飞凌嵌入式ElfBoard ELF 1板卡-使用AHT20进行环境监测之编写程序

编程步骤

（一）打开设备

fd = open(AHT20_DEV, O_RDWR);

if(fd < 0) {

printf("can't open file %srn", AHT20_DEV);

return -1;

}

设置宏定义AHT20_DEV为设备节点/dev/aht20，使用open以可读写的方式打开，如果打开错误返回-1。

（二）读取数据

ret = read(fd, databuf, sizeof(databuf));

read函数的作用是把从设备中读取到的数据存到databuf数组中。

（三）数据类型转换

c1 = databuf[0]*1000/1024/1024;  //

t1 = databuf[1] *200*10/1024/1024-500;

hum = (float)c1/10.0;

temp = (float)t1/10.0;

因为温湿度不能用常量表示，所以需要做相应数学计算转换成浮点量。

（四）关闭设备

close(fd);

详细代码

elf1_cmd_aht20.c：

#include "stdio.h"

#include "unistd.h"

#include "sys/types.h"

#include "sys/stat.h"

#include "sys/ioctl.h"

#include "fcntl.h"

#include "stdlib.h"

#include "string.h"

#include <poll.h>

#include <sys/select.h>

#include <sys/time.h>

#include <signal.h>

#include <fcntl.h>




#define AHT20_DEV "/dev/aht20"




int main(int argc, char *argv[])

{

int fd;

unsigned int databuf[2];

int c1,t1;

float hum,temp;

int ret = 0;




fd = open(AHT20_DEV, O_RDWR);

if(fd < 0) {

printf("can't open file %srn", AHT20_DEV);

return -1;

}




while (1) {

ret = read(fd, databuf, sizeof(databuf));

if(ret == 0) { /* ?????? */




 c1 = databuf[0]*1000/1024/1024;  //

 t1 = databuf[1] *200*10/1024/1024-500;

 hum = (float)c1/10.0;

 temp = (float)t1/10.0;




printf("hum = %0.2f temp = %0.2f rn",hum,temp);

usleep(500000);

}

}

close(fd);

return 0;

}