[Tfug] Network connectors

[Bexley Hall]

Hi Adrian,

> > First, thinking about what indicators typically are used for:
> > - link established
> > - collision
> > - speed
> 
> You forgot a couple:
>   - activity

I figured that information was conveyed temporally over another
indicator (e.g., wink the LINK indicator to show traffic).

>   - duplex

I figured that was on the switch.  I.e., there's nothing the user
can *do* about it (on my end) if the link autonegotiates as HDX
instead of FDX  :-/

(remember, there is basically *no* user interface on my end of
the wire!)

> > Is there a standard color scheme for the indicators?  It
> > seems like LINK is typically yellow?  But, I see a few
> > different choices for the speed indicator...
> 
> I rarely see collision any longer, since the days of hubs,

Agreed.  Though it could be useful in sorting out FDX/HDX
mismatches.

> duplex pops up more often. The "typical" light arrangement 
> I see depends on how many LEDs there are:
>  - For 2 LED jacks: right LED green for 100baseT/ yellow
> for 10base, left LED 
> green (sometime yellow only on that side) flashing on for
> traffic, possibly yellow for half-duplex or collision.

Ah, that's an interesting spin.  Makes more sense to flash
the speed indicator -- i.e., make it a "tri-color" LED
(green/yellow/BLACK in your example) -- than to flash the
LINK indicator (since "BLACK" there means "no link" if it
is steady state)

>  - For 1 LED jacks: LED green for 100base, yellow for
> 10base, LED flashes off (creating flicker) on receipt of packet.
> 
> There really isn;t any sort of standard. Some are now
> showing both 100base and 10base as yellow, because its 
> allegedly so much *slower* than 1000base mode...
> as if many of these devices could actually push/pull that much. Most 

Yes.  In my case, the MAC+PHY can only run 10/100 so silly
to coverboth of those speeds with a single color and use the
"other" color for Gb -- since it will always be "off"  :>

> network chips have 2 pins already for driving LED
> indications. Heck... even 
> the PIC18F97 Im currently playing with (which has a
> built-in ether MAC) has 2 
> pins, RA0 and RA1, that can be configured to automatically
> show the link status (up/down), speed, duplex, and/or traffic.

Yes, the PHY I am using will do that.  But, I can also override
it's "automatic" functions.  It, for example, won't directly drive
a bicolor LED (speed).  And, I am not sure I want to let it
decide when to illuminate the LEDs as they waste a lot
(relatively speaking) of power.  I.e., I may use the management
interface to deliberately turn the LEDs on and off when *I*
want, instead of when the PHY wants to do it.

> > Finally, is there something *more* informative that these
> > indicators could be used for?
> 
> I think having port speed (slow/fast) and activity is invaluable
> for quick diagnostics. Anything more than that and your going to have
> to dig into configuration to figure out what's wrong.

OK, now think about how you *typically* use the indicators.
When you first connect the CAT5, you watch for LINK to come on.
This reassures you that the cable is good.

If it went out 10 seconds later AND YOU EXPECTED IT TO DO SO,
you would have obtained the information you need (in that initial
10 second period) and it wouldn't be wasting power thereafter.

If, some time later, you suspected the device was not working
properly, you could always unplug and replug the cable (to
restart that 10 second "display").  Recall, unplugging the
cable will remove power from the device in most of the
cases I am addressing...

Activity is the tougher one.  You probably *won't* be expecting
to see activity on the line when you first make the connection.
Unless you have "started" whatever talks to this box before
you made the connection (assuming that is even possible!).
So, it seems like activity is something you have to show
"periodically".  -- But, that needn;t be every millisecond
(packet)!

> I simple bi-color LED show 
> green/yellow for port speed and flashing for activity seems
> the most informative.

So, BLACK steady state is "no LINK"
GREEN blink is 100Mb activity
YELLOW blink is 10Mb activity

If I show activity very sporadically (i.e., LED is off most
of the time.  Once a second, I flash the color corresponding to
the speed the link is operating at for some brief interval?

So, the only indication I don't have is "POWER ON".
I'll have to think about other combinations (e.g., if I can
find a RED/GREEN LED I can use red/green/yellow/black as
indications.)

Thanks!
--don