Re: usb to serial
On Sun, 4 May 2008 13:49:24 +1000 (EST)
Daniel Dalton <daniel.dalton@iinet.net.au> wrote:
> I'm a blind debian user and therefore use a braille display.
> So I need to connect it somehow.
> The display is a piece of hardware that is usually connect with a serial
> cable, but since my new box only has a usb available, no serial I must use
> usb to serial.
I have a similar situation with my laptop, which doesn't have 'legacy'
ports such as serial, so I use USB to serial adaptors for my serial
equipment.
> So does anyone know of the following:
>
> - a supported usb to serial cable for linux that works with the kernel?
These adaptors are 'smart', i.e. they contain electronics to do the
conversion, so as with hardware generally with linux, what counts is
the chipset. I believe that many of these devices use the Prolific
PL2303 chipset, which shows up with 'lsusb', at least in my case, as
"ID 067b:2303 Prolific Technology, Inc. PL2303 Serial Port". This
chipset has kernel support via the pl2303 driver. I have another
adaptor whose ID apparently isn't in the database; nothing shows up
other than the numerical ID. It is also grabbed by pl2303 (although
IIANM, that wasn't the case several months ago, when I first acquired
it), but it doesn't seem to be working properly, as opposed to the
Prolific one, which works fine.
I purchased both my adaptors on Ebay. They are virtually identical in
appearance, except for color; both have attractive silver cables
sheathed in clear plastic, but the Prolific has black plastic covering
the two cable ends (serial and USB), while the other has translucent
green. This may not help you.
I originally bought these adaptors to use with serial modems, but I was
never able to get them to work properly, and I never figured out why.
I'm currently using the Prolific to manage a headless box via a serial
(null modem) cable, and it works perfectly. The other one is not
working properly, as above.
These things start at about $5 (USD), including shipping (to the USA)
on Ebay. If you search there for 'usb serial', the first bunch of hits
seem to be the sort of units that I bought. There are both green
headed ones, as well as black headed ones, but I don't know if the
color is a reliable indicator of the chipset.
> (If so could you please provide a model number or brand?) Or even better
> if you know where I can get one of these from?
> Perhaps you could show me an add on ebay?
> (I had a look, but don't really understand the info and I am having
> trouble using my computer obviously.)
> - If the kernel supports it will a software daemon (brltty) support it?
I don't know brltty, but I'd say almost certainly yes. I'm no kernel /
hardware expert, but basically, the kernel driver creates a virtual
serial port, which should appear identical to an actual one to
userspace.
Good luck!
> Daniel Dalton
Celejar
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