[PLUG] USB Serial Port Adapters

Fred James fredjame at fredjame.cnc.net
Fri Jun 17 18:48:43 PDT 2011

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?
Fred James

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