Stephen added his entry in the Open 7400 Logic competition, he made a LCD backpack that uses the SPI interface. Using two 74LS595 serial to parallel shift registers connected in series, he successfully sends data to the 16×2 LCD and adjusts the backlight brightness, by sending 2 bytes over the SPI.
The first byte to be sent is displayed on the LCD, and bits 1:3 of the second byte are used to adjust the backlight brightness with 32 levels available. The LSB of the second byte is the RS pin of the LCD.
Via the forum.