關於串口編程的總結

這部分源碼一直沒變過，不過如今Android Studio已經支持Cmake方式了，因此不須要單獨編譯動態連接庫了，能夠直接修改Cmake文件和C文件html

說明

開源庫： https://github.com/cepr/android-serialport-apijava

1. 參照AS的帶C方式建立cpp文件夾，記得把配置也加上。
2. 把開源庫中的 SerialPort.c 和 SerialPort.h 拷貝下來，放入cpp文件夾中
3. 建立CMake文件，我這裏直接拷貝的AS的 CMakeLists.txt

通過以上3步，基本工做就作完了，這時候你的cpp庫有3個文件： CMakeLists.txt 文件， c文件和頭文件。android

而後剩下的就是定義調用串口的文件了ios

修改代碼

修改SerialPort頭文件和C代碼

如下是 SerialPort.c 文件，除了輸出的 JNICALL 基本沒啥要改的git

• 格式是Java_包名_類名_方法名 ，用下劃線隔開
• 下面要建立的java類及方法必定要嚴格對應
• 頭文件和C代碼的 JNICALL 保持同名

/* * Copyright 2009-2011 Cedric Priscal * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */

#include <termios.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>
#include <jni.h>

#include "SerialPort.h"

#include "android/log.h"
static const char *TAG="serial_port";
#define LOGI(fmt, args...) __android_log_print(ANDROID_LOG_INFO, TAG, fmt, ##args)
#define LOGD(fmt, args...) __android_log_print(ANDROID_LOG_DEBUG, TAG, fmt, ##args)
#define LOGE(fmt, args...) __android_log_print(ANDROID_LOG_ERROR, TAG, fmt, ##args)

static speed_t getBaudrate(jint baudrate)
{
	switch(baudrate) {
	case 0: return B0;
	case 50: return B50;
	case 75: return B75;
	case 110: return B110;
	case 134: return B134;
	case 150: return B150;
	case 200: return B200;
	case 300: return B300;
	case 600: return B600;
	case 1200: return B1200;
	case 1800: return B1800;
	case 2400: return B2400;
	case 4800: return B4800;
	case 9600: return B9600;
	case 19200: return B19200;
	case 38400: return B38400;
	case 57600: return B57600;
	case 115200: return B115200;
	case 230400: return B230400;
	case 460800: return B460800;
	case 500000: return B500000;
	case 576000: return B576000;
	case 921600: return B921600;
	case 1000000: return B1000000;
	case 1152000: return B1152000;
	case 1500000: return B1500000;
	case 2000000: return B2000000;
	case 2500000: return B2500000;
	case 3000000: return B3000000;
	case 3500000: return B3500000;
	case 4000000: return B4000000;
	default: return -1;
	}
}

/* * Class: android_serialport_SerialPort * Method: open * Signature: (Ljava/lang/String;II)Ljava/io/FileDescriptor; */
JNIEXPORT jobject JNICALL Java_com_jiataoyuan_serialport_SerialPort_open
  (JNIEnv *env, jclass thiz, jstring path, jint baudrate, jint flags)
{
	int fd;
	speed_t speed;
	jobject mFileDescriptor;

	/* Check arguments */
	{
		speed = getBaudrate(baudrate);
		if (speed == -1) {
			/* TODO: throw an exception */
			LOGE("Invalid baudrate");
			return NULL;
		}
	}

	/* Opening device */
	{
		jboolean iscopy;
		const char *path_utf = (*env)->GetStringUTFChars(env, path, &iscopy);
		LOGD("Opening serial port %s with flags 0x%x", path_utf, O_RDWR | flags);
		fd = open(path_utf, O_RDWR | flags);
		LOGD("open() fd = %d", fd);
		(*env)->ReleaseStringUTFChars(env, path, path_utf);
		if (fd == -1)
		{
			/* Throw an exception */
			LOGE("Cannot open port");
			/* TODO: throw an exception */
			return NULL;
		}
	}

	/* Configure device */
	{
		struct termios cfg;
		LOGD("Configuring serial port");
		if (tcgetattr(fd, &cfg))
		{
			LOGE("tcgetattr() failed");
			close(fd);
			/* TODO: throw an exception */
			return NULL;
		}

		cfmakeraw(&cfg);
		cfsetispeed(&cfg, speed);
		cfsetospeed(&cfg, speed);

		if (tcsetattr(fd, TCSANOW, &cfg))
		{
			LOGE("tcsetattr() failed");
			close(fd);
			/* TODO: throw an exception */
			return NULL;
		}
	}

	/* Create a corresponding file descriptor */
	{
		jclass cFileDescriptor = (*env)->FindClass(env, "java/io/FileDescriptor");
		jmethodID iFileDescriptor = (*env)->GetMethodID(env, cFileDescriptor, "<init>", "()V");
		jfieldID descriptorID = (*env)->GetFieldID(env, cFileDescriptor, "descriptor", "I");
		mFileDescriptor = (*env)->NewObject(env, cFileDescriptor, iFileDescriptor);
		(*env)->SetIntField(env, mFileDescriptor, descriptorID, (jint)fd);
	}

	return mFileDescriptor;
}

/* * Class: cedric_serial_SerialPort * Method: close * Signature: ()V */
JNIEXPORT void JNICALL Java_com_jiataoyuan_serialport_SerialPort_close
  (JNIEnv *env, jobject thiz)
{
	jclass SerialPortClass = (*env)->GetObjectClass(env, thiz);
	jclass FileDescriptorClass = (*env)->FindClass(env, "java/io/FileDescriptor");

	jfieldID mFdID = (*env)->GetFieldID(env, SerialPortClass, "mFd", "Ljava/io/FileDescriptor;");
	jfieldID descriptorID = (*env)->GetFieldID(env, FileDescriptorClass, "descriptor", "I");

	jobject mFd = (*env)->GetObjectField(env, thiz, mFdID);
	jint descriptor = (*env)->GetIntField(env, mFd, descriptorID);

	LOGD("close(fd = %d)", descriptor);
	close(descriptor);
}

修改CMake文件

• add_librarygithub

  • 1參設置庫名(你要在java中加載的庫名稱)，
  • 2參設置共享(基本都是SHARE)，
  • 3參設置源文件的相對路徑(由於在同一目錄下，直接寫文件名便可)

• find_libraryweb

  這個東西我也沒搞明白，看說明是用來搜索庫路徑的，可是由於有默認值，因此只須要指定NDK就好了，並且刪了也不影響什麼express

• target_link_librariesapache

  • 1參指定目標庫，就是上面設置的庫
  • 2參用來鏈接到日誌庫，已經包含在nkd中了，若是你的 find_library 默認的話，這裏也默認就好了，若是 find_library 刪掉的話，這裏也刪掉

# For more information about using CMake with Android Studio, read the
# documentation: https://d.android.com/studio/projects/add-native-code.html

# Sets the minimum version of CMake required to build the native library.

cmake_minimum_required(VERSION 3.4.1)

# Creates and names a library, sets it as either STATIC
# or SHARED, and provides the relative paths to its source code.
# You can define multiple libraries, and CMake builds them for you.
# Gradle automatically packages shared libraries with your APK.

add_library( # Sets the name of the library.
        SerialPort
        # Sets the library as a shared library.
        SHARED
        # Provides a relative path to your source file(s).
        SerialPort.c)


# Searches for a specified prebuilt library and stores the path as a
# variable. Because CMake includes system libraries in the search path by
# default, you only need to specify the name of the public NDK library
# you want to add. CMake verifies that the library exists before
# completing its build.

find_library( # Sets the name of the path variable.
        log-lib

        # Specifies the name of the NDK library that
        # you want CMake to locate.
        log)

# Specifies libraries CMake should link to your target library. You
# can link multiple libraries, such as libraries you define in this
# build script, prebuilt third-party libraries, or system libraries.

target_link_libraries( # Specifies the target library.
        SerialPort
        # Links the target library to the log library
        # included in the NDK.
        ${log-lib})

建立SerialPort

這個文件我改了一點，變化不大，你也能夠直接用開源庫中的，主要內容以下：api

• 獲取串口：改動部分爲將可讀寫改成可讀寫可執行
• 獲取讀寫流
• 設置jni方法 ，打開和關閉，其中打開方法是私有方法

/* * Copyright 2009 Cedric Priscal * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */

package com.jiataoyuan.serialport;

import android.util.Log;

import java.io.File;
import java.io.FileDescriptor;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

public class SerialPort {

    private static final String TAG = "SerialPort";

    static {
        System.loadLibrary("SerialPort");
    }

    /* * Do not remove or rename the field mFd: it is used by native method close(); */
    private FileDescriptor mFd; //文件描述
    private FileInputStream mFileInputStream;  // 輸入流
    private FileOutputStream mFileOutputStream;  // 輸出流

    /** * 獲取串口 * * @param device 設備 * @param baudrate 波特率 * @param flags 標誌符 * @throws SecurityException * @throws IOException */
    public SerialPort(File device, int baudrate, int flags) throws SecurityException, IOException {

        /* 檢查訪問權限 */
        if (!device.canRead() || !device.canWrite()) {
            try {
                /* Missing read/write permission, trying to chmod the file */
                Process su;
                su = Runtime.getRuntime().exec("/system/bin/su");
                String cmd = "chmod 777 " + device.getAbsolutePath() + "\n"
                        + "exit\n";
                su.getOutputStream().write(cmd.getBytes());
                if ((su.waitFor() != 0) || !device.canRead()
                        || !device.canWrite()) {
                    throw new SecurityException();
                }
            } catch (Exception e) {
                e.printStackTrace();
                throw new SecurityException();
            }
        }

        // 若是打不開返回null
        mFd = open(device.getAbsolutePath(), baudrate, flags);
        if (mFd == null) {
            Log.e(TAG, "native open returns null");
            throw new IOException();
        }
        mFileInputStream = new FileInputStream(mFd);
        mFileOutputStream = new FileOutputStream(mFd);
    }

    // Getters and setters
    public InputStream getInputStream() {
        return mFileInputStream;
    }

    public OutputStream getOutputStream() {
        return mFileOutputStream;
    }

    // JNI
    private native static FileDescriptor open(String path, int baudrate, int flags);

    public native void close();


}

封裝SerialPortActivity

爲啥封裝成這樣子，由於個人串口調試助手，因此最後改爲這樣子了，通俗易懂

/* * Copyright 2009 Cedric Priscal * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */

package com.jiataoyuan.serialport;

import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.content.DialogInterface.OnClickListener;
import android.os.Bundle;

import com.jiataoyuan.dronetrack.R;
import com.jiataoyuan.dronetrack.utils.MyConstantUtils;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.security.InvalidParameterException;


public abstract class SerialPortActivity extends Activity {

  protected SerialPort mSerialPort;
  protected OutputStream mOutputStream;
  private InputStream mInputStream;
  private ReadThread mReadThread;

  // 根據須要修改線程
  private class ReadThread extends Thread {

      @Override
      public void run() {
          super.run();
          int size;
          byte[] buffer = new byte[64];
          StringBuilder sb = new StringBuilder();
          while (!isInterrupted()) {

              try {

                  if ((size = mInputStream.read(buffer)) != -1) {
                      sb.append(new String(buffer, 0, size));
                      onDataReceived(sb.toString());
                  }
              } catch (IOException e) {
                  e.printStackTrace();
                  return;
              }
          }

      }
  }

  // 打印錯誤消息彈框
  private void DisplayError(int resourceId) {
      AlertDialog.Builder b = new AlertDialog.Builder(this);
      b.setTitle("Error");
      b.setMessage(resourceId);
      b.setPositiveButton("OK", new OnClickListener() {
          public void onClick(DialogInterface dialog, int which) {
              SerialPortActivity.this.finish();
          }
      });
      b.show();
  }

  @Override
  protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);

      try {
          if (null == mSerialPort) {
              // 1參 串口 根據你的串口狀況填入，如"/dev/ttyS4" ， "/dev/ttyS1"
              // 2參 波特率 根據約定填入，如19200 ，115200
              // 3參 標誌位 根據約定填入，沒有填0
              mSerialPort = new SerialPort(new File(MyConstantUtils.SerialPortPath), MyConstantUtils.baudrate, 0);
          }
          mOutputStream = mSerialPort.getOutputStream();
          mInputStream = mSerialPort.getInputStream();

          /* Create a receiving thread */
          mReadThread = new ReadThread();
          mReadThread.start();
      } catch (SecurityException e) {
          DisplayError(R.string.error_security);
      } catch (IOException e) {
          DisplayError(R.string.error_unknown);
      } catch (InvalidParameterException e) {
          DisplayError(R.string.error_configuration);
      }
  }

  // 定義接收的抽象方法
  protected abstract void onDataReceived(String buffer);

  // 發送消息
  public void sendMsg(byte[] msg) {
      try {
          mOutputStream = mSerialPort.getOutputStream();
          if (msg.length > 0) {
              mOutputStream.write(msg);
              mOutputStream.flush();
          }

      } catch (IOException e) {
          e.printStackTrace();
      }
  }

  // 關閉端口
  public void closeSerialPort() {
      if (mSerialPort != null) {
          mSerialPort.close();
          mSerialPort = null;
      }
  }

  @Override
  protected void onDestroy() {
      if (mReadThread != null)
          mReadThread.interrupt();
      closeSerialPort();
      mSerialPort = null;
      super.onDestroy();
  }
}

調用

要調用的Activity須要繼承 SerialPortActivity ，並實現 onDataReceived 方法

• 收

  @Override
  protected void onDataReceived(String buffer) {
      mBuffer = buffer;
      Handler handler = new Handler(Looper.getMainLooper());
      handler.postDelayed(runnable, 100);
  
  }

• 發

  private void send(String msg) {
      sendMsg(msg.getBytes());
  }
  
  private void send(byte[] msg) {
      sendMsg(msg);
      L.e(new String(msg));
  }

• 開關串口都在 SerialPortActivity 的create和destroy方法中調用了，應用邏輯無需管理