Characters lost using serial over usb (cdc_acm) in u-boot.

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1

Hi,
I finally managed to connect to ttyACM0 with minicom when my
beagleaboard xM is inside u-boot.

For that purpose, I've followed this tutorial (method 2):
http://blog.engine12.com/?p=72

However, I have problems with the received characters since sometimes
some of them are lost, i.e. if I execute "printenv" command several
times I get different results.

This has been tested on several Beagleboards and two different
versions of u-boot.
Also minicom, cutecom and cu clients have been used getting the same
results.

2

Make sure you have the correct settings on the serial port. Are you using a USB to serial adapter? If you are then make sure you have the latest drivers. Some USB to serial cables work better than others.

Gerald

3

Dear Javi,

[…]

However, I have problems with the received characters since sometimes
some of them are lost, i.e. if I execute "printenv" command several
times I get different results.

This has been tested on several Beagleboards and two different
versions of u-boot.
Also minicom, cutecom and cu clients have been used getting the same
results.

please paste a example how the output looks like when characters are
lost.

What do you run on your host system? Using Debian GNU/Linux I noticed
that a network driver/module was loaded when plugging in the
USB-to-serial adapter which interfered with the transfer. Removing that
module using `modprobe -r yourmodulename` fixed the issue for me.

Thanks,

Paul

PS: Please make always sure to also mention the things from your subject
line in your message.

4

Sorry,
I think I didn't express the problem with enough clarity.

What I am using is not a USB to serial adapter.
It's a USB gadget Ethernet CDC-ACM, which allows a host PC to see the
beagleboard as a /dev/ttyACM0 through USB, directly (no HW adapters).

And I've been investigating further and I've found more people with
the same issue:

http://comments.gmane.org/gmane.comp.boot-loaders.u-boot/99482