Re: Serial over CAT5

[Andy.Powell@xxxxxxx]

At 12:16 03/03/00 +0000, you wrote:

>Get yourself down to your local Maplin, and buy the cheapest meter
they
>have.  It costs about £7, it's fairly naff, but will probably do
everything
>you need a multimeter to do.  I've got a better
all-singing/all-dancing one
>that I usually use, but the little analogue one still wins
occasionally!

That's cheaper that a set of new bike
lights! :-)

>Who needs 1% accuracy?  Maybe on one occasion in 1000?  Just
about every
>time I need a multimeter, it's either to see relative changes, or for
a
>quick 'working' or 'not working' answer... If it had a 1 digit
display,
>that would probably be enough for most occasions.  

I certainly wouldn't need that much
accuracy - I acutally wouldn't know how
to utilise that sort of accuracy
properly - so a £7 multimeter sounds like 
my best bet.

>It depends what they implement- just Tx and Rx would only need 2 pairs,
but
>if it also passes 1 handshake in each direction, it might use all
4.
>That's assuming it's all balanced, they could have bodged it onto 3
wires
>if it doesn't need to work over long distances (more than 5-10m
say).

I don't need handshaking as the
hardware at the other end doesn't support it.


>You can pass mV down cat-5 safely... if it's high impedance you will
get
>noise added though...  what are you wanting to use it for?
 

Ok, here goes - I've recently purchased
a Matrix-Orbital (www.matrix-orbital.com)
LCD display (40 X 4) with a PC AT
keyboard interface. I've plugged in the receiver 
part of an Airtech IR keyboard into
this socket and use my Pronto to send 'key presses'
to my application (MP3 Player/X10
control). The idea is to have a single cable, if possible,
to take the serial connection for the
LCD, 5v power for the LCD, the audio from the sound card
and the serial connection for the
ibutton. The ibutton is used to effectively store (although 
the idea is to use a simple serial
number based ibutton) preferred settings for the lighting and music 
preferences of each member of the
household. Though as always with these things someone has to 
have the ibutton that is classed as
GOD. I guess it's a poor man's Gates palace. The LCD is used
to provide status information and menu
options to control the MP3/X10 PC. Because of the PC AT keyboard
interface on the LCD it means that
hotkeys to control the application are a thing of the past (I never
liked them anyway) - or worse the
application would always have to be on top! - Sorry we're talking 
MSWindows here...

>If it's the ibuttons again (piecing together a number of your
postings!),

Oh no - someones building poster
profiles - eek ;-)


>Contact Dallas and ask them if they have tested it on cat-5 if you
don't
>fancy ploughing through calculations or data sheets... they've been
very
>helpful in the past.  ibuttons are in a middling position on
my
>ever-growing todo list (ie lots of ideas and designs, no time to build
them
>yet!), so keep me posted on progress!

I guess all of us here have 20 million different projects on the go - and
like
you say there doesn't seem to be enough
time in a week to start them all let alone
finish them... What we need is to win
the lottery so we can give up work and get on
with the things we want to do - then
again if you win enough to give up work then
we'd probably all 'get a man in' to do
it for us whilst we caught some rays in
Barbados!

Andy




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