RE: Progress on the xAP to C-Bus gateway

[Kevin Hawkins]

Now fairly well settled on the Rabbit as the likely implementation
platform - although C is doing my head in (exercise is always painful). I
still haven't received one of the Lantronix parts but I think I can rule it
out as a non starter.
I have now got the serial I/O to the C-Bus SIM working with all the
checksum routines etc - and it is maintaining the state tables correctly.
From the xAP side I have the Ethernet based send/receive working and I have
rudimentary message filtering set up and a web server running although I
have not incorporated configuration of the xAP filters from the web server
yet. I am looking at supporting ftp uploads of web pages etc. I am
increasingly thinking that the W32 app is not going to be worth releasing.
On my development system I have a 4 line lcd display and keypad that
is displaying the atomic clock synchronised time (as received over xAP)and
CallerID plus also the C-Bus activity. I still have to handle some of the
identification of C-Bus groups by name but I can currently display the
level
of any group and alter the levels including raise/lower from the keypad. I
don't envisage this keypad/display as being part of the final hardware
though - unless anyone has strong views ? I will post some photos soon !
The Rabbit provides for a variety of spare interfaces (6 serial and
around 50 parallel I/O lines) although no analogue (A/D or D/A). This
actually would make a very versatile xAP I/O device but there is a question
of just how much I/O support circuitry I build onto a board - which
increases the price. Obviously the 'raw' signals are available but they are
not protected in any way (you can blow it up if you stick too many volts
in)
and they are not at the most common levels eg RS232 or TTL. My thoughts
currently are to support either just a couple of serial interfaces, one
dedicated to the C-Bus SIM and one that could be used either as a xAP
serial
connection (rather than Ethernet)or, in my case I will probably also attach
my alarm panel. Thinking about it possibly supporting 4 serial interfaces
is
best.
So final target price ?? Circa £50 - plus you need either an RS232
C-Bus module or the smaller (and much lower cost) C-Bus SIM (£50ish) and a
Rabbit core which is circa £50. ie £100 or £150 depending on your interface
to C-Bus.
Lastly I have uncovered one last option which is to use a commercial
board that is currently available that includes far more I/O. This would
raise the cost by about £50 but is far easier for me (manufacturing wise)to
produce and provides a host more features for potential use. Standard
interfaces provided for memory (MMC/CF/SD), serial I/O for USB(serial
emulation only)+ RS232 + RS485 + 1 wire (!), and an 8 channel 12 bit A to D
which can also support voice I/O. Also there is a low cost option for a 1/4
vga graphic touchscreen - either mono or colour.
The plus here is that the programming interface is included too (via
USB) so I can just send you firmware updates as I find the gremlins or add
new features and of course the really big advantage is so many interfaces
and therefore later expansion options. The negative is that only I could
really support the extra interfaces and I don't want to turn this into a
development nightmare, (or even promise that I will ever support them). The
gotcha is that I can't make source code available for the C-Bus
implementation, at least not the protocol detail as it is under NDA so I
need to think a little more carefully about this route.
So, all in all I am quite pleased, and although still quite a way
away from having a final product,I can see the path much more clearly now.
As always if anyone has any input please post back to this list or
offlist if you prefer - I'm very open at this stage to feature requests,
implementation thoughts or indeed suggestions on the number and type of
other interfaces you might find useful.

Kevin