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girzel

Member

Registered: 2010-06-27

Posts: 74

Driver for Prolific usb-to-serial connector?

I'm trying to connect to a Soekris 6501 router over a null modem serial cable, just trying to get the system installed. I'm using minicom to establish the connection, but no matter what baud speed or other configuration I use, I always get gibberish on the terminal once the router boots. I've gone through all the reasonable options, and get gibberish every time.

I've started to suspect the cable or its driver as the source of the problem. The cable is a Prolific Technology PL2303 Serial Port Device (I can post the complete lsusb if it's useful), and I'm using the stock pl2303 module. When I plug in the USB end, dmesg gets a whole bunch of these:

pl2303 ttyUSB0: usb_serial_generic_read_bulk_callback - nonzero urb status: -884

Ending with:

pl2303_set_control_lines - failed: -19

but then

usb 3-2: pl2303 converter now attached to ttyUSB0

For fun I tried doing "cat /dev/ttyUSB0", then touching pins two and three on the connector together with a wire. That immediately spat gibberish out into the terminal. I had originally been going to try to echo something to the device file, to see if I could get it to work on loop, but just connecting the wires started it barfing.

I have no idea if any of the above is normal, or indicative of some sort of problem. Googling indicates that there's also a pl203x driver somewhere, which might work better with Prolific stuff, but I thought I'd post here before I started trying to compile drivers.

Thanks for any and all pointers!

Eric

ewaller

Administrator

From: Pasadena, CA

Registered: 2009-07-13

Posts: 20,675

Re: Driver for Prolific usb-to-serial connector?

What happens if you short 2 and 3 together, then type characters in the terminal.
When you short 2 and 3 together, I hope it was on the adapter only with the router detached.  Otherwise, you will have two transmitters tied together.  That does not work well on RS-232.

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girzel

Member

Registered: 2010-06-27

Posts: 74

Re: Driver for Prolific usb-to-serial connector?

This is a usb to serial cable -- there's pins only at one end, so I have to have the router detached to get at them!

Now, of course, it's stopped doing it. I rebooted the computer a bit ago, which is probably unrelated, but at any rate now when I touch 2 and 3 together I get no output. I open two terminal windows, one listening to /dev/ttyUSB0 with cat, and the other to echo to the same device file, and nothing happens at all. I can then plug the cable into the router, start minicom, power up the router, and I still get the same gibberish, no matter what the baud speed. I really don't know what's going on!

Thanks...

R00KIE

Forum Fellow

From: Between a computer and a chair

Registered: 2008-09-14

Posts: 4,734

Re: Driver for Prolific usb-to-serial connector?

I have one usb-serial adapter which also seem to have a pl2303 and this is what I get:

usb 3-2: new full-speed USB device number 3 using ohci-pci
usbcore: registered new interface driver usbserial
usbcore: registered new interface driver usbserial_generic
usbserial: USB Serial support registered for generic
usbcore: registered new interface driver pl2303
usbserial: USB Serial support registered for pl2303
pl2303 3-2:1.0: pl2303 converter detected
usb 3-2: pl2303 converter now attached to ttyUSB0

According to lsusb this is the converter:
0557:2008 ATEN International Co., Ltd UC-232A Serial Port [pl2303]

I would try to check if the converter is really working on another machine, that one might be broken or a fake.

Edit:
Typo.

Last edited by R00KIE (2014-07-16 08:06:23)

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R00KIE
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