Serial driver 16550a on Beaglebone Black

Greg Gallagher greg at
Mon Mar 30 17:14:05 CEST 2020

On Mon, Mar 30, 2020 at 11:08 AM Michał Hanusek via Xenomai
<xenomai at> wrote:
> Hello.
> How to enable a driver 16550a (xeno_16550A) and configure the serial port?
> I loaded the driver to the kernel (for the /dev/ttyS4 port) but the device in the /dev/rtdm/rtser... location did not appear.

Do you have the vanilla kernel driver loaded as well?  You need to
unbind the serial port you want the 16550A to work with.
I don't think this has been tested on beaglebone black but I could be wrong.
> Please help.
> Linux kernel 4.9.88 + Xenomai patch
I would use a newer kernel and ipipe patch, 4.9 is currently no
supported.  I don't think it get the gpio fixes either.

> root at beaglebone:/home/debian# lsmod
> Module                  Size  Used by
> xeno_16550A            17350  0
> root at beaglebone:/home/debian# modprobe xeno_16550A io=0x481A8000 irq=159 baud_base=115200 start_index=0
> root at beaglebone:/home/debian# cat /proc/tty/driver/serial
> serinfo:1.0 driver revision:
> 0: uart:8250 mmio:0x44E09000 irq:158 tx:11568 rx:98 brk:63 RTS|CTS|DTR|DSR
> 1: uart:unknown port:00000000 irq:0
> 2: uart:unknown port:00000000 irq:0
> 3: uart:unknown port:00000000 irq:0
> 4: uart:8250 mmio:0x481A8000 irq:159 tx:2 rx:1 brk:1 CTS|DSR
> 5: uart:unknown port:00000000 irq:0
> root at beaglebone:/home/debian# setserial /dev/ttyS4
> /dev/ttyO4, UART: 8250, Port: 0x0000, IRQ: 159
> root at beaglebone:/home/debian# ls /dev/rtdm/
> autotune        memdev-private  memdev-shared   memdev-sys      switchtest      timerbench
> Szanujemy Twoją prywatność, dbamy o bezpieczeństwo Twoich danych osobowych,  Sprawdź szczegóły !


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