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roaming | Here's a recent thread with a good discussion of this topic:
http://u15205752.onlinehome-server.com/forums/thread-view.asp?tid=4...
Briefly, a standard serial cable goes straight through - pin 1 to 1, pin 2 to 2, 3 to 3, etc. A null modem reverses 2 and 3, so 1 goes to 1, 2 goes to 3, 3 goes to 2, 4 to 4, etc. They are both data communication standards, and were never intended to be used for power/ground. Unfortunately, they have been bastardized by some manufacturers to serve more than their intended purpose, which means you have to be careful when connecting devices.
Why does it matter? Because devices transmit and receive on different pins. If you are transmitting on pin 2 from Device A, and Device B is also trying to transmit data on the wire that is connected to Device A pin 2, you're not going to have communication. You can't have TX and RX on the same line in serial communications.
Edited by torn 3/19/2008 13:30
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Serial cable & null modem cable, what exactly are these?
