After the successful launch and increasing popularity of the Raspberry Pi Pico, creator 'zadi15' has developed a C library for interfacing LCD screens with the board dubbed "picoLCD."
As the project is ongoing, we can expect some more improvements to the open source C library. But if you plan to interface the HD44780-based LCD controller with the board, this library simplifies the process. It's as easy as just copying the .c and .h files for your project along with some minor changes.
"Rather than reading through data sheets to figure out the correct set of instructions to send to the screen, picoLCD attempts to make it a simpler process while still being extremely versatile," zadi15 says. The library has been tested successfully for 16x2 LCDs, but we are yet to receive a confirmation on 20x4, 40x2, and 16x4 displays.
The above reference image shows the connections required between Pi Pico and LCD for 8-bit operation. According to zadi15, the LCD backlight should be powered via an external 5V source.