Uart2 Banana PI M3

[O to the o]

Hi

 

I'm trying to understand how to enable Uart 2 for serial communication with a mcu on the banana pi (trying to connect a board running klipper to it).

I connected the Uart of the board to CON1-P08 and CON1-P10 of the Banana PI M3 according to all i can find those pins are tx/rx for UART2.

 

So far i figured out that the UART should be one of the /dev/ttyS* ones if i'm not mistaken, I can see /dev/ttyS to /dev/ttyS7 but am missing the /dev/ttyS1

 

user@bananapim3:~$ ls /dev/tty*
/dev/tty    /dev/tty11  /dev/tty15  /dev/tty19  /dev/tty22  /dev/tty26  /dev/tty3   /dev/tty33  /dev/tty37  /dev/tty40  /dev/tty44  /dev/tty48  /dev/tty51  /dev/tty55  /dev/tty59  /dev/tty62  /dev/tty9     /dev/ttyS2  /dev/ttyS6
/dev/tty0   /dev/tty12  /dev/tty16  /dev/tty2   /dev/tty23  /dev/tty27  /dev/tty30  /dev/tty34  /dev/tty38  /dev/tty41  /dev/tty45  /dev/tty49  /dev/tty52  /dev/tty56  /dev/tty6   /dev/tty63  /dev/ttyACM0  /dev/ttyS3  /dev/ttyS7
/dev/tty1   /dev/tty13  /dev/tty17  /dev/tty20  /dev/tty24  /dev/tty28  /dev/tty31  /dev/tty35  /dev/tty39  /dev/tty42  /dev/tty46  /dev/tty5   /dev/tty53  /dev/tty57  /dev/tty60  /dev/tty7   /dev/ttyACM1  /dev/ttyS4  /dev/ttyUSB0
/dev/tty10  /dev/tty14  /dev/tty18  /dev/tty21  /dev/tty25  /dev/tty29  /dev/tty32  /dev/tty36  /dev/tty4   /dev/tty43  /dev/tty47  /dev/tty50  /dev/tty54  /dev/tty58  /dev/tty61  /dev/tty8   /dev/ttyS0    /dev/ttyS5

 

I'm glad for anyhelp and any idea

 

 

[O to the o]

Also to add how to get 1-wire to work ?

[going]

13.06.2024 в 23:13, O to the o сказал:

how to enable Uart 2

 

In this file for UART2:

allwinner/sun8i-a83t.dtsi

...
		/omit-if-no-ref/
			uart2_pb_pins: uart2-pb-pins {
				pins = "PB0", "PB1";
				function = "uart2";
			};
		};
...
	uart2: serial@1c28800 {
			compatible = "snps,dw-apb-uart";
			reg = <0x01c28800 0x400>;
			interrupts = <GIC_SPI 2 IRQ_TYPE_LEVEL_HIGH>;
			reg-shift = <2>;
			reg-io-width = <4>;
			clocks = <&ccu CLK_BUS_UART2>;
			resets = <&ccu RST_BUS_UART2>;
			status = "disabled";
		};

 

By analogy with uart0 here:

dts/allwinner/sun8i-a83t-bananapi-m3.dts#L383

you can write an additional node:

&uart2 {
	pinctrl-names = "default";
	pinctrl-0 = <&uart2_pb_pins>;
	status = "okay";
};

But it will work if you build the DTB directly when compiling the kernel.
Because without adding this node, the contact description node for uart2 will be omitted.

That is, it is not in the standard DTB.

 

You can write an overlay in which you need to specify both nodes:

/dts-v1/;
/plugin/;

/ {
	compatible = "allwinner,sun8i-a83t";

	fragment@0 {
		target-path = "/aliases";
		__overlay__ {
			serial2 = "/soc/serial@1c28800";
		};
	};

	fragment@1 {
		target = <&pio>;
		__overlay__ {
			uart2_pb_pins: uart2-pb-pins {
				pins = "PB0", "PB1";
				function = "uart2";
			};
		};
	};

	fragment@2 {
		target = <&uart2>;
		 __overlay__ {
			pinctrl-names = "default";
			pinctrl-0 = <&uart2_pb_pins>;
			status = "okay";
		};
	};
};

 

Regards

[O to the o]

Thanks @going can the overlay be added into a running kernal or does that also require compilation ?

 

[going]

28 минут назад, O to the o сказал:

can the overlay be added into a running kernal

 

Save the overlay file to sun8i-a83t-uart2.dts name.

Compile the overlay:
dtc -I dts -O dtb -o sun8i-a83t-uart2.dtbo sun8i-a83t-uart2.dts

copy sun8i-a83t-uart2.dtbo file to /boot/dtb-**-sunxi/overlay/

Add to /boot/armbianEnv.txt file line:

overlays=uart2

after the line overlay_prefix=sun8i-a83t

sudo nano /boot/armbianEnv.txt

 

[going]

For reference:
Extract the applied final dts from the current file system:

dtc --sort -I fs -O dts  /sys/firmware/devicetree/base > cur-dts-out.txt

 

[O to the o]

Thanks

Did that and the dtc command shows UART2 being present in the devicetree, any idea how to identify it in all the /dev/tty* options ? New appeared

 

Also if i wanna use 1-wire do i also need to add an overlay ?

[going]

2 часа назад, O to the o сказал:

Also if i wanna use 1-wire do i also need to add an overlay ?

I think you need to try to do the overlay yourself.
Do it by analogy with this:

https://github.com/armbian/sunxi-DT-overlays/blob/master/sun8i-h3/sun8i-h3-w1-gpio.dts

https://github.com/armbian/sunxi-DT-overlays/blob/master/sun50i-h5/sun50i-h5-w1-gpio.dts

 

2 часа назад, O to the o сказал:

any idea how to identify it in all the /dev/tty*

 

8 часов назад, going сказал:

fragment@0 {
		target-path = "/aliases";
		__overlay__ {
			serial2 = "/soc/serial@1c28800";
		};
	};

May be /dev/ttyS2

 

This can be described using aliases:

sun8i-a83t-bananapi-m3.dts#L54