In the "New LiquidCrystal / schematics" page on the wiki, every configuration ties the LCD R/W pin to the ground, except the I2C interface schematic, that controls it from an output of the I2C expander.
Is this an error? If so, I'd like to free a second output pin on the PCF8574 for another use (e.g. backlight control). Or is this the only configuration where the lib needs to actually read the display? (to poll the "busy" flag maybe?)
Thanks for your help! I know I could read the code (and probably will in the coming days), but having you giving a definite answer (and maybe editing the wiki) would help others, so I'm taking the chance! If you want, I may try to create a pull request if I succeed in adding code to control backlight through the I2C interface.