Agon

The Agon is available in a number of flavours:

  • Agon Light: The original by Bernado
  • Agon Light 2: A remixed yet fully compatible board by Olimex
  • Console8: Another remix by Heber with extra features that transforms the Agon into a console.

The hardware was designed by Bernado Kastrup, the designer of the Cerberus 2080, with a little input from myself and Andy Toone. It is a modern and fully open-sourced eZ80 based microcomputer with VGA output, audio, and keyboard connectors.

The board has 512Kb of SRAM, and there is 128Kb of flash memory built into the eZ80. Additional storage can be added via the micro SD card connector.

Audio and video is handled by the VDP (Visual Display Processor) – an ESP32 running custom firmware on top of the FabGL library. The ESP32 is connected to the eZ80 via a fast serial link, and will enable code running on the eZ80 to output text, graphics and sound via BBC Basic-like character sequences (VDU commands). It will also send information back to the eZ80 such as keypresses and terminal status.

There are a number of GPIO ports exposed at the bottom of the board, connected to the spare eZ80 and ESP32 GPIO ports.

Early versions of the official Quark firmware were written by me. It is now a team effort with a number of long term contributors adding new features.

The Agon Light boots into MOS on start-up. This is a DOS-like command-line that allows the user to navigate around the SD card, perform file operations, and launch applications, and is configurable via a text file on the SD card.

The MOS also provides an API for application developers who are interested in coding for the Agon Light, and include vectors for file and graphics for C and assembly language programmers.

For those who are looking for an easier language to code in, the Agon Light comes complete with a tweaked version of R.T.Russell’s excellent BBC Basic for Z80 on SD card. This can be configured to run on power-up for a genuine 8-bit experience, with the power of BBC Basic combined with Agon specific features: file I/O, colour graphics, sound, and access to the eZ80 GPIO ports.

There is an updated version of BBC BASIC in the works that runs in the eZ80’s 24-bit ADL mode. This extends the memory available to BASIC from around 48K to just under 500K, and will add features from later versions of BBC BASIC in due course.

Source code for the MOS, VPD and BBC Basic are available on GitHub, as are the manufacturing files and BOM for the PCB.

Full documentation for the Agon can now be found on the official Wiki.