Terminal

[BillO]

While I'd love a VT100 I probably be better off with fixing my truck first. The last VT100 I saw on fleabay in 100% working condition went for nearly $4000. Out of my price range. So I'm working on a project to build an ASCII terminal based on Geoff Grahams PIC based terminal.

The idea is to design a PC board for it to make it easy to mount to the back of a cheap and cheerful LCD VGA monitor. It will get it's power from the monitor and use a PS2 keyboard to hopefully end up with a useable standalone terminal for use with my Altair 8800c and other retro style projects.

If anyone is interested I can document the project here.

This project is progressing well.

The green board is version 1 and the red board version 2. There will be a version3 at some point.

The changes from version 1 to version 2 are as follows. On the first try I had the com port set up as DCE. However, my 8800C is also set up as DCE so I went with DTE on version2 so I could connect up with a simple strait-through cable. Also I buggered up the VGA and to some extent the PS/2 keyboard connector patterns in the first version so for version 2 I improved all the connector patterns. I also changed from a barrel power connector to a .1” Molex, spiffed up the silk screen a bit, added mounting holes and dropped the copper pours.

Here is V1 built up. Note the screwdriver pointing to an LED. I used a red LED to drop the 5V input to 3.6V for the PIC chip as I didn’t have any 3.3V regulators knocking around.

Here is my V2 build. Since this is not the final design I just wired it for green color rather than use a dip switch. This time I had 3.3V regulators.

For V3 I’m going to drop the composite video out and reduce the size of the board a bit. I’m also going to experiment around with using a USB keyboard as they are easier to find than the PS/2 units.

See below for more ...

[toml_12953]

While I'd love a VT100 I probably be better off with fixing my truck first. The last VT100 I saw on fleabay in 100% working condition went for nearly $4000. Out of my price range. So I'm working on a project to build an ASCII terminal based on Geoff Grahams PIC based terminal.

The idea is to design a PC board for it to make it easy to mount to the back of a cheap and cheerful LCD VGA monitor. It will get it's power from the monitor and use a PS2 keyboard to hopefully end up with a useable standalone terminal for use with my Altair 8800c and other retro style projects.

If anyone is interested I can document the project here.

Sure! It sounds like a good idea. We're always interested in ways to save money.

[AltairClone]

Hi Bill,

This has been done a few times, but I think I it sounds like a great project to do yourself.

Mike

[BillO]

Here I’ve got the monitor opened up to add the 5V power tap (black and red wires).

The backs of these monitors usually have some structure moulded into them for strength that leaves lots of space for screws with which to mount the board on the back.

Here it is all ready to go. I used a short (1’) VGA cable to keep things a bit tidier.

[BillO]

And here it is in use.

[AltairClone]

Wow, you’ve done a great job with this! As you mentioned, a USB option for the keyboard would be a good feature for the next rev.

Mike

[BillO]

Just an update...

I have found a modified firmware for this which provides for a USB keyboard. I'll need to order some bits and pieces for the next version to try this out and design a new board for testing.

https://github.com/dhansel/TerminalUSB

While it works with the 8800C as it stands, it does not work with some other old systems I have so I am also going to add a TTL to RS232 level converter (MAX232) to V3 so it is more generally applicable.

[BillO]

The version 3 boards came in on Friday and I built one up .. only to discover that I misplaced my PIC32MX250f128b chips. Spent all weekend looking for them. Sigh! Anyway, I have some more coming from Digi-Key. I'm sure once they arrive I will be tripping over the ones I misplaced.

So, here is what it looks like:

Of course, at his point in time it is untested.

However some things of note:
It is considerably smaller
It fully supports the RS232 standard
It uses wired USB keyboards which are far more available than the PS/2 style.

There will probably be a V3.1 as I have already discovered little things about this that I'd like to change.

I'll update when I get to test it.

[Wayne Parham]

Looks great!

[Curto]

I like it!