This mrbgem implements a driver for the Hitachi HD44780 character LCD standard. It is copied directly from the Denko CRuby gem, and runs on mruby as-is.
It's based on the datasheet as well as the Adafruit implementation.
This is meant to be used as part of mruby-denko. See that repo for ESP-IDF project templates that run mruby on the ESP32.
This gem is included in all builds by default, and the examples folder of that repo contains examples for it.