Re: [LHA-misc] lonworks

[C. R. B. I. <cr...@ea...>]

Date sent:      	Fri, 03 Nov 2000 10:36:49 -0500
From:           	Neil Cherry <nc...@ho...>
Organization:   	Linux Home Automation
To:             	lin...@li...
Subject:        	Re: [LHA-misc] lonworks
Send reply to:  	lin...@li...

> > 
> > On a side note (and an interesting one at that), I spoke with a few
> > vendors at the EH Expo who develop periperhals and controllers that use
> > RS-485 networks to communicate (they'll remain nameless but you can
> > probably guess)  One idea that was tossed about was possibly developing
> > a standard control protocol for HA RS-485 networks.  This way a
> > controller from one vendor could be used with the peripherals from
> > another and vice versa.
> > 

> > It was just talk, but I was excited by it and plan to pursue it in what
> > limited time I have.  THough many folks said RS-485 basedf HA was doomed
> > by PC based systems, they are still alive and well with multiple vendors
> > developing products (both separately and together)
> 
---x---
> 
> > I mention this because I'd want to make sure you all were involved since
> > I expect that Linux HA would be RS-485 capable at some point and I'd
> > want it to be able to support a std protocol if one was ever developed.
> > 
> > Thoughts?
> 

I think it's sufficiently important that the project should be 
collecting specs and docs on every RS485-based protocol that comes 
along, not only for reference material towards designing one or more 
appropriate protocols for LHA purposes, but also for providing 
translation layers so that devices which speak those protocols can be 
brought under the umbrella.

Some of the translations may be mere packet translation, and those 
can be handled within the host. Others (particularly for access-
control, where frequent polling and peremptory challenges are part of 
how you make sure the reader-terminal at the end of the wire is still 
the one you installed there) will have to be managed by 
microcontrollers, in which case having a 'lingua franca' that's wide 
enough, and with a wide-enough address space, to handle the required 
messaging, will allow the MCU code to be done cleanly.

I don't think RS485 is going to go away anytime soon. Despite the 
lack of a single standard protocol equivalent to the Hayes command-
set for RS232 modems, ANSI/VT100 screen controls for VDTs, and 
slip/ppp for serial network connections, it's still the most cost-
effective way to talk fast to a small embedded box at the other end 
of a local wire, equivalent to I2C for on-board / in-system 
connections and four-wire optoisolated serial for longer wire runs 
and runs in hostile territory.

cr