Android应用层对proc节点的读写

    前段时间用android端开发物联网，其中用到了485通讯，关于485通讯知识的介绍：http://blog.chinaunix.net/uid-26921272-id-3506640.html

    232通讯是两根数据线一个收一个发，但是485通讯是两线合作收发，芯片有一个状态控制端，也就是控制端口的高低电平来决定是收状态还是发状态，android上是用proc节点的方式控制处理器外部端口的状态的，下面就是如何读取proc节点：

核心代码示例：

File myFile = new File("proc/tp_debug/debug_switch");          FileWriter fr;          try {              fr = new FileWriter( myFile );              fr.write("1"); //1是发送出数据，0是接收进数据              fr.close();          }          catch (IOException e) {                e.printStackTrace();          }

实际场景应用实例：

package com.hehe.haha;import java.io.File;import java.io.FileWriter;import java.io.IOException;import java.io.InputStream;import java.io.OutputStream;import android.os.Bundle;import android.util.Log;import com.hehe.haha.base.BaseActivity;import com.hehe.haha.base.BaseApp;import com.hehe.haha.base.SerialPort;/**send and receive of serial port*/ public abstract class SerialPortActivity extends BaseActivity {private static final String TAG = "SerialPortActivity";protected BaseApp mApplication;protected SerialPort mSerialPort;protected OutputStream mOutputStream;private InputStream mInputStream;private ReadThread mReadThread;private class ReadThread extends Thread {@Overridepublic void run() {super.run();int maxLength = 10;byte[] buffer = new byte[maxLength];//缓存区while (!isInterrupted()) {try {int size;if (mInputStream == null) {return;}size = mInputStream.read(buffer);//防止溢出if (size == 10) {onDataReceived(buffer, 10);}} catch (IOException e) {e.printStackTrace();return;}}}}@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);try {mApplication = (BaseApp) getApplication();mSerialPort = mApplication.getSerialPort();mOutputStream = mSerialPort.getOutputStream();mInputStream = mSerialPort.getInputStream();/* Create a receiving thread */mReadThread = new ReadThread();mReadThread.start();} catch (Exception e) {DisplayError(R.string.error_configuration);}}/** * send order *  * @param str */protected void sendOrder(String str) {try {Log.i("send data", str);setSerialStu(1);for (int i = 0; i < str.length(); i = i + 2) {//Integer.parseInt(str.substring(i, i + 2), 16)mOutputStream.write(Integer.parseInt(str.substring(i, i + 2), 16));//new String(text).getBytes()}setSerialStu(0);} catch (Exception e) {e.printStackTrace();}}/**         *这里是今天笔记的重点         * set status of 485 * @param stu * 1 is send，0 is receive */protected void setSerialStu(int stu) {File SerialCtrl = new File("proc/rp_button/485_ctrl");FileWriter fr;try {fr = new FileWriter(SerialCtrl);//485:0-- rx   1-- txswitch (stu) {case 0:fr.write("0");Log.i("ConsoleActivity", "this is receive");break;case 1:fr.write("1");Log.i("ConsoleActivity", "this is send");break;}fr.close();} catch (IOException e) {e.printStackTrace();}}        //接收数据时调用protected abstract void onDataReceived(final byte[] buffer, final int size);@Overrideprotected void onDestroy() {if (mReadThread != null)mReadThread.interrupt();mApplication.closeSerialPort();mSerialPort = null;super.onDestroy();}}

如果不清楚proc节点控制程序是否正常工作，可以先用应用层控制一个led指示灯的状态，如果灯的状态受控，proc节点读写成功。