On April 15, 2011 at 19:57, Ernie Bornn-Gilman said...
39, I think you're wiring your cables as null cables, and insertion of a null modem adaptor switches the Tx and Rx to the way you should be making them.
That would mean, though, that machines would have to made to switch those wires at one end. That sounds a bit tricky.
Someone please tell me if normal RS232 cables switch Tx and Rx frm end to end.
I use Cat5 with RJ45 connectors for RS-232. Its a straight 568A cable. Always straight from end to end and pinning is done at the adapter.
I then use RJ45 to DB9 adapters at each end. Both ends are pinned the same 23578 for a straight DB9 cable. So you get continuity if you test pin 2 from end to end. This is a standard serial cable.
2-2
3-3
5-5
7-7
8-8
If the device requires a null modem cable i just remove 1 of the 'straight pinned' DB9/RJ45 adapters and replace it with a 'null pinned' adapter. Now i have a null modem cable.
2-3
3-2
5-5
7-8
8-7
Straight or null cover 99% of the serially controlled/RS-232 devices. Most will work with only pins 2,3&5. I do 7&8 out of habit. I was once told not to connect them unless the manual said to but so far no issues have popped up.
