How to Use PCA9865: Examples, Pinouts, and Specs

The PCA9685 is a 16-channel I2C bus LED driver with an integrated PWM (Pulse Width Modulation) controller. Manufactured by NXP Semiconductors, this component is designed to provide precise control of LED brightness and color mixing. It is widely used in applications such as LED displays, RGB lighting systems, robotics (e.g., servo motor control), and other projects requiring multiple PWM outputs.

The PCA9685 simplifies the process of controlling multiple LEDs or servos by offloading the PWM generation from the microcontroller, freeing up resources for other tasks. It supports a wide range of operating voltages and is compatible with popular microcontrollers like Arduino, Raspberry Pi, and others.

The PCA9685 has the following key technical specifications:

• Operating Voltage (Vcc): 2.3V to 5.5V
• Logic Voltage Levels: Compatible with 3.3V and 5V logic
• PWM Resolution: 12-bit (4096 steps)
• Number of Channels: 16 independent PWM outputs
• PWM Frequency Range: Adjustable from 24 Hz to 1526 Hz
• I2C Address Range: Configurable via 6 address pins (up to 62 devices on the same bus)
• Maximum Output Current per Channel: 25 mA (sink) or 10 mA (source)
• Operating Temperature Range: -40°C to +85°C
• Package Type: TSSOP-28

The PCA9685 comes in a 28-pin TSSOP package. Below is the pin configuration:

1. Power Supply:

   • Connect the VCC pin to a 3.3V or 5V power source, depending on your system.
   • Connect the GND pin to the ground of your circuit.

2. I2C Communication:

   • Connect the SDA and SCL pins to the corresponding I2C pins on your microcontroller.
   • Use pull-up resistors (typically 4.7kΩ) on the SDA and SCL lines if not already present.

3. Address Configuration:

   • Use the A0-A5 pins to set the I2C address of the PCA9685. Each pin can be connected to VCC (logic high) or GND (logic low) to configure the address.

4. PWM Outputs:

   • Connect LEDs, servos, or other devices to the LED0-LED15 pins. Ensure that the current draw does not exceed the maximum ratings.

5. External Clock (Optional):

   • If a custom PWM frequency is required, connect an external clock signal to the EXTCLK pin.

Below is an example of how to control the PCA9685 using an Arduino UNO to dim an LED connected to channel 0.

• Connect VCC to the Arduino's 5V pin.
• Connect GND to the Arduino's GND pin.
• Connect SDA to the Arduino's A4 pin.
• Connect SCL to the Arduino's A5 pin.
• Connect an LED (with a current-limiting resistor) to the LED0 pin.

#include <Wire.h>
#include <Adafruit_PWMServoDriver.h>

// Create an instance of the PCA9685 driver
Adafruit_PWMServoDriver pwm = Adafruit_PWMServoDriver();

void setup() {
  // Initialize I2C communication
  Wire.begin();
  
  // Initialize the PCA9685 with the default I2C address (0x40)
  pwm.begin();
  
  // Set the PWM frequency to 1000 Hz
  pwm.setPWMFreq(1000);
}

void loop() {
  // Gradually increase brightness on channel 0
  for (int i = 0; i < 4096; i++) {
    pwm.setPWM(0, 0, i); // Set PWM value for channel 0
    delay(1);            // Small delay for smooth dimming
  }

  // Gradually decrease brightness on channel 0
  for (int i = 4095; i >= 0; i--) {
    pwm.setPWM(0, 0, i); // Set PWM value for channel 0
    delay(1);            // Small delay for smooth dimming
  }
}

• Power Supply: Ensure that the power supply can handle the total current draw of all connected devices.
• I2C Pull-Up Resistors: Verify that pull-up resistors are present on the SDA and SCL lines to ensure reliable communication.
• PWM Frequency: Choose an appropriate PWM frequency for your application. For servos, a frequency of 50 Hz is typical.
• Output Enable (OE): Use the OE pin to disable all outputs when needed (e.g., during system initialization).

1. No Response from PCA9685:

   • Check the I2C connections (SDA, SCL) and ensure pull-up resistors are present.
   • Verify the I2C address configuration (A0-A5 pins).

2. LEDs Not Lighting Up:

   • Ensure the LEDs are connected with the correct polarity.
   • Check the current-limiting resistors and ensure they are appropriate for the LEDs.

3. PWM Output is Erratic:

   • Verify that the power supply is stable and sufficient for the load.
   • Check for noise or interference on the I2C lines.

Q: Can the PCA9685 control servos?
A: Yes, the PCA9685 is commonly used to control servos. Set the PWM frequency to 50 Hz and adjust the duty cycle to control the servo position.

Q: How many PCA9685 modules can I connect to a single I2C bus?
A: Up to 62 PCA9685 modules can be connected to a single I2C bus by configuring the A0-A5 address pins.

Q: Can I use an external clock with the PCA9685?
A: Yes, you can connect an external clock signal to the EXTCLK pin to set a custom PWM frequency.

Q: Is the PCA9685 compatible with 3.3V microcontrollers?
A: Yes, the PCA9685 is compatible with both 3.3V and 5V logic levels.