APC UPS control system Connecting a APC USB UPS to either a PC USB or Serial Port, Cables, 136

Connecting a APC USB UPS to either a PC USB or Serial Port

An interesting fact is that the USB ports (actually an RJ45 connector) on APC UPSes not only speak USB, but also serial apcsmart and dumb voltage-signalling as well! This is something that one of our users discovered by accident. With the Custom RJ45 cable (actually a RJ45 to serial cable) described below plugged into the APC UPS USB socket at one end and the other end plugged into a serial port on your PC, any APC USB UPS (except some of the newer really low cost models) will act as a serial-line device.

Cables

You can either use the cable that came with your UPS (the easiest if we support it) or you can make your own cable. We recommend that you obtain a supported cable directly from APC.

If you already have an APC cable, you can determine what kind it is by examining the flat sides of the two connectors where you will find the cable number embossed into the plastic. It is generally on one side of the male connector.

To make your own cable you must first know whether you have a UPS that speaks the apcsmart protocol or a “dumb” UPS that uses serial port line voltage signalling.

If you have an apcmart UPS, and you build your own cable, build a Smart- Custom cable. If you have a voltage-Signalling or dumb UPS, build a Simple- Custom cable. If you have a BackUPS CS with a RJ45 connector, you can build your own Custom-RJ45 cable.

Smart-Custom Cable for SmartUPSes

SMART-CUSTOM CABLE
Signal Computer		UPS
	DB9F	DB9M
RxD	2 --------------------	2	TxD	Send
TxD	3 --------------------	1	RxD	Receive
GND	5 --------------------	9	Ground

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