Default Address: 0x27 for PCF8574T chip; 0x3F for PCF8574AT chip; please check which chip you have on i2c interface. (Before you upload the code to the control board, please download the LiquidCrystal_I2C library). Compatible with all devices with I2C interfaces, such as for Arduino, raspberry pi, beagle bone black, tinker board, stm32, esp32 and more. It is a high-performance serial bus with bus rules and high-speed or low-speed device synchronization required for multi-master systems. The I2C bus has only two bidirectional signal lines, a serial data line (SDA) and a serial clock line (SCL). LCD2004+I2C 2004 20x4 2004A Blue/Green screen HD44780 Character LCD /w IIC/I2C Serial Interface Adapter Module for arduino. The LCD has always been a device that acts as a window in human-computer interaction. For example, the prompt window on some instrument devices, the temperature and humidity prompt box, the device running status monitor, and the prompt screen of the counting device all have LCD figures.