PCA9685

A library for using PCA9685 on linux via /dev/i2c-N. Does what it says on the tin, extremely simple API (looking to add a bit more functionality soon).

API documentation

Method documentation

• PCA9685::PCA9685: takes the address and bus number of the i2c device. For a PCA9685 on bus 0 and at the default address 0x40 use PCA9685::PCA9685(0x40, 0)
• PCA9685::init: call to acquire the i2c device and initialize the PCA9685. Seperate function call so you can construct the object statically and initialize it at a different time
• PCA9685::setPWM: set the PWM timings for channel channel. on and off are times at which the signal is high or low respectively.

PWM information

The PCA9685's prescaler is set to a constant of 11 in this library, corresponding to 500hz. Since the PCA9685 is a 12bit device, on and off times are between 0-4096. The following simple code can be used to make setting servo pulse widths easier (in 1us increments):

void setServo(int channel, int pulse) {
    int pulse_length = 1000000 / 500 / 4096;
    int pulse2 = pulse * 1000;
    pulse2 /= pulse_length;
    pca9685.setPWM(channel, 0, pulse2);
}

Including in your projects

Using this in non-ros/non-catkin environments is a use case that is coming soon, but if you are already using ros, simply add this package to your repository! This task is simple with wstool, so use that. After doing that, the headers for using this library are located at <PCA9685/PCA9685.h>. Happy tinkering!