RS485 UART RTS control issues.

[reasonx]

Armbianmonitor:

https://paste.armbian.com/sihofajiqe

Hello. Im trying to configurate and adapt OrangePI Zero 2W board to a custom extension board with multiple RS485 drivers.

For now, im trying to configurate a single secondary UART (UART2) to initialize with muxed Rx\Tx pins and in RS485 (with software driven RTS pin).

My current DT overlay is:

Spoiler

/dts-v1/;
/plugin/;

/ {
    compatible = "allwinner,sun50i-h616", "allwinner,sun50i-h618";

    fragment@0 {
        target = <&uart2>;

        __overlay__ {
            status = "okay";
            pinctrl-names = "default";
            pinctrl-0 = <&uart2_rs485_pins>;
            rts-gpios = <&pio 7 4 0>; // PH4 in ACTIVE HIGH
            linux,rs485-enabled-at-boot-time;
            rs485-rts-active-high;
            rs485-rts-delay = <55000 55000>; // Delay are set huge to visiually check RTS with scope, with 1/50 it still do not work.
        };
    };

    fragment@1 {
        target = <&pio>;
        __overlay__ {
            uart2_rs485_pins: uart2_rs485_pins {
                pins = "PH5", "PI6";
                function = "uart2";
            };
        };
    };
};

 

And it is partially works. Works as UART. Able to send and receive data with muxed Rx\Tx.
For RTS... its complicated. Seems RTS(PH4 GPIO) are initialized and acquired by UART2 software, and stay low during initial idling.

After im trying to send any data (echo 123 >> /dev/ttyS2), RTS goes HIGH and stuck in this state before reboot.

Im have tried to send big blob at 9600 and check the RTS with statserial.
But as i see, RTS is 1 (active???) from inital to complete and after, and never changes.