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To preface this question: I'm not able to get to a parts store any time soon. I'm well aware that I could buy what I need, but I'm trying to make do with the tools and hardware I already have.

I found a cable that is 10pin RJ-45(48?)-to-USB. The jack has leads on 1(red), 4(brown), 7(black), 9(white), and 10(green). Not sure what's Tx, Rx, ground, data, uni/bi-di, etc. Nothing is striped. Upon cutting the jack from the end of the cable and peeling back the insulation, there was no lead for 4(brown) that I could see. Could the metal insulation have been grounded to 4(brown)? Is there a way to salvage this cable with an 8pin RJ-45 to be used as a console cable for my Linux box router?

EDIT: The cable appears to be part of a UPS from one of the several home security systems in the building.

Shankensteinium
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1 Answers1

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Despite the similar "serial" name, serial ports and USB use completely incompatible signalling. To connect a serial console port to USB, you would need an active cable with a converter chip.

Make sure that's what you have: when the USB end is connected to a computer, it should be immediately recognized as a COM port by your OS (even if the other end is dangling free).

(The "USB-to-RJ45" cables sold for APC UPS will not work. They're passive adapters, and the UPS actually speaks the full USB protocol – not RS232 – over its RJ port.)

You could in theory assemble a console cable yourself. Most "USB-to-serial" cables sold nowadays use chips like Prolific PL2303, perhaps FTDI FT232RL or Microchip MCP2200 (search for "USB UART converter"). I don't know what additional parts may be required.

If your router really has a RJ-45 console port, the pinout is likely called "rollover cable".

grawity
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