UART

Introduction

ITX-3588J supports RS232, RS485, UART0, UART1 interfaces

RS232 and UART0 can only be used

RS485 and UART1 can only be used

The serial interface diagram of the ITX-3588J development board is as
follows:


How to use jumper to select RS232 or UART0, RS485 or UART1:


RS232: 8 and 9 are shorted, 11 and 12 are shorted

UART0: 8 and 7 are shorted, 11 and 10 are shorted

RS485: 2 and 3 are shorted, 5 and 6 are shorted

UART1: 2 and 1 are shorted, 5 and 4 are shorted

For example, if you choose to use RS232 or RS485, the jumper
connection diagram is as follows:


RS232 and RS485 are recommended to use official FC10 to DP9 serial
port cable. The serial port cable sequence of different manufacturers
may be different, which will cause the serial port to fail to
communicate.


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
UART1.

File path "kernel-5.10/arch/arm64/boot/dts/rockchip/rk3588-firefly-
itx-3588j.dtsi"

   /* uart/232/485 */
   &uart0{
       pinctrl-0 = <&uart0m2_xfer>;
       status = "okay";
   };

   &uart1{
       pinctrl-0 = <&uart1m1_xfer>;
       status = "okay";
   };

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

   RS232 or UART0:   /dev/ttyS0
   RS485 or UART1：  /dev/ttyS1

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

"RS485" to connect "FC10 to DP9 serial cable";

"FC10 to DP9 serial cable" to connect "host serial adapter (USB to 485
serial port module)";

"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/ttyS1 is the RS485 node
   echo "firefly RS485 test..." > /dev/ttyS1

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/ttyS1       # turn off echo
   cat /dev/ttyS1

   # 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..."