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PWM.java
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/* -*- mode: java; c-basic-offset: 2; indent-tabs-mode: nil -*- */
/*
Copyright (c) The Processing Foundation 2015
Hardware I/O library developed by Gottfried Haider as part of GSoC 2015
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General
Public License along with this library; if not, write to the
Free Software Foundation, Inc., 59 Temple Place, Suite 330,
Boston, MA 02111-1307 USA
*/
package processing.io;
import processing.io.NativeInterface;
import java.io.File;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.Arrays;
/**
* @webref
*/
public class PWM {
int channel;
String chip;
/**
* Opens a PWM channel
* @param channel PWM channel
* @see list
* @webref
*/
public PWM(String channel) {
NativeInterface.loadLibrary();
int pos = channel.indexOf("/pwm");
if (pos == -1) {
throw new IllegalArgumentException("Unsupported channel");
}
chip = channel.substring(0, pos);
this.channel = Integer.parseInt(channel.substring(pos+4));
if (NativeInterface.isSimulated()) {
return;
}
// export channel through sysfs
String fn = "/sys/class/pwm/" + chip + "/export";
int ret = NativeInterface.writeFile(fn, Integer.toString(this.channel));
if (ret < 0) {
if (ret == -2) { // ENOENT
System.err.println("Make sure your kernel is compiled with PWM_SYSFS enabled and you have the necessary PWM driver for your platform");
}
// XXX: check
if (ret == -22) { // EINVAL
System.err.println("PWM channel " + channel + " does not seem to be available on your platform");
}
// XXX: check
if (ret != -16) { // EBUSY, returned when the pin is already exported
throw new RuntimeException(fn + ": " + NativeInterface.getError(ret));
}
}
// delay to give udev a chance to change the file permissions behind our back
// there should really be a cleaner way for this
try {
Thread.sleep(500);
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
}
}
/**
* Disables the PWM output
* @webref
*/
public void clear() {
if (NativeInterface.isSimulated()) {
return;
}
String fn = String.format("/sys/class/pwm/%s/pwm%d/enable", chip, channel);
int ret = NativeInterface.writeFile(fn, "0");
if (ret < 0) {
throw new RuntimeException(NativeInterface.getError(ret));
}
}
/**
* Gives ownership of a channel back to the operating system
* @webref
*/
public void close() {
if (NativeInterface.isSimulated()) {
return;
}
// XXX: implicit clear()?
// XXX: also check GPIO
String fn = "/sys/class/pwm/" + chip + "/unexport";
int ret = NativeInterface.writeFile(fn, Integer.toString(channel));
if (ret < 0) {
if (ret == -2) { // ENOENT
System.err.println("Make sure your kernel is compiled with PWM_SYSFS enabled and you have the necessary PWM driver for your platform");
}
// XXX: check
// EINVAL is also returned when trying to unexport pins that weren't exported to begin with
throw new RuntimeException(NativeInterface.getError(ret));
}
}
/**
* Lists all available PWM channels
* @return String array
* @webref
*/
public static String[] list() {
if (NativeInterface.isSimulated()) {
return new String[]{ "pwmchip0/pwm0", "pwmchip0/pwm1" };
}
ArrayList<String> devs = new ArrayList<String>();
File dir = new File("/sys/class/pwm");
File[] chips = dir.listFiles();
if (chips != null) {
for (File chip : chips) {
// get the number of supported channels
try {
Path path = Paths.get("/sys/class/pwm/" + chip.getName() + "/npwm");
String tmp = new String(Files.readAllBytes(path));
int npwm = Integer.parseInt(tmp.trim());
for (int i=0; i < npwm; i++) {
devs.add(chip.getName() + "/pwm" + i);
}
} catch (Exception e) {
}
}
}
// listFiles() does not guarantee ordering
String[] tmp = devs.toArray(new String[devs.size()]);
Arrays.sort(tmp);
return tmp;
}
/**
* Enables the PWM output
* @param period cycle period in Hz
* @param duty duty cycle, 0.0 (always off) to 1.0 (always on)
* @webref
*/
public void set(int period, float duty) {
if (NativeInterface.isSimulated()) {
return;
}
// set period
String fn = fn = String.format("/sys/class/pwm/%s/pwm%d/period", chip, channel);
// convert to nanoseconds
int ret = NativeInterface.writeFile(fn, String.format("%d", (int)(1000000000 / period)));
if (ret < 0) {
throw new RuntimeException(fn + ": " + NativeInterface.getError(ret));
}
// set duty cycle
fn = fn = String.format("/sys/class/pwm/%s/pwm%d/duty_cycle", chip, channel);
if (duty < 0.0 || 1.0 < duty) {
System.err.println("Duty cycle must be between 0.0 and 1.0.");
throw new IllegalArgumentException("Illegal argument");
}
// convert to nanoseconds
ret = NativeInterface.writeFile(fn, String.format("%d", (int)((1000000000 * duty) / period)));
if (ret < 0) {
throw new RuntimeException(fn + ": " + NativeInterface.getError(ret));
}
// enable output
fn = String.format("/sys/class/pwm/%s/pwm%d/enable", chip, channel);
ret = NativeInterface.writeFile(fn, "1");
if (ret < 0) {
throw new RuntimeException(fn + ": " + NativeInterface.getError(ret));
}
}
/**
* Enables the PWM output with a preset period of 1 kHz
* @webref
*/
public void set(float duty) {
set(1000, duty);
}
}