A20 UARTs enable/disable and module/driver

[Klaus]

Hi,

 I would like to build a simple rs485 interface to the A20-OLinuxino-Micro board.

I was looking into utilizing one of the UARTs (6 or 7) on EXT1 or EXT2 and add an external driver chip to it.

While I just find ttyS0 (on 0x01c28000), ttyS1 (on 0x01c29800) and ttyS2 (on 0x01c29c00), it seems all other UARTs are also assigned to a module (serial8250?).

Code Select Expand

# find /sys/devices/ -name 'ttyS*'
/sys/devices/platform/soc/1c28000,serial/tty/ttyS0
/sys/devices/platform/soc/1c29c00,serial/tty/ttyS2
/sys/devices/platform/soc/1c29800,serial/tty/ttyS1
/sys/devices/platform/serial8250/tty/ttyS6
/sys/devices/platform/serial8250/tty/ttyS4
/sys/devices/platform/serial8250/tty/ttyS7
/sys/devices/platform/serial8250/tty/ttyS5
/sys/devices/platform/serial8250/tty/ttyS3
How can I find out
- which module/driver is used to access ttyS0, ttyS1 and ttyS2
- if ttyS3 - ttyS7 are 'active' and which modile/driver was used
- how do enable/disable any ttySx and/or prevent the kernel to automatically load a module for it ?

I would guess some of it should be done in the device tree. Can someone recommend/link some HowTo's to get started with that?

Thanks in advance,
Klaus

[LubOlimex]

Have you tried the overlays approach:

https://github.com/OLIMEX/OLIMEX-sunxi-overlays

https://github.com/OLIMEX/OLIMEX-sunxi-overlays/tree/master/sun7i-a20

[Klaus]

Thanks for the input, but unfortunately this does not get me any further in regards to drivers/modules. :-(

BTW:  OLIMEX-sunxi-overlays refers to armbian-config System->Hardware.
Here it seems uart2 to uart7 are disabled and could be enabled, but board actually 'finds' uart0 (as ttyS0), uart6 (as ttyS1) and uart7 (as ttyS2) during the boot process. Therefor, in the armbian-config, uart1 is missing and the correct status (enabled) of uart6/7 is not shown. :-(

[mauricio]

Hello, sorry by the dumb question

I'm using an Olimex A20 Micro

When I try to open serial connection to /dev/ttyS2, I receive

Code Select Expand

sudo python3 -m serial.tools.miniterm /dev/ttyS2 9600
could not open port '/dev/ttyS2': Could not configure port: (5, 'Input/output error')
Serial command work fine with /dev/ttyS0, I mean , connection stablished

So, I'd like to open (enable) /dev/ttyS2, but I can't figure out  how

I guess my option is to build debian package, from https://github.com/OLIMEX/OLIMEX-sunxi-overlays/tree/master/sun7i-a20

But what to do after that ?, where to place or what to do with that "output" folder files ?

Please any help is appreciated, thanks

[JohnS]

Do you have /dev/ttyS2 ?

I have, using Debian buster - but I don't know what you used.

(Try some other Olimex image.)

John

[LubOlimex]

If you use one of the official images you can run script:

~#olinuxino-overlay – it provides easy way to enable or disable different hardware assignments – different I2C, SPI, UART, CAN, PWM, etc;

This is one of our Olimax-made scripts, the rest are:

~#olinuxino-display – allows setting different video output;

~#olinuxino-sd-to-emmc – allows booting from eMMC; transfers the Linux file system from the card to the eMMC memory (if your board has one); boot is placed in SPI flash memory;

~#olinuxino-sd-to-sata – allows booting from the SATA disk; transfers the Linux file system from the card to external SATA disk; boot is placed in SPI flash memory.

The official images for A20-OLinuXino-MICRO can be found here:

http://images.olimex.com/release/a20/


If you don't know what image to use, try the Bionic Base image.

[mauricio]

Hello

Thank you !

Yes, I'm using olimex official image A20-OLinuXino-buster-base-20200731-135406.img.7z

I'll try run olinuxino-overlay and comment here my results

Thanks

[mauricio]

Hello

It works

I just did

Code Select Expand

#sudo find / -name 'olinuxino-overlay'
#/usr/sbin/olinuxino-overlay
#cd /usr/sbin
#sudo ./olinuxino-overlay

At the opened UI, I selected both

sun7i-a20-uart6.dtbo
sun7i-a20-uart7.dtbo

Code Select Expand

#sudo reboot

Awesome !!

Thank you all