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开发板：STM32MP157A

温湿度传感器：si7006

显示器（数码管）：m74hc595

遇到的问题：循环采集温湿度传感器数值，并将数值发送给数码管的时候两者存在竞态关系，导致数码管显示亮度很暗

解决办法：采用多线程或者多进程解决内核竞态问题

驱动代码

#include <linux/init.h>
#include <linux/module.h>
#include <linux/i2c.h>
#include <linux/fs.h>
#include <linux/device.h>
#include "head.h"unsigned int major;
struct class *cls;
struct device *dev;
struct i2c_client *client1;//读取温湿度的函数
int i2c_read_hum_tem(char reg)
{short value;char r_buf[]={reg};int ret;//封装消息struct i2c_msg r_msg[]={[0]={.addr=client1->addr,.flags=0,//先写.len=sizeof(r_buf),.buf=r_buf,},[1]={.addr=client1->addr,.flags=1,.len=2,.buf=(char *)&value,},};//将消息传送ret=i2c_transfer(client1->adapter,r_msg,2);if(ret!=2){printk("消息传输失败\n");return -EIO;}return value;//将读取到的温湿度返回
}int si7006_open(struct inode *inode,struct file *file)
{printk("%s:%s:%d\n",__FILE__,__func__,__LINE__);return 0;
}long si7006_ioctl(struct file *file,unsigned int cmd,unsigned long arg)
{int tem,hum,ret;switch(cmd){case GET_HUM://读取湿度//读取湿度的逻辑hum=i2c_read_hum_tem(0xE5);ret=copy_to_user((void *)arg,&hum,4);//int类型4个字节if(ret){printk("copy_to_user error\n");return ret;}break;case GET_TEM://读取温度//读取温度的逻辑tem=i2c_read_hum_tem(0xE3);ret=copy_to_user((void *)arg,&tem,4);if(ret){printk("copy_to_user error\n");return ret;}break;}return 0;
}int si7006_close(struct inode *inode,struct file *file)
{printk("%s:%s:%d\n",__FILE__,__func__,__LINE__);    return 0;
}//操作方法结构体
struct file_operations fops={.open=si7006_open,.unlocked_ioctl=si7006_ioctl,.release=si7006_close,
};//给对象分配空间并且初始化
int i2c_probe(struct i2c_client *client,const struct i2c_device_id *id)
{client1=client;//字符设备驱动的注册major=register_chrdev(0,"si7006",&fops);if(major<0){printk("register_chrdev failed\n"); return major;}printk("register_chrdev success\n");//设备节点的创建//向上提交目录cls=class_create(THIS_MODULE,"si7006");if(IS_ERR(cls)){printk("向上提交目录失败\n");return -PTR_ERR(cls);}printk("向上提交目录成功\n");//向上提交设备节点dev=device_create(cls,NULL,MKDEV(major,0),NULL,"si7006");if(IS_ERR(dev)){printk("向上提交设备节点失败\n");return -PTR_ERR(dev);   }printk("向上提交设备节点成功\n");return 0;
}int i2c_remove(struct i2c_client *client)
{//销毁节点device_destroy(cls,MKDEV(major,0));//销毁目录class_destroy(cls);//注销字符设备驱动unregister_chrdev(major,"si7006");return 0;
}
//定义设备树匹配的表
struct of_device_id oftable[]={{.compatible="hqyj,si7006",},{},
};//分配IIC驱动信息对象
struct i2c_driver i2c_drv={.probe=i2c_probe,.remove=i2c_remove,.driver={.name="si7006",.of_match_table=oftable,},
};module_i2c_driver(i2c_drv);
MODULE_LICENSE("GPL");

应用层代码

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <arpa/inet.h>
#include "head.h"
#include <pthread.h>int number=1000;
int *p=&number;
int flag = 0;void *shuma_callback(void *arg)
{while(1){//将温湿度传给数码管ioctl显示,发送数据ioctl(*(int *)arg,GET_SHUMA,p);}   pthread_exit(NULL);
}int main(int argc,char const *argv[])
{int tem,hum;float tem1,hum1;int fd_i2c=open("/dev/si7006",O_RDWR);if(fd_i2c<0){printf("设备文件打开失败\n");exit(-1);}//温湿度值采用数码管显示int fd_spi=open("/dev/m74hc595",O_RDWR);if(fd_spi<0){printf("设备文件打开失败\n");exit(-1);}pthread_t tid_1;if(pthread_create(&tid_1,NULL,shuma_callback,(void *)&fd_spi)!=0){fprintf(stderr,"pthread_create failed__%d__\n",__LINE__);return -1;}pthread_detach(tid_1);//分离线程while(1){//获取数据ioctl(fd_i2c,GET_HUM,&hum);ioctl(fd_i2c,GET_TEM,&tem);printf("hum=%d,tem=%d\n",hum,tem);//大小端转换hum=ntohs(hum);tem=ntohs(tem);//计算数据hum1=125.0*hum/65536-6;tem1=175.72*tem/65536-46.85;printf("hum1=%d,tem1=%d\n",hum1,tem1);number=(int)hum1 * 100 + (int)tem1;sleep(1);}pthread_join(tid_1,NULL);//阻塞等待tid_1线程退出return 0;
}

头文件

#ifndef __HEAD_H__
#define __HEAD_H__#define GET_SHUMA _IOR('m',2,int)//获取数码管的功能码
#define GET_HUM _IOR('m',1,int)//获取湿度的功能码
#define GET_TEM _IOR('m',0,int)//获取温度的功能码#endif