FTDI USB serial interface problems

[MrJackHamilton]

I've been trying to get an FTDI-USB serial device to be recognized by the SOM RT with no luck, even after reading the numerous posts including hacking the Linux etc/udev directories.

Firstly, I've read the NI RT version 14 is supposed to support the FTDI USB serial - it does not. I see the following in MAX (This issue has been reported numerous times for earlier versions of RT.

It 'appears' detected but "Not Present".  This very well written post details how to recognize and configure USB devices - which we've followed to a point.

https://decibel.ni.com/content/docs/DOC-39148

However, We cannot get write access to the etc/udev/rules.d to drop the supposed rule to allow the FTDI-USB serial to work!.

Rule: ATTRS{manufacturer}=="FTDI", ATTRS{serial}=="FTESP4BN", SYMLINK+="FTESP4BN", MODE="0666"

So we're stuck as it appears no one had Write WebDAV or  mapped drive privlages for this directory at all. Even with admin/ password implemented (you need to instigate a login password over the default no-password)

Questions:

1. Is the FTDI USB serial supposed to work out-of-box?

2. Do I really need to hack the Linux dev registry to get it to work?

3. Will adding this rule make is work?

4. Why can't I add rules, or access directories, with admin rights?

PS: We even tried writing code on the RT to update the file, or drop a file in the rules dir...but get permission errors.

PPS: Please don't tell me to post this to another forum!.

Regards

Jack Hamilton

I've attached the putty logs of all my SSH terminal checks of the USB hardware  - which appears to show that the FTDI USD device is properly detected in Linux and *Fine*....inspite of this MAX shows the VISA. The SOM firmware is now updated to 2.5.

[tannerite]

Jack,

I know you stated not to re-direct you to another forum, but I assure you that the team that has the knowledge to help you is in the LabVIEW Real-Time Community page. This is question should be generic to NI Linux Real-Time and not the SOM. In fact, there have been similar questions posted there with other NI Linux Real-Time targets that support Zynq:

https://decibel.ni.com/content/thread/24030?tstart=0

The user that originally asked this question ultimately created a post that you linked to above. There is also a forum for myRIO, that uses the Zynq-7010 that has a good summary in the solution section:

http://forums.ni.com/t5/Academic-Hardware-Products-ELVIS/FTDI-interfacing-With-myRIO-Linux-RT/m-p/29...

Our team does not specialize in the higher-level software aspects and we do not have the expertise to answer these higher-level software questions. Again, this is community is meant for hardware development questions. We certainly know the correct teams to contact with different SOM software questions and other questions that are outside of our areas of expertise, and can help in that aspect.

If you have tried the steps outlines in the above posts and are still not able to enumerate your device, I would recommend posting on the top link to request additional help.

- Tanner

[MrJackHamilton]

Tannerite,

We abandoned using USB completely after about 16hrs of engineering time making attempts to hack the Linux.

Although I did not try the linked work-around. I am pretty certain it will not work...the Linux file system on the SOM appears to be different from MyRIO and cRIO-9068. AND the device directory is LOCKED and cannot be updated or written to by casual FTP or the WebDAV on the SOM.

It looks like the RT guys at NI made some changes to the Linux implementation of the SOM that are not documented.

I actually prefer NOT using USB, Serial is simpler and also provides for lower level control of how often the my SOM wants to needs to read the serial interface.

Regards

Jack Hamilton

[Frisbee]

Hey Jack,

Sorry to hear that you are having problems with your FTDI USB device. If you do decide to attempt the USB route again, I have included a few ideas that may help.

Per our Linux target/USB KB, you can tryrunning the modeprobe ftdi_sio command before plugging in your module (you can check that the module is loaded using the lsmod command). By manually loading the driver, we can be sure that it is present when the USB device is physically attached.

Only the admin account has write permission to the /etc and the /etc/udev/ directories, so setting up network file transfer to them is not recommended. The easiest method would be to enable SSH access for the target in NI MAX and then use a hyperterminal client like PuTTY to access the SOM's shell (KB for the process). Once you are logged in to the device using the admin account, you can navigate to the udev directory and use a text editor like vi to add the desired rule.

If you would prefer to modify the file on a networked computer, you could transfer the file to a more open directory on the target (one less restrictive file permissions) and then move the updated file to /etc/udev/ manually.

The NI Linux Real-Time OS that you find on the SOM is the same as what is on our ARM-based NI Linux Real-Time cRIOs and myRIOs. They have the same file system and use the same drivers, so we can expect general tutorials for one to extend to the others. As they were not linked in your initial post, you may find the following documents helpful while setting up the USB connection:

Community Post: Using USB-RS485 or other USB-to-COM devices on myRIO.

External Link: LabVIEW Hacker, myRIO USB Serial Device

Best of luck!

[MrJackHamilton]

Frisbee,

Not to be unkind, but you did not read the full content of my post. Also, if you go to the KB links that you and others recommend, they are strewn with pages of comments about how they don't work.

Maybe my SOM's are different than all others, the Device tty\ does NOT exist on the SOM, so I'm not sure where the "They are identical" statement comes in.

Linux CMD line DOES NOT allow copying a file from one open location to a locked location...it's pretty robust in it's security.

It would be nice is someone from NI support would try this.

Regards

Jack Hamilton