Banana PI M2 Zero - UART3 921600 speed config

[Josep de la Fuente]

Hello,

Is it possible to set the speed of the UART3 to 921600 baud instead of 115000? How to do it?

I need to connect to an arduino at that speed. I have tried with minicom but I can't get it.

I have also tried to put the following command

dtoverlay=miniuart-bt

in /boot/armbianEnv.tx but it doesn't work either.

to 115000 if I can connect well, therefore the port works correctly

Is there any way?

[wollik]

Hi Josep,

sorry for the late reply, I just seen your questeion.
The hardware chip for UART3  (/dev/ttyS3) is a 16550A and supports a Base-baud of 150000. 
So the highest possible baud rate you can get out of this chip is 150 000.

To set it to 150000 Baud you have to:

1) enable the UART3 via armbian.config,
2) install the tool setserial
3) enable for customer speed by:
setserial -a /dev/ttyS3 spd_cust

4) set the divisor to 1 by:

setserial -a /dev/ttyS3 divisor 1

5) activate the UART by:

stty -F /dev/ttyS3 38400  <-- will get an error, but this is o.k.

 

Here is my output:

pi@bananapim2zero:~$ setserial -a /dev/ttyS3
/dev/ttyS3, Line 3, UART: 16550A, Port: 0x0000, IRQ: 46
        Baud_base: 1500000, close_delay: 50, divisor: 0
        closing_wait: 3000
        Flags: spd_normal

pi@bananapim2zero:~$ setserial -a /dev/ttyS3 spd_cust
pi@bananapim2zero:~$ setserial -a /dev/ttyS3 divisor 1
pi@bananapim2zero:~$ setserial -a /dev/ttyS3
/dev/ttyS3, Line 3, UART: 16550A, Port: 0x0000, IRQ: 46
        Baud_base: 1500000, close_delay: 50, divisor: 1
        closing_wait: 3000
        Flags: spd_cust

pi@bananapim2zero:~$ stty -F /dev/ttyS3 38400
pi@bananapim2zero:~$

Regards
wollik