How to use your ATEN UC-232A USB adapter with Linux

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Hardware

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Hi! I'm Ingo Hoffmann, at the moment I work as a network analyst, designing network solutions using technologies such as VPN, VLAN, Gigabit Ethernet and so on. I do also implement the solutions that I design.

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This article describes the solution of a problem that I had for a long time. How to get a ATEN UC-232A adapter to work? After much research I figured out how easy it is.

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The hardware

The ATEN UC-232A is a RS232 serial line to USB adapter. It provides an additional RS232 serial line without the need of spending an extra interrupt (IRQ). It is a simple cable that you just plug into a USB port.

What did I use ?

To get the USB adapter to work with Linux I initially used my Slackware 8.0 box with kernel 2.4.8. Today I am using 2.4.13 and it's still working fine. You need at least a 2.4.6 kernel. The driver for this RS232 serial line to USB converter is fairly new and was introduced with the 2.4.6 kernel.

The fun part

To start with you need, of course, the source code of the kernel, duh. :-)
Then:

Choose the USB section;
Compile the USB subsystem as module. This provides more flexibility and you'll don't use it every time you start your Linux system.
Choose you USB driver, UHCI or OHCI. It'll depends on your USB controller hardware (that is your motherboard). I tested it with both and worked fine.
Choose USB-to-Serial.
Choose it as module also and then select Generic driver and the most important part is the driver Profilic PL-2303. It is almost impossible to guess that because it does not say so on the ATEN hardware. The PL-2303 is the chip used by the UC-232A and probably some other adapters.
Save the configuration and compile + install your kernel.

Next run "make modules_install" reboot and the load the modules:

modprobe your-usb-driver. uhci-usb or ohci-usb
mount -t usbdevfs none /proc/bus/usb
modprobe pl2303

If it work, you'll see on your syslog that the system found the Profilic device and mapped it to /dev/ttyUSB0 or to usb/tts/01 if you have devfs.
To create /dev/ttyUSB0 run

mknod /dev/ttyUSB0 c 188 0

and then

chmod 666 /dev/ttyUSB0

Enjoy it!