🚀 go-pugleaf

In article <1992Sep15.150015.7409@sbctri.sbc.com> tadams@sbctri.sbc.com (Tom. Adams 529-7860) writes:
>I was wasting time in a meeting, and came up with an idea that seems
>interesting to me.  Consequently I'm sure it's been done, or more likely
>been shown to be just incredibly stupid. :)
>
>I'd like to connect multiple devices to an RS232 line, buswise.  All devices
>would either be programable, (i.e. PC's) or be frontended by a (cheap)
>microprocessor.  I'm wondering if CSMA/CD is a reasonable way to manage 
>very low speed bus contention.  If so, it would seem reasonable to transmit 
>address information, data, CRC's etc over the wire.  I'm not quite sure
>how to manage the Collision detect part, since I can't just look at 
>voltage levels on the wire.  Applications would be low volume data logging
>and control systems, ridiculously overpriced burglar alarms, etc.
>
Icom uses this system with their computer-controllable amateur radio
transceivers and general-coverage receivers.  They call it their CI-V
system.  Each type of radio has a different default address (which can be
changed).  This way, you can connect multiple radios to one computer and
control them independently.  They do TTL out of the back of the radio, so a
level converter is also needed.  This is how I became interested in this, I
have an article on radio-computer interfacing coming out in 1/93 QST.

My new Ten-Tec Omni VI has the same system.  I'm running it at 19.2K, but
only have the one radio hooked up.

To check for collision, just listen to what you transmit.  If you don't hear
the same thing you sent then there was a collision.  Good luck.


			Wally Blackburn AA8DX
			wrb@ccsitn.att.com