Linux user Access for a USB-Serial Device
In the old days, PCs always came with RS-232 serial ports, allowing them to be connected to various devices such as modems, bar code readers, PDAs, etc. I use serial ports for programming microcontrollers, so I was surprised to find that my new laptop didn't come with a serial port. Computers without serial ports are becoming more and more common, since 90% of consumers don't need them; luckily for those of use who do need serial ports, USB to serial adapters are available on the web and in local stores. I chose to purchase a keyspan high-speed USB-serial adapter, since the packaging claimed support for linux; but the instructions here should apply to any working usb-serial device.
When I plugged in the device, a port
automatically created. Keep in mind that I am using Slackware 10.1
and kernel 2.6.10; your distribution might give you slightly different
results. Now, here's the problem: that device was created without
user read/write permissions!
bash-3.00$ ls -l /dev/tts/USB0 crw-rw---- 1 root uucp 188, 0 2005-03-06 17:31 /dev/tts/USB0
It's great that everything worked automatically, but of course, if I can't access the device from my account, it is pretty much useless to me. This is a typical linux problem; the system gets you 99% of the way there, leaving you with the nearly impossible challenge of covering that last 1%.
Open up the file
/etc/group and find the line beginning
uucp. You need to add your username to the list of
users at the end of this line, so that it looks like
uucp::14:uucp,paulLog out and log in again; thats it!