DRIVING A LIGHT EMITTING DIODE BI-COLOUR MATRIX DISPLAY

8x8 matrix LED

There are many inexpensive 8x8 LED displays available but these usually require some additional driver software or hardware chip to make them operational. However, Adafruit has developed a range of LED displays with accompanying driver chips alongside software libraries for the Arduino.

There are many different devices supported - 8x8 single and bi-colour matrix, 4-digit 7-segment, LED bar, etc. These devices usually come as a partially assembled kit with only minor soldering required. The kit comprises the LED display, a single row header and a small PCB with a surface mounted Holtek HT16K33 chip already fitted. The interface is I2C, which means only four connections are required: 0V, +5V, clock and data. Each device has three pairs of solder pads that can be connected to set the device's address - 3 bits allows 8 devices on the same I2C bus with address 0x70 to 0x77 inclusive. Leaving a pair unconnected gives a value of 0; connected, 1.

If you choose to use the 1.2" 8x8 single colour modules, there is a labelling error on the backpack PCB and the solder pad address labels A1 and A2 are swapped.

Addressing Schema

Arduino PinLED Backpack PinI2C Name
GND1GND
+5V2+5V
A43Clock
A54Data