Make a COM1 to COM2 crossover cable
This method describes how to make a COM1 to COM2 crossover cable, without using a soldering iron.
This means that you can transmit into COM1 using a standard terminal program, and receive these same bytes into COM2.
Note: this method is only
recommended to link two serial ports on the same machine, as the ground line
is not attached. It also does not link the flow control lines.
What you need
All these bits are available at any computer store. I purchased all these pieces from Dick Smith Electronics.
What you do
Poke the header into pins 2 and 3 of the gender bender, as shown in figure 2 below.
As shown in figure 3 below, the transmit pin 3, and the receive pin is pin 2.
Depending on which piece of equipment you're talking about, the transmit
pin and receive pin changes. The PC's transmit pin transmits into the devices
receive pin, and vice versa.
Make sure pin 2 is going to pin 3 (ie: transmit connected to receive), and pin 3 is going to pin 2 (ie: receive connected to transmit). The completed article is shown in figure 4 below. Put a slight bend on the pieces of wire to make sure that there is good electrical contact.
How to test
As you can see, typing in COM1 is received in COM2, and vice-versa.
Other things to note
In a normal crossover cable, all the flow control lines are connected. Also, to be fair, the ground line should be connected. However, in this case it's not so bad because both COM ports are from the same computer.
This is a quick way to verifying that both COM1 and COM2 are working. If you are serious about using a crossover cable, construct a proper one.
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