Fixing the UART (serial) port of the ZedBoard on kubuntu - Hello world example

Hi Gabriel,

I ran into some frustrations getting USB-UART to work under CentOS 7 but was able to piece together some workarounds related to permissions and udev rules.  Some of this information may be useful to you and I posted my workarounds on this thread here:

http://microzed.org/content/how-connect-zedboard-centos-7

I know those exact workarounds probably only work for CentOS 7, but they may steer you down the right path.

Also, Sven Andersson has a page on his blog where he connects to ZedBoard using his Ubuntu virtual machine.

http://svenand.blogdrive.com/archive/172.html#.VNTZqmjF-Sp

Since Kubuntu is probably more similar to Ubuntu, perhaps that would also be useful to you.

Regards,

-Kevin

Hi Kevin,

Thank you for your answer.

I've tried your udev tricks but it did not work for me...

I also took a look at Sven's tutorial and found nothing about the UART configuration except the dialog group thing (which I've already done). Actually, the JTAG port was tricky to set up but it's ok for me now and I don't really want to mess up my set up reinstalling it as I don't think it will change anything to the UART port behavior. But I wonder if using the Mac layer before the VB virtualization can help to get it working.

As an additional test, I took my 5kg gaming laptop to give the UART port a try on windows and it worked. But I am not really happy with it as I can't stand working on windows and I don't really want a 5kg terminal when I work on my zedboard. I just now know that the board works properly.

To sum up, I can connect to the UART port as a ttyACM0 node is created as soon as I plug the board.

I can use various terminals to watch at the ttyACM0 port (with or without sudo).

Then, nothing reach the terminal, which stays desperately empty.

The UART works on windows with my board.

I actually found nobody who managed to use the UART port on a native Ubuntu, which worries me a little bit.

So here come a few questions:

- Do you think that reinstalling the JTAG driver in the same way than Sven would change anything for the UART ?

- I've done this to check if I can do something "serial communications related" on my system and I can. But I understand that it proves nothing when it commes to UART-USB stuff.

- I've also read this article which seems to say that a UART-USB connection is supposed to lead to a ttyUSB node whereas I only have a ttyACM node. Do you have any idea if it can be a clue ?

Regards,

Gabriel

PS: If you wonder why is my English approximate, then I confess, I'm French ;P
And I am also far from being a Linux expert (I am not a neophyte either) so I apologize if I say stupid things sometimes...

Hi Gabriel,

I realize that getting the terminal to work under Kubutu would be ideal for you but it could come at the cost of lots of investment of your time.  I would venture to guess that your time is worth something valuable, so at some point an alternative solution to the current path will be more appealing.

It sounds like you are running Kubuntu on a Virtual Machine under OSX, is that correct?  If so, can you use the terminal from OSX for USB-UART?  I usually do that for my virtual machines since there is usually plenty of headache in the translation layer for USB between the host OS and the Guest OS for it to rarely (if ever) work.  In my previous post, I was able to get the USB-UART to work fine on a native CentOS install (not virtualized at all).  Also, I have used ZedBoard USB-UART just fine under Ubuntu 10.04 LTS when we wrote Appendix III of the ZedBoard Getting Started Guide:

http://microzed.org/sites/default/files/documentations/GS-AES-Z7EV-7Z020-G-V7.pdf

If you are running Linux on ZedBoard, another option may be to connect to your ZedBoard remotely over SSH terminal using the built-in Ethernet.  This has the added benefit of the connection being completely secured if you are worried about people snooping on your work over the network.

Regards,

-Kevin

Hi Kevin,

I am running a native Kubuntu unlike Sven in his famous tutorial who run Ubuntu in VB on OSX flawlessly.

I've tried to connect to Kubuntu on my other computer and with both USB3 and 2 this time with the very same result: Nothing. As it almost exactly the same OS, it just proves that my main Kubuntu behaves normally.
 

If you tell me that you used it on an older version of Ubuntu, then I'll start thinking that there is a driver incompatibility with the newest kernel. The latest version of the cp210x driver is supposed to be compatible with the 3.x.x kernels. They are kind of late ;P. I'll try the oldest liveUSB I can find to find if an older version of Ubuntu gives better results for me.

Even if I don't really care about security for now, running Linux on the ZedBoard might be most convenient option once it is set up. This time I know that my Ethernet port and my ssh tool work fine !

Thank you very much for your help. I don't think that anyone except the driver makers themselves can do anything for the UART now.

I'll give a feedback once I'll have more information.

Regards,

Gabriel

Hi again,

Well, It seems that it is a driver issue.

I can read the port with a live Ubuntu12.04 installation out of the box simply with "sudo cat /dev/ttyACM0" and this release has a 3.x.x kernel. I've contacted Silicon Lab to try know if they are aware of something with the cp210x driver and the 4.x.x kernels.

In a nutshell : to communicate with a zedboard through UART, use windows ( =/ ), OSX ( $$$ ) or an old linux (<3  3.x.x kernel). 

Thanks again for your help,

Gabriel

Hi Gabriel,

Thank you for updating us on your findings.  I am glad that you were able to get it working, despite the older version of Ubuntu, at least it gives you a reference point to see what has changed making it easier to isolate the cause of USB-UART to no longer function under the newer kernel.

The USB-UART on ZedBoard is implemented using a Cypress CY7C64225 device rather than a Silicon Labs device like we use on MicroZed/PicoZed so you likely won't get very far asking the Silicon Labs folks about the driver issue.

If you do find out something about an updated USB-UART driver, please share your results the community.

Regards,

-Kevin