PCA9685 PWM Controller

PHP Class to enable control of the Adafruit PCA9685 16-channel PWM/Servo I2C Interface

I wrote this to allow me to control the Adafruit PCA9685 PWM board to do some custom LED lighting in my living room. The only code I could find for this was in Python. I've been a PHP developer for nearly 20 years, so I naturally wanted to code in something I was more comfortable with.

It took a lot of reading and piecing together a way to get this working including reviewing quite a bit of the 52-page datasheet for the PCA9685 chip (linked below). In the end, it was worth it as I can now control all the channels of this great little board from a web page on any device in the house.

As much trouble as I had, I figured others might have the same issues. I decided I'd put the code together as a Composer package and make it available on Packagist. I hope it helps somebody else.

Requirements

I'm not going to show how you can get PHP7 & Nginx running on your Raspberry Pi, there are lots of other resources for that kind of thing.

This code does require that you have already enabled I2C support and installed the i2c-tools.

For my new (purchased Jan 2017) Raspberry Pi 3, this was easy as I only had to edit the /boot/config.txt file and uncomment the dtparam=i2c_arm=on line and reboot.

Then I installed the I2C tools:

sudo apt-get install -y python-smbus
sudo apt-get install -y i2c-tools

You can read up a bit more here: https://learn.adafruit.com/adafruits-raspberry-pi-lesson-4-gpio-setup/configuring-i2c

Resources

Interface board can be purchased directly from Adafruit here:

https://www.adafruit.com/product/815

Datasheet for the PCA9685:

https://cdn-shop.adafruit.com/datasheets/PCA9685.pdf

Installation

Installation is best accomplished with Composer (https://getcomposer.org/)

composer require "phpdreams/pca9685":"dev-master"

Usage

require_once(__DIR__ . '/vendor/autoload.php');

use PHPDreams\PCA9685\PCA9685;

$pwm = new PCA9685();

I've setup two ways to set the PWM level of any given channel. You can do it by percent or by setting the on and off points.

Set Channel Output by Percent:

$pwm->setPWMpercent($channel, $percent);

Channel is a number from 0 to 15.

Manually setting the on and off points:

$pwm->setPWM($channel, $countOff, $countOn = 0);

You can set the on and off points in the 4096-count cycle. So setting a channel to turn off at at 2048 would be a 50% duty cycle.

If you don't set an 'On' point, it will default to 0.

Set ALL channels to a value:

$pwm->setAll($channel, $countOff, $countOn = 0);

Set refresh frequency in Hz:

$pwm->setFrequency($frequency);

Defaults to 200Hz refresh.