Problem Enable UART


I have a problem with UART on BeagleBone Black. I succeeded to enable UART1 but UART2 asked me a problem and I can do anything on this port.
I’m on : Linux beaglebone 4.4.91-ti-r133
I activated firmware with this : (on /boot/uEnv.txt)

###Overide capes with eeprom

and activated everything I needed (all uart and 1 I2C) a little lower in the same file :

##Example v4.1.x

Others UART have the same problem…
I have also this : debian@beaglebone:/boot$ ls -l /dev/ttyS*

crw–w---- 1 root tty 4, 64 Dec 12 15:23 /dev/ttyS0
crw-rw---- 1 root dialout 4, 65 Dec 12 15:36 /dev/ttyS1
crw-rw---- 1 root dialout 4, 66 Dec 12 15:34 /dev/ttyS2
crw-rw---- 1 root dialout 4, 67 Dec 12 15:23 /dev/ttyS3
crw-rw---- 1 root dialout 4, 68 Dec 12 15:23 /dev/ttyS4
crw-rw---- 1 root dialout 4, 69 Dec 12 15:23 /dev/ttyS5

Then all the UART are activated right?

But I can’t communicate with my device… and it’s work with UART1… Do you have a solution?


Probally ancient u-boot in eMMC, run this script to confirm:

sudo /opt/scripts/tools/


I THINK with the 8250 driver and the beaglebone/board images, 6 UART’s show up in the /dev/ directory as /dev/ttyS0… /dev/ttyS5 by default, but that doesn’t mean that all of those 6 UARTs are enabled. You have to explicitly enable them. For instance, if you login as root and start poking around in /sys/class/tty/ttyS*, you’ll see that some of the UARTs have an irq of 0, which I think is a sign that they’re disabled.