24 Jan
2011
24 Jan
'11
12:52 p.m.
You won't believe this... the pigtail cable inside
the PC, from
the motherboard COM2 header to the back-panel DB25, had been
installed one position off (by me, of course) =3D:^O
The nonstandard location of TxD and ground on the DB25 should have
been my first clue, but I just ass-umed that it was something
unique to the PC and not EIA RS-232...
Actually, if a PC serial port is a DB25, it's nearly always wired as a
subset of the RS232 standard, and as a DTE.
It's easy to be wise after the event, of course, but if I'd seen a
supposed serial port on a DB25 connector with the signals in the wrong
places, I would ahve checked things out. I don't recall you mentioning
this 'odd' pinout earlier, but I maw well ahve bmissed it/
-tony