temperature.c

< 嵌入式系统编程>>源代码解析光盘,包括这本书各章节的示例代码（无密码）

#include <rtl.h>
#include <rtl_fifo.h>

#include <time.h>
#include <pthread.h>
#include <asm/io.h>
#include "rt_com.h"
#include "rt_comP.h"
#include <stdio.h>

pthread_t thread;
int fd_fifo;
int period=100000000;
int fifo_size=4000;


int a,temp;
void *temperature(void *t) {

	//makes  a realtime thread as periodic
	pthread_make_periodic_np (thread, gethrtime(), period);

	temp=10;

	do {
		int n;
		int i;
		char b[210]={};
		char a[1];
		for(i=1;i<=10;i++)
		{
			//suspend the current thread until the next period
			pthread_wait_np();
		}
		//attempts to read total characaters to buffer  from the realtime serialport com
		n = rt_com_read(0, b, sizeof(b));

		if (n > 0) {
			b[n] = 0;
			rtl_printf("%s", b);
		}

		 if(temp  != 50 ){

		     a[0]=temp;
		     //writes 1 chraracter from buffer to the realtime serial port com
		     rt_com_write(0, a, 1);
		     temp = 10 + temp;
		  }
		  else{
		      temp = 10;
		      a[0]=temp;
		      //writes 1 chraracter from buffer to the realtime serial port com
		      rt_com_write(0, a, 1);
             }



	} while (1);

	return 0;
}

/* This module begins the entire process by creating an execution thread with init_module */

int init_module(void)
{
	pthread_attr_t attr;
	struct sched_param sched_param;
	int thread_status;
	//it is used to dynamically changed the parameters of each realtime serial port
	rt_com_setup(0, 38400, RT_COM_PARITY_NONE, 1, 8);

	//to initialize threads attribute object
	pthread_attr_init (&attr);
	//to examine and change the CPU pthread attribute
	pthread_attr_setcpu_np(&attr, 0);
	sched_param.sched_priority = 1;
	//dynamic thread scheduling parameters access
	pthread_attr_setschedparam (&attr, &sched_param);
	//creating the thread and maintaining its parameters status
	thread_status = pthread_create (&thread,  &attr, temperature, (void *)1);

	return 0;
}

/* This module ends the entire process by clearing the  execution thread with cleanup_module */
void cleanup_module(void)
{
	//it delete the realtime thread
	pthread_delete_np (thread);
	rt_com_setup(0, -1, 0, 0, 0);
}