Posted by Druin on January 08, 2002 at 08:35:00:
In Reply to: Keyboard interface posted by Ron on January 08, 2002 at 07:38:09:
Some thoughts are...generally from the keyboard emulators I've seen out there, they do their programming directly through the keyboard port itself, no need for extra RS232 tieing up. THe keyboard port is bidirectional, eg the way the LEDs are turned on and other host-to-keyboard signals...you can do searches on PS/2 protocol etc and find out about that...you can write a PC program that will access the keyboard port and send hex codes that your emulator can sit and wait to detect, and then jump to the routines for config.
With keyboard thru ports, all I know roughly is usually one keyboard device gets to be the real master, receiving commands from the PC host...and the pass through device is a slave that can't get those features, unless your emulator will retransmit (something I was thinking of if I build an encoder)..so I forget examples of what I mean but I think one fact is you wouldn't get LEDs working on the slave keyboard and maybe some actual features like the typematic rate if you set it...that was one of the bi-directional types of communication the keyboard/host do. So that's a possible thing to look out for with master/slave.
Relays toturn lights on and off may be overkill, depending what you're switching, you may want to just provide transistor output drivers (to which you can later put relays if it calls for it)...or opto isolators, etc.
All this talk makes me wish I had more hobby time instead of work-electronics time...
: RS232 port for PC programming
: keyboard through port so you can have your control panel and keyboard hooked together at the same time.
: 3 optional relays for turning lights on and off.