The L-Star project combines a real 65C02 processor with a Propeller microcontroller to replicate early home computers such as the Apple 1 or the Ohio Challenger / UK-101. You can invent your own Single Board Computer too, of course!

The Propeller can run the 65C02 at up to 1 MHz, and the 128KB RAM chip can be used as RAM or ROM. There are connectors for a black-and-white monitor (NTSC or PAL), and a PS/2 keyboard. Any hardware that can't be emulated by the Propeller can be attached to the expansion port.

Future plans include an emulator for Commodore PET / CBM computers and the Acorn Atom / Hob-bit computer. I'm also considering an expansion board to emulate the KIM-1 / Elektor Junior.

The hardware design and software are Open Source, licensed under the MIT license, and shared via Github.

Why did I make it?

Building your own computer from scratch, and having a deep understanding of how it works, is (arguably) a lost art. The purpose of this kit is to share the feeling of accomplishment that you get when you build an actual computer from scratch, and know even the smallest details of how it works. This kit should be easy to assemble if you have some soldering experience, and hopefully helps you to understand and control how a typical 8-bit computer system "sees the world". But even if you're not interested in that "deep knowledge" and just want to relive the days of that particular 1970s/1980s computer you once played with, that's okay too.

If you're interested in the kit but don't want to do any soldering, I will assemble and test your kit for you, for a couple of dollars extra. You should not attempt to solder the kit yourself if you've never soldered any electronic projects before.

What makes it special?

There are many replica projects in the market today. Many of them are very good and I bought a number of them myself. It's fun to solder a board together and make it work like an old computer, even if that old computer (and its software) wouldn't be very useful in today's world. What I want to accomplish with L-Star overlaps with the purpose of other replica projects (nostalgia and education) but I want L-Star to go a little further, and make the project more valuable by making it more flexible in some ways, and more focused in other ways:

• Many replica projects that I've seen, replicate a single computer, but L-Star can replicate many computers (one at a time, and within limits of course).
• Unlike other projects with EPROMs on board, you don't need an EPROM programmer or UV eraser. The EEPROM that holds the Propeller firmware is updated through a serial port (usually connected to a USB port).
• Instead of using old chips that may be unreliable or difficult to find or both, L-Star uses only chips that are currently in production. Old chips are either emulated with the Propeller or can be attached to the expansion port.
• Virtualizing hardware with an FPGA is certainly interesting, but it would require learning VHDL or Verilog if you would want to make any changes. That's outside the scope of the L-Star project, so there are no FPGA's or CPLD's or PAL's or GAL's on the motherboard. They can still be attached to the expansion port, of course.

It's definitely not possible to emulate all 6502 systems from the 1970s and 1980s with just a 65C02 and a Propeller and an SRAM chip. But I think the hardware of L-Star Plus is simple enough to understand, and flexible enough to be useful.

What's included?

The L-Star Plus kit includes:

• 65C02 processor by Western Design Center: a version of the 6502 processor that's still in production and can run at 3.3V;
• Propeller microcontroller by Parallax: an 8-core microcontroller at 80MHz;
• 64KB I2C EEPROM by Microchip: Holds the firmware for the Propeller;
• 128KB Static RAM chip by Alliance Semiconductor: This is used as ROM or RAM, or a combination, depending on the project;
• RCA connector: Used to generate black-and-white video output by some projects;
• Mini-DIN connector: Used to connect a PS/2 keyboard by some projects;
• Two low-drop voltage regulators (5V and 3.3V);
• Sockets for all ICs except the voltage regulators;
• 2.5mm barrel socket for power supply;
• Two mini tactile switches (push buttons) to reset the Propeller and the 65C02, and headers to connect your own switches if you want;
• Header for the Prop Plug;
• Headers for an expansion port (expansion boards coming soon);
• Headers and jumpers for a jumper-block to change the configuration;
• All necessary passive components: resistors, capacitors, crystal, power switch, LED;
• High-quality 80x100mm (approx.) Printed Circuit Board;

To prevent ESD and shipping damage, all IC's will be shipped on conductive foam and the kit will be packaged in a bag inside a box.

Build instructions are online as a web page or can be downloaded as PDF.

If you don't want to solder the kit together, I will be happy to do it for you for a small extra fee; just select the option when you order;

What else will you need?

The following items you have to provide yourself. If there's anything you don't have and you're not sure if you need it, or where to buy it, please contact me and I will answer all your questions as best as I can.

• A power supply (e.g. wall wart) with an output voltage between 7V and 15V DC (2.5mm barrel plug, center positive), and a maximum current of at least 1A (1000mA); (*)
• A Prop Plug from Parallax; (**)
• A computer with a USB port that can be used to install firmware into the Propeller, and to communicate via the (USB) serial port;
• Optional but recommended: a PS/2 keyboard to control some of the projects you can run on L-Star;
• Optional but recommended: an NTSC or PAL video monitor, preferably CRT based, to see video output of some of the projects. The video output is black-and-white, and a CRT-based monitor is recommended over an LCD monitor.

(*) It's possible to remove the 5V regulator and connect a 5V DC, 1A power supply. The build instructions will explain how to do this.

(**) I offer a limited supply of Prop Plugs as an optional extra. I charge slightly more than what Parallax charges, but you won't have to deal with ordering that separately. If you don't have one, make sure you add it to your order!

More Information

If you have any questions or suggestions, please contact me!

Follow the progress of this project on Hackaday.

Once you have the kit, check out L-Star.org for building instructions. I'm also working on some tutorials that will be posted there.

Software and printable build instructions are on my Github repository.