MAX7219_library

Library for control of an 8x8 LED matrix driven by MAX7219 display driver (Fig. 1). Tested on Arduino Uno, Arduino Nano and STM32 NUCLEO-F446RE development boards. This library was written with the intention to be used for a microcontroller based gaming console.

Fig. 1. MAX7219 display driver chip with an 8x8 LED matrix.

Features

• Easy driver configuration with dedicated functions, normal operation can be initialized with a single function.
• Arduino library features software implemented SPI protocol which allows unconstrained selection of CS, CLK and DATA pins.
• STM32 library features hardware implemented SPI protocol which does not allow arbitrary selection of CLK and DATA pins.
• Each LED is controlled individually.

Functions

• void init();
• void clear();
• void sendData(uint8_t reg_address, uint8_t data);
• void switchLED(uint8_t column, uint8_t row, uint8_t data);

Installation

Arduino

Arduino IDE

1. Download and extract the library ZIP file.
2. Place the MAX7219_Arduino folder in the Arduino libraries folder (example: C:\Users\Darius\Documents\Arduino\libraries).
3. Launch Arduino IDE and open the example sketch for testing (File > Examples > MAX7219_Arduino > fill_screen).

PlatformIO

1. Download and extract the library ZIP file.
2. Create a Platform IO project.
3. Place the MAX7219_Arduino folder in the lib folder inside the project directory.
4. Copy and paste the example code (fill_screen.ino) to main.cpp in src folder.
5. Compile and upload the code.

STM32

To use MAX7219 display driver with STM32 microcontroller you will also need a logic level converter. The logic high level for the driver should be at least 3.5 V which is not low enough to be reliably controlled by the STM32.

STM32CubeIDE

1. Download and extract the library ZIP file.
2. Launch STM32CubeIDE and create a workspace where you like.
3. Place the MAX7219_STM32 folder in the created workspace directory.
4. In STM32CubeIDE close the Information center window and go to File > Import > General > Existing Projects into Workspace.
5. Select the imported folder as the root directory.
6. (Optional) View the MAX7219.h and MAX7219.cpp files in Core > Inc and Core > Src folders respectively, as well as the main.cpp file.
7. Compile and upload the code.

This library was tested using the STM32 NUCLEO-F446RE development board. In the case of another board or some unexpected errors due to different software version here is what to do:

1. In STM32CubeIDE create a new project and go through the usual setup of the development board.
2. In the .ioc file set up the SPI protocol the way that its shown in Fig. 2.

Fig. 2. SPI configuration.

3. Place the MAX7219.h and MAX7219.cpp files in Core > Inc and Core > Src folders respectively.
4. In the main.c file add lines of code shown below.

#include "MAX7219.h"
MAX7219 matrix(&hspi1);
int main(void){
	matrix.init();
	while (1){
		for(uint8_t intensity=0;intensity<=15;intensity++){
			matrix.sendData(intensity_reg_addr, intensity);
			for(uint8_t i=0;i<8;i++){
				for(uint8_t j=0;j<8;j++){
					matrix.switchLED(i,j,1);
					HAL_Delay(50);
				}
			}
			matrix.clear();
		}
	}
}

5. Compile and upload code.