Is it possible to change the baud rate of the UART to a custom value like 100.000 bits/s?
In the datasheet of the AM335x Sitara the different modes are:
2.4 Kbps
9.6 Kbps
19.2 Kbps
38.4 Kbps
57.6 Kbps
115.2 Kbps
But I read on this forum that they did set the baud rate to 500k.
https://groups.google.com/forum/#!topic/beagleboard/EEe7xAkCPkQ
The library that I use (libbulldog) doens’t support custom baudrates, and this one makes use
of the termios.h (which also doesn’t support other baudrates).
Does anyone know how to change the baud rate to a custom value? I need this because I want
to read a bus from a commercial product which works on 100.000 bits/s. (SBus from Futaba).
I am new to programming microcontrollers, so my knowledge of setting registers etc. is limited.
kind regards,
Stein
The AM335x Sitara processor has two registers, divisor high and divisor low, where you can set the preferred divisor.
With the formula ‘baudrate = clock / (over sampling x divisor)’ you can calculate the divisor for the desired baudrate.
There are 2 modes, 16x and 13x, for the over sampling. I will use the 16x mode.
I want to have a baudrate of 100 kbps, so my divisor needs to be 30. This gives an error of 0%.
You can find information about these registers at page 4270 in the datasheet of the AM335x
Does anyone know how I can set these registers?
kind regards,
Stein
Stein,
I am in the same boat!! I need to set the UART to 250k baud for DMX512 lighting. According to your below math, this should be 16x oversampling and a divisor of 12 for me.
I hope there is a way to set these values via command line and/or config files.
This stuff here is interesting, but I’m not sure how (or if) I can change these numbers?
debian@vBBB20:/sys/devices/ocp.3/481a8000.serial/tty/ttyO4$ ls
close_delay custom_divisor device iomem_base io_type line power type uevent
closing_wait dev flags iomem_reg_shift irq port subsystem uartclk xmit_fifo_size
debian@vBBB20:/sys/devices/ocp.3/481a8000.serial/tty/ttyO4$ sudo cat uartclk
48000000
debian@vBBB20:/sys/devices/ocp.3/481a8000.serial/tty/ttyO4$ sudo cat custom_divisor
0
Looks interesting, but not sure how to manipulate these things? Device Tree? DTC? Config files?
I am watching this thread closely now. Thx!
-frenchy
DId you guys have any luck? I need to get 250k working on a beaglebone black as well