PWM

Pulse-width modulation (PWM), or pulse-duration modulation (PDM), is a modulation technique used to encode a message into a pulsing signal.

Using a PWM Interface in Driver

Configuring driver.json

To use a PWM interface in a driver, you need to have an input with type "pwm" in the driver.json:

{
    "models": [],
    "inputs": {
        "pwm": {
            "type": "pwm",
            "args": {
                "frequency": 200
            }
        }
    }
}

In the JSON configuration above, the first "pwm" is just the name of the PWM interface (you can change it to something else if you want to),
which will be used as the key to get the interface instance in the driver.
And the "type": "pwm" informs Ruff framework to distribute an PWM interface instead of others.

Arguments

frequency

The frequency of output square wave, defaults to 200.

PWM interfaces may share the same frequency due to hardware limitations,
You might get errors if you are trying to get PWM interfaces with different frequencies.

Writing a Driver

'use strict';

var driver = require('ruff-driver');

module.exports = driver({
    attach: function (inputs) {
        this._pwm = inputs['pwm'];
    },
    exports: {
        setHalfDuty: function (callback) {
            this._pwm.setDuty(0.5, callback);
        }
    }
});

API References

Methods

setDuty(duty[, callback])

Ruff available: v1.6.0
Ruff Lite available: v0.6.0

Set the duty ratio (0~1) of the interface.

setFrequency(frequency[, callback])

Ruff available: v1.6.0
Ruff Lite available: v0.6.0

Set the frequency of the interface, please refer to argument frequency for limitations.

getDuty(callback)

Ruff available: v1.6.0
Ruff Lite available: v0.6.0

callback - function(error, duty)

Get the duty of the interface.

getFrequency(callback)

Ruff available: v1.6.0
Ruff Lite available: v0.6.0

callback - function(error, frequency)

Get the frequency of the interface.