PCA9685-16-Channel 12-Bit PWM/Servo Driver——The Ultimate Guide for Makers

				
					#include "stm32f1xx_hal.h"

I2C_HandleTypeDef hi2c1;

// PCA9685 registers and constants
#define PCA9685_ADDR 0x40
#define MODE1_REG 0x00
#define MODE2_REG 0x01
#define PRESCALE_REG 0xFE
#define LED0_ON_L 0x06
#define LED0_ON_H 0x07
#define LED0_OFF_L 0x08
#define LED0_OFF_H 0x09

// 12-bit resolution (0-4095)
#define PWM_MAX 4095

void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_I2C1_Init(void);
void PCA9685_Init(void);
void PCA9685_SetPWM(int channel, int on, int off);
void PCA9685_SetRGB(int ledIndex, int r, int g, int b);
void RGBMatrix_Fade(void);

int main(void) {
  HAL_Init();
  SystemClock_Config();
  MX_GPIO_Init();
  MX_I2C1_Init();
  PCA9685_Init();

  while (1) {
    RGBMatrix_Fade();
    HAL_Delay(5000);
  }
}

void PCA9685_Init(void) {
  uint8_t buf[2];
  // Set to sleep mode to change prescale
  buf[0] = MODE1_REG;
  buf[1] = 0x10; // Sleep mode
  HAL_I2C_Master_Transmit(&hi2c1, PCA9685_ADDR, buf, 2, 100);
  // Set PWM frequency to 1000Hz (for smooth LED dimming)
  float freq = 1000.0f;
  float prescale = 25000000.0f / (4096.0f * freq) - 1.0f;
  buf[0] = PRESCALE_REG;
  buf[1] = (uint8_t)prescale;
  HAL_I2C_Master_Transmit(&hi2c1, PCA9685_ADDR, buf, 2, 100);
  // Wake up
  buf[0] = MODE1_REG;
  buf[1] = 0x00; // Normal mode
  HAL_I2C_Master_Transmit(&hi2c1, PCA9685_ADDR, buf, 2, 100);
  // Set output mode to totem pole
  buf[0] = MODE2_REG;
  buf[1] = 0x04;
  HAL_I2C_Master_Transmit(&hi2c1, PCA9685_ADDR, buf, 2, 100);
}

void PCA9685_SetPWM(int channel, int on, int off) {
  uint8_t buf[5];
  buf[0] = LED0_ON_L + 4 * channel;
  buf[1] = on & 0xFF;
  buf[2] = (on >> 8) & 0xFF;
  buf[3] = off & 0xFF;
  buf[4] = (off >> 8) & 0xFF;
  HAL_I2C_Master_Transmit(&hi2c1, PCA9685_ADDR, buf, 5, 100);
}

void PCA9685_SetRGB(int ledIndex, int r, int g, int b) {
  // Map LED index (0-15) to RGB channels
  int rCh = ledIndex + 0;
  int gCh = ledIndex + 1;
  int bCh = ledIndex + 2;
  // Ensure values are within 0-4095
  r = r < 0 ? 0 : (r > PWM_MAX ? PWM_MAX : r);
  g = g < 0 ? 0 : (g > PWM_MAX ? PWM_MAX : g);
  b = b < 0 ? 0 : (b > PWM_MAX ? PWM_MAX : b);
  // Set PWM for each color channel
  PCA9685_SetPWM(rCh, 0, r);
  PCA9685_SetPWM(gCh, 0, g);
  PCA9685_SetPWM(bCh, 0, b);
}

void RGBMatrix_Fade(void) {
  // Fade from red to green to blue
  for (int i = 0; i <= PWM_MAX; i += 10) {
    for (int led = 0; led < 16; led++) {
      PCA9685_SetRGB(led, i, PWM_MAX - i, 0);
    }
    HAL_Delay(5);
  }
  for (int i = 0; i <= PWM_MAX; i += 10) {
    for (int led = 0; led < 16; led++) {
      PCA9685_SetRGB(led, 0, i, PWM_MAX - i);
    }
    HAL_Delay(5);
  }
  for (int i = 0; i <= PWM_MAX; i += 10) {
    for (int led = 0; led < 16; led++) {
      PCA9685_SetRGB(led, PWM_MAX - i, 0, i);
    }
    HAL_Delay(5);
  }
}

// STM32 Cube-generated functions (SystemClock, I2C, GPIO)
void SystemClock_Config(void) {
  RCC_OscInitTypeDef RCC_OscInitStruct = {0};
  RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;
  RCC_OscInitStruct.HSEState = RCC_HSE_ON;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
  RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
  RCC_OscInitStruct.PLL.PLLMUL = RCC_PLL_MUL9;
  if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK) {
    Error_Handler();
  }
  RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
                              |RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2;
  RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
  RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
  RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV2;
  RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;
  if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_2) != HAL_OK) {
    Error_Handler();
  }
}

static void MX_I2C1_Init(void) {
  hi2c1.Instance = I2C1;
  hi2c1.Init.ClockSpeed = 100000;
  hi2c1.Init.DutyCycle = I2C_DUTYCYCLE_2;
  hi2c1.Init.OwnAddress1 = 0;
  hi2c1.Init.AddressingMode = I2C_ADDRESSINGMODE_7BIT;
  hi2c1.Init.DualAddressMode = I2C_DUALADDRESS_DISABLE;
  hi2c1.Init.OwnAddress2 = 0;
  hi2c1.Init.GeneralCallMode = I2C_GENERALCALL_DISABLE;
  hi2c1.Init.NoStretchMode = I2C_NOSTRETCH_DISABLE;
  if (HAL_I2C_Init(&hi2c1) != HAL_OK) {
    Error_Handler();
  }
}

static void MX_GPIO_Init(void) {
  __HAL_RCC_GPIOB_CLK_ENABLE();
}

void Error_Handler(void) {
  while(1) {
    // Blink LED on error
  }
}