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
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;
}
}
}
