Beaglebone A5, debian wheezy, UART4

Hi *,

actually I am playing with UARTS and the beaglebone A5.
I want to controll a stepper motor driver by using the /dev/ttyO4.
When I use an USB Serial TTL 3,3 V converter (/dev/ttyUSB0)
everything works finde (minicome, ser2net, …)

But if using one of the boards UARTS (for example /dev/ttyO4)
the connection cannot bei done.

The stepper motor driver has also a USB Serial TTL 3,3V
interface. Thus the bone and the driver are at the same level.

Has there somebody a solution für this issue?

Thanks in advance and kind regards,


(still pending)

Hi Gerrit,

Try these two lines to pinmux for ttyO4 (assume debugfs is mounted at /debugfs):

sudo echo 0x0006 > /debugfs/omap_mux/gpmc_wpn # uart4_txd on mode 6
sudo echo 0x0026 > /debugfs/omap_mux/gpmc_wait0 # uart4_rxd on mode 6


Hi George,
thanks for your quick reply.

indeed the debugfs was not mounted.

mount -t debugfs none /sys/kernel/debug

No I can do pin muxing.

Thank you very much.


Hi George,

now it is working. The beaglebone can talk to the stepper motor driver.