[wxsig] T238+, X1W-1. X1W-2 and AAG, crossed over

[John Koster]

On Sun, 8 Jul 2007, Rasputin Novgorod wrote:

> > A little history, as I remember it,   Seems like the 3rd rev of the
> > AAG WX 
> > STN came out while the T238+ was in the final stages of going into
> > kit 
> > production, so there wasn't much chance of modifying it.  John was
> > still 
> > working with alpha versions of his two boards, so he hedged his bet
> > and 
> > put the jumper options.  No one has ever come up with an explantion
> > as to 
> > why AAG decided to be different.  
> > 
> > What can be done?
> 
> The British still drive on the wrong side of the road.

But it makes for fun when you visit the carribean islands and rent a car.

> 
> First I made a custom cable for the AAG. Got in trouble
> a month later swapping cables around, and forgetting that. 
> So I cut the traces on my AAG and modified it to conform to
> the rest of the T238+, X1W-1. X1W-2 world.
> 
> You know, it always annoyed me, that instead of using a
> standard telephone cord available anywhere, to interconnect,
> we have to snip off and replace the plug at on end, with
> crossed over wires.
> 

It is a pain, but then there appears to be both types on the market place.  
I have a box full of cables in the garage and I find both types.  The
telco's a long time ago figured out that they needed to make the new
electronic phones polarity independent just like the old rotary dial
phones to avoid reversed polarity problems.  If you had 6 jacks in your
house, you could garantee one of them was reversed.

I've always been annoyed that the telephone connector has become a catch 
all for some many applications.  

I don't know why Dallas chose to use the RJ11 on their WX Station.  I've
worked for companies that used 1-wire devices, and there's not one RJ11 in
the circuit to the devices.  We also determined that CAT5 wasn't best
choice for getting the longest reliable runs.  However we were looking for
300 or more foot runs (to a single iButton).

How difficult are the trace cuts in the AAG unit?  Does the AAG require +5
to operate or can it still be powered from the data line the way the
original Dallas WX Station?  Is the AAG unit the only one 'backwards'?

If the AGG unit doesn't require +5, and it's the only one that needs 
modification, then it would make sense to cut on it.  It shouldn't be too 
hard to isolate pins 1 and 4, but I'd have to see the actual PCB layout to 
be sure.  If there's a GND plane around pin 4 it might be difficult unless 
there's the little heat relief traces between the actual pad and GND 
copper (like 4 spokes on a wheel). 

Of course there's the problem of voiding the AAG warranty by cutting 
traces. 

-- 
73,
John, W9DDD