[time-nuts] Thunderbolt serial connection - null modem or straight through?

Hal Murray hmurray at megapathdsl.net
Tue May 20 16:36:16 EDT 2008

> I can't quickly determine from the Thunderbolt manual which cable type
> I need.  The connector on the Thunderbolt suggests it's DCE (female
> connector), but I suspect it's actually configured as DTE (i.e.
> null-modem cable needed). 

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)

These are my opinions, not necessarily my employer's.  I hate spam.

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