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I have a LogiLink USB-To-Serial adapter. This has the PL2303 chip inside. When I insert the device:

[26064.927083] usb 7-1: new full speed USB device using uhci_hcd and address 9
[26065.076090] usb 7-1: New USB device found, idVendor=067b, idProduct=2303
[26065.076099] usb 7-1: New USB device strings: Mfr=1, Product=2, SerialNumber=0
[26065.076105] usb 7-1: Product: USB-Serial Controller
[26065.076110] usb 7-1: Manufacturer: Prolific Technology Inc.
[26065.079181] pl2303 7-1:1.0: pl2303 converter detected
[26065.091296] usb 7-1: pl2303 converter now attached to ttyUSB0

So the device is recognized and the converter is attached to ttyUSB0. When I do screen /dev/ttyUSB0 9600 I get the error:

bash: /dev/ttyUSB0: Permission denied

So I went looking in the file permissions. ls -l from the /dev folder reports:

crw-rw----  1 root dialout 188,   0 2011-04-26 15:47 ttyUSB0

I added my user lars to the dialout group. When I use the commands groups under lars it shows that I'm in the group. Though I still recieve the permissions denied error, as lars, and as root.

I'm trying to connect to a console cable to configure some Cisco switches. My OS is OpenSuse 11.3 x86_64 with kernel version 2.6.34.7-0.7-desktop.

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did you logout and log back in after the group add? –  mfarver Apr 26 '11 at 15:39
    
Yes I did. I logged out. When that didn't help I rebooted. Still the same error. –  Exsisto Apr 27 '11 at 6:37
    
Don't know about SUSE, but when I get a weird permissions issue on Redhat I check selinux. –  mfarver Apr 28 '11 at 3:26
    
I'm not running SELinux –  Exsisto May 24 '11 at 7:17
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2 Answers

To eliminate the possibility that this might be a 'screen' issue, try:

setserial -a /dev/ttyS0

to check for access permission, and then see if you can communicate using 'minicom'.

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First, verify your config and access:

$ stty -F /dev/ttyUSB0
speed 38400 baud; line = 0;
kill = ^H; min = 100; time = 2;
-icrnl -imaxbel
-opost -onlcr
-isig -icanon -echo

Now configure them in a safer mode:

$ stty -F /dev/ttyUSB0 9600 sane

and

$ stty -F /dev/ttyUSB0
speed 9600 baud; line = 0;

now, if screen won't work, you could try minicom or cu. I like cu, small and efficient, it use your tty as terminal, like ssh you could end a session by hitting ~. or send a break with ~#.

cu -l ttyUSB0

(notice that there is no /dev/ ;)

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