiting delivery from JLCPCB:

• Baffa-2 Soundcard (based on AY-3-8910 IC)
• Baffa-2 Real-time Clock
• Baffa-2 Harddrive IDE
• and Baffa-2 512KB Ram with flash Rom

This year I will have new challenges so this will be my last hardware project for a while. It's been a lot of fun to understand deeply how a computer works and its digital electronics. I believe I will be able to apply this knowledge to real research projects very soon.

For more information see my repositories on Github or the links to projects:

• Github Profile
• Baffa-2 Homebrew Microcomputer
• Baffa-1 Homebrew CPU Minicomputer

May 2022 be a very successful year for everyone and I hope that we can meet again in person with the end of the pandemic...

Update (Jan, 16th) - Baffa-2 Goes Mario (Baffa-2 Soundcard demo):