8. UART Usage

8.1. Description

AIO-3576JD4 use UART3 for RS485, which is /dev/ttyS3 in system. And UART8 for RS232, which is /dev/ttyS8 in system.

And GPIO3_A3 is used for direction control of RS485, pull it up will change RS485 to send mode, pull it down will change RS485 to receive mode.

Users can use /sys/class/gpio subsystem to control this GPIO.

  • GPIO3_A3 config output

echo 99 > /sys/class/gpio/export
echo out > /sys/class/gpio/gpio99/direction

  • GPIO3_A3 set high, RS485 send: echo 1 > /sys/class/gpio/gpio99/value

  • GPIO3_A3 set low, RS485 receive: echo 0 > /sys/class/gpio/gpio99/value

Interfaces:

_images/usage_uart_interface.jpg