UART

Introduction

AIO-3588SJD4  supports RS232, RS485 interfaces

The serial interface diagram of the AIO-3588SJD4  development board is
as follows:


DTS configuration

The RS232 interface of the development board is extended by the main
control UART0, and the RS485 interface is extended by the main control
UART3.

File path "kernel-5.10/arch/arm64/boot/dts/rockchip/aio-3588sjd4.dtsi"

   &uart0 {
       status = "okay";
       pinctrl-names = "default";
       pinctrl-0 = <&uart0m2_xfer>;
   };

   &uart3 {
       status = "okay";
       pinctrl-names = "default";
       pinctrl-0 = <&uart3m2_xfer>;
   };

After configuring the serial port, the nodes on the software
corresponding to the hardware interface are:

   RS232 :   /dev/ttyS0
   RS485 ：  /dev/ttyS3

Send and receive verification

Users can use different host's USB-to-serial adapters to send and
receive data to the serial port of the development board according to
different interfaces. For example, the debugging steps of RS485 are as
follows:

(1) Connect the hardware

USB to "RS485" serial port cable

"Host serial adapter (USB to 485 to serial module)" connect to the
host

(2) Development board sends, host receives

   # The host terminal executes first:
   # /dev/ttyUSB0 is the node of the host serial adapter, modify it according to the actual situation
   cat /dev/ttyUSB0

   # The development board debugs the serial port terminal and executes:
   # /dev/ttyS3 is the RS485 node
   echo "firefly RS485 test..." > /dev/ttyS3

The host terminal will receive the string "firefly RS485 test..."

(3) Host sends, development board receives

   # To debug the serial terminal on the development board, execute first:
   # /dev/ttyS1 is the RS485 node
   busybox  stty -echo -F /dev/ttyS3     # turn off echo
   cat /dev/ttyS3

   # The host terminal executes:
   # /dev/ttyUSB0 is the node of the host serial adapter, modify it according to the actual situation
   echo "firefly RS485 test..." > /dev/ttyUSB0

The development board debugs the serial terminal to receive the string
"firefly RS485 test..."