MAXI09OS

Summary

MAXI09OS is an operating system for my MAXI09 8 bit 6809 SBC. It is very much a work in progress. It is not another of those cut-down Unix available for the 6809, but rather it borrows ideas from a few different OSes and implements some of my own. The principle reason this thing exists is for the fun in writing it, and as a means to learn about the mechanics of writing an 8 bit OS.

Rough list of features

• Simple single-link list based dynamic memory allocator
• Objects are usually stored in a double-linked list, which uses the same dummy link in the list header as AmigaOS for speed
• Preemptive task switching, simple round robin
• Device driver model for IO abstraction
• Interrupt usage is currently limited to UART port rx
• Signal/Wait mechanism borrowed from AmigaOS but 8 bit signals
• Drivers for...
  • SC16C654 QUAD UART
  • V9958 text-mode console, with 6 virtual consoles
  • Non repeating or repeating timers
  • Joystick ports
  • IDE block device
• Debug monitor task
• MinixFS file layer, read only
• Startings of a simple command Shell

TODO

• Drivers for...
  • 6522 parallel printer port
  • SPI controller
    • Real Time Clock (DS1305)
    • Analogoue joysticks
    • SPI EEPROM
• OPL2 (no idea how that will work yet)
• Better terminal emulation in console driver
• Write support for the Minix FS layer
• More Shell commands
  • Date set and get with RTC
  • Copy file
  • Create directory
  • Etc..
• Command redirection so files can be printed
• Maybe write a basic full screen editor

More info

If you want to learn more about this project, or the MAXI09 board, the best place to start is probably my blog.