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8-bit ATmega1284 retro computer
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README.md

The Amethyst Colour Video System

https://www.youtube.com/watch?v=6GKgxBEGH1M

The Amethyst is a retro-styled "home computer" built around an Atmel ATmega1284 microcontroller. It features composite (NTSC) video output with both high-color and high-resolution modes, mono audio output, and a full-travel mechanical keyboard. It includes a full-featured implementation of the powerful Forth programming language, with graphics and sound commands, debugger, and screen editor. A single USB Type-B cable provides 5V power as well as serial communication with a PC. Amethyst is compatible with the Optiboot (Arduino) bootloader, and new firmware may be uploaded to it without a specialized programming device.

Full specifications

  • ATmega1284 microcontroller (8-bit) running at 14.318 MHz

  • 16KB internal memory (16352 bytes available for applications)

  • 4KB nonvolatile EEPROM memory

  • Mechanical keyboard with Cherry MX keyswitches

  • NTSC color and monochrome composite video output:

    • 256-color, 16-color, and 4-color bitmap graphics at resolutions up to 160x200 pixels
    • Monochrome bitmap graphics at resolutions up to 640x200 pixels
    • 40x25 and 80x25 monochrome text modes
    • 40x25 color text mode
    • 40x25 color tiled graphics modes
  • Single-channel audio output (pulse wave or PWM)

  • USB serial communication at speeds up to 57600 baud

  • Four SPI expansion ports for peripherals, controllers, and storage devices

  • Only 6 chips (ATmega1284, FT320X, 2x 74HC157, 2x 74HC166)

TODO 1/5/20: add more detailed docs, instructions, and BOM

About

Amethyst is a hobby project and is not currently available for purchase in kit or built form.

Copyright 2019 Matt Sarnoff.

https://twitter.com/txsector

http://msarnoff.org

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