OrangePi通过sysfs控制GPIO接口
什么是sysfs
Sysfs 是 Linux 2.6 所提供的一种虚拟文件系统。这个文件系统不仅可以把设备
（devices）和驱动程序(drivers) 的信息从内核输出到 用户空间，也可以用来对设备和驱
动程序做设置。
sysfs 的目的是把一些原本在 procfs 中的，关于设备的部份，独立出来，以‘设备层次结构
架构’（device tree）的形式呈现。这个文件系统由 Patrick Mochel 所写，稍后
Maneesh Soni 撰写 "sysfs backing store path"，以降低在大型系统中对存储器的需
求量。
使用的硬件
这里使用的是Orange Pi One，有40Pin的扩展接口，类似树莓派，使用方法也类似。
系统是使用的安卓4.4
导出Gpio接口：
echo XX > /sys/class/gpio/export（其中XX为你要导出的GPIO引脚编号，后面会说到引脚编号计算方法）
如果成功的话，这一步会在/sys/class/gpio目录下生成 /sys/class/gpio/gpioXX
设定IO方向：
echo "out" > /sys/class/gpio/gpioXX/direction（输出）
echo "in" > /sys/class/gpio/gpioXX/direction（输入）
设定输出值：
echo 1 > /sys/class/gpio/gpioXX/value
echo 0 > /sys/class/gpio/gpioXX/value
或者：
echo "high" > /sys/class/gpio/gpioXX/direction（输出，同时置高）
echo "low" > /sys/class/gpio/gpioXX/direction（输出，同时置低）
取消导出：
echo XX > /sys/class/gpio/unexport
引脚映射计算
Orange Pi One 外设的GPIO如下：
计算公式：
(P后面的字母在字母表中的位置 - 1) * 32 + 后面的数字
例如：
PA0计算得到：0 ------>(1-1)*32+0
PA1计算得到：1 ------->(1-1)*32+1
PA15计算得到：15 ------->(1-1)*32+15
PD14计算得到：110 ------->(4-1)*32+14
PC1计算得到：65 ------->(3-1)*32+1
在Java层控制
package com.donute.robot.entities;
import com.donute.robot.utils.ShellUtils;
/**
* Created by zhouyufei on 2017/1/4.
*/
public class Gpio {
public static final int HIGH=1;
public static final int LOW=0;
public static final String IN="in";
public static final String OUT="out";
public static final String DISABLE="disable";
private String path;
private String direction=DISABLE;
private int number;
public Gpio(int number) {
this.number = number;
ShellUtils.execCommand("echo "+number+" > /sys/class/gpio/export",true);
path="/sys/class/gpio/gpio"+number;
}
public Gpio openAsOut(){
direction=OUT;
ShellUtils.execCommand("echo "+direction+" > "+path+"/direction",true);
return this;
}
public Gpio openAsIn(){
direction=IN;
ShellUtils.execCommand("echo "+direction+" > "+path+"/direction",true);
return this;
}
public Gpio close(){
direction=DISABLE;
ShellUtils.execCommand("echo "+number+" > /sys/class/gpio/unexport",true);
return this;
}
public void write(int value){
ShellUtils.execCommand("echo "+value+" > "+path+"/value",true);
}
public int read(){
ShellUtils.CommandResult result=ShellUtils.execCommand("cat "+path+"/value",true,true);
if (result.result==0){
try{
return Integer.parseInt(result.successMsg);
}catch (Exception e){
return -1;
}
}else {
return -1;
}
}
public String getDirection() {
return direction;
}
public int getNumber() {
return number;
}
}
ShellUtil代码
package com.donute.robot.utils;
/**
* Created by zhouyufei on 16/7/31.
*/
import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.List;
/**
* ShellUtils
* <ul>
* <strong>Check root</strong>
* <li>{@link ShellUtils#checkRootPermission()}</li>
* </ul>
* <ul>
* <strong>Execte command</strong>
* <li>{@link ShellUtils#execCommand(String, boolean)}</li>
* <li>{@link ShellUtils#execCommand(String, boolean, boolean)}</li>
* <li>{@link ShellUtils#execCommand(List, boolean)}</li>
* <li>{@link ShellUtils#execCommand(List, boolean, boolean)}</li>
* <li>{@link ShellUtils#execCommand(String[], boolean)}</li>
* <li>{@link ShellUtils#execCommand(String[], boolean, boolean)}</li>
* </ul>
*
* @author <a href="http://www.trinea.cn" target="_blank">Trinea</a> 2013-5-16
*/
public class ShellUtils {
public static final String COMMAND_SU = "su";
public static final String COMMAND_SH = "sh";
public static final String COMMAND_EXIT = "exit\n";
public static final String COMMAND_LINE_END = "\n";
private ShellUtils() {
throw new AssertionError();
}
/**
* check whether has root permission
*
* @return
*/
public static boolean checkRootPermission() {
return execCommand("echo root", true, false).result == 0;
}
/**
* execute shell command, default return result msg
*
* @param command command
* @param isRoot whether need to run with root
* @return
* @see ShellUtils#execCommand(String[], boolean, boolean)
*/
public static CommandResult execCommand(String command, boolean isRoot) {
return execCommand(new String[] {command}, isRoot, true);
}
/**
* execute shell commands, default return result msg
*
* @param commands command list
* @param isRoot whether need to run with root
* @return
* @see ShellUtils#execCommand(String[], boolean, boolean)
*/
public static CommandResult execCommand(List<String> commands, boolean isRoot) {
return execCommand(commands == null ? null : commands.toArray(new String[] {}), isRoot, true);
}
/**
* execute shell commands, default return result msg
*
* @param commands command array
* @param isRoot whether need to run with root
* @return
* @see ShellUtils#execCommand(String[], boolean, boolean)
*/
public static CommandResult execCommand(String[] commands, boolean isRoot) {
return execCommand(commands, isRoot, true);
}
/**
* execute shell command
*
* @param command command
* @param isRoot whether need to run with root
* @param isNeedResultMsg whether need result msg
* @return
* @see ShellUtils#execCommand(String[], boolean, boolean)
*/
public static CommandResult execCommand(String command, boolean isRoot, boolean isNeedResultMsg) {
return execCommand(new String[] {command}, isRoot, isNeedResultMsg);
}
/**
* execute shell commands
*
* @param commands command list
* @param isRoot whether need to run with root
* @param isNeedResultMsg whether need result msg
* @return
* @see ShellUtils#execCommand(String[], boolean, boolean)
*/
public static CommandResult execCommand(List<String> commands, boolean isRoot, boolean isNeedResultMsg) {
return execCommand(commands == null ? null : commands.toArray(new String[] {}), isRoot, isNeedResultMsg);
}
/**
* execute shell commands
*
* @param commands command array
* @param isRoot whether need to run with root
* @param isNeedResultMsg whether need result msg
* @return <ul>
* <li>if isNeedResultMsg is false, {@link CommandResult#successMsg} is null and
* {@link CommandResult#errorMsg} is null.</li>
* <li>if {@link CommandResult#result} is -1, there maybe some excepiton.</li>
* </ul>
*/
public static CommandResult execCommand(String[] commands, boolean isRoot, boolean isNeedResultMsg) {
int result = -1;
if (commands == null || commands.length == 0) {
return new CommandResult(result, null, null);
}
Process process = null;
BufferedReader successResult = null;
BufferedReader errorResult = null;
StringBuilder successMsg = null;
StringBuilder errorMsg = null;
DataOutputStream os = null;
try {
process = Runtime.getRuntime().exec(isRoot ? COMMAND_SU : COMMAND_SH);
os = new DataOutputStream(process.getOutputStream());
for (String command : commands) {
if (command == null) {
continue;
}
// donnot use os.writeBytes(commmand), avoid chinese charset error
os.write(command.getBytes());
os.writeBytes(COMMAND_LINE_END);
os.flush();
}
os.writeBytes(COMMAND_EXIT);
os.flush();
result = process.waitFor();
// get command result
if (isNeedResultMsg) {
successMsg = new StringBuilder();
errorMsg = new StringBuilder();
successResult = new BufferedReader(new InputStreamReader(process.getInputStream()));
errorResult = new BufferedReader(new InputStreamReader(process.getErrorStream()));
String s;
while ((s = successResult.readLine()) != null) {
successMsg.append(s);
}
while ((s = errorResult.readLine()) != null) {
errorMsg.append(s);
}
}
} catch (IOException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
if (os != null) {
os.close();
}
if (successResult != null) {
successResult.close();
}
if (errorResult != null) {
errorResult.close();
}
} catch (IOException e) {
e.printStackTrace();
}
if (process != null) {
process.destroy();
}
}
return new CommandResult(result, successMsg == null ? null : successMsg.toString(), errorMsg == null ? null
: errorMsg.toString());
}
/**
* result of command
* <ul>
* <li>{@link CommandResult#result} means result of command, 0 means normal, else means error, same to excute in
* linux shell</li>
* <li>{@link CommandResult#successMsg} means success message of command result</li>
* <li>{@link CommandResult#errorMsg} means error message of command result</li>
* </ul>
*
* @author <a href="http://www.trinea.cn" target="_blank">Trinea</a> 2013-5-16
*/
public static class CommandResult {
/** result of command **/
public int result;
/** success message of command result **/
public String successMsg;
/** error message of command result **/
public String errorMsg;
public CommandResult(int result) {
this.result = result;
}
public CommandResult(int result, String successMsg, String errorMsg) {
this.result = result;
this.successMsg = successMsg;
this.errorMsg = errorMsg;
}
}
}