Re: [1-wire]Re: [Owfs-developers] What software do you (plan to)

[Paul A. <pal...@ea...>]

How do you monitor device arrival/departure. I've been looking through
the documentation and it isn't obvious (beside polling).

Paul

On Mon, 2003-08-25 at 20:12, Vadim Tkachenko wrote:
> According to Paul Alfille:
> 
> > On Sat, 2003-08-23 at 18:46, Nicolas Huillard wrote:
> 
> > > Vadim Tkachenko wrote:
> > > >>* will it need alarms or detection of new devices (like iButton arrival)
> > > > 
> > > > Definitely. And departure, too. For me, this is a mission critical thing: If
> > > > the switches or sensors are gone, that's really bad.
> > > 
> > > I agree. It's critical that devices attached to the network remain attached.
> > > I was referencing iButton comming temporarily (like ID chips), that the 
> > > software must intercept to act accordingly (ie. open the door).
> > > I don't know if OWFS has a mechanism to allow such detection of unknown 
> > > devices.
> > > 
> > > NH
> > > 
> > 
> > Can either of you expand on this? Why do you want arrival and departure
> > notices?
> 
> In my case, a departure of a device means a network failure, either
> transient or permanent. Since the actuators control multi thousand dollar
> hardware, and the hardware itself may be pretty dumb, alarm notifications
> are critical, otherwise the losses will be huge. They will also be further
> complicated by the fact that it will be extremely difficult to talk to home
> warranty company or a manufacturer and convince them that the HVAC unit is
> at fault, not the DIY piece of hardware and software.
> 
> > Are you scanning for ibutton contacts?
> 
> Not yet, however, if DZ ever gets to implement a "Bill Gates" mode when you
> can touch the socket with your iButton and have the house set up your way,
> then yes.
> 
> > OWFS doesn't care if devices come or go. The current implementation is
> > almost entirely stateless. It only knows that a device might exist
> > because it's ID is the filename. It will only read existing devices.
> > There should be know ghosts, and no memory creep.
> 
> That's OK, but arrival/departure notifications are a must for mission
> critical applications.
>  
> > I plan to have a fancier caching version, perhaps with hash tables, and
> > cache of volatile (temperature) and stable (switch states) data, but
> > I suspect it will introduce other problems.
> 
> Yes, it will. Every time a switch departs and then arrives back, you must
> make sure its state is the same as before departure (if there was no control
> input in the meantime). I've tried to make this transparent, it worked more
> or less fine, but slow since it was competing with other 1-wire traffic.
> 
> > Paul Alfille
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