[CentOS] EXTERNAL: Re: USB Serial Ports

Fri Nov 17 15:56:59 UTC 2017
Wells, Roger K. <wellsr at leidos.com>

On 11/17/2017 10:06 AM, Denniston, Todd A CIV NAVSURFWARCENDIV Crane, 
JXVS wrote:
>> -----Original Message-----
>> From: Chris Olson [mailto:chris_e_olson at yahoo.com]
>> Sent: Thursday, November 16, 2017 5:42 PM
>> To: CentOS Mailing List
>> Subject: [CentOS] USB Serial Ports
>> We have several CentOS 6 systems that are used in various configurations
>> of test equipment.  One of the primary functions of these systems is the
>> connectivity to serial ports of some operational systems that have serial
>> port control requirements.  Lack of interface bus slots led us to the use
>> of USB connected serial ports on these CentOS 6 systems.
>> We first used these USB connected serial ports in our RHEL 5 test equipment
>> systems.  With RHEL 5, shut down and boot up of the systems would often
>> cause the serial ports to have a different driver name, even though we had
>> not changed the ports where the USB devices were plugged in.  This caused
>> software access problems until we discovered what could be done using the
>> udev rules to lock in the driver names.
>> This problem seems to have gone away in our newer systems with CentOS 6,
>> and we would like to make sure that it does not return.  We are deploying
>> some of the systems and do not want to have software access issues in the
>> field where fixes are more difficult.  We would like to know if there is
>> some underlying factor that has solved this problem for us.  Any ideas on
>> what to check would be greatly appreciated.
> I have no idea why it is working better under 6, but it is possible to use UDEV rules to force them to be at expected /dev/my_tty* locations using vendor_ID/device_ID/serial_number combinations.  Once you figure that out, you should even be able to use the same (or at least similar) rules under 7.
I have been using udev rules for usb serial ports for a few years now.
First on CentOS 6.? , IIRC, now on 7.4, and simultaneously on several 
Fedora releases, currently F26.
I would be glad to send the file that I put in /etc/udev/rules.d/ if 
that would help in any way
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Roger Wells, P.E.
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