How to Use Adafruit Charlieplex 9x16 Red: Examples, Pinouts, and Specs

The Adafruit Charlieplex 9x16 Red is a versatile and compact LED matrix display that leverages the charlieplexing technique to control 144 red LEDs using a minimal number of microcontroller pins. This matrix is ideal for creating eye-catching displays for alphanumeric characters, simple graphics, and animations. Its small form factor makes it perfect for wearable electronics, small handheld devices, and any project where space is at a premium.

• Wearable electronics
• Message boards
• Portable game displays
• Battery-powered signs
• Educational projects to demonstrate charlieplexing

• LED Color: Red
• Matrix Size: 9 columns x 16 rows
• Number of LEDs: 144
• Operating Voltage: 3.3V - 5V
• Max Current per LED: 20mA
• Communication: I2C interface

1. Power Connections: Connect the VCC pin to the power supply (3.3V or 5V) and the GND pin to the ground of your circuit.
2. I2C Communication: Connect the SDA and SCL pins to the corresponding I2C data and clock lines on your microcontroller.
3. Address Selection: The ADDR pin can be connected to GND or VCC to select between two I2C addresses. This allows for two matrices to be used on the same I2C bus.

• Ensure that the power supply voltage matches the operating voltage of the matrix.
• Limit the current to each LED to a maximum of 20mA 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 displaying static images, it's recommended to use a low duty cycle to prevent LED overheating.

#include <Wire.h>
#include <Adafruit_IS31FL3731.h>

// Create the LED driver object
Adafruit_IS31FL3731 matrix = Adafruit_IS31FL3731();

void setup() {
  Wire.begin(); // Start I2C
  matrix.begin(); // Initialize the LED matrix
}

void loop() {
  // Display a pattern on the matrix
  for (uint8_t i = 0; i < 9; i++) {
    for (uint8_t j = 0; j < 16; j++) {
      matrix.drawPixel(i, j, (i + j) % 2 ? 255 : 0); // Checkerboard pattern
    }
  }
  delay(500);
  matrix.clear(); // Clear the display
  delay(500);
}

• LEDs Not Lighting Up: Ensure that the power supply is correctly connected and within the operating voltage range. Check the I2C connections and verify that the correct I2C address is being used.
• Dim LEDs: Confirm that the current limiting resistors are appropriate and that the power supply can deliver sufficient current.
• Flickering Display: This may be due to a poor connection or insufficient power supply. Check all connections and ensure the power supply is stable.

• Double-check wiring against the pin configuration table.
• Use a multimeter to verify the voltage at the VCC pin and the continuity of the I2C lines.
• If using multiple matrices, ensure that each has a unique I2C address.
• Consult the Adafruit IS31FL3731 library documentation for additional functions and examples.

Q: Can I use more than one Charlieplex 9x16 Red matrix at a time? A: Yes, you can use two matrices on the same I2C bus by setting different addresses using the ADDR pin.

Q: How do I control individual LEDs? A: Individual LEDs can be controlled using the drawPixel function provided by the Adafruit IS31FL3731 library.

Q: What is the maximum brightness for the LEDs? A: The maximum brightness is achieved by setting the LED current to 20mA. However, for extended lifespan and reliability, it is recommended to operate at a lower current.

Q: Can I use this matrix with a 3.3V system? A: Yes, the matrix can operate at 3.3V, but ensure that the I2C logic levels are compatible with your microcontroller.