硬件平台：S3C6410
操作系统：Ubuntu、windows
板子系统：Android
开发工具：jdk，ndk，eclipse
本次测试从linux内核模块编译开始，以S3C6410的pwm驱动为例。
pwm_6410.c:
#include <linux/module.h>#include <linux/kernel.h>#include <linux/fs.h>#include <linux/init.h>#include <linux/delay.h>#include <linux/poll.h>#include <linux/clk.h>#include <linux/cdev.h>#include <linux/device.h>#include <linux/miscdevice.h>#include <linux/interrupt.h>#include <plat/regs-timer.h>#include <plat/gpio-cfg.h>#include <asm/irq.h>#include <asm/io.h>#include <asm/mach/time.h>#include <asm/uaccess.h>#include <mach/map.h>#include <mach/regs-clock.h>#include <mach/regs-gpio.h>#include <mach/hardware.h>#include <mach/gpio-bank-e.h>#include <mach/gpio-bank-f.h>#include <mach/gpio-bank-k.h>#include <mach/regs-irq.h>#define DEVICE_NAME "pwm"static struct semaphore lock;static void PWM_Set_Freq( unsigned long freq ){ unsigned long tcon; unsigned long tcnt; unsigned long tcfg1; unsigned long tcfg0; unsigned long pclk; unsigned tmp; struct clk *clk_p; printk ("Freq is %d",freq); tmp = readl(S3C64XX_GPFCON);//PWM GPF15 tmp &= ~(0x3U << 30);// Timer1 tmp |= (0x2U << 30); writel(tmp, S3C64XX_GPFCON); tcon = __raw_readl(S3C_TCON); tcfg1 = __raw_readl(S3C_TCFG1); tcfg0 = __raw_readl(S3C_TCFG0); tcfg0 &= ~S3C_TCFG_PRESCALER0_MASK; tcfg0 |= (50 - 1); tcfg1 &= ~S3C_TCFG1_MUX1_MASK; tcfg1 |= S3C_TCFG1_MUX1_DIV16; __raw_writel(tcfg1, S3C_TCFG1); __raw_writel(tcfg0, S3C_TCFG0); clk_p = clk_get(NULL, "pclk"); pclk = clk_get_rate(clk_p); tcnt = (pclk/50/16)/freq; __raw_writel(tcnt, S3C_TCNTB(1)); __raw_writel(tcnt/2, S3C_TCMPB(1)); tcon &= ~(0xf << 8); tcon |= (0xb << 8); __raw_writel(tcon, S3C_TCON); tcon &= ~(2 << 8); __raw_writel(tcon, S3C_TCON);}void PWM_Stop( void ){ unsigned tmp; tmp = readl(S3C64XX_GPFCON); tmp &= ~(0x3U << 30);// set GPF15 writel(tmp, S3C64XX_GPFCON);}static int s3c64xx_pwm_open(struct inode *inode, struct file *file){ if (!down_trylock(&lock)) return 0; else return -EBUSY;}static int s3c64xx_pwm_close(struct inode *inode, struct file *file){ up(&lock); return 0;}static long s3c64xx_pwm_ioctl(struct file *filep, unsigned int cmd, unsigned long arg){ switch (cmd) { case 1: if (arg == 0) return -EINVAL; PWM_Set_Freq(arg); break; case 0: PWM_Stop(); break; } return 0;}static struct file_operations dev_fops = { .owner = THIS_MODULE, .open = s3c64xx_pwm_open, .release = s3c64xx_pwm_close, .unlocked_ioctl = s3c64xx_pwm_ioctl,};static struct miscdevice misc = { .minor = MISC_DYNAMIC_MINOR, .name = DEVICE_NAME, .fops = &dev_fops,};static int __init dev_init(void){ int ret; init_MUTEX(&lock); ret = misc_register(&misc); printk (DEVICE_NAME"\tinitialized\n"); return ret;}static void __exit dev_exit(void){ misc_deregister(&misc);}MODULE_LICENSE("GPL");module_init(dev_init);module_exit(dev_exit);Makefile添加：obj-$(CONFIG_PWM_S3C6410) += pwm_6410.oKconfig添加：
config PWM_S3C6410 tristate "pwm" depends on CPU_S3C6410
make menuconfig配置内核后编译内核
make zImage后启动Android系统ls /dev会看到名称为pwm的设备驱动
驱动已经加载好，这时候就要编写Android下的测试程序。JNI是Java Native Interface的缩写，即Java本地调用，它允许java代码和其他语言写的代码进行交互。写测试程序时使用JNI方式实现。
eclipse建立一个新的应用工程，取名为pwm，包名为com.example.pwm
默认生成的java代码：PwmActivity.java
package com.example.pwm;import android.os.Bundle;import android.app.Activity;import android.view.Menu;import android.view.View;public class PwmActivity extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_pwm); } @Override public boolean onCreateOptionsMenu(Menu menu) { // Inflate the menu; this adds items to the action bar if it is present. getMenuInflater().inflate(R.menu.activity_pwm, menu); return true; }}添加本地方法：package com.example.pwm;import android.os.Bundle;import android.app.Activity;import android.view.Menu;import android.view.View;public class PwmActivity extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_pwm); } @Override public boolean onCreateOptionsMenu(Menu menu) { // Inflate the menu; this adds items to the action bar if it is present. getMenuInflater().inflate(R.menu.activity_pwm, menu); return true; } public static native int pwm_set_freq(int i, int j); static { System.loadLibrary("pwm"); // 添加 C/C++动态库导入方法 }}编辑res/layout下activity_pwm.xml
添加button控件
<Button android:id="@+id/pwm_on" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_above="@+id/textView1" android:layout_alignLeft="@+id/textView1" android:layout_marginBottom="39dp" android:onClick="onPwmOnClicked" android:text="@string/pwm" />编辑res/values下strings.xml
添加
<string name="pwm">pwm</string>PwmActivity.java中添加：
public void onPwmOnClicked(View v){ pwm_set_freq(1,200); }PwmActivity.java：package com.example.pwm;import android.os.Bundle;import android.app.Activity;import android.view.Menu;import android.view.View;public class PwmActivity extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_pwm); } @Override public boolean onCreateOptionsMenu(Menu menu) { // Inflate the menu; this adds items to the action bar if it is present. getMenuInflater().inflate(R.menu.activity_pwm, menu); return true; } public void onPwmOnClicked(View v){ pwm_set_freq(1,200); //按下按键就输出波形 } public static native int pwm_set_freq(int i, int j); static { System.loadLibrary("pwm"); // 添加 C/C++动态库导入方法 ，这个库需要使用NDK工具编译生成。 } }上述步骤就绪后，编译工程，再将该工程拷贝到Ubuntu下工程目录下创建jni文件夹：
使用javah命令生成jni头文件
注意冒号后没有空格
生成的头文件：
com_example_pwm_PwmActivity.h:
/* DO NOT EDIT THIS FILE - it is machine generated */#include <jni.h>/* Header for class com_example_pwm_PwmActivity */#ifndef _Included_com_example_pwm_PwmActivity#define _Included_com_example_pwm_PwmActivity#ifdef __cplusplusextern "C" {#endif#undef com_example_pwm_PwmActivity_MODE_PRIVATE#define com_example_pwm_PwmActivity_MODE_PRIVATE 0L#undef com_example_pwm_PwmActivity_MODE_WORLD_READABLE#define com_example_pwm_PwmActivity_MODE_WORLD_READABLE 1L#undef com_example_pwm_PwmActivity_MODE_WORLD_WRITEABLE#define com_example_pwm_PwmActivity_MODE_WORLD_WRITEABLE 2L#undef com_example_pwm_PwmActivity_MODE_APPEND#define com_example_pwm_PwmActivity_MODE_APPEND 32768L#undef com_example_pwm_PwmActivity_MODE_MULTI_PROCESS#define com_example_pwm_PwmActivity_MODE_MULTI_PROCESS 4L#undef com_example_pwm_PwmActivity_MODE_ENABLE_WRITE_AHEAD_LOGGING#define com_example_pwm_PwmActivity_MODE_ENABLE_WRITE_AHEAD_LOGGING 8L#undef com_example_pwm_PwmActivity_BIND_AUTO_CREATE#define com_example_pwm_PwmActivity_BIND_AUTO_CREATE 1L#undef com_example_pwm_PwmActivity_BIND_DEBUG_UNBIND#define com_example_pwm_PwmActivity_BIND_DEBUG_UNBIND 2L#undef com_example_pwm_PwmActivity_BIND_NOT_FOREGROUND#define com_example_pwm_PwmActivity_BIND_NOT_FOREGROUND 4L#undef com_example_pwm_PwmActivity_BIND_ABOVE_CLIENT#define com_example_pwm_PwmActivity_BIND_ABOVE_CLIENT 8L#undef com_example_pwm_PwmActivity_BIND_ALLOW_OOM_MANAGEMENT#define com_example_pwm_PwmActivity_BIND_ALLOW_OOM_MANAGEMENT 16L#undef com_example_pwm_PwmActivity_BIND_WAIVE_PRIORITY#define com_example_pwm_PwmActivity_BIND_WAIVE_PRIORITY 32L#undef com_example_pwm_PwmActivity_BIND_IMPORTANT#define com_example_pwm_PwmActivity_BIND_IMPORTANT 64L#undef com_example_pwm_PwmActivity_BIND_ADJUST_WITH_ACTIVITY#define com_example_pwm_PwmActivity_BIND_ADJUST_WITH_ACTIVITY 128L#undef com_example_pwm_PwmActivity_CONTEXT_INCLUDE_CODE#define com_example_pwm_PwmActivity_CONTEXT_INCLUDE_CODE 1L#undef com_example_pwm_PwmActivity_CONTEXT_IGNORE_SECURITY#define com_example_pwm_PwmActivity_CONTEXT_IGNORE_SECURITY 2L#undef com_example_pwm_PwmActivity_CONTEXT_RESTRICTED#define com_example_pwm_PwmActivity_CONTEXT_RESTRICTED 4L#undef com_example_pwm_PwmActivity_RESULT_CANCELED#define com_example_pwm_PwmActivity_RESULT_CANCELED 0L#undef com_example_pwm_PwmActivity_RESULT_OK#define com_example_pwm_PwmActivity_RESULT_OK -1L#undef com_example_pwm_PwmActivity_RESULT_FIRST_USER#define com_example_pwm_PwmActivity_RESULT_FIRST_USER 1L#undef com_example_pwm_PwmActivity_DEFAULT_KEYS_DISABLE#define com_example_pwm_PwmActivity_DEFAULT_KEYS_DISABLE 0L#undef com_example_pwm_PwmActivity_DEFAULT_KEYS_DIALER#define com_example_pwm_PwmActivity_DEFAULT_KEYS_DIALER 1L#undef com_example_pwm_PwmActivity_DEFAULT_KEYS_SHORTCUT#define com_example_pwm_PwmActivity_DEFAULT_KEYS_SHORTCUT 2L#undef com_example_pwm_PwmActivity_DEFAULT_KEYS_SEARCH_LOCAL#define com_example_pwm_PwmActivity_DEFAULT_KEYS_SEARCH_LOCAL 3L#undef com_example_pwm_PwmActivity_DEFAULT_KEYS_SEARCH_GLOBAL#define com_example_pwm_PwmActivity_DEFAULT_KEYS_SEARCH_GLOBAL 4L/* * Class: com_example_pwm_PwmActivity * Method: pwm_set_freq * Signature: (II)I */JNIEXPORT jint JNICALL Java_com_example_pwm_PwmActivity_pwm_1set_1freq (JNIEnv *, jclass, jint, jint);#ifdef __cplusplus}#endif#endif将头文件拷贝到jni目录下，jni目录下创建pwm.c：
#include <jni.h> #include <stdio.h> #include <stdlib.h> #include <fcntl.h> #include <unistd.h> #include <sys/ioctl.h> #include <android/log.h> #define LOG_TAG "PWM" //android logcat #define LOGI(...) __android_log_print(ANDROID_LOG_INFO,LOG_TAG,__VA_ARGS__ ) #define LOGE(...) __android_log_print(ANDROID_LOG_ERROR,LOG_TAG,__VA_ARGS_ _) jint JNICALL Java_com_example_pwm_PwmActivity_pwm_1set_1freq(JNIEnv *env, jclass thiz, jint cmd, jint freq) { //函数名与头文件中的保持一致 int fd; fd = open("/dev/pwm",O_RDWR); if (fd < 0) { printf ("Open /dev/pwm file error\n"); return -1; } ioctl(fd,1,200); close (fd); return 0;}jni目录下创建Android.mk
LOCAL_PATH := $(call my-dir)include $(CLEAR_VARS)LOCAL_MODULE := pwmLOCAL_SRC_FILES := pwm.cLOCAL_LDLIBS := -llogLOCAL_C_INCLUDES := $(MY_ANDROID_SOURCE)/frameworks/base/core/jni/android/graphics \$(MY_ANDROID_SOURCE)/external/skia/include/core \$(MY_ANDROID_SOURCE)/external/skia/include/images \$(MY_ANDROID_SOURCE)/frameworks/base/include \$(MY_ANDROID_SOURCE)/system/core/include include $(BUILD_SHARED_LIBRARY)命令ndk-build，如果工程目录下没有libs/armeabi，那么就创建armeabi
生成了libpwm.so就是我们在Android应用工程中需要的库文件
static { System.loadLibrary("pwm"); // 添加 C/C++动态库导入方法 } 将含有libpwm.so的工程文件从Ubuntu中考到windows，eclipse打开工程，编译生成apk
pwm.apk
在板子上安装，控制终端下输入命令：
pm install -f pwm.apk
安装成功提示success之后，点开软件，点击pwm按钮。
示波器输出200Hz百分之五十的波形，测试成功。