RS485 automatically to control DE pin

[ABK]

Hi,

 

I am using Nanopi Neo board and I need RS485 driver to control DE pin automatically.

I have prepared DTS Overlay file:

 

/dts-v1/;
/plugin/;

/ {
    compatible = "allwinner,sun8i-h3";

    fragment@0 {
        target = <&uart1>;
        __overlay__ {
            status = "okay";
            pinctrl-names = "default";
            pinctrl-0 = <&uart1_pins &uart1_de_pin>;
            rs485-rts-gpios = <&gpio6 8 0>;  /* PG8 active-low */
            linux,rs485-enabled-at-boot-time;
            rs485-rts-delay = <0 300>;
        };
    };

    fragment@1 {
        target = <&uart2>;
        __overlay__ {
            status = "okay";
            pinctrl-names = "default";
            pinctrl-0 = <&uart2_pins &uart2_de_pin>;
            rs485-rts-gpios = <&gpio0 2 0>;  /* PA2 active-low */
            linux,rs485-enabled-at-boot-time;
            rs485-rts-delay = <0 300>;
        };
    };
};
 

I produced dtbo file from dts one with the command: dtc -@ -I dts -O dtb -o rs485.dtbo rs485.dts

 

I copied this rs485.dtbo file to /boot/dtb/overlay. Also I added rs485 string to ArmbianEnv.txt and rebooted. 

But only TX works, RX doesn't. 

 

What should  I do else to make it work?

Edited September 2, 2025 by ABK

[laibsch]

spendist is the maintainer of the Nanopi Neo.  Maybe he has something to say.

 

Did you try another kernel?  Another OS?