RE: Displays around the house - direct to a pc or via tcp/ip

["Dr John Tankard" <john@xxxxxxx>]

> John,
>
> The idea is that the xAP broadcast protocol is sufficiently
> open that output handlers can be written for either.
>
> A PC would use a general IP stack, and then chuck stuff out
> to serial. An embedded device would use its own IP stack, and
> process on-board.

That=92s ok if we understand what this means, to have multi drop we cannot<= BR> use RS232 (unless we daisy chain displays and messages get passd down
the line to reach the correct device (ie two serial ports one each
display)), so this means we need a IO card for the pc or a custom RS232
<> 485 converter. I don=92t know what the cost is for a  card, r= emember
that many people are using old PC's for HA and we need to source ones
which work both bus styles. Lets say that the card is say =A330

If we had a controler with a ethernet port and RS485, this could act as
a bridge with lots of expansion posibilities, this embedded controler is going to be =A350 to =A370 (if rabbit based, perhaps less on a different less powerfull platform), since most pople would want more than one
display the extra cost does not look that bad, coupled with the benefits it offers over a pc solution.

Low power operation, could still work fro extended periods of power
outages
Web control possible without a pc
Does not use up 232 ports on PC, leaving them free for other stuff
Posibility of connecting bridge to HV, again without PC
If not on backup power, would always re-boot without user invervention
Protocol for displays can be very very simple as its private to the
controler
Not pc dependant, the house keeps working after tweeking the HA PC :-)
Likley to have higher WAF as there is no PC required

As it=92s a key decision in the development of such devices, I think it
needs resolving and agreeing before people rush of and start
coding/soldering

There are benefits the other way round which must be weighed in :-

For people who just want 1 display, they could just swap the MAX chip
and have it just RS232
Cost, perticuly for single display apps
People who already have a PC on full time
Quicker to develop
Easer to develop, no need for a developlemt system, in the case of
Rabbit I think there is only a couple of us with systems.

It might be worth a short pro/con discussion and a vote.

I will go with the flow, but from my viewpoint the controler method
appears to offer so much more for a small cost

Just my 2p worth.

John

> At a early stage it needs deciding on how the displays
> connect. From what I have read so far the plan is direct to a
> PC, this is fine and I will help with the development however
> personally I think it would be much better to have some form
> of controller handling mult-drop displays which in turn
> connects to the PC( perhaps via tcp/ip.  Reasons:-
>
> 1) not PC dependant
> 2) can work with other kit
> 3) 1 controller could handle a lot of displays and could
> start of just reporting back/ relaying messages, but later
> could do other stuff
> 4) the cost for one controller form many displays would be small
> 5) lends its self to web control if necessary without a PC
> 6) costs to have a PC with loads of serial ports
> 7) noise from a PC on all the time
> 8) lighting strike could take out the PC
> 9) cuts down on cable
> 10) much more flexable
> 11) easy to make the transition from bridge to control function
>
> Just a few idea's
>
> John
>
>
>
>
>
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