Re: Multi-serial USB Device

[Paul Bender <pebender@san.rr.com>]

On 1/30/2010 10:05 AM, Paul Dugas wrote:
> First, please point me where I should be asking if this is not the
> place.  Thanks.
>
> I've got a number of USB devices I need to connect to a data-logging
> machine.  Each device presents as 3 USB serial ports which are
> properly recognized and setup as ttyUSB[0-2] once I added the right
> vendor and product numbers to the module loader configs.  When I
> connect the second device, I get ttyUSB[3-5].  I've been able to setup
> udev rules that recognize the serial numbers for each of the devices
> and can setup symlinks; i.e. ttyLogger1USB[0-2] ->  ttyUSB?.
> Something like so...
>
>      KERNEL="ttyUSB*", SYSFS{serial}="111", SYMLINK+="ttyLogger1USB%n"
>      KERNEL="ttyUSB*", SYSFS{serial}="222", SYMLINK+="ttyLogger2USB%n"
>      KERNEL="ttyUSB*", SYSFS{serial}="333", SYMLINK+="ttyLogger3USB%n"
>
> My hitch is that the %n values on the end of the SYMLINK setting
> result in 0-2 for the first logger found, 3-5 for the second, etc.  I
> really want them to be 0-2 for all of the loggers.  But, looking at
> the udevinfo for the 3 ports on one logger, they're identical.
>
> I tried adding a PROGRAM setting to run a little script that looked to
> count the /dev/ttyLogger1USB* devices had already been created and it
> always returned 0.  Are the device files and symlinks created in
> parallel or in bulk at the end and thus this approach wouldn't work?
>
> I tried another PROGRAM that opened the port and polled the logger to
> see what port this was (that's supported by the device's protocol) but
> the device file didn't exist yet.  Is there a way to trigger this
> approach after the device file has been created? Is there a way to
> temporarily create the device in the script instead?
>
> Anyone got a suggestion on how to solve this?

I suspect that the device presents itself as 3 USB serial interfaces on 
one USB device. If so, then you should be able to use bInterfaceNumber 
to set the USB serial device number. For example,

KERNEL="ttyUSB*", SYSFS{serial}="111", \
   SYMLINK+="ttyLogger1USB$attr{bInterfaceNumber}"
KERNEL="ttyUSB*", SYSFS{serial}="222", \
   SYMLINK+="ttyLogger2USB$attr{bInterfaceNumber}"
KERNEL="ttyUSB*", SYSFS{serial}="333", \
   SYMLINK+="ttyLogger3USB$attr{bInterfaceNumber}"