PCA9685

The PCA9685 is an I2C-bus controlled 16-channel LED controller optimized for LCD
Red/Green/Blue/Amber (RGBA) color backlighting applications. Each LED output has its
own 12-bit resolution (4096 steps) fixed frequency individual PWM controller that operates
at a programmable frequency from a typical of 40 Hz to 1000 Hz with a duty cycle that is
adjustable from 0 % to 100 % to allow the LED to be set to a specific brightness value.
All outputs are set to the same PWM frequency.

begin() init() setLEDDimmed() sample code 如下: PCA9685 ledDriver; void setup() { Serial.begin(9600); // set up serial Serial.println("Serial Started"); Wire.begin(); // Wire must be started! ledDriver.begin(B111000); // Address pins A5-A0 set to B111000 ledDriver.init(); } void loop() { // Notice: setLEDDimmed cannot be used in a loop to give you a pleasant // "turning-up" of the LED. This is because each time you set a level for a LED // it will calculate random timing intervals for the PWM function in the chip // This is done in order to distribute current consumptions of the full time period. for(int level=5;level>=0;level--) { for(int i=0; i<16; i++) { ledDriver.setLEDDimmed(i,level*20); delay(100); } } for(int level=0;level<=5;level++) { for(int i=0; i<16; i++) { ledDriver.setLEDDimmed(i,level*20); delay(100); } } } //Register defines from data sheet
	#define PCA9685_MODE1 0x00 // location for Mode1 register address
	#define PCA9685_MODE2 0x01 // location for Mode2 reigster address
	#define PCA9685_LED0 0x06 // location for start of LED0 registers
	#define PCA9685_I2C_BASE_ADDRESS B1000000
	class PCA9685
	{
	public:
	//NB the i2c address here is the value of the A0, A1, A2, A3, A4 and A5 pins ONLY
	//as the class takes care of its internal base address.
	//so i2cAddress should be between 0 and 63
	PCA9685();
	void begin(int i2cAddress);
	bool init();
	void setLEDOn(int ledNumber);
	void setLEDOff(int ledNumber);
	void setLEDDimmed(int ledNumber, byte amount);
	void writeLED(int ledNumber, word outputStart, word outputEnd);
	private:
	void writeRegister(int regaddress, byte val);
	word readRegister(int regAddress);
	// Our actual i2c address:
	byte _i2cAddress;
	};

#include "PCA9685.h"
	PCA9685::PCA9685() {}
	void PCA9685::begin(int i2cAddress) {
	_i2cAddress = PCA9685_I2C_BASE_ADDRESS | (i2cAddress & B00111111);
	}
	bool PCA9685::init() {
	delay(1);
	writeRegister(PCA9685_MODE1, (byte)0x01); // reset the device
	delay(1);
	bool isOnline;
	if (readRegister(PCA9685_MODE1)==0x01) {
	isOnline = true;
	} else {
	isOnline = false;
	}
	writeRegister(PCA9685_MODE1, (byte)B10100000); // set up for auto increment
	writeRegister(PCA9685_MODE2, (byte)0x10); // set to output
	return isOnline;
	}
	void PCA9685::setLEDOn(int ledNumber) {
	writeLED(ledNumber, 0x1000, 0);
	}
	void PCA9685::setLEDOff(int ledNumber) {
	writeLED(ledNumber, 0, 0x1000);
	}
	void PCA9685::setLEDDimmed(int ledNumber, byte amount) { // Amount from 0-100 (off-on)
	if (amount==0) {
	setLEDOff(ledNumber);
	} else if (amount>=100) {
	setLEDOn(ledNumber);
	} else {
	int randNumber = (int)random(4096); // Randomize the phaseshift to distribute load. Good idea? Hope so.
	writeLED(ledNumber, randNumber, (int)(amount*41+randNumber) & 0xFFF);
	}
	}
	void PCA9685::writeLED(int ledNumber, word LED_ON, word LED_OFF) { // LED_ON and LED_OFF are 12bit values (0-4095); ledNumber is 0-15
	if (ledNumber >=0 && ledNumber <= 15) {
	Wire.beginTransmission(_i2cAddress);
	Wire.write(PCA9685_LED0 + 4*ledNumber);
	Wire.write(lowByte(LED_ON));
	Wire.write(highByte(LED_ON));
	Wire.write(lowByte(LED_OFF));
	Wire.write(highByte(LED_OFF));
	Wire.endTransmission();
	}
	}
	//PRIVATE
	void PCA9685::writeRegister(int regAddress, byte data) {
	Wire.beginTransmission(_i2cAddress);
	Wire.write(regAddress);
	Wire.write(data);
	Wire.endTransmission();
	}
	word PCA9685::readRegister(int regAddress) {
	word returnword = 0x00;
	Wire.beginTransmission(_i2cAddress);
	Wire.write(regAddress);
	Wire.endTransmission();
	Wire.requestFrom((int)_i2cAddress, 1);
	// int c=0;
	//Wait for our 2 bytes to become available
	while (Wire.available()) {
	//high byte
	// if (c==0) { returnword = Wire.read() << 8; }
	//low byte
	// if (c==1) {
	returnword |= Wire.read();
	//}
	//c++;
	}
	return returnword;
	}

Reference https://github.com/kasperskaarhoj/PCA9685-Arduino-Library