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

The Adafruit 14-segment LED Alphanumeric Backpack Yellow-Green is a versatile display module capable of showing numbers, letters, and symbols with high visibility in a yellow-green hue. This component is ideal for adding a simple, bright display to any microcontroller project. Common applications include digital clocks, thermometers, counters, and any project requiring alphanumeric output.

• Display Color: Yellow-Green
• Character Height: 0.54 inches
• Operating Voltage: 2.3V to 5.5V
• Max Current (per segment): 80mA
• Interface: I2C
• I2C Addresses: 0x70-0x77 selectable with solder jumpers

1. Power Connections: Connect the VCC pin to your microcontroller's 5V output and the GND pin to ground.
2. I2C Connections: Connect the SDA and SCL pins to your microcontroller's I2C data and clock lines, respectively.
3. Address Selection: If using multiple displays, set unique I2C addresses using the solder jumpers on the back of the module.

• Ensure that the power supply 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.
• When daisy-chaining multiple displays, verify that the total current does not exceed the power supply's capabilities.

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

Adafruit_AlphaNum4 display = Adafruit_AlphaNum4();

void setup() {
  display.begin(0x70);  // Initialize the display with its I2C address
  display.setBrightness(15);  // Set the display brightness (0-15)
  display.writeDisplay();  // Write data to the display
}

void loop() {
  display.clear();  // Clear the display buffer
  display.writeDigitAscii(0, 'H');  // Set 'H' on the first digit
  display.writeDigitAscii(1, 'E');  // Set 'E' on the second digit
  display.writeDigitAscii(2, 'L');  // Set 'L' on the third digit
  display.writeDigitAscii(3, 'P');  // Set 'P' on the fourth digit
  display.writeDisplay();  // Send buffer to the display
  delay(1000);  // Wait for a second
}

• Display Not Lighting Up: Check the power connections and ensure the I2C address is correctly set.
• Garbled Characters: Ensure there are no loose connections and the I2C lines are properly connected.
• Dim Display: Adjust the brightness setting in your code or check the power supply voltage.

• Double-check wiring, especially the I2C connections.
• Use the i2cdetect utility or similar to confirm the device's address on the I2C bus.
• Ensure that the library versions for Adafruit_GFX and Adafruit_LEDBackpack are up to date.

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 5V and 3.3V systems.

Q: How many of these displays can I chain together? A: You can chain up to 8 displays using different I2C addresses, from 0x70 to 0x77.

Q: Can I display custom characters or symbols? A: Yes, the Adafruit GFX library allows you to define custom bitmaps for characters and symbols.

For further assistance, consult the Adafruit support forums or the product's official documentation.