questions about VT-100 emu board

[Giovi Alex]

I'm building my own Altair-duino from scratch, using the David Hansel's instructions.

I also planned to buy a Chris Davis' VT-100 I/O board (aka I/O expansion kit) to put inside the cabinet, but I have some doubts:

1) can I plug it directly on my Arduino Due (I'm not using the Chris' kit) ? I guess I can, but it's worth asking.

2) Different fro the Geoff's original project, it hasn't a composite plug, just two pins. Can I plug a composite connector to the composite pins?

3) If I can use a composite output, how can I switch it between PAL and NTSC? I've read in the David Hansel's instructions (here: https://github.com/dhansel/VDM1/blob/master/README.md) the Geoff's board has a jumper for that, but I can't see anything similar on the Chris' board. I planned to use a b/w CRT television or monitor with A/V input (ok VGA has a better resolution but I wish to preserve the original '70 feeling).

[wils...@gmail.com]

You definitely can plug directly into the Cue. I built a little mini CP/M computer by connecting a due and.a Terminal board, no 8800 front  panel. 

[Tom Van Hoorick]

Hello i also built my Altair clone from scratch 

For the terminal and AT modem i currently use a VT132 standalone.

If you want to use composite signal there is a VT100 terminal kit @

https://www.budgetronics.eu/en/building-kits/ascii-vt100-video-terminal-building-kit/a-25776-20

i believe you can select ntsc as wel as PAL with this kit

Op maandag 16 augustus 2021 om 16:31:31 UTC+2 schreef wils...@gmail.com:

[wperko]

Hi, 

I just ordered the Altair-Duino kit last Friday.  Hope to have it by the end of this week.  Back in 1975 I built a MITS Altair 8800 from kit (100,000 solder points)  sadly, I didn't keep it, but this new  Altair-Duino kit should be a fun replacement.  OTOH, I still have all the original MITS Altair documentation ... and also a nice size library of programs (back in the day, they came on printed paper ... photocopies)  Most sold for $2/program.  

I refurbished a couple of IMSAI 8080s for people several years ago and accumulated a bunch of S-100 boards.  Now I'm trying to sell off all the S-100 stuff since it's very nearly impossible to find an original cabinet with motherboard and working power supply.  

Antique/Vintage Computer Docs & Software ForSale (brainless.org)

This stuff includes cassette tapes for 4K and 8K MITS/Microsoft BASIC and an original Super Star Trek tape and manual.  Some Sol-20 and even a little Apple II stuff too besides a big pile of chips, CPUs, ROMs etc.  

I can't wait to start typing in old forgotten programs that I have on paper.  Don't know yet how to save the work to the microSD card though.  

IF you know any collectors, please pass the link on.  I really could use the cash.  

[Giovi Alex]

thanks to everybody.
I decided for the Chris Davis' kit, that seems to be quite straightforward, since it was ready for the Altair-duino yet, so I don't even need to program the chip; the one that Tom told me was interesting too, but it seems they didn't ship to Brazil. I will tell you the result.

[Chris Davis]

I don't remember a PAL jumper on Geoff's original board.  Maybe that was selectable in the Shift-F12 menu?  I've never really used the composite signal because the resolution of the composite signal is not really very good.  I'm sure you can do it with my kit, because it follows Geoff's schematic, but I don't know if it would be worth the trouble.

My I/O board has the pins labeled on the 14-pin connector, so it would not be difficult to connect it to a homebrew Altair-duino.  I've also attached a schematic which should help (J8 is the connector to the I/O board.)

[Giovi Alex]

Yep. I've bought it  because it seemed to me the best and easiest choice for the Altair-Duino, even if probably the Geoff's board would work fine too. I've just received the e-mail with the USPS tracking to Brazil, it will take a while. I've seen there's a Composite connector on our board; is it where I would take the composite output from?

I've read about the Geoff's specs and I'm quite sure there's a way to select the PAL/NTSC mode, but I can't recall now how.

Yes of course the composite output isn't as good as VGA, but I planned to keep it visually retro, so I wish to find some kind of B/W old CRT monitor... back in the '70s it was what they had available. But of course, maybe an old 14" CRT VGA monitor will be vintage enough for that :-)

Thanks for the schematics!

[Chris Davis]

I took a look and the composite mode is selectable in the setup menu (Shift-F12).  You can connect a composite connector to the two pins next to the VGA connector.

I was able to ship it Priority Mail since it would fit in a flat-rate padded envelope.  So it will hopefully show up a little sooner.

[Giovi Alex]

Great! Many thanks!