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Old 06-20-2014, 08:30 PM   #1
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ttyUSB0 settings affect stdout on a different uart

I have an atmel926 based SBC with an on-board uart for stdin/stdout/stderr. I've connected a USB device with ftdi USB serial to this SBC. when I open ttyUSB0 and change settings such as baud rate, it affects the uart. Also writing to the ttyUSB0 is output on stdout I.e. the uart channel.

I don't know what is going on. It seems to me that these would be 2 separate serial channels. Is it maybe something in Uboot? Any help would be greatly appreciated!
Old 06-30-2014, 07:57 AM   #2
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Do you know the device identification for the on-board UART? What is it? Because I'm wondering if that is /dev/ttyUSB0 and your added USB serial is /dev/ttyUSB1.

A view of your system log from boot up and then insertion of your serial USB device would be helpful to see if you can post that.

You are correct that they should be 2 separate serial channels.

I don't see why uboot would have any relevance? You are running Linux at the time of these problems, correct?

Other things to check and report:

cat /proc/tty/driver/usbserial
dmesg | grep tty >> tty.log
and then post that log; however the entire system log is likely more useful.
Old 07-03-2014, 10:07 AM   #3
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Smile solved

dear rtmistler
your comments provided the sanity check I needed. Turns out that I was incorrectly applying settings to the old termios dev. I didn't realize that the samples I found saved the old for restoration purposes and that I needed to create a new termios dev for the new settings.


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