1.3.1进程附属例程

（这个是pwm和LED拼凑起来的代码，写的很烂，很烂，就没加备注。总之是很烂的代码。要是初学的话可以看一下，要是但凡会一点的话，就不要在意这些细节了~~~哈哈~~~）

这个是进程的简单应用

一.

本程序实际上是前面几个程序的一个简单的整合程序.用到了pwm列成.LED列成和进程列成，可以锻炼大家对较大程序的理解。(自写)

二．重点掌握函数：

        无新函数

三．要求水平

掌握程序原理和结构，之后管道与共享内存都用到了这个程序。

四．由于使用了前面所用到的程序所以没有加备注。

#include <stdio.h>#include <stddef.h>#include <termios.h>#include <unistd.h>#include <stdlib.h>#include <sys/ipc.h>#include <sys/shm.h>#include <sys/stat.h>#include <sys/ioctl.h>#include <sys/types.h>#include"pthread.h"#define PWM_IOCTL_SET_FREQ1#define PWM_IOCTL_STOP0#define ESC_KEY0x1bint temp;static int fd = -1;static void close_buzzer(void);void open_led(int on,int led_on);int led_ons(int leds,char i);void delay(int times);void reader_function();void writer_function();static int getch(void){struct termios oldt,newt;int ch;if (!isatty(STDIN_FILENO)) {fprintf(stderr, "this problem should be run at a terminal\n");exit(1);}// save terminal settingif(tcgetattr(STDIN_FILENO, &oldt) < 0) {perror("save the terminal setting");exit(1);}// set terminal as neednewt = oldt;newt.c_lflag &= ~( ICANON | ECHO );if(tcsetattr(STDIN_FILENO,TCSANOW, &newt) < 0) {perror("set terminal");exit(1);}ch = getchar();// restore termial settingif(tcsetattr(STDIN_FILENO,TCSANOW,&oldt) < 0) {perror("restore the termial setting");exit(1);}return ch;}static void open_buzzer(void){fd = open("/dev/pwm", 0);if (fd < 0) {perror("open pwm_buzzer device");exit(1);}// any function exit call will stop the buzzeratexit(close_buzzer);}static void close_buzzer(void){if (fd >= 0) {ioctl(fd, PWM_IOCTL_STOP);close(fd);fd = -1;}}static void set_buzzer_freq(int freq){// this IOCTL command is the key to set frequencyint ret = ioctl(fd, PWM_IOCTL_SET_FREQ, freq);if(ret < 0) {perror("set the frequency of the buzzer");exit(1);}}static void stop_buzzer(void){int ret = ioctl(fd, PWM_IOCTL_STOP);if(ret < 0) {perror("stop the buzzer");exit(1);}}main(){pthread_t reader;pthread_t writer;pthread_create(&reader,NULL,(void*)&reader_function,NULL);pthread_create(&writer,NULL,(void*)&writer_function,NULL);while(1);}void writer_function(){    int last;    int off;    int led_on=-1;    int f_led;    while(1)    {        off=1;        led_on++;        if(led_on==4)        {            led_on=0;        }        open_led(1,led_on);        for(f_led=3;f_led>0;f_led--)        {        last=led_ons(led_on,off);        open_led(0,last);        off++;        }        delay(temp*8);    }}void reader_function(){    int freq = 1000 ;open_buzzer();printf( "\nBUZZER TEST ( PWM Control )\n" );printf( "Press +/- to increase/reduce the frequency of the BUZZER\n" ) ;printf( "Press 'ESC' key to Exit this program\n\n" );    while(1)    {        int key;        set_buzzer_freq(freq);        temp=((21000-freq)/10);        printf( "\tFreq = %d\n", freq );        key = getch();        switch(key)        {        case '+':            if( freq < 20000 )                freq += 10;            break;        case '-':            if( freq > 11 )                freq -= 10 ;            break;        case ESC_KEY:        case EOF:            stop_buzzer();            exit(0);        default:            break;        }    }}void open_led(int on,int led_on){int ss;ss= open("/dev/leds0", 0);if (ss< 0){    ss= open("/dev/leds", 0);}if (ss< 0){    perror("open device leds");    exit(1);}ioctl(ss, on, led_on);close(ss);                          //delete????????}int led_ons(int leds,char i){    int a;    a=leds;    for(i;i>0;i--)    {        a++;        if(a==4)         {a=0;}    }    return a;}void delay(int times){    int i;    for(;times>0;times--)      for(i=0;i<400;i++);}