DEC Keyboard Mouse Emulator (was RE: Backing up VAX/VMS?) - test-drb@ccmp.vtda.org

13 Jan 2008

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Subject: Re: DEC Keyboard Mouse Emulator (was RE: Backing up VAX/VMS?)
   From: Jim Brain <brain at jbrain.com>
   Date: Sun, 13 Jan 2008 14:22:49 -0600
     To: General Discussion: On-Topic and Off-Topic Posts <cctalk at
classiccmp.org>

Bob Armstrong wrote:

  I found details of the keyboard and mouse
protocol in the back of
 a Microvax manual, and have been toying with the idea of building
 a small embedded controller to take a PC (PS2) keyboard and mouse,
 and emulate the DEC equivalents to the VAX - would anyone else be
 interested in this?

   I'd be very interested, not because I have a shortage of DEC keyboards or
 mice, but because it'd allow me to use my VAXstation or PRO-380 on a KVM
 switch along with various PCs.  The KVM switch can handle the video, but it
 can't cope with the DEC keyboards and mice.

   I suspect that this may not be as easy as you think, but if you're serious
 I'll build the hardware if you write the firmware.
    Would this work help in any way:

http://www.kbdbabel.org/

"PS2 Keyboard ---> DEC VT320 ..." 
Save for theres nothing I can find at the site of anything for that.
It appears thats a "proposed" project.  I checked SourceForge and 
didn't find any code there.

Briefly:

PS2 keyboard do a scan code and send it serially with a sperate clock 
line.  They also use the same serial path to recieve data.

DEC keyboards also use a serial path save for it's RS423
 and at 4800 baud RS423. The format of the data is different 
(not scancode!).

Here is a site that has the basic LK201 data:  

http://www.netbsd.org/docs/Hardware/Machines/DEC/lk201.html#electrical

To go from PS2 to DEC one must both reconcile the different codings and
how data is transmitted.  I'd say PS2 to DEC is easiest direction
as the PS2 scan codes are known and can be translated to anything.
I believe the DEC keyboard uses a simpler code that is one byte for 
keydown and another for keyup.  

Allison

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Jim 