General Purpose I/O for UNIBUS PDP-11 Machines

[NF6X]

The thread about controlling Christmas tree lights with a PDP-8 got me thinking about doing general purpose I/O (GPIO) with my PDP-11/44 once I get it up and running. Being able to control a bank of relays would be quite useful. Having general purpose digital and/or analog I/O would also be cool. So, I wonder what options there are for doing that?

Perusing the Field Guide to QBUS and UNIBUS Modules suggests some vintage possibilities. M1801 is listed as a 16 bit reed relay output board. M7843 (DR11-K) looks like a general purpose digital I/O board. It looks like there was a whole bunch of stuff as part of the LPS11 Lab Peripheral System.

I wonder if there were other interesting options. And what are the chances of my finding any of this stuff today? A single eBay search suggests it's all made of unobtainium.

I gambled on an M7985 board off eBay recently for $50 shipped. I think it's a GPIB interface, so assuming that it is, and it works or I can fix it, and I can find/write software to drive it (a lot of ifs!), that will open up options for interfacing with test equipment.

Then there's always the option of talking to things over a serial port. I think that my PDP-11/44 parts heap includes lots of serial ports. But talking to something like an Arduino and telling it to flip relays just sounds like cheating to me.

There's also the nuclear option: What if I made my own UNIBUS card? Don't hold your breath waiting for me to get that done, anybody...

 

[AK6DN]

The M7860 DR11-C is 'the' PDP-11 UNIBUS parallel I/O board. 16b input, 16b output programmed I/O parallel ports. Been around since the very early days of the PDP-11 UNIBUS. Here is a picture: http://www.retrotechnology.com/pdp11/exhibit/DR11C.jpg

Of course it is not that easy to find these days, but every now and then one becomes available. Used a lot in PDP-11s that were attached to any process control or other third party equipment.

DR11-K is a later version (more bells and whistles) of the DR11-C design.

 

[cruff]

The M7860 DR11-C is 'the' PDP-11 UNIBUS parallel I/O board. 16b input, 16b output programmed I/O parallel ports.

A bit off topic, but the popularity of the DR11-C spawned some equivalent boards for other busses. I used some VMEbus equivalent boards in a pair of Sun 4 systems running SunOS to drive two Dicomed film recorders for a number of years, producing B&W microfiche and color 35mm and 4x5 film output. The same servers also interfaced to some early digital video recorders to produce Beta and VHS tapes (and a third format used in broadcasting that I forget the name of now) you could only buffer up 30 seconds of video at a shot.

 

[Marty]

Hi All;
Looking at the M7860, its do-able to wire-wrap your own.. The Board doesn't have that much on it compared to some Boards.. If you can't find one.. It all depends on Your Money Situation, Your Skills and Your Time.. Not in any particular order.. I would say Time being the most important..
THANK YOU Marty

 

[RSX11M+]

You would not need the entire DR11 since you only want outputs. I'd think a much simpler solution should be possible if you have to resort to a DIY wire wrap. Any idea how many individual lights you want to control?

A serial bus device would allow you to control more lights, be extensible, be "Remote-able" over only UTP wire, and work with any SLU - even a PC should your PDP fail temporarily. (Though you could still credit the PDP - to keep it "Safe" from "Cleanups") I suppose this approach does lack a certain... "sex appeal" however.

 

[dave_m]

I wonder if there were other interesting options. And what are the chances of my finding any of this stuff today?

I am not familiar with the PDP11, but there must be a board equivalent to the Data General NOVA 4040 board. This board had all the circuitry required to interface to the computer bus and plenty of wire wrap IC sockets for your custom application.