Re: TI-H: Ein Reich, Ein IR Link

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Re: TI-H: Ein Reich, Ein IR Link

On Tue, 28 Oct 1997, Mel Tsai wrote:

> I don't think there should be a collaborative effort on the IR link.
> Some people obviously know more than others about what's involved, so
> what's the point of having everyone on the same team?  The people who
> know less would only drag the others down.  That's just my opinion of
> course :).  It only takes one person to come up with an IR link, and
> may the best designer win!  From what I've seen that hasn't happened
> yet.

Well, okay, actually I don't care very much about howthe actual
development is done, but I want the final product to be good (if there
ever will be anything). I'll still not be on the team. If one IR link team
isn't a good ide, then OK, let's have some anarchy.

> >- It _must_ be 100% compatible with _any_ protocol out there, including the TI
> >protocol, I2C, the Expander SF protocol, the protocol used by the TI Light
> >Flasher etc. The only allowed exception is speed, because it's impossible
> >to make an IR link that's as fast as a real link cable. But still, it
> >should be as fast as possible. Perhaps a high carrier frequency, like 500
> >kHz, would help here?
> 
> Standard infared LED's cannot be switched at that rate.  They can
> barely be switched at 100khz much less 500khz.  Also to be compatible
> with other devices it must be modulated at a standard rate like 40khz
> which is what the hp48 and standard Tv/VCR remotes use.

You're right. But there are IR modules that can. If using them doesn't
seem like a good idea, then let's not use them.

> >- It mustn't suffer too easily from interference from the sun, lamps and so
> >on. It would also be very good if TV, VCR and other remote controls
> >wouldn't interfere with its operation. Again, a high carrier frequency
> >might be the key.
> 
> The point of modulation is to get rid of possible ambient light
> interference... but you can't get rid of stuff from other IR devices.
> It will always have some signal interference when you're modulating
> past a certain rate, especially with the crude filtering that a cheap
> IR link will have.

Hmm. The Sharp 500kHz modules promise that IR remotes don't interfere with
their operation.

> >- It must have a relatively long range. I don't know what's possible, but
> >I'd say ten metres in normal lighting conditions etc. is a minimum.
> 
> Well, that ain't gonna happen but oh well :).

Lots of things aren't gonna happen.. :)

> >You are, of course, allowed to disagree with me. It's possible that
> >somewhere out there someone has already made a link that meets all these
> >criteria (and possibly even more?), but I've not yet heard of such a
> >project. Mel Tsai is, as far as I know, going to implement an IR link in
> >his Expander II/III projects, so he should also be contacted.
> 
> I have scrapped the IR link idea simply becaues I no longer see any
> point...  Can anyone honestly say that the IR link will be worth the
> work?  "Oh boy mommy, look I can send stuff to my friend who's 5 feet
> away THROUGH THE AIR!"  It's magic!" :).

Seems as if that would be the main reason for people to have an IR link
(and other TI hardware as well), but have you ever really been able to
understand the motives of nerds? :) If something's cool, then it is
justified to spend time and money for it.
(Yes, I'm a nerd myself..)

> I have been through all the possible designs (haven't looked much at
> what's been done within the past week by others, but what I've seen
> is, umm, well, I think you know what I've seen :).  Not one of the
> design's I've come up with will meet these criteria:  cheap, easy to
> build, good accuracy, acceptable speed, and small size.

Well, there have been at least two announcements of new IR link designs,
but I don't think they're worth much..

> My only real opinion on this is that we should COMPLETELY AVOID
> proprietary IR controllers like IR communcation chipsets, unless it's
> like an IrDA comm IC.  Just do it with discrete or highly available
> electronics.  Trust me :).

Oh, whatever if it works. But you're probably right.

> >I'm starting to believe that meeting these criteria without having a
> >microcontroller involved is just about impossible. 
> 
> You have seen the light!  OH YEAH BABY :).

I've seen the IR light... :)

> (If I sound cranky it's probably because of my 5 hrs/night sleep
> average this past week :).

Not much less than I've had...if I'd slept more I probably wouldn't have
written all these messages...

-Ozone

*** Osma Suominen *** ozone@clinet.fi *** http://www.clinet.fi/~ozone ***
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