[PLUG] USB Serial Port Adapters

Jason Barnett jason.barnett71 at gmail.com
Sat Jun 18 09:49:01 PDT 2011


Here is a link that gives an example of this exact situation.  The example
shows using a FTDI chip and having the UDEV rule compare against the serial
number of the device so it should work for specific devices.

https://wiki.archlinux.org/index.php/Bus_pirate

Jason

On Fri, Jun 17, 2011 at 8:45 PM, Fred James <fredjame at fredjame.cnc.net>wrote:

> Jackman wrote:
> > Why can't udev rules be applied here?
> >
> > On Fri, Jun 17, 2011 at 6:48 PM, Fred James <fredjame at fredjame.cnc.net>
> wrote:
> >
> >> Tim Wescott wrote:
> >>
> >>> (omissions for brevity)
> >>>   I did an experiment: I started with my Fax
> >>> modem and the board I'm developing plugged in.  I did ls /dev/ttyU*.
> >>> Then I unplugged the development board and did ls again.  Then I
> plugged
> >>> in a debugger that has its own USB serial port adapter, and did ls
> >>> again.  Here's my results:
> >>>
> >>> tim at servo:~$ ls /dev/ttyU*
> >>> /dev/ttyUSB0  /dev/ttyUSB1
> >>> tim at servo:~$ ls /dev/ttyU*
> >>> /dev/ttyUSB0
> >>> tim at servo:~$ ls /dev/ttyU*
> >>> /dev/ttyUSB0  /dev/ttyUSB1
> >>>
> >>> What _did_ happen is that at different times the same device -- ttyUSB1
> >>> -- got mapped to different physical devices.  That is what I _do not_
> >>> want to happen.  What I want to happen is to plug in the development
> >>> board and have /dev/ttyUSBdevelop appear, and to plug in the debugger
> >>> and have /dev/ttyUSBdebug appear (or some similar me-defined mapping).
> >>> Different devices.  Different, _unique_, identifiers.
> >>>
> >>> Otherwise, every time I plug a bunch of stuff in to the machine, I'm
> >>> going to have to do a bunch of hand work to figure out what ports map
> to
> >>> what devices at the moment.
> >>>
> >>>
> >> Tim Wescott
> >> Thought 1:  If you can use CLI (command line interface) to determine
> >> what you need to know, then a (BASH) script can be written to do that.
> >> Thought 2:  If a device can be identified (example: ttyUSB1 is the
> >> debugger), then it can be mounted to a directory (example: ~/debugger)
> >> Thought 3:  If 1 and if 2, then the two can be written together in a
> script.
> >> Does any of that help?
> >> Regards
> >> Fred James
> >>
> Jackman
> According to <http://reactivated.net/writing_udev_rules.html#about>, it
> can ...
> "
>
> udev rules are flexible and very powerful. Here are some of the things
> you can use rules to achieve:
>
>    * Rename a device node from the default name to something else
>    * Provide an alternative/persistent name for a device node by
>      creating a symbolic link to the default device node
>    * Name a device node based on the output of a program
>    * Change permissions and ownership of a device node
>    * Launch a script when a device node is created or deleted
>      (typically when a device is attached or unplugged)
>    * Rename network interfaces
>
> "
> Regards
> Fred James
>
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