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PCA9685 I2C 16-channel PWM/servo driver Node.js module
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README.md

PCA9685 I2C 16-channel PWM/servo driver module

NPM version

This is an npm module that can interact with the PCA9685 I2C 16-channel PWM/servo driver. Information on the PCA9685 can be found here and it is available for purchase at Adafruit.

Usage

var i2cBus = require("i2c-bus");
var Pca9685Driver = require("pca9685").Pca9685Driver;

var options = {
    i2c: i2cBus.openSync(1),
    address: 0x40,
    frequency: 50,
    debug: false
};
pwm = new Pca9685Driver(options, function(err) {
    if (err) {
        console.error("Error initializing PCA9685");
        process.exit(-1);
    }
    console.log("Initialization done");

    // Set channel 0 to turn on on step 42 and off on step 255
    // (with optional callback)
    pwm.setPulseRange(0, 42, 255, function() {
        if (err) {
            console.error("Error setting pulse range.");
        } else {
            console.log("Pulse range set.");
        }
    });

    // Set the pulse length to 1500 microseconds for channel 2
    pwm.setPulseLength(2, 1500);

    // Set the duty cycle to 25% for channel 8
    pwm.setDutyCycle(8, 0.25);

    // Turn off all power to channel 6
    // (with optional callback)
    pwm.channelOff(6, function() {
        if (err) {
            console.error("Error turning off channel.");
        } else {
            console.log("Channel 6 is off.");
        }
    });

    // Turn on channel 3 (100% power)
    pwm.channelOn(3);
});

Note that you need to construct the i2c-bus object and pass it in to the module along with the I2C address of the PCA9685 PWM/servo driver.

Options

  • i2c: The I2cBus object used to communicate to the PWM/servo driver.
  • address: The I2C address of the PCA9685 PWM/servo driver.
  • frequency: The frequency to use for the PWM/servo driver. 50 is standard for servos, but higher frequencies might work better for driving LEDs without obvious flicker.
  • debug: If truthy, then debug messages will be printed on the console during operations.

Debugging

This project uses the debug library for debugging. This allows you to enable debugging using environment variables or in code before constructing the Pca9685Driver object. The name of the debugging stream produced by the library is pca9685.See the debug library documentation for more information.

TypeScript

This project is written in TypeScript. The library can be used by plain JavaScript as shown above, and the typing information is also included with the library so that anyone wishing to use Typescript will gain the benefits of the type information.

Acknowledgements

This module was based on Adafruit's Raspberry-Pi Python Code Library and the adafruit-i2c-pwm-driver NPM module.

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