AVR-Chat

Russell Shaw wrote:

> Peter Jakacki wrote:
> > Russell Shaw wrote:
> >>It is no different now than then. Back then, RS232 was run around and
> >>between buildings for terminals and mainframes. If you still want to
> >>run those distances, you'll want +/-15V
> > No, it is different and that is just the point. Nobody runs RS-232
> > between buildings, do you? If we don't go as far as using fibre then we
> > would use a balanced line drive like RS-422, but never ever RS-232. 
> Yes,
> > I still want to run those distance, but no, I am not stuck in the 60's
> > because I use RS-422/485 or some other means.
> I run rs232 from my workroom to the garage (30m).

  Perhaps so.  That doesn't make your practice reasonable.

> At my previous job, rs232 was run from the lab to various measuring 
> equipment
> outside (10-20m).

  Poor engineering management?

> I know of several radio hams that run rs232 from their radio room to 
> things
> outside and up radio towers (10-30m).


  With all due respect to radio amateurs, who, as a group, have 
contributed greatly to the advancment of communications technology, they 
*ARE*, by self-definition, amateurs, after all.

> RS232 was designed for unterminated lines which keeps things simple,
> especially for multi-drop star networks. RS485 requires a single backbone
> with terminator.
> RS232 can be fed thru radio coax and separated out with a filter, unlike
> rs485 which requires a balanced line.
> http://www.rs485.com/rs485spec.html
> RS485 requires three wires but rs232 only needs two.


  Not the last time I looked.  Unless you are making a unidirectional 
connection, you need at LEAST 3 wires for a proper RS232-C link.  
Ground, TX and RX.

tom