[Xml1-wire-devel] New hub design, request for input

[Bruce B. <bb...@sy...>]

We are thinking very seriously of doing a quick OneWire hub design, which
would have at least two DS2409s on it, for at least two branch outputs.

Naturally we'd want to include tagging ability, perhaps a DS2433 on the aux
branch of each DS2409. Then the main branch output is the active branch of
OneWire devices. Then you can tell for sure that the tagging 2433 you are
reading is definitely the correct one since it's the only device on the aux
output.

Alternatively, if you use both 2409 outputs as switched branches, then you
get twice as many but the tagging is not quite so clean. If the 2433 was on
each output, then it's hard to tell if the 2433 you are reading is the
tagging 2433 of this 2409 or some other 2433 on the branch.

Our intent is that this "hub" would be something you would string along a
OneWire "backbone". For example one hub per floor or section of a building,
with one branch per office or room.

Each hub would also have a rugged switching regulator which could supply
power to its branches. The power could be switched so that it was only on
when the branch was selected. It would be the same or similar to our STEP
boards, at least 8-24VDC input, 1A 5V output. The hub power would go just
to the branches, the backbone would be powered by the sockets board.
Shorting out one branch would only affect that branch (assuming we switch
each branch's regulated 5V), if we didn't then it would still only affect
the branches of that hub.

If memory serves, some branches would want to be powered all the time so
that, for example, temperature alarms could be sampled at once? Has someone
used these devices in this mode?

The hubs could also be cascaded so that a branch could have switched
"leaves", although it seems this level of complexity could drive you nuts
pretty quickly. Point is, the hub and its power circuit would allow this.

This would be a rugged industrial grade device with series resistors on
each branch and diode clamps, etc to guard against long cable runs on each
branch.

The "trunk" oneWire would have RJ12s and screw terminals for easy
connection to any common Dallas-compliant TINI socket board (all the eXX
and all Systronix sockets use the same pinout). The branches would have
pluggable screw terminals, maybe also RJ12s for the maximum of flexibility.

Each 2409 would also have an LED to indicate status and power.

An interesting question is how quickly TINI could switch branches and
perform some useful task, so that a switched branch could do something
interesting like door access, if possible.

Any security issues which might affect hardware design? We could include an
iButton socket on the hub board - where should it be? On the aux output
with the tagging device?

Input welcome.

- Bruce
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