Adafruit i2c SPI character LCD backpack

LCD backpacks reduce the number of pins needed to connect to an LCD. LCDs are a fun and easy way to have your microcontroller project communicate with you. Character LCDs are common and easy to obtain, available in various colors and sizes. We have written tutorials on using character LCDs with an Arduino or similar microcontroller, but the number of pins necessary to control the LCD can be restrictive, especially for ambitious projects. We wanted to create a 'backpack' (add-on circuit) that would reduce the number of pins without significant expense.

By using simple I2C and SPI input/output expanders, we have reduced the number of pins needed (only 2 pins are required for I2C) while still making it easy to interface with the LCD. For Arduino users, we provide an easy-to-use library that is backwards compatible with projects using the '6 pin' wiring. The breakout comes with a 2-pin and 3-pin terminal block (you can snap it together to make a 5-pin terminal and then solder it to the backpack for easy wiring).

This backpack will work with any 'standard' character LCD, from 8x1 to 20x4 sizes, as long as they have a 16-pin single-line connection header at the top. We suggest using our blue and white 20x4 or 16x2 LCDs. It does not work with the 16x2 OLED displays. You can try to connect our RGB 16x2 or 20x4 LCDs, but this backpack will not control the RGB backlight, so you'll have to use the backpack only for the 14 digital I/O pins (pins #1-14) and connect the backlight pins (#15-#18) directly to your microcontroller with 4 extra wires for color/PWM control as if they were just an RGB LED.

For advanced users, this project can be used for general-purpose I/O expansion. The MCP23008 has 8 I/O pins (7 are connected) with optional pull-ups, and the SPI 74HC595 has 7 connected outputs.

This board/chip uses I2C 7-bit address between 0x20-0x27, selectable with jumpers.