Today I released my project that shows how to build a display that can be remotely controlled via CAN bus. I plan to use it as Smart Home remote control. For interaction with the controller it has a rotary encoder attached that emits CAN bus messages for different actions. With this setup, a remote counterpart like the Raspberry Pi can supply an interactive menu. The project is hosted on GitHub: https://github.
After buying an HD44780 compatible LCD together with an I2C interface board (which has an PCF8574T soldered on it) I tried to output some text in C on it but the display just stayed black - or after changing some GPIOs, it stayed blue. I measured every pin of the PCF8574T and got the following scheme: PCF8574T <-> HD44780 P0 -- RS P1 -- R/W P2 -- EN P4 -- DB4 P5 -- DB5 P6 -- DB6 P7 -- DB7 R/W should be mapped to GND if the HD44780 should not talk back to the CPU.