6. UART Usage¶

6.1. Brief¶

AIO-3588SJD4-AI supports RS232 and RS485

The serial interfaces are as follows:

_images/uart_interface.jpg

The board’s RS232 is from UART9 and RS485 is from UART6.

DTS file: `kernel/arch/arm64/boot/dts/rockchip/rk3588-firefly-aio-3588sjd4-ai.dtsi

&uart6 {
        pinctrl-0 = <&uart6m1_xfer>;
        status = "okay";
};

&uart9 {
        pinctrl-0 = <&uart9m2_xfer>;
        status = "okay";
};

So the corresponding nodes in system are:

RS232 :   /dev/ttyS9
RS485 :   /dev/ttyS6

Pin GPIO1_A2 is used for RS485 direction control. Pull up this GPIO means RS485 is in send mode, pull down means RS485 is in receive mode.

User can use /sys/class/gpio sub-system to control GPIO.

All serial default baudrate is 9600, and 8 data bits, 1 stop bit, no flow control. User can use “echo” and “cat” command to simply test serials.