Building a 4x4x4 LED Cube Controlled with STM32F401

LED cubes are an excellent way to learn about electronics, microcontroller programming, and creative visual effects. This project involves building a 4x4x4 LED matrix and controlling it with an STM32F401 microcontroller. The 4x4x4 LED cube consists of 64 LEDs arranged in 4 layers, with each layer containing 16 LEDs. Using multiplexing, we light up individual LEDs or create dynamic patterns without requiring 64 GPIO pins.

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How the 4x4x4 LED Cube Works

1. Hardware Layout:

   • The cube is structured in a grid where each LED is connected to a row and column.
   • Each layer has a common cathode, and the columns connect the anodes.

2. Multiplexing Control:

   • Only one layer is powered at a time, and the LEDs within that layer are controlled using the column connections.
   • By rapidly switching between layers (persistence of vision), we create the illusion that all LEDs are on simultaneously.

3. STM32 Control:

   • GPIO pins control the rows and columns, while timer interrupts or DMA handle multiplexing efficiently.

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Components Required

1. STM32F401 Development Board (e.g., Nucleo F401RE)
2. 64 LEDs
3. 16 Resistors (for current limiting)
4. 4 NPN transistors (for layer switching)
5. 4x4x4 LED matrix structure
6. Breadboard and wires

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Circuit Design

LED Cube Connections

• Anodes (Columns):
  Each column is connected to a GPIO pin through a current-limiting resistor.
• Cathodes (Layers):
  Each layer is connected to the collector of an NPN transistor. The transistor base is controlled by a GPIO pin through a resistor.

STM32 Connections

• Use 16 GPIO pins for columns.
• Use 4 GPIO pins for layers via transistors.
• Configure additional pins for debugging or input (optional).

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Code Implementation

STM32CubeIDE Setup

1. GPIO Configuration:

   • Set 16 pins as outputs for controlling columns.
   • Set 4 pins as outputs for layer selection (with transistors).

2. Timers:

   • Use a timer to manage layer switching (e.g., every 2 ms).

3. Interrupts or DMA:

   • For efficient LED control, use interrupts or DMA to update the column data.

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Example Code

#include "stm32f4xx_hal.h"

#define NUM_LAYERS 4
#define NUM_COLUMNS 16

uint16_t column_data[NUM_LAYERS][NUM_COLUMNS] = {
    {0x1, 0x2, 0x4, 0x8, ...}, // Pattern for Layer 0
    {0x10, 0x20, 0x40, 0x80, ...}, // Pattern for Layer 1
    ...
};

volatile uint8_t current_layer = 0;

void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef *htim) {
    if (htim->Instance == TIM3) { // Timer 3 handles multiplexing
        // Turn off all layers
        HAL_GPIO_WritePin(GPIOx, LAYER_PINS, GPIO_PIN_RESET);
        
        // Set column data for the current layer
      for (int col = 0; col < NUM_COLUMNS; col++) {

        HAL_GPIO_WritePin(GPIOx, COLUMN_PINS[col], 

        (column_data[current_layer][col]) ? GPIO_PIN_SET : GPIO_PIN_RESET);
        }
        
        // Turn on the current layer
        HAL_GPIO_WritePin(GPIOx, LAYER_PINS[current_layer], GPIO_PIN_SET);
        
        // Move to the next layer
        current_layer = (current_layer + 1) % NUM_LAYERS;
    }
}

int main(void) {
    HAL_Init();
    SystemClock_Config();
    
    // Initialize GPIO and Timer
    MX_GPIO_Init();
    MX_TIM3_Init();
    
    HAL_TIM_Base_Start_IT(&htim3); // Start timer with interrupt
    
    while (1) {
        // Main loop can be used for updating patterns or other logic
    }
}

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Pattern Generation

Patterns are defined by updating the column_data array. Examples include:

1. Static Patterns: Light up specific LEDs.
2. Dynamic Patterns: Rotate LEDs in a wave, spiral, or bounce effect.
3. 3D Animations: Create flowing shapes, letters, or symbols.

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Tools and Techniques

1. STM32CubeMX: Configure GPIO pins and timers easily.
2. HAL Library: Simplifies hardware interaction.
3. Debugging: Use a serial interface or LEDs to debug patterns.

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Videos

1. Prototype Testing Video

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Conclusion

Building a 4x4x4 LED cube using STM32F401 is a rewarding project that combines hardware design, microcontroller programming, and creative coding. With multiplexing, we efficiently control all LEDs with minimal GPIO usage, creating mesmerizing visual effects. This project is a stepping stone to creating larger LED cubes or integrating more advanced features like Bluetooth control or music synchronization.

Take the first step, and let your imagination light up!