Re: USB serial adapters - resolution
On Tue, Jul 18, 2006 at 12:10:54AM +0100, Digby Tarvin wrote:
> I have just tried connecting a USB serial adapter to my Debian Etch
> system, and happily it seems to have been recognised and worked right
> out of the box....
>
> But these things seem to come with very little documentation, and what
> I havn't yet discovered how to interrogate it to find out what
> baud rates, formats or other stty options it supports (other than
> using trial and error)?
>
> Anyone know if this information can be found?
Didn't get any takers on this, so I have done some more investigating,
and my conclusions are as follows..
Having failed to find any way of determining device capabilities
from within Linux, I decided to attempt to find out if the information
was there to be found by plugging the device into a system running a
less capable but more common operating system to see what it could
tell me. The assumption being that it would have to be able to find
it out in order to be able to provide the menu based configuration
that its users depend on.
What I found was that Windows seems to require a manufacturer supplied
driver before it would talk to the device. That seems to answer the
question, as the only reason that I can think of for requiring a
custom driver for Windows for something with a sufficiently standard
inferface to work out of the box with Linux is that that is the only
way for windows to know the settings it can offer in the menus.
As I didn't have a driver for the borrowed USB/serial adapter I was
trying to use, and it didn't have any marking to identify a manufacturer,
I bought a new one for GBP 13.00, which also worked fine on my Etch
system. I loaded up the Windows drivers, and that identified the following
capabilities (in case anyone is searching for information on compatible
devices):
Manufacturer:
Prolific (driver 16/7/2003)
Speeds:
75,110,134,150,300,600,1200,1800,2400,4800,7200,[9600],
14400,19200,38400,57600,115200,128000
Data Bits:
4,5,6,7,[8]
Parity:
Even,Odd,[None],Mark,Space
Stop bits:
[1],1.5,2
Flow control
Xon/Xoff,Hardware,[none]
Receive Buffer
up to 14
Transmit buffer
up to 16
So my conclusion is that whilst the Linux driver can operate the
serial adapters, they ship with Windows drivers which are the only
way the manufacturers make the capabilities/limitations available.
That is probably the only reason why drivers are required when using
these devices with Windows. In short, windows can't work it out
either, so the information is provided in the form of a driver that
Linux can't use..
One last thing I noticed about the one I bought (NEWlink USB Serial
Adapter) was it came with a piece of paper called the 'quick installation
guide' which basically told you how to install the windows driver, and
said "For more information, please refer to the Users Manual on the supplied
CD-ROM" but when I checked, there was no such manual. This is all there was:
MAC
MAC/MAC 10.1.x~10.3
MAC/MAC 10.1.x~10.3/PL2303_1.0.8b4.pkg
MAC/MAC 10.1.x~10.3/PL2303_1.0.8b4.pkg/Contents
MAC/MAC 10.1.x~10.3/PL2303_1.0.8b4.pkg/Contents/PkgInfo
MAC/MAC 10.1.x~10.3/PL2303_1.0.8b4.pkg/Contents/Resources
MAC/MAC 10.1.x~10.3/PL2303_1.0.8b4.pkg/Contents/Resources/English.lproj
MAC/MAC 10.1.x~10.3/PL2303_1.0.8b4.pkg/Contents/Resources/English.lproj/PL2303_1.0.8b4.info
MAC/MAC 10.1.x~10.3/PL2303_1.0.8b4.pkg/Contents/Resources/PL2303_1.0.8b4.bom
MAC/MAC 10.1.x~10.3/PL2303_1.0.8b4.pkg/Contents/Resources/PL2303_1.0.8b4.pax
MAC/MAC 10.1.x~10.3/PL2303_1.0.8b4.pkg/Contents/Resources/PL2303_1.0.8b4.sizes
MAC/MAC 8X&9X
MAC/MAC 8X&9X/ProlificUSBSerial.sit
WINDOWS
WINDOWS/DRemover98_2K.exe
WINDOWS/PL2303.CAT
WINDOWS/SER2PL.INF
WINDOWS/SER2PL.SYS
WINDOWS/SER9PL.SYS
WINDOWS/SERSPL.INF
WINDOWS/SERSPL.VXD
WINDOWS/SERWPL.INF
Nothing that looks like a user manual....
So in conclusion, Linux compatability seems pretty good, but if you have
specific requirements there seems to be no way to tell if a particular
device will do what you want other than to buy one, install it on a Windows
machine (or presumably MacOS) to find out what its capabilities are,
and then install on a Linux machine to verify that it is compatable.
Or else to find a posting like this from someone who has already tried
a particular device. (www.newlinkproducts.co.uk if anyone is interested,
though I am not endorsing this manufacturer - if you find one that
is more Linux aware, then let us know).
Regards,
DigbyT
--
Digby R. S. Tarvin digbyt(at)digbyt.com
http://www.digbyt.com
--
Digby R. S. Tarvin digbyt(at)digbyt.com
http://www.digbyt.com
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