# Project Terminus

A project 8-bit computer based on the Alphasmart and Freewrite

# Design Ideas

## Goal

The goal is to create a portable, 8-bit computer from base components, that is at least as functional as an Alphasmart or Freewrite device, and preferrably, has functionality more similar to a Tandy WP-2. Would also be good if the device can improve on some of the design problems of those devices, such as having a positionable screen.

## Architecture

Currently, the best looking architecture to build the computer around looks like the [RC2014](https://rc2014.co.uk/).

This will mean that the computer is a Z80 based system.

## Operating System

Still looking into operating systems. Potential options include CP/M and CollapseOS, but definitely would prefer other options if they exist.

## Serial Terminal

Originally was looking into epaper for a display, but am leaning against it due to issues with slow refresh rates. Instead, looking for LCDs that can be driven by an Arduino that might be able to serve as a full TTL terminal. If that fails, can also use a [diy-VT100](https://www.madresistor.com/diy-vt100/) for the display, and a [USB Host](https://www.hobbytronics.co.uk/usb-host-keyboard) or [E1115 converter](https://www.adafruit.com/product/1136) for keyboard input.

## Case Inspiration

The final product will likely use a 3d printed case, potentially using a modified version of the [HALGRID P-1 Raspberry Pi Laptop Computer Shell](https://www.thingiverse.com/thing:4603966) (itself, based on the [GRID Compass](https://spectrum.ieee.org/image/MzYzMjg3MQ.jpeg)).

# Components

## Microcontroller
Preferred microcontroller would be a Raspberry Pi Pico, since it has a large amount of SRAM, and built in hardware for UART and SPI.

## Input
Likely use an E1115F module from Adafruit as a PS/2 to TTL decoder for keyboard input. Will require a level shifter to convert to 3.3v logic for the Pico. Will also require a 5v supply in order to power the keyboard, but has a 3.3v regulator to provide power to some other component. Reserving half of UART0 for the Pico for the keyboard.

## Display
Still trying to decide if wanting to use an eInk or LCD display. Can likely run the eInk easily off of a set of AA batteries, but might also be able to use the LCD with AA batteries. Would prefer at least a 5" screen of some kind, wider the better.

## Addons

### Wifi
An ESP8266/ESP01 module could be used to add wifi, and be interfaced with the Pico using UART1.