On Thu, 10 May 2007, Mark Polhamus wrote:
> Eben King wrote:
>> Anybody used a USB <-> serial cable? I had this bright idea of hooking
>> my UPS to the computer. I understand lots of nifty stuff can be
>> accomplished through such a connection.
>>
>> Unfortunately, my UPS's cable is serial on both ends, and my computer's
>> sole serial port is occupied by a modem. I looked aroung for a USB
>> variant. Since the "S" in "USB" stands for "serial", I thought it
>> shouldn't be too hard to find. Unfortunately, it was. The only USB
>> cables I found had an RJ-45 on the other end.
>>
>> So, I figured I could put either the modem (it only gets Caller-ID data,
>> so flow control and speed aren't that important) or the UPS (2400 BPS
>> sez the manual, so ditto) on the USB <-> serial cable I have. But, I've
>> never used it but once (and that was in The Other OS). Help?
I tried plugging the UPS into the USB <-> serial cable, but:
On the first attempt, everything was "live" when I inserted the plug (DB-9)
and the UPS shut off immediately. Crud. OK, now that it wass down, things
weren't likely to get worse, so I went ahead and hooked it up. The UPS came
up OK (as long as I let it finish the self-test before booting the
computer).
Then, during the boot sequence, the UPS powered off. My guess is that when
the USB port is initialized, the transition from "no power" to "power" makes
the converter go through an initialization sequence, part of which means
"shut down now" to the UPS. Said sequence is not a concern to the modem
(and in any case it's rather less vital) so I switched the connections.
> I've used USB to Serial converters on Linux and Windows. They actually
> work better on Linux since drivers are built into recent kernels and there
> is nothing to install. They present a virtual comm port interface, so to
> your software they look just like another serial port, "/dev/ttyUSB0" or
> some such.
Thanks. I found out about "lsusb" so I could find what my device _really_
is.
> Keyspan model USA-19HS is the one I have used the most, which has some
> sort of TI chip.
lsusb says:
Bus 001 Device 005: ID 067b:2303 Prolific Technology, Inc. PL2303 Serial Port
so I went in the kernel configuration and compiled
<M> USB Prolific 2303 Single Port Serial Driver
Modprobed it, udev created the node /dev/ttyUSB0, and off I went. Not sure
what'll happen next time I boot.
> Had multiples plugged in at the same time, it all just works,
> although you have to pay attention to make sure you associate the
> correct device entry with each converter.
Are they differentiable by udev, or once it's created the devices it's up to
you to figure out which one is ttyUSB[0123]?
-- -eben QebWenE01R@vTerYizUonI.nOetP royalty.mine.nu:81And we never failed to fail / It was the easiest thing to do -- CSN
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