This is the development board I've just created.
I've already posted all relative software on this forum (see below).
Hardware list:
Voltage converter 3 to 5 Vcc for I2C
I2C RTC Clock
I2C LCD driver + LCD
Active 3V buzzer
Relay board 3V
Infrared Led receiver
Blue Led 3V
TP-Link TL-WDR4300
Note: +3V from serial interface, +5V from USB port, GPIO 0,1,2,3 from JTAG
https://forum.openwrt.org/t/how-to-add-20x4-lcd-hd44780-to-a-openwrt-router-via-i2c/28722
https://forum.openwrt.org/t/how-to-install-rtc-hardware-clock-pcf8563-i2c/43566
