package com.pi4j.wiringpi;
/*
* #%L
* **********************************************************************
* ORGANIZATION : Pi4J
* PROJECT : Pi4J :: Java Library (Core)
* FILENAME : SoftPwm.java
*
* This file is part of the Pi4J project. More information about
* this project can be found here: http://www.pi4j.com/
* **********************************************************************
* %%
* Copyright (C) 2012 - 2013 Pi4J
* %%
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
* #L%
*/
import com.pi4j.util.NativeLibraryLoader;
/**
* <p>
* WiringPi includes a software-driven PWM handler capable of outputting a PWM signal on any of the
* Raspberry Pi's GPIO pins.
* </p>
*
* <p>
* There are some limitations. To maintain a low CPU usage, the minimum pulse width is 100uS. That
* combined with the default suggested range of 100 gives a PWM frequency of 100Hz. You can lower
* the range to get a higher frequency, at the expense of resolution, or increase to get more
* resolution, but that will lower the frequency. If you change the pulse-width in the drive code,
* then be aware that at delays of less than 100uS wiringPi does it in a software loop, which means
* that CPU usage will rise dramatically, and controlling more than one pin will be almost
* impossible.
* </p>
*
* <p>
* Also note that while the routines run themselves at a higher and real-time priority, Linux can
* still affect the accuracy of the generated signal.
* </p>
*
* <p>
* However, within these limitations, control of a light/LED or a motor is very achievable.
* </p>
*
* <p>
* <b> You must initialize wiringPi with one of wiringPiSetup() or wiringPiSetupGpio() functions
* beforehand. wiringPiSetupSys() is not fast enough, so you must run your programs with sudo. </b>
* </p>
*
* <p>
* Before using the Pi4J library, you need to ensure that the Java VM in configured with access to
* the following system libraries:
* <ul>
* <li>pi4j</li>
* <li>wiringPi</li>
* <li>pthread</li>
* </ul>
* <blockquote> This library depends on the wiringPi native system library.</br> (developed by
* Gordon Henderson @ <a href="https://projects.drogon.net/">https://projects.drogon.net/</a>)
* </blockquote>
* </p>
*
* @see <a href="http://www.pi4j.com/">http://www.pi4j.com/</a>
* @see <a
* href="https://projects.drogon.net/raspberry-pi/wiringpi/software-pwm-library/">https://projects.drogon.net/raspberry-pi/wiringpi/software-pwm-library/</a>
* @author Robert Savage (<a
* href="http://www.savagehomeautomation.com">http://www.savagehomeautomation.com</a>)
*/
public class SoftPwm {
// private constructor
private SoftPwm() {
// forbid object construction
}
static {
// Load the platform library
NativeLibraryLoader.load("pi4j", "libpi4j.so");
}
/**
* <p>int softPwmCreate (int pin, int initialValue, int pwmRange);</p>
*
* <p>
* This creates a software controlled PWM pin. You can use any GPIO pin and the pin numbering
* will be that of the wiringPiSetup function you used. Use 100 for the pwmRange, then the value
* can be anything from 0 (off) to 100 (fully on) for the given pin.
* </p>
*
* @see <a
* href="https://projects.drogon.net/raspberry-pi/wiringpi/software-pwm-library/">https://projects.drogon.net/raspberry-pi/wiringpi/software-pwm-library/</a>
*
* @param pin The GPIO pin to use as a PWM pin.
* </p>
* @param value The value to initialize the PWM pin (between 0 <i>(off)</i> to 100 <i>(fully
* on)</i>)
* @param range The maximum range. Use 100 for the pwmRange.
* @return The return value is 0 for success. Anything else and you should check the global
* errno variable to see what went wrong.
*/
public static native int softPwmCreate(int pin, int value, int range);
/**
* <p>void softPwmWrite (int pin, int value);</p>
*
* <p>
* This updates the PWM value on the given pin. The value is checked to be in-range and pins
* that haven't previously been initialized via softPwmCreate will be silently ignored.
* </p>
*
* @see <a
* href="https://projects.drogon.net/raspberry-pi/wiringpi/software-pwm-library/">https://projects.drogon.net/raspberry-pi/wiringpi/software-pwm-library/</a>
* @param pin The GPIO pin to use as a PWM pin.
* @param value The value to initialize the PWM pin (between 0 <i>(off)</i> to 100 <i>(fully
* on)</i>)
*/
public static native void softPwmWrite(int pin, int value);
}