[rescue] E450 Console puzzler

Mouse mouse at Rodents-Montreal.ORG
Thu Jan 11 21:30:46 CST 2018

> [...]  I'm playing with my new-to-me Sun E450.  [...]

> If I hook up a serial console that's known to work on other Suns
> (VT320), I get output to the screen, but no keystrokes are
> recognized.
> [...]
> devaliases shows the device tree I would expect, but there is an
> alias "keyboard!" with the same tree as "keyboard", but with
> ":forcemode" appended.  I have not checked another of my machines (or
> Google) to see if this is normal.

I'm fairly sure I've seen :forcemode on some of my Suns, and I'm fairly
sure I don't have an E450, so I think it is shared with other machines.
I'm not sure whether it was on keyboard or ttya, and, in either case,
I'm not sure what it means.

I am, however, moderately sure it's not distinctive to your machine,
nor to E450s in general.

> Googling this, I come up with a reference to a similar situation
> where the problem was an "incorrectly wired cable".  Since my
> terminal/cables work OK on a SparcClassic and LX, I would assume it
> would be OK on the E450, but I've been wrong before.

I would tend to assume that too, but I also have seen very strange
failure modes from miswired cables, especially if signal ground is one
of the miswired pins.

I'd suggest breaking out a voltmeter and verifying that none of the
conductors are being driven by both ends at once (ie, if you unplug one
end and look at which pins are driven, then unplug the other end and
check likewise, no pins are driven in both tests).  If I wanted to be
paranoid, which in this case I well might, I'd turn everything off,
including unplugging power, and verify that there's a
very-low-resistance path from the ground pin(s) to the chassis.

I don't know how much of an electronics geek you are, so this may be
explaining something you already know, but in case not: to check which
pins are driven, if your voltmeter has very-high-impedance inputs, the
simple thing to do is to put a resistor of maybe 10K in parallel with
the meter, between the pin you're measuring and ground.

Another possibility is that the serial port input is just plain fried.
Does the machine have a second serial port?  If so, have you tried
using it?  (If it has a DB25 for serial, it may have both ports on a
single connector; Sun did that with, eg, the SS20.  In that case, you
need a breakout cable, or at least an adapter, which is easy to make if
you've got the connectors and wire and the skill to use them; I can
describe the pinout if you want.  Sun also made breakout cables; I
assume third parties did too, but I've never personally seen one that
was neither a Sun one nor one I made.

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