I've been playing around with my BBB for about a month now and got 
everything up and running. Today I spent the whole day to get UART loopback 
to work on Debian. It simply doesn't work! Tried with Qt (cross-compiled 
and all samples are working), QSerialPortInfo::availablePorts().count() 
returns zero. At first I thought it can be a QtSerialPort issue. So I did a 
loop back on UART1 and UART2 (P9.21 connected to P9.26 and P9.22 connected 
to P9.24). Then opened "minicom -b 9600 -D /dev/ttyO1" and "minicom -b 9600 
-D /dev/ttyO2" in two separate terminals. I expected to see whatever I type 
in each one of the terminals on the other one. But that wasn't the case. 
Nothing happens! Any idea what's wrong?

Here's some info about my setup:

*Fresh install of 
"BBB-eMMC-flasher-debian-7.7-console-armhf-2014-10-29-2gb.img.xz". Didn't 
modify anything. *

*"uname -a": *
Linux arm 3.14.22-ti-r31 #1 SMP PREEMPT Fri Oct 24 20:50:46 UTC 2014 armv7l 
GNU/Linux

*"dmesg | grep ttyO":*
[    0.000000] Kernel command line: console=ttyO0,115200n8 
root=UUID=a52b5fd5-953d-458c-94d0-0cf2ff1c7115 ro rootfstype=ext4 rootwait 
fixrtc quiet init=/lib/systemd/systemd
[    2.799292] 44e09000.serial: ttyO0 at MMIO 0x44e09000 (irq = 88, 
base_baud = 3000000) is a OMAP UART0
[    2.800424] console [ttyO0] enabled
[    2.802247] 48022000.serial: ttyO1 at MMIO 0x48022000 (irq = 89, 
base_baud = 3000000) is a OMAP UART1
[    2.803710] 48024000.serial: ttyO2 at MMIO 0x48024000 (irq = 90, 
base_baud = 3000000) is a OMAP UART2
[    2.805198] 481a8000.serial: ttyO4 at MMIO 0x481a8000 (irq = 61, 
base_baud = 3000000) is a OMAP UART4
[    2.806622] 481aa000.serial: ttyO5 at MMIO 0x481aa000 (irq = 62, 
base_baud = 3000000) is a OMAP UART5

*"ls -al /dev/ttyO*":*
crw-rw---- 1 root tty     249, 0 Oct 29 19:06 /dev/ttyO0
crw-rw---T 1 root dialout 249, 1 Nov 14 17:41 /dev/ttyO1
crw-rw---T 1 root dialout 249, 2 Nov 14 17:41 /dev/ttyO2
crw-rw---T 1 root dialout 249, 4 Jan  1  2000 /dev/ttyO4
crw-rw---T 1 root dialout 249, 5 Jan  1  2000 /dev/ttyO5


I appreciate anything that might help! :)

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