The hd44780 library contains functions to interact with a 2 line LCD display. The display is controlled by a Hitachi hd44780 dot matrix LCD display controller which in turn is accessed through a pcf8574 I2C I/O expander.

pigpio library calls communicate with the pcf8574. The library provides functions to initialize pigpio and the hd44780 chip, control the display and cursor and write to the display. It is also possible to read back memory contents.