Simple Tut for Serial Backpacks – 4 Wires & a Few Lines of Code | #I2C
Backpacks. Breakouts. HATs. Capes. Shields. Sometimes it can get a bit confusing figuring out why things are called what they are. But while some names are simply re-brands of an idea, others perform specific functions regardless of who has their logo silkscreened on the board. In this post from Norwegian Creations they explain, quite simply, what and why a serial backpack is what it is, as it pertains to LCD character display:
The purpose of a serial backpack is to use less GPIO pins on your MCU or Arduino. Physically speaking, a serial backpack is a circuit board that can be attached directly to the display or connected to the display via wires. The MCU or Arduino is connected to the serial backpack via some kind of digital serial communication (eg. UART, I2C or SPI). This way you can send commands to the LCD with a considerably less amount of GPIO pins.