[time-nuts] Thunderbolt serial connection - null modem or straight through?
Matthew Smith
matt at smiffytech.com
Tue May 20 17:59:58 EDT 2008
Quoth Hal Murray at 2008-05-21 06:06...
> My standard setup for debugging RS-232 cabling is one of those gizmos with a
> handful of LEDs. They are green for one polarity and red for the other.
> Mine is actually a 25 pin version so it lives with a pair of 25-9 adapters.
> I use it with a straight-through cable (extension cord) to position it out
> where I can see it.
>
> Connect it to one side. Look at the lights. Then disconnect it from that
> side and connect it to the other side. Different LEDs should light up. If
> they overlap, you have troubles. If both sides light TD or RD, you need a
> null-modem type cable. (or to remove the one you are already using)
A good breakout box is an essential tool for anyone working with serial
links. (At least I think so!)
My old 'Interfaker' has both male and female DB25 connectors on either
side and a switch for each line. The switches mean that any line can be
broken and re-patched using rows of 0.1" sockets and little patch leads.
Typical use is when you need to reverse RXD and TXD - just flick the
switches off for those lines and hook in the patch cables.
I started using these beasties back in the days when I was running a
load of Wyse terminals off an IBM6150 (RT/PC in the USA). That's before
I ever SAW a Pee-Cee; oh happy days... Thing is, even in this day of
serial to USB adapters, I wouldn't let anyone take my old Interfaker away!
Cheers
M
--
Matthew Smith
Smiffytech - Technology Consulting & Web Application Development
Business: http://www.smiffytech.com/
Personal: http://www.smiffysplace.com/
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