Android应用层对proc节点的读写

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 {

		@Override
		public 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;
				}
			}
		}
	}

	@Override
	protected 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-- tx
			switch (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);

	@Override
	protected 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。