Serial connection CAT5 instead of RS232 and Null Modem or Straight cable.

Applications Hardware
1

Hello,

I want to connect a VT520 terminal to p3 linux box.

I have two questions regarding the connection. First,
is it possible to use RJ45 instead of RS232
cable. (with DB9 pin to RJ45 and DB25 to RJ45 converter).

Second point is that; do i need null modem cable or
straight cable for the connection?

Thank you.

2

The kind of cable doesn't really matter as long as it has the right pins. Those adapters are expensive though.

3

i'm looking for cat5 and rj45 because it's cheaper.

4

The Terminal is DTE, the computer end is trickier. If you are connecting to COM1 or COM2 then those ports are also DTE, so you will need a null modem cable.
If you are connecting to a multiport serial card, then you will have to look at the documentation, as some ports can be set either DTE or DCE via software.
All you really need to do is buy an extra RJ45 to RS232 (either 9 or 25 pin) adapter, and wire one for DCE and the other for DTE.

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5

Yes, i need null modem but i don't know how to connect pins in order to set db 9pin->RJ45
and db25pin->RJ45(i need to dbs, 9pin for system and 25pin for the vt).

Thanks.

6

rs232 pinout - Google Search

You only need to connect three wires, pin 2 (red) , 3(green) and 7(black) on the 25 pin end.
On the 9 pin end connect pins 2(red),3(green), and 5(black).
Set the terminal to use xon-xoff flow control.

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