Vgavt1593

vgavt1593

Marco Maccaferri's Propeller VT100 Terminal, in a box

Overview

This is a remix of Marco Maccaferri's VGA Serial Terminal for RC2014. It is specifically adapted to be used with Stephen C Cousins' SC131 Z180 pocket computer. It fits into the same Hammond 1593N enclosure, making for a neat and tidy setup when combined with an SC131. Of course, it can also be used with any other retrocomputer or device that expects a VT100-like terminal, connected over "TTL-Serial" raw RS232.

VGA terminal stacked with SC131 computer

Terminal description

Details about the terminal itself are covered by Marco's project (this remix largely just changes the form factor). For detailed information, see his project page.

Serial interfaces

Connection to a computer is provided through an FTDI-style pin header, wired to the same pinout. Specifically, it is wired as a DTE (just like an FTDI dongle), so it can be wired directly to a DCE (like an SC131). A second passthrough port is provided to permit a PC connection to the same computer. This passthrough port is wired as a DCE, so FTDI cables can be connected directly. An AND gate mixes the terminal and passthrough connections together, so both can be used simultaneously. Transmitting from both at the same time will send gibberish; in testing this is relatively rare, and XMODEM at least will retransmit if this happens.

Usage

This terminal lets you use your SC131 (or other retrocomputer) standalone, without dependency on another computer. In addition, a modern computer can be connected to the passthrough port as needed. This is useful for sending files over XMODEM, for example.

Power

5V power is received through a standard 5.5/2.1mm barrel jack connection, center positive. The device optionally sends power to the connected computer (selectable by a jumper on JP1 - this is expected by SC131). In most cases, JP1 should be left installed. Wall adapters in this voltage and configuration are common, or a USB to 5.5mm cable can be used (examples here).

Why are the plugs on the front?

Because I ran out of room on the enclosure's panels. Between two FTDI headers, 5V in, reset, power switch, VGA, and USB, there wasn't even room left for a power LED. The serial ports are on the same side as the SC131 ones at least, so those can be connected together cleanly with a 6-pin Dupont cable.

Initial setup

The parts specified are not pre-programmed; they will need to be programmed before use. Either a Prop-Plug can be used on the assembled board, or a TL866 or CH341 can be used on the bare EEPROM. Instructions (and firmware) for programming can be found at the same link as above.

Part selection

Bill Of Materials and part references are below. Note that the right-angle headers have to be a specific type to align with the panel PCBs - they need to have the plastic "end stopper" on the "business" side of the angle, not the side you solder to the PCB. Headers from Pololu, Sparkfun, and Adafruit are like this, as is the Mouser listing below. Most eBay etc listings are not like this, and will not align correctly. If the appropriate headers cannot be sourced, double-row right-angle headers can be used, with the top row of pins removed.

The other headers can be snapped from regular breakaway header, for which eBay is substantially cheaper; the Mouser listings are provided for convenience. The specified parts are just the ones I used, and can be substituted as needed - Mouser links provided for convenience and reference. The case is available in other colours!