I am trying to enable UART 1 to 5 at boot without log in. It's for a quadcopter project where the BBB is the flight computer. So I wrote a python script and launch it at boot using Cron.
When I do a "dmesg | grep tty", I get the following:
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[ 0.000000] Kernel command line: console=tty0 console=ttyO0,115200n8 root=/dev/mmcblk0p2 ro rootfstype=ext4 rootwait fixrtc quiet init=/lib/systemd/systemd
[ 0.000000] console [tty0] enabled
[ 0.535141] 44e09000.serial: ttyO0 at MMIO 0x44e09000 (irq = 72) is a OMAP UART0
[ 0.547010] console [ttyO0] enabled
[ 16.415168] 48022000.serial: ttyO1 at MMIO 0x48022000 (irq = 73) is a OMAP UART1
[ 16.657944] 48024000.serial: ttyO2 at MMIO 0x48024000 (irq = 74) is a OMAP UART2
[ 17.151622] 481a8000.serial: ttyO4 at MMIO 0x481a8000 (irq = 45) is a OMAP UART4
I know UART 3 only have a TX, but I only use it to communicate one way to a pwm controller.
I was able to use the device tree files here and manually enable 3 and 5.
http://www.armhf.com/beaglebone-black-s ... tbo-files/
But when I edit the /boot/uboot/uEnv.txt , it gave me error trying to enable them.
Surprisingly, when I use the built-in BB-UART5, it works.
But there is no built-in BB-UART3.
Thanks,