APC UPS won't talk to me

[notme]

http://www.apcupsd.com/

This site has much information about communication with the APC UPS's.

This is a diagram of the cable that came with my Backup-Pro UPS 650 (model
BP650S):

APC Part# - 940-0095B
Signal Computer UPS
DB9F DB9M
DTR 4 ----*
CTS 8 ----|
DSR 6 ----|
DCD 1 ----*
GND 5 ---------------*---- 4 Ground
|
*---- 9 Common
RI 9 ----*
|
RxD 2 ----*--------------- 2 On Battery
TxD 3 ----------[####]---- 1 Kill UPS Power
4.7K ohm

Apparently it uses voltage-level signaling not serial communication.

But I see no reason this won't work via a USB-serial adapter. When the RxD or
TxD line is brought low, a bit is set or cleared in the buffer in the
USB-serial driver.

It's a whole other story whether OS X will recognize such signals.

Why wouldn't this work with the USB-serial adapter?

Thanks.

 

[VAXman- @SendSpamHere.ORG]

[Re-posted with new subject and more appropriate NG's)

Using a USB-to-Serial adapter to connect a laptop to APC UPS' RS232 serial
port.

No signs of communication from the UPS. The laptop's OS has an
auto-recognition feature that enables built-in power-down options if/when the
UPS communicates its presence.

To add in: Many of the basic APC UPS's don't use true serial
communications. They just use some of the control lines to signify power
out, low battery, and to signal the UPS to do a shutdown. I don't know
if it will work correctly through a USB-to-serial adapter.

My work computer has a BP650M with a self-made cable. It's just a
standard 9-pin serial cable, but the UPS end is slightly rewired, and I
think there is also a resistor. It's just using the stock Win2K support.

That's correct. The basic model simply toggle the equivalent of DTR high
or log to signal that the UPS is or is not providing power from battery.

An AC UPS that speaks their (not so incredibly) "Smart" prototcol, namely
the SmartUPS and more expensive APC UPS options, uses a serial cable that
is wired:

APC UPS
1 <==> 3
2 <==> 2
9 <==> 5

In fact, if you plug in a standard, full-signal, 9 pin cable to both the
APC and CPU, you run the risk of powering down the APC real fast.

FWIW, I sell an APC US solution in the OpenVMS space. I have seen this
communications problem with APC UPSs all too many times.

--
VAXman- A Bored Certified VMS Kernel Mode Hacker VAXman(at)TMESIS(dot)ORG

http://www.quirkfactory.com/popart/asskey/eqn2.png

"Well my son, life is like a beanstalk, isn't it?"

 

[Jasen Betts]

[Re-posted with new subject and more appropriate NG's)

Using a USB-to-Serial adapter to connect a laptop to APC UPS' RS232 serial
port.

No signs of communication from the UPS. The laptop's OS has an
auto-recognition feature that enables built-in power-down options if/when the
UPS communicates its presence.

Ideas?

UPSes don't normally speak serial. More often, they simply connect two
pins together, treating the serial port as a general-purpose I/O port.
This won't work with a USB-to-serial converter, as there is no serial data
to convert.

yeah it will, usb-to-serial adaptors duplicate the same modem control
pins and signals, applications that don't do direct IO port access
will work just fine on usb-serial adaptors.

I did that myself last month.

 

[Nobody]

Apparently it uses voltage-level signaling not serial communication.

But I see no reason this won't work via a USB-serial adapter. When the RxD or
TxD line is brought low, a bit is set or cleared in the buffer in the
USB-serial driver.

A USB-to-serial-adaptor is not a DAQ interface. It doesn't simply send a
stream of pin states or state-change events directly to the host.

A typical USB-to-serial adaptor[1] will expect a sequence consisting of a
start bit, 8 data bits, an optional parity bit and 1 or 2 stop bits, all
occurring at the configured (or auto-detected) baud rate.

[1] CDC, ACM = Communication Device Class, Abstract Control Model.

When it sees such a signal (IOW, when the UART says "a byte has been
received"), it will queue the the received byte to be sent to the host.

It may also inform the host if the control lines (DCD, DSR, RI) change,
but this feature (SERIAL_STATE notification) is optional.

Based upon your wiring diagram, if you can find a USB-to-serial adaptor
which supports the Ring Indicator (RI) line, you should be okay. Or if you
can find one which supports DSR or DCD, you can make your own cable which
uses this line instead.

You may have better luck with DSR or DCD. RI is the least useful signal,
as you can just have the modem driver listen for a "RING" response from
the modem. If the RS-232 driver is 4-in-4-out (e.g. MAX238), it's likely
that RI is the one which will be ignored.

Also, note that you can't directly query the state of CTS (the device just
NAKs Tx packets if the Tx buffer is full), so if the RS-232 driver is
2-in-2-out (e.g. MAX232), you're out of luck, as none of DCD, DSR or RI
will be monitored.

FWIW, the USB CDC specification is at:

http://www.usb.org/developers/devclass_docs/usbcdc11.pdf