On Wed, Aug 15, 2012 at 12:21 AM, Paul Alfille <[email protected]> wrote:
> Hi Pedro,

Hi Paul, thanks for looking into this. I've gotten the modules in the
mail today and did some initial setup. I still have the DS2480B on
order but the simple case of doing a point-to-point wireless
replacement of a serial line seems to work fine.  Once I get the
onewire bus chips I'll try the simple case of running owfs over this
link to see how reliable it is. It should work fine as there seems to
be prior art from as far back as 2007:

http://www2.buoy.com/pipermail/weather/2007-February/007437.html

> This looks very possible, though after reading the libxbee man pages, it
> seems you need to full port and baud rate for each device.

I'm not sure what you mean by this. You'd have a single Xbee dongle
connected to a PC running owfs, using a single port and baud rate.
Through that dongle you can send frames with any destination address.
It's a packet switched network, but instead of Ethernet/IP it uses
it's own packet format.

Looking at http://attie.co.uk/libxbee/getting_started/ my
understanding is that xbee_setup gets you a "network interface", an
eth1 of sorts. After that xbee_conNew gets you individual connections
of any of several types to any of several destinations. An equivalent
to socket connect() if you will with different destination IP and
protocol options. So the single port/baud is only for the connection
to the local xbee node from which you can open logical links to any
number of remote nodes.

> Sending and receiving data seems easy. How do you query the zigbee network
> to find devices?

There's a broadcast address and packets have source addresses so it
may be possible to just occasionally do a broadcast ping/echo style
discovery.

Since there's surely no sane way to test if there's a DS2480B attached
to the node without possibly messing up another node type (that's not
expecting the onewire init sequence on the UART) a good compromise is
to use the broadcast method to list all the xbee nodes so that
something like "owdir /zigbee" lists all of them. And then only try to
read the onewire bus on "owdir /zigbee/<64bitID>/onewire/". That way
it's in the user's hands to not mess up any non owfs UART connected
sensors in his network.

Ideally owfs would also expose the xbee native IO options. Something
like "owread /zigbee/<64bitID>/PIN1" reading pin1 on the xbee itself.
The only use case that would leave out is sensors that have something
other than onewire attached to the UART, where you'd want to code up a
custom app for it. I don't know if read/write to
"/zigbee/<64bitID>/UART" would be an appropriate way to handle that.

Pedro

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