Can't open USB port (ckermit)
 

Hello all,

I am having some trouble opening up my USB ports using kermit. I didn't have this problem until yesterday. Before then I could use kermit to access USB ports via:

$ kermit -l /dev/ttyUSB0

Now when I do this I get an error saying can't access device.

I had two ubuntu versions on my computer when the error initially occurred, 8.04lts and 9.04. At the time I was using 8.04 so I decided to restart and use 9.04 to see if the same error occurred, and it did. After this I decided to reformat the whole HD and just install 8.04. Still I get the same error.

This seems very puzzling. Literally one minute it was working and the next it was not. No system changes, nothing. I have tried USB1, USB2 etc with the same error. I looked in /dev and can't see any ttyUSB* at all.

I have no trouble using a USB mouse, or an external HD, or anything else it seems. I just can't get the port to open. I have also tried to open the port to read data from an IMU. That was when it first stopped working actually. I unplugged the IMU to straighten a pin and then after that the port would not open.

Any input would be great as I am completely baffled by this. I don't know if this makes any sense but my hypothesis is that something has been switched (almost physically)in the way the port is communicated with (or something like that) and thats why I can't open it even when I reformat.

Thanks in advance,
Dylan.

I read this thread and tried a few things:
http://www.linuxquestions.org/questi...evices-585426/
No success.

Possibly a dumb question, but since you're using USB via minicom, I assume you're using a USB to serial device? Did you verify that the converter is still working, or that you don't have a bad cable?

Since you ran a good diagnostic chain, and even rebooted (and reformatted!), your system, chances of it being a device lock or some other software problem are slim. Can you post the output of "ls -l /dev/ttyUSB0", and "dmesg" (from after you plug the USB converter in)

Hello,

Yes it is a USB-to-RS232 cable.

Print out from "dmesg"

[ 217.064980] usb 2-2: new full speed USB device using uhci_hcd and address 7
[ 217.175347] usb 2-2: device not accepting address 7, error -71
[ 217.209096] usb 2-2: new full speed USB device using uhci_hcd and address 8
[ 217.346527] usb 2-2: device not accepting address 8, error -71
[ 217.389377] usb 2-2: new full speed USB device using uhci_hcd and address 9
[ 217.433947] usb 2-2: device descriptor read/64, error -71
[ 217.510571] usb 2-2: device descriptor read/64, error -71
[ 217.569490] usb 2-2: new full speed USB device using uhci_hcd and address 10
[ 217.609253] usb 2-2: device descriptor read/64, error -71
[ 217.713319] usb 2-2: device descriptor read/64, error -71


Print out from "ls -l /dev/ttyUSB0"

ls: cannot access /dev/ttyUSB0: No such file or directory

I have tried to use (as root):
"echo Y > /sys/module/usbcore/parameters/old_scheme_first"
http://www.mepis.org/node/5860

Also I tried (as root):
"echo -1 > /sys/module/usbcore/parameters/autosuspend"
http://ubuntuforums.org/showthread.php?t=797789

Both were unsuccessful. I'm not sure what else to try. If there is somekind of error when I insert the cable does that mean that the driver is not working properly?

I have also removed "brltty" (some variety of braille package) that apparently conflicts with ttyUSB0. Of course, unsuccessful :), but i don't think that had anything to do with it based on the "dmesg" output.
https://answers.launchpad.net/ubuntu/+question/5503

I'm going to get another cable and try that. I have already tried another of the same make. Perhaps that is where the problem lies, although I have used the current cable successfully more that 50 times. The only other options I can think of involve hammers...

Dylan.

Well, hammers are certainly more fun, but not as effective. :)

You've walked a good diagnostic trail, but based on the error from dmesg, and on the lack of the /dev/ttyUSB0 device, it indicates a hardware problem. The dmesg lines say it tried to create the device, but couldn't get good results from the hardware. The lack of the ttyUSB0 says that too, since it'll 'auto-create' when you plug it in. There is information about that 'read/64' error on some of the kernel mailing lists, but it essentially says "hardware problem". :)

One other thing it COULD be...did you try a different USB port? The USB hardware on your system could have died too, and the dongle could be fine...