LED Matrix Demo

This project demonstrates how to use a 32×8 LED matrix display. The display comprises four connected 8×8 panels, each of which is powered by a MAX7219 chip:

Front and rear view of LED matrix

The matrix is controlled via an SPI interface. It has the following pins: CLK, CS, DIN, GND & VCC. 5V is required to operate the matrix. In this demo an Arduino Uno clone is used to control the matrix. A separate power supply is used to power the matrix to avoid overloading the Uno's built in power source.

A breadboard was used to connect the Uno to the LED matrix as shown below:

Breadboard circuit with Uno and LED matrix

Power from my bench power supply comes from the left and is connected to the breadboard via crocodile clips. A second pair of smaller crocodile clips connects the power to the LED matrix. Note the electrolytic capacitor across the power rails to smooth the power. I think the capacitor should be between 470μF and 1000μF.

The Uno is powered via its USB connection:

Arudino pin	Attached to
GND	Ground rail of the breadboard and from there to the GND pin of the LED matrix and the power supply ground.
10 (SPI CS)	LED matrix CS pin.
11 (SPI COPI)	LED matrix DIN pin.
13 (SPI SCK)	LED matrix CLK pin.

Additionally, the matrix's VCC pin is connected to the breadboard's 5V rail.

The demo source code is available from the cahamo/demo-projects repository on GitHub. The relevant code will be found in the max7219-led-matrix--uno directory. All the C++ code is in max7219-led-matrix--uno/src/main.cpp.

This demo is a PlatformIO project for use with Visual Studio Code. It can be modified for use with the Arduino IDE simply by copying the code from max7219-led-matrix--uno/src/main.cpp into a new, blank Arduino API project and ensure that the MD_MAX72XX and MD_Parola libraries by MajicDesigns are installed.

Once the code is compiled and uploaded to the Uno and the external power supply is switched on you should see the text <Hello> begin to scroll quickly down the display before pausing a while and then scrolling again. You can see the demo running in the following video.