8. UART¶

8.1. Introduction¶

AIO-3588JD4 has one RS232 interfaces and one RS485 interface

The serial interface diagram of the AIO-3588JD4 development board is as follows:

_images/usage_uart_interface.jpg

8.2. DTS configuration¶

The RS232 interface of the development board is extended by the main control UART1, and the RS485 interface is extended by the main control UART6.

File path kernel/arch/arm64/boot/dts/rockchip/aio-3588jd4.dtsi

/* RS485 */
&uart6{
        pinctrl-0 = <&uart6m1_xfer>;
        status = "okay";
};

/* RS232 */
&uart1{
        pinctrl-0 = <&uart1m1_xfer>;
        status = "okay";
};

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

RS232:   /dev/ttyS1
RS485：  /dev/ttyS6

8.3. 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(AIO-3588JD4 RS485 is half-duplex and requires gpio to control transmission and reception):

(1) 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…”

(2) Host sends, development board receives

echo 34 > /sys/class/gpio/export
echo out > /sys/class/gpio/gpio34/direction

# To debug the serial terminal on the development board, execute first:
# /dev/ttyS1 is the RS485 node
echo 0 > /sys/class/gpio/gpio34/value
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 1 > /sys/class/gpio/gpio34/value
echo "firefly RS485 test..." > /dev/ttyUSB0

The development board debugs the serial terminal to receive the string “firefly RS485 test…”