SGI Indigo Keyboard and mouse adapter

megaimg

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Nov 24, 2021
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Hello guys, need your help... I just finish repairing a Indigo PSU and I think the unit is operational.....R3000 with basic video card....but I dont have HD, keyboard and mice.....I am looking for the adapter to use a ps/2 combination.,...waiting for a dim-8 to db9 to verify console....

Any recommendation!
 
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Elf

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Feb 4, 2019
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Unfortunately I don't believe there are any options currently on the market. The two choices were the Drakware adapter and this older PIC based adapter that occasionally appeared on eBay (but is no longer listed).

I would either endeavor to find a used version of one of those -- which will be difficult -- or to find an original Indigo (or earlier) keyboard and mouse, which might be slightly easier to locate but still not very readily available, and much more expensive.
 

megaimg

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Nov 24, 2021
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If they are not going to make this adapter anymore, they must share the project with the community so we can build our own!
 
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Elf

Storybook
Feb 4, 2019
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Regarding the schematics, whenever you see a 5V or GND connection (or any other commonly named stub connection), anything with the same label is generally considered to be interconnected.

Your choice of oscillator seems to match up with the original design, just being a TTL/CMOS 10 MHz clock source.

One piece of advice especially since the board has a lot of space on it currently: I would try to place all components on one side. Doing so will ease assembly or open up more assembly options. It's harder to reflow boards that have surface mount components on both sides, for example.
 

megaimg

New member
Nov 24, 2021
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Regarding the schematics, whenever you see a 5V or GND connection (or any other commonly named stub connection), anything with the same label is generally considered to be interconnected.

Your choice of oscillator seems to match up with the original design, just being a TTL/CMOS 10 MHz clock source.

One piece of advice especially since the board has a lot of space on it currently: I would try to place all components on one side. Doing so will ease assembly or open up more assembly options. It's harder to reflow boards that have surface mount components on both sides, for example.
Thanks, finish the redesign....
 

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nuclear

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Jun 3, 2020
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nuclear.mutantstargoat.com
There are multiple things bothering me about this design. First and foremost, we don't have the source code for the firmware. That's a show-stopper right there for me, but moreover I think the hardware design is rather clunky:
  • 2x microcontrollers seem completely unnecessary. I'm pretty sure a single MCU can handle both keyboard and mouse easily.
  • Ignoring the +8v/-8v supply provided by the SGI port, and using a charge pump (max232) starting from a single 5v rail to re-create the split signal levels seems rather awkward.

Also, unless I'm missing something in the SGI docs, it seems to specify +/-5v for the signal levels, while max232 will try to go higher than that, typically to +/-8v according to the datasheet. I'm sure there's some tolerance and clamping diodes built in to the port, but I'm not entirely comfortable with this arrangement, though I guess it's probably ok.

I intend to design a new converter (because I just acquired an indigo, and I don't have a keyboard/mouse for it), starting from my amiga PS/2 keyboard interface: https://github.com/jtsiomb/a500kbd and release the whole thing as free hardware design with free firmware under the GPL.

If anyone wants to collaborate on this, I'm also on the discord server as "nuclear", so we can chat there about it (preferably talk to the bot version of me, connected through the IRC bridge).
 
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steeph

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Feb 21, 2021
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I believe that this thread has been missing here for a while now. The problem of Indigo (1) and other old SGIs without a compatible keyboard came up in different places on the net every now and then, but the answers have become more and more negative, hopeless and sparse. I've been looking for a solution to this for a while myself. I think I probably saw the last original older SGI keyboards sell on ebay about two years ago while I was waiting for a cheaper opportunity to come up. It never did and now there aren't even keyboards to buy that could be used to reverse engineer the protocol or record the signals. I haven't seen any adapter offered anywhere in the time since I'm looking for one. So, thank you, @megaimg, for getting this rolling again.

The schematics and firmware for the older two PIC version are actually still available: https://web.archive.org/web/20120415042231/http://www.irisindigo.com/index.php/Indigo_to_PS-2_Keyboard_converter
Oh, wow. I wasn't able to find those hex files anywhere. I only came across copies of (parts of) that page with dead links. Now that I know that they were in that wiki, they seem easy to find. Thanks for posting the link!

2x microcontrollers seem completely unnecessary. I'm pretty sure a single MCU can handle both keyboard and mouse easily.
Please be aware that even the slightest lag can be noticeable and a great annoyance to some people. Especially with the mouse it's important to have no lag. Apparently this is a problem with USB adapters. Hopefully not for simple serial-to-serial adapters. So, you're probably right.

Of course I don't mind if the design is improved upon. (Both hardware and software aren't perfect.) But I also hope that nobody gets discouraged to make one of these, in any working version and form factor, by critical posts. I'd be happy with a hardly working, crappy built pile of badly soldered leftover components. As long as it does anything it's infinitely better than what I have now: Only incompatible keyboards.

I could probably built one of these myself. But it's been 20 years since I've programmed a PIC in school and this would be my second time. I don't have as much time for additional little projects like this as I'd like to have. So I'm in the market for a working PS/2 adapter for my Indigo. Just letting everybody know in case somebody makes more than they need.

I haven't been receiving email notifications from this forum in the past. And I'm not an active member (sorry), so it might be a while before I see that I got a message.
 
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