stm32f407 iic 9685驱动16通道PWM的代码

以下是使用STM32F407和I2C驱动PCA9685的16通道PWM的基本代码：

#include "stm32f4xx.h"
#include "i2c.h"

#define PCA9685_ADDRESS 0x40

#define MODE1          0x00
#define MODE2          0x01
#define PRESCALE       0xFE
#define LED0_ON_L      0x06

#define ENABLE_AUTO_INC 0x20
#define SLEEP           0x10
#define ALLCALL         0x01

#define PWM_FREQ 50

#define MIN_PULSE_WIDTH 64
#define MAX_PULSE_WIDTH 4096

void PCA9685_init(void);
void PCA9685_setPWM(uint8_t num, uint16_t on, uint16_t off);
void PCA9685_setServoPulse(uint8_t num, double pulse);

int main(void)
{
    SystemInit();
    I2C_init();
    PCA9685_init();

    while(1)
    {
        // set servo position to 0 degrees
        PCA9685_setServoPulse(0, 500);
        // wait for 1 second
        for(uint32_t i = 0; i < 10000000; i++);
        // set servo position to 90 degrees
        PCA9685_setServoPulse(0, 1500);
        // wait for 1 second
        for(uint32_t i = 0; i < 10000000; i++);
        // set servo position to 180 degrees
        PCA9685_setServoPulse(0, 2500);
        // wait for 1 second
        for(uint32_t i = 0; i < 10000000; i++);
    }
}

void PCA9685_init(void)
{
    I2C_start();
    I2C_write(PCA9685_ADDRESS << 1);
    I2C_write(MODE1);
    I2C_write(ENABLE_AUTO_INC | ALLCALL);
    I2C_stop();

    I2C_start();
    I2C_write(PCA9685_ADDRESS << 1);
    I2C_write(MODE2);
    I2C_write(SLEEP);
    I2C_stop();

    uint8_t prescale = (uint8_t)((25000000 / (4096 * PWM_FREQ)) - 1);

    I2C_start();
    I2C_write(PCA9685_ADDRESS << 1);
    I2C_write(PRESCALE);
    I2C_write(prescale);
    I2C_stop();

    I2C_start();
    I2C_write(PCA9685_ADDRESS << 1);
    I2C_write(MODE1);
    I2C_write(ALLCALL);
    I2C_stop();

    for(uint8_t i = 0; i < 16; i++)
    {
        PCA9685_setPWM(i, 0, 0);
    }
}

void PCA9685_setPWM(uint8_t num, uint16_t on, uint16_t off)
{
    I2C_start();
    I2C_write(PCA9685_ADDRESS << 1);
    I2C_write(LED0_ON_L + (4 * num));
    I2C_write(on & 0xFF);
    I2C_write(on >> 8);
    I2C_write(off & 0xFF);
    I2C_write(off >> 8);
    I2C_stop();
}

void PCA9685_setServoPulse(uint8_t num, double pulse)
{
    pulse = (pulse < MIN_PULSE_WIDTH) ? MIN_PULSE_WIDTH : pulse;
    pulse = (pulse > MAX_PULSE_WIDTH) ? MAX_PULSE_WIDTH : pulse;

    uint16_t value = (uint16_t)(pulse * 4096 / 20000);

    PCA9685_setPWM(num, 0, value);
}

需要注意的是，上述代码中的`I2C_init()`和`I2C_start()`等函数都需要根据具体的硬件平台和I2C驱动程序进行修改。此外，代码中使用的PWM频率为50Hz，可根据需要进行修改。另外，`PCA9685_setServoPulse()`函数用于设置舵机的位置，可根据具体的舵机型号进行修改。