DIY Null Modem Cable with Hardware Flow Control

I recently got caught out by not having a functioning Null Modem cable with Hardware Flow Control pins connected. A bit of a niche one, but I did have several hundred HP switch console cables. I did a bit of reverse engineering thanks to Google, and managed to get a pinout. I used two HP console cables, snipping off the RJ45 plug, and connecting the wires. The pins in the RJ45 connector correspond to the COM/RS232 connector at the other end thus:

RJ45 Pin Cable Colour COM Pin
1 Black 8
2 Brown 6
3 Red 2
4 Orange 5
5 Yellow 1
6 Green 3
7 Blue 4
8 Purple 7

You’ll need to connect the cables in the following manner to build the cable:

RJ45 Pins 2-3 need to be connected (Red+Green)

RJ45 Pins 4-6 need to be connected (Blue+Brown)

RJ45 Pins 5 need to be connected to eachother (i.e. Orange+Orange)

RJ45 Pins 8-7 need to be connected (Purple+Black).

Of course, there will be two of each colour – ensure they all follow the above.

You should now have a working Null Modem cable with Hardware Flow Control pins connected.

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