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I've a cubieboard2 running arch linux with a custom linux kernel. In the cubieboard2 I plugged in my usb-serial device (like an arduino), the device is recognized as CDC ACM. My linux kernel has the CDC options enabled in the configuration, as I saw in this page, but, I can't use the serial port /dev/ttyACM0 using the applications minicom or pyserial.

Minicom just says that it can't open the serial port. Pyserial is able to open the port, but when I try reading it the result is:

SerialException: device reports readiness to read but returned no data (device disconnected or multiple access on port?)

Yet in pyserial if I try to write a byte the result is other:

SerialException: write failed: [Errno 5] Input/output error.

Other weird things happen when I close the serial port, it changes its name, in other words, when I close the /dev/ttyACM0 it changes to /dev/ttyACM1.

I've tried my device in my laptop and it works fine with both, pyserial and minicom.

cubieboard2 info:

$ uname -a
Linux alarm 3.4.61-rt77-ARCH+ #10 SMP PREEMPT RT Thu Apr 17 13:58:20 BRT 2014 armv7l GNU/Linux

my kernel config file: http://pastebin.com/raw.php?i=6LfsRyek

My guess is that it's missing having some kernel option enabled, but I don't know which.

Any idea?

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It seems to me that the problem is your device. It might enumerate OK, but behaves unexpectedly when further communications are performed. Try using Wireshark with usbmon (eventually tshark if you don't have an X session). The ttyACM1 name is usually due to re-enumeration after a faulty communication.

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