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 talk back to you.
Character LCDs are common, and easy to get, available in tons of colors and sizes. Adafruit have written tutorials on using character LCDs with an Arduino (or similar microcontroller) but find that the number of pins necessary to control the LCD can be restrictive, especially with ambitious projects. They wanted to make a 'backpack' (add-on circuit) that would reduce the number of pins without a lot of expense.
By using simple I2C and SPI input/output expanders, Adafruit have reduced the number of pins while still making it easy to interface with the LCD. Only 2 pins are needed for I2C, 3 for SPI. For Arduino and CircuitPython/Python users, Adafruit provide an easy-to-use library that is backwards compatible with projects using the '6 pin' wiring. This backpack comes with pre-soldered 2-pin and 3-pin terminal block to make a 5-pin terminal 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. It does not work with the 16x2 OLED displays.
This backpack now comes with a big re-spin that makes lots of improvements:
- Adafruit added a 3-5V boost circuit for this backpack to control 5V LCDs even with 3V power and logic.
- The contrast potentiometer is much nicer and easier to twist using a small screwdriver.
- Added SparkFun qwiic compatible STEMMA QT connectors for the I2C bus so you don't even need to solder the I2C and power lines. Just wire up to your favorite micro using a STEMMA QT adapter cable. QT Cable is not included, but we have a variety in the shop.
- Functionality and size/shape are the same - mechanically and code-wise, it is a drop-in replacement.
- Adafruit have also updated this PCB with Adafruit Pinguin to make a lovely and legible silkscreen.
Advanced users can repurpose the backpack 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.
Technical Details
EagleCAD PCB GitHub files and Fritzing object available in the product tutorial
- This board/chip uses I2C 7-bit address between 0x20-0x27, selectable with jumpers
- Works with 16x2 and 20x4 Character LCDs
- It does not work with 16x2 OLED displays
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Saving you 4 pins, every day