Stephen Willcock's BeanZee Is a Simple, Compact Zilog Z80 Single-Board Computer with Custom Monitor
Building on an earlier breadboard version, this little PCB serves as a basic 10MHz Z80 system with 32kB of RAM and ROM.
Self-described "eight-bit hobby hacker" Stephen Willcock has released design files for a compact single-board computer built around Zilog's beloved Z80 microprocessor: the BeanZee, a more robust implementation of an earlier breadboarded prototype.
"Way back when I first held a soldering iron, PCBs were not easy for the hobbyist to make (or to have made), but today it’s much simpler," Willcock writes. "There are a number of suppliers who will produce PCBs from uploaded Gerber files and ship them to you. Most of the schematics for this build are the same as the breadboard computer but I decided to make a few small changes that might increase the board's usefulness, for very little effort."
The resulting single-board computer is based on the Zilog Z80 microprocessor — a device that was in active production from its introduction as Zilog's first product in 1976 to June last year, when Zilog parent Littelfuse ceased accepting orders and discontinued both the original Z80 and the newer Z180, though not the eZ80 embedded family. Willcock's machine runs the CPU at 10MHz, though this can be overridden with an external clock, and pairs it with a period-appropriate 32kB of RAM and 32kB of ROM on an electrically erasable programmable ROM (EEPROM) chip.
Designed as a basic system for development and experimentation the BeanZee has no video output; instead, it hosts a USB to serial adapter that provides access to a serial bus — and a monitor program which is under development. "I am (slowly) developing Marvin, a simple monitor program, through which I expect to provide the means to load and execute a program on the BeanZee via the USB interface," Willcock explains. "However, as an alternative, I have also ported the MINT minimalist interpreter, which so far looks like it can perform this function well."
More information on the BeanZee is available on Hackaday.io and on Willcock's own blog; KiCad project files and Gerber files are available on GitHub under the permissive MIT license, with Marvin the monitor's source code in a separate repository under the same license.