How to Use Adafruit 14-segment LED Alphanumeric Backpack Pure Green: Examples, Pinouts, and Specs

The Adafruit 14-Segment LED Alphanumeric Backpack is a versatile and easy-to-use display module capable of showing alphanumeric characters with high visibility thanks to its pure green LEDs. This module is ideal for adding a readable interface to any microcontroller project, including clocks, counters, and message displays. The I2C interface simplifies connectivity, allowing multiple displays to be controlled with just two pins.

• Digital clocks and timers
• Counter displays
• Message boards
• User interfaces for projects
• Readouts for sensors and other devices

• Display Color: Pure Green
• Operating Voltage: 2.3V to 5.5V
• Max Current (per segment): 80mA
• I2C Interface Address Range: 0x70 - 0x77 (selectable with solder jumpers)
• Dimensions: 1.4" x 1.75" x 0.25" (without headers)

1. Connect the GND pin to the ground of your microcontroller.
2. Connect the VCC pin to a 2.3V to 5.5V power supply.
3. Connect the SDA and SCL pins to the I2C data and clock lines on your microcontroller.

• Ensure that the power supply voltage does not exceed 5.5V to prevent damage.
• Use pull-up resistors on the I2C data and clock lines if your microcontroller does not have built-in pull-ups.
• To avoid ghosting or flickering, ensure that the refresh rate is high enough when multiplexing displays.
• When chaining multiple displays, ensure that each display has a unique I2C address by setting the solder jumpers on the back of the PCB.

#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_LEDBackpack.h>

Adafruit_AlphaNum4 alpha4 = Adafruit_AlphaNum4();

void setup() {
  alpha4.begin(0x70);  // Initialize the display with the I2C address 0x70
}

void loop() {
  alpha4.writeDigitAscii(0, 'A');  // Display 'A' on the first digit
  alpha4.writeDigitAscii(1, 'd');  // Display 'd' on the second digit
  alpha4.writeDigitAscii(2, 'a');  // Display 'a' on the third digit
  alpha4.writeDigitAscii(3, 'F');  // Display 'F' on the fourth digit
  alpha4.writeDisplay();           // Send the data to the display
  delay(1000);                     // Wait for a second
}

• Display Not Lighting Up: Check the power connections and ensure that the voltage is within the specified range. Also, verify that the I2C address matches the one in your code.
• Characters Not Displaying Correctly: Ensure that the library is correctly installed and that the I2C lines are properly connected with pull-up resistors if needed.
• Dim Display: Check if the current limit is too low or if the power supply voltage is insufficient.

• Double-check wiring, especially the I2C connections.
• Use the i2cdetect utility or similar tools to confirm that the display is detected on the I2C bus.
• Adjust the brightness setting in your code if the display is too dim or too bright.
• If using multiple displays, ensure that each one has a unique I2C address.

Q: Can I use this display with a 3.3V system? A: Yes, the display operates from 2.3V to 5.5V, making it compatible with both 3.3V and 5V systems.

Q: How many of these displays can I chain together? A: You can chain up to eight displays together, each with a unique I2C address set by the solder jumpers.

Q: Do I need to install any libraries to use this display with an Arduino? A: Yes, you will need to install the Adafruit_GFX and Adafruit_LEDBackpack libraries, which are available through the Arduino Library Manager.

Q: Can I display special characters or symbols? A: The 14-segment display can show a wide range of characters and symbols. Check the library documentation for supported characters.