An EPROM-based Command Cartridge for the Timex Sinclair 2068 Computer.

by Mark J. Blair nf6x@nf6x.net

This board allows you to create new Command Cartridges for the Timex Sinclair model 2068 computer, using ordinary EPROMs or ROMs. For KiCad source files, see this GitHub repository:

https://github.com/NF6X/ts2068cart

Also, here’s a video about the card on YouTube:

https://www.youtube.com/watch?v=EYMBuVz32ZE

Adapt 34 Pin Floppy Drives to 50 Pin Controllers

by Mark J. Blair nf6x@nf6x.net

This board is a cable adapter to allow 3.5" or 5.25" floppy disk drives to be connected to computer systems with floppy disk controllers that are designed for use with 8" floppy disk drives. For more information, see the GitHub repository:

https://github.com/NF6X/fd50to34

Here is the tag for this specific release:

https://github.com/NF6X/fd50to34/releases/tag/v3

RS232 level shifter for the Raspberry Pi Model B

by Mark J. Blair nf6x@nf6x.net

This board is an RS232 level shifter for the Raspberry Pi Model B, which is the version with a 26-pin J1 next to an 8-pin J5. It is not intended for use with any other versions of the Raspberry Pi board. The external RS232 connection is via an RJ45 jack wired to the Yost serial port wiring standard.

It provides full hardware handshaking, with the following pin assignments:

0 ohm series resistors allow rewiring as necessary.

Kicad design files available at Github

This design is open source with no license restrictions and no warranty. Use at your own risk.

TRS-80 Model 4 (Gate Array Version) ROM B/C EPROM Adapter

This board allows a 2764 EPROM to be plugged into the ROM B/C socket (U4) of a TRS-80 Model 4 computer. It is applicable to the gate array version only, which is easily identified by noting the orientation of the RS-232 serial port connector. That connector will face towards the rear of the gate array version computer, or downwards on a non-gate-array version computer.

ROM B/C is an MCM68A364 mask-programmed ROM, and it is not pin-compatible with common 2764 EPROMs. This board adapts the pinout, and also allows the original mask-programmed ROM to be reinstalled and selected with a jumper or remote switch.

The primary motivation of this project is to support the new auto-boot menu feature of the FreHD hard disk emulator without requiring soldered modifications of the computer itself, and also allowing the original ROM to be selected when desired.

Design files for this project may be found at:

https://github.com/NF6X/M4-GA-ROM-BC

Additional information may be found at:

http://www.nf6x.net/tag/M4-GA-ROM-BC

M4-GA-ROM-BC is a free hardware design: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

M4-GA-ROM-BC is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with M4-GA-ROM-BC. If not, see http://www.gnu.org/licenses/.

4k-64k EPROM-based Cartridge for Tandy/TRS-80 Color Computer.

See http://www.nf6x.net/tag/cocoeprompak/ for more details.

All design files available at https://github.com/NF6X/CoCoEPROMpak under GPLv3 license.